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Popular Articles (March 2015)

Includes the top 50 most frequently downloaded documents for this publication according to the most recent monthly usage statistics.
  • 1. Demystifying Envelope Tracking: Use for High-Efficiency Power Amplifiers for 4G and Beyond

    Publication Year: 2015 , Page(s): 106 - 129
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (17091 KB)  

    The efficiency of a radio-frequency (RF) power amplifier (PA) is generally defined as the ratio between the desired transmitted radio power and the total power from a power supply, which is rather low in average with modern high peak-to-average-power-ratio (PAPR) signals, as illustrated in Figure 1(a). Consequently, a small improvement in the efficiency of the RF PA can have substantial benefits for a wireless system and cut the overall costs of system operations. View full abstract»

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  • 2. Safe for Generations to Come: Considerations of Safety for Millimeter Waves in Wireless Communications

    Publication Year: 2015 , Page(s): 65 - 84
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4682 KB)  

    With the increasing demand for higher data rates and more reliable service capabilities for wireless devices, wireless service providers are facing an unprecedented challenge to overcome a global bandwidth shortage. Early global activities on beyond fourth-generation (B4G) and fifth-generation (5G) wireless communication systems suggest that millimeter-wave (mmWave) frequencies are very promising for future wireless communication networks due to the massive amount of raw bandwidth and potential multigigabit-per-second (Gb/s) data rates [1]?[3]. Both industry and academia have begun the exploration of the untapped mmWave frequency spectrum for future broadband mobile communication networks. In April 2014, the Brooklyn 5G Summit [4], sponsored by Nokia and the New York University (NYU) WIRELESS research center, drew global attention to mmWave communications and channel modeling. In July 2014, the IEEE 802.11 next-generation 60-GHz study group was formed to increase the data rates to over 20 Gb/s in the unlicensed 60-GHz frequency band while maintaining backward compatibility with the emerging IEEE 802.11ad wireless local area network (WLAN) standard [5]. View full abstract»

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  • 3. Boosting the Efficiency: Unconventional Waveform Design for Efficient Wireless Power Transfer

    Publication Year: 2015 , Page(s): 87 - 96
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3188 KB)  

    Traditionally, wireless power is delivered through single-carrier, continuous-wave (CW) signals. Most research efforts to enhance the efficiency of wireless power transfer systems have been confined to the circuit-level design. However, in recent years, attention has been paid to the waveform design for wireless power transmission. It has been found that signals featuring a high peak-to-average power ratio (PAPR) can provide efficiency improvement when compared with CW signals. A number of approaches have been proposed, such as multisines/multicarrier orthogonal frequency division multiplex (OFDM) signals, chaotic signals, harmonicsignals, ultrawideband (UWB) signals, intermittent CW (ICW) signals, or white-noise signals. This article reviews these techniques with a focus on multisines/multicarrier signals, harmonic signals, and chaotic signals. A theoretical explanation for efficiency improvement is provided and accompanied by experimental results. Circuit design considerations are presented for the receiver side, and efficient transmission architectures are also described with an emphasis on spatial power combining. View full abstract»

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  • 4. GaN HEMT: Dominant Force in High-Frequency Solid-State Power Amplifiers

    Publication Year: 2015 , Page(s): 97 - 105
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2517 KB)  

    The gallium nitride (GaN) high-electron-mobility transistor (HEMT) has emerged as the dominant force in high-frequency solid-state power amplifiers (PAs)-not that it does not have competition. Silicon (Si) bipolar junction transistors (BJTs) and Si laterally diffused metal-oxide-semiconductor (LDMOS) field-effect transistors (FETs) are still commercially available. They are viable alternatives to GaN HEMTs in aerospace/defense applications such as L-band transponders/interrogators for the identification friend or foe; Link 16 data links; electronic warfare; and surveillance radar; and, in the case of Si LDMOSs, commercial cellular base stations. These older technologies can be favored due to their mature heritage, good performance, and low cost. The pseudomorphic HEMT (PHEMT) is ubiquitous in microwave and millimeter-wave power applications. Vacuum electron devices (VEDs) still reign in the regime of brute power. The GaN HEMT has been displacing these technologies as it has matured and costs have come down. View full abstract»

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  • 5. Narrowband Transmitters: Ultralow-Power Design

    Publication Year: 2015 , Page(s): 130 - 142
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4944 KB)  

    Recent advancements in integrated radio design have enabled many new applications ranging from wearable health-care or fitness monitors to Internet of Things devices, structural integrity monitors, and beyond. In many of these applications, device size and battery life are of critical importance. Since radios often consume a significant portion of the power budget in small sensing nodes [1], reducing radio power consumption is an effective way to decrease battery size or increase battery life. Reducing radio power consumption can be challenging as there are important tradeoffs between power consumption and performance metrics such as radiated output power, linearity, sensitivity, channelization capabilities, and interference sensitivity. Low-power radio designs often sacrifice one or more of these metrics in the pursuit of low overall power consumption. View full abstract»

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  • 6. Harvesting Wireless Power: Survey of Energy-Harvester Conversion Efficiency in Far-Field, Wireless Power Transfer Systems

    Publication Year: 2014 , Page(s): 108 - 120
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2667 KB) |  | HTML iconHTML  

    The idea of wireless power transfer (WPT) has been around since the inception of electricity. In the late 19th century, Nikola Tesla described the freedom to transfer energy between two points without the need for a physical connection to a power source as an "all-surpassing importance to man". A truly wireless device, capable of being remotely powered, not only allows the obvious freedom of movement but also enables devices to be more compact by removing the necessity of a large battery. Applications could leverage this reduction in size and weight to increase the feasibility of concepts such as paper-thin, flexible displays, contact-lens-based augmented reality, and smart dust, among traditional point-to-point power transfer applications. While several methods of wireless power have been introduced since Tesla's work, including near-field magnetic resonance and inductive coupling, laser-based optical power transmission, and far-field RF/microwave energy transmission, only RF/microwave and laser-based systems are truly long-range methods. While optical power transmission certainly has merit, its mechanisms are outside of the scope of this article and will not be discussed. View full abstract»

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  • 7. Body Electric: Wireless Power Transfer for Implant Applications

    Publication Year: 2015 , Page(s): 54 - 64
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2865 KB)  

    The electrical properties of biological cells, tissues, and organs studied in electrophysiology not only provide information about the normal/abnormal activities of human bodies but also provide a means to directly restore, repair, replace, or recreate physiological functions in humans to improve quality of life. For example, cardiac pacemakers, implanted in millions of patients, deliver electrical pulses into the right atrium and/or the right/both ventricles to control abnormal heart rhythms. Electrical activities of neurons such as action potentials (specific waveforms of voltage fired by neurons) have been studied for neurodisorders. Recordings of electric signals spatially and temporally around the brain and central nervous system, such as electroencephalography [(EEG) electrical activities along the scalp from the brain] and evoked potential responses (measurement of the time and waveform changes for nerves in other parts of the body in response to electrical stimulation of the brain), help to understand brain functions and diagnose diseases such as multiple sclerosis (nerve cells in the brain and spinal cord gradually degrade causing problems in muscle control and cognition). As activation to targeted tissues, neurostimulation triggers neurons with electrical voltages or currents to excite signal propagation in the nervous system to restore functions. Sensations such as hearing and vision can be restored by cochlear or retinal implants. Tremors can be controlled with deep brain stimulation in the subthalamic nucleus and the globus pallidus interna areas to manage Parkinson?s Disease and dystonia (both with symptoms of involuntary muscle contractions and tremors). Chronic pain can be inhibited by electrically stimulating the periaqueductal gray and periventricular gray areas in the brain for nociceptive pain, and the ventral posterolateral/posteromedial nucleus for neuropathic pain. Brain?computer interfaces have been developed for motor neuroprosthetics, such- as robotic hands, arms, or legs that can be controlled by thoughts with decoded action potentials or EEG signals from the brain for patients with paralysis. Recently, experiments on electrical stimulation in the uperolateral branch of the medial forebrain bundle have found a significant antidepressant effect for major depression, especially treatment-resistant depression. View full abstract»

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  • 8. Getting to the heart of the matter: considerations for large-signal modeling of microwave field-effect transistors

    Publication Year: 2015 , Page(s): 76 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2632 KB)  

    The field-effect transistor (FET) has just three terminals. One is a gate that controls current flowing between the source and drain terminals. It is simple enough, and so widely accepted as a workhorse in microwave applications, that it must be fairly well understood?or is it? Hidden between those terminals is a treasure trove of complicated interactions that have taken years to sort out. Just when we think we know all we need to know, someone asks for double the power, to move up to the next band, or even to do it all again in a new semiconductor material, and so the story continues. View full abstract»

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  • 9. Composite right/left-handed transmission line metamaterials

    Publication Year: 2004 , Page(s): 34 - 50
    Cited by:  Papers (371)  |  Patents (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3109 KB) |  | HTML iconHTML  

    Metamaterials are artificial structures that can be designed to exhibit specific electromagnetic properties not commonly found in nature. Recently, metamaterials with simultaneously negative permittivity (/spl epsiv/) and permeability (μ), more commonly referred to as left-handed (LH) materials, have received substantial attention in the scientific and engineering communities. The unique properties of LHMs have allowed novel applications, concepts, and devices to be developed. In this article, the fundamental electromagnetic properties of LHMs and the physical realization of these materials are reviewed based on a general transmission line (TL) approach. The general TL approach provides insight into the physical phenomena of LHMs and provides an efficient design tool for LH applications. LHMs are considered to be a more general model of composite right/left hand (CRLH) structures, which also include right-handed (RH) effects that occur naturally in practical LHMs. Characterization, design, and implementation of one-dimensional and two-dimensional CRLH TLs are examined. In addition, microwave devices based on CRLH TLs and their applications are presented. View full abstract»

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  • 10. Substrate Integrated Waveguide Filters: Design Techniques and Structure Innovations

    Publication Year: 2014 , Page(s): 121 - 133
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4647 KB)  

    Because of the inherent structural flexibility in coupling design and topological arrangement, substrate integrated waveguide (SIW) filter topologies enjoy better out-of-band frequency selectivity and/or in-band phase response with the allocation of finite transmission zeros (FTZs). In the first article in this series, basic design rules and fundamental electrical characteristics have been presented that indicate the superior performances of SIW structures and their filter applications. Advanced design techniques and innovative structure features have recently been reported in a large number of publications. They include cross couplings realized by physical and nonphysical paths and SIW filters with dual-mode or multimode techniques. Miniaturization-enabled techniques including low-temperature cofired ceramic (LTCC) technology have been developed and applied to the development of SIW filters to reduce the size for low-gigahertz applications using nontransverse electromagnetic (non-TEM) modes. Wideband SIW filters, multiband SIW filters, and reconfigurable SIW filters have also been reported by various research groups. This article reviews these advanced and innovative SIW filter technologies, and related examples are presented and discussed. View full abstract»

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  • 11. RF MEMS switches and switch circuits

    Publication Year: 2001 , Page(s): 59 - 71
    Cited by:  Papers (365)  |  Patents (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1365 KB) |  | HTML iconHTML  

    MEMS switches are devices that use mechanical movement to achieve a short circuit or an open circuit in the RF transmission line. RF MEMS switches are the specific micromechanical switches that are designed to operate at RF-to-millimeter-wave frequencies (0.1 to 100 GHz). The forces required for the mechanical movement can be obtained using electrostatic, magnetostatic, piezoelectric, or thermal designs. To date, only electrostatic-type switches have been demonstrated at 0.1-100 GHz with high reliability (100 million to 10 billion cycles) and wafer-scale manufacturing techniques. It is for this reason that this article will concentrate on electrostatic switches View full abstract»

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  • 12. A Compact L-Band Bandpass Filter with RF MEMS-Enabled Reconfigurable Notches for Interference Rejection in GPS Applications

    Publication Year: 2015 , Page(s): 81 - 88
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2342 KB)  

    In light of today's crowded radio spectrum and the high level of receiver sensitivity required to receive very weak signals, mitigating interference (cosite, intentional jamming, or from other sources) has become a very important topic of research. The recent controversy regarding the use of spectrum close to the global positioning system (GPS) bands is the motivation for the IEEE Microwave Theory and Techniques Society 2014 International Microwave Symposium (IMS2014) Tunable Radio-Frequency (RF) Microelectromechanical Systems (MEMS) Filter Student Design Competition, held in Tampa, Florida. Although there are frequency bands reserved for GPS, there is sometimes interference from undesired signals from a variety of sources, such as radio emissions in adjacent bands, intentional/unintentional jamming, and naturally occurring space weather. Ensuring the continuity of GPS service requires the protection of its spectrum from interference. This competition was intended to interest students in the design of innovative RF front-end solutions to address this issue. This article describes the work of the winners of the first-place award. View full abstract»

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  • 13. Stacked Yagi-Uda Array for 2.45-GHz Wireless Energy Harvesting

    Publication Year: 2015 , Page(s): 67 - 73
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2469 KB)  

    Wireless energy harvesting is currently a popular topic in radiofrequency (RF) engineering. Electromagnetic (EM) energy coming from different kinds of sources has to be collected by the harvester and efficiently converted into dc power. Practical applications include wireless charging systems and dc powering of RF identification (RFID) chips. Space applications were also investigated. Therefore, the third Wireless Energy Harvesting Student Design Competition was organized during the 2014 IEEE Microwave Theory and Techniques Society International Microwave Symposium (IMS2014) in Tampa, Florida. View full abstract»

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  • 14. RF MEMS phase shifters: design and applications

    Publication Year: 2002 , Page(s): 72 - 81
    Cited by:  Papers (83)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (9860 KB) |  | HTML iconHTML  

    Recent results obtained with MEMS phase shifters demonstrate that their performance is much better than GaAs phase shifters using either standard (switched-line, reflect-line) or distributed designs. The reliability of MEMS phase shifters is worse than of single switches since they employ 8-16 MEMS switches and do not tolerate a failure in any of the switches. On the other hand, a large phased array will still function properly, albeit with a slightly decreased efficiency and higher sidelobes if 3-4% of the phase shifters fail. Currently, the failure mechanisms of MEMS switches are being investigated and will greatly benefit the reliability of MEMS phase shifters. Also, the hermetic packaging of MEMS phase shifters is not straightforward, due to their relatively large size. It is for these reasons that the authors believe that MEMS phase shifters will be mostly used in satellite and defense applications in the next five years View full abstract»

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  • 15. A High-Sensitivity Radar System Featuring Low Weight and Power Consumption

    Publication Year: 2015 , Page(s): 99 - 105
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1764 KB)  

    In this article, a lightweight, low-power radar system for vibration monitoring has been presented. Based on a theoretical analysis of the competition scenario, an optimized system concept has been developed. The radar front end is able to sequentially evaluate the in-phase and quadrature component of the received signal with only a single hybrid coupler and power detector, reducing the overall weight to 5 g including the power-supply cable. A low duty cycle of 1% allowed the power to average 1.5 mW. As the minimum required sensitivity was limited to 0.5-mm oscillation amplitude, the most challenging parts in this student competition were, in our opinion, the tight power and weight optimizations. As the competition required only vibration detection butno ranging, a minimalistic system concept optimized for this application was proposed. The system features a free-running VCO sourced directly from the power supply without any further stabilization. For ranging applications, temperature changes as well as supply and tuning voltage variations at the VCO could have a severe impact on the system's accuracy. However, for pure vibration detection of a well-defined target, this is not a problem. Further improvements could be achieved when designing a customized 24-GHz oscillator, optimized for high efficiency [9] and fast turn-on time. In addition, the necessary number of measurements per second could be further investigated. Currently, with ten measurements per second, there is a convenient safety margin against false detections; however, fewer measurements would directly reduce the duty cycle and thus the average power consumption of the system. View full abstract»

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  • 16. Packaged Tunable Combline Bandpass Filters

    Publication Year: 2015 , Page(s): 93 - 98
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2586 KB)  

    This article describes the design of a packaged tunable bandpass filter used for the Student Filter Design Competition held during the 2014 International Microwave Symposium (IMS2014) in Tampa, Florida. The focus of the 2014 competition was to demonstrate a tunable bandpass filter between two wide separated bands. The first band is 4.25-4.4 GHz, and the second band is 6.25-6.4 GHz. The tunable filter must be realized on a printed circuit board with planar and lumped surface-mounted components and required to be assembled in an open-tooled FP118118-1 package [1] securely sealed with a copper tape lid. The entire package was mounted on an evaluation board, with 50-X traces connecting the radio-frequency (RF) input and output pins to 50-X female subminiature version A (SMA) connectors. The evaluation board also had a trace that connects the dc control pin of the package to a pad on the perimeter of the evaluation board. The filter performance was measured at the SMA interfaces with a dc voltage level from 0 to 20 V to shift the passbands of the tunable bandpass filter using a varactor [Microwave Associates (M/A) Com 46H202]. View full abstract»

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  • 17. A Novel Low Phase Noise X-Band Oscillator

    Publication Year: 2015 , Page(s): 127 - 135
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2968 KB)  

    In this article, we presented an X-band oscillator based on a novel CCMR using SIW technology. The measured results show that the proposed oscillator using active complementary coupled metamaterial has low phase noise and a good FOM for a given size and dc power consumption. View full abstract»

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  • 18. The last barrier: on-chip antennas

    Publication Year: 2013 , Page(s): 79 - 91
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3752 KB) |  | HTML iconHTML  

    This paper has presented a comprehensive overview of on-chip antennas, which remain the last bottleneck for achieving true SoC RF solutions. CMOS remains the mainstream IC technology choice but is not well suited for on-chip antennas, requiring the use of innovative design techniques to overcome its shortcomings. Codesign of circuits and antennas provide leverage to the designer to achieve optimum performance. The layout of on-chip antennas is dictated by foundry specific rules whereas characterization of on-chip antennas requires special text fixtures. For future highly integrated SoC solutions, foundries will have to provide special layers for efficient on-chip antenna implementations, as they currently do for on-chip inductors. In many of the emerging applications such as THz communication, implantable systems and energy harvesting, on-chip antennas have shown immense potential and are likely to play a major role in shaping up future communication systems. View full abstract»

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  • 19. Hassle-Free Vitals: BioWireleSS for a Patient-Centric Health-Care Paradigm

    Publication Year: 2014 , Page(s): S25 - S33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2012 KB)  

    Continuous monitoring of vital information via a wireless medium has become an integral part of next-generation health-care technologies. The benefits of a wireless monitoring technique include facilitating in-home care services, reduction of the cost of frequent visits to hospitals, and lightening of the burden to the elderly persons. The development of miniature, lightweight, and energy-efficient circuit solutions for biomedical sensor applications has been made possible by the tremendous recent advancements in health-care monitoring technologies, micro- and nanofabrication processes, and wireless communications. Exuberant growth of the wireless sensor networks has opened up a new and innovative application of wireless technology in health care. The advancement of wireless technology has led to the development of the recently proposed comprehensive patient monitoring systems such as wireless body area network (WBAN) and body sensor network (BSN). Implantable and wearable sensors are integral components of these networks and are employed for monitoring various levels of physiological activities. Wireless sensor technology provides an effective tool for instant access to patient data, laboratory test results, and clinical histories as well as insurance information, thereby ensuring immediate health care in case of emergency, eliminating the lengthy clinical decision. This biomedical wireless technology has resulted in a new health-care concept known as telemedicine, which facilitates the monitoring of in-home patient care by incorporating smart medical devices and WBANs. In this scheme, implantable and wearable sensors are placed within the vicinity of the patient's body and various physiological parameters are monitored and transmitted wirelessly to a nearby hub station and subsequently to the remote health-care provider via a secure wireless communication network. The telemedicine platform can also be configured for identification of the object location, medicin- reminder, or emergency alert in case of any sign of fatal disease. As a result of the recent developments in biomedical wireless technologies, the traditional clinic-centric health care is giving way to a patient-care centric health-care concept. This translational health-care concept facilitates the multidirectional integration of basic research, patient-oriented research, and population-based research, with the long-term aim of improving the health of the public. However, the successful integration of this new health-care paradigm hinges on the proper interpretation, storage, and dissemination of the large data sets generated by the all implantable and wearable devices within the wireless network. View full abstract»

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  • 20. Green Communications: Digital Predistortion for Wideband RF Power Amplifiers

    Publication Year: 2014 , Page(s): 84 - 99
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3357 KB)  

    The RF PA, as one of the most essential components in any wireless system, suffers from inherent nonlinearities. The output of a PA must comply with the linearity requirement specified by the standards. Due to its satisfactory linearization capability, DPD has been widely accepted as one of the fundamental units in modern and future wideband wireless systems. With the help of this flexible digital technology, the inherent linearity problem of PAs operating in the saturation region can be significantly improved, which enables us, the wireless engineers, to create more suitable RF transceiver architectures to provide wireless access with better user experience (linearity perspective) and less power waste (power efficiency perspective). This moves us one more step towards the ultimate green communications. In this article, we discussed the DPD techniques in the context of linearizing nonlinear RF PAs. As the computing-horsepower and the transistor-density of digital IC increases while the cost per transistor decreases, the concept that uses digital enhancement techniques to eliminate active analog imperfects will gain more attention from both industry and academia. View full abstract»

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  • 21. A New Wave in Electrosurgery : A Review of Existing and Introduction to New Radio-Frequency and Microwave Therapeutic Systems

    Publication Year: 2015 , Page(s): 14 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5182 KB)  

    A review of experimentally and commercially available therapeutic systems that use radio-frequency (RF) and microwave energy is provided in the first part of this article. The second part considers new advanced electrosurgical systems that combine the advantages associated with the use of low-frequency RF energy and high-frequency microwave energy to enhance the overall clinical effect and discusses how the frequency of operation and the design of the antenna structure can be optimized to ensure the desired tissue effects are achieved. Consideration is also given to how the latest developments in high-frequency semiconductor power technology developed for the communications sector are enabling new microwave and millimeter-wave energy-based electrosurgical systems to be developed and commercialized at an affordable cost. View full abstract»

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  • 22. WebLab: A Web-Based Setup for PA Digital Predistortion and Characterization [Application Notes]

    Publication Year: 2015 , Page(s): 138 - 140
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (978 KB)  

    The WebLab that is described here was initially motivated by the 2014 IEEE Microwave Theory and Techniques Society International Microwave Symposium's (IMS2014's) Student Design Competition on Digital Predistortion (DPD) Linearization, described in "Accurate Linearization with Low-Complexity Models Using Cascaded Digital Predistortion Systems," by Barradas et. al on page 94 in this issue of IEEE Microwave Magazine. To make a comparison of DPD algorithm performance, it is necessary to have one device under test (DUT), a Doherty power amplifier (PA), and one measurement setup for everybody to use. This was not a problem for the finals of the competition because the competitors would all be physically present at the same location. However, for the preparations starting half a year in advance, this posed a serious problem. The solution we implemented takes advantage of the fact that most universities today provide a decent Internet connection for their employees and students. A remotely accessible WebLab seemed to be a viable solution to the problem of letting the competitors practice on the actual DUT using the same measurement setup before the final competition at IMS2014. We decided to construct a Web-based remote-controlled PA measurement setup that allowed any user (not only the competitors) to upload his or her own input data and download the resulting measured output data. The Web page and instructions for using it can be found at http://dpdcompetition.com. View full abstract»

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  • 23. Substrate Integrated Waveguide Filter: Basic Design Rules and Fundamental Structure Features

    Publication Year: 2014 , Page(s): 108 - 116
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2732 KB)  

    The electromagnetic (EM) spectrum is becoming more crowded, and it is densely populated with various wireless signals and parasitic interferers in connection with communication and sensing services. Increasingly sophisticated radio-frequency (RF), microwave, and millimeter-wave filters are required to enable the selection and/or rejection of specific frequency channels. This will occur in future generations of the wireless system, such as the current hotly debated fifth-generation communication systems, where the spectral channelization of a heterostructured wide-band signals will be critical in support of a host of coexisting bandwidths or speeds and applications. Bandpass filters have been the most useful and popular types for such applications and are the most difficult to design and develop in practice. Other types of filters such as notch (stopband) and lowpass filters have also been widely used in many systems, and their design is generally perceived less critical with respect to band-pass filters. This article will focus on the presentation and discussion of bandpass filters. Design factors or parameters of filters, such as selectivity, cost, miniaturization, sensitivity to environmental effects (temperature and humidity, for example), and power handling, combined with predefined in-band and out-of-band performance metrics, are critical specifications of the design with respect to the development of RF and microwave front ends. This is indispensable for the efficient utilization of frequency spectrum resources and the cost-effective enhancement of wireless system performances. View full abstract»

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  • 24. A Wideband Balun for HF, VHF, and UHF Applications

    Publication Year: 2014 , Page(s): 86 - 91
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (865 KB) |  | HTML iconHTML  

    There is an industry need for wideband baluns to operate across several decades of bandwidth covering the HF, VHF, and UHF spectrum. For readers unfamiliar with the term "balun," it is a compound word that combines the terms balanced and unbalanced. This is in reference to the conversion between a balanced source and an unbalanced load, often requiring an impedance transformation of some type. It's common in literature to see the terms "balanced" and "unbalanced" used interchangeably with the terms "differential" and "single-ended," and this article will also share this naming convention. These devices are particularly useful in network matching applications and can be constructed at low cost and a relatively small bill of materials. Wideband baluns first found widespread use converting the balanced load of a dipole antenna to the unbalanced output of a single-ended amplifier. These devices can also be found in solid-state differential circuits such as amplifiers and mixers where network matching is required to achieve the maximum power transfer to the load. In the design of RF power amplifiers, wideband baluns play a critical role in an amplifier's performance, including its input and output impedances, gain flatness, linearity, power efficiency, and many other performance characteristics.This article describes the theory of operation, design procedure, and measured results of the winning wideband balun presented at the 2013 IEEE Microwave Theory and Techniques Society (MTT-S) International Microwave Symposium (IMS2013), sponsored by the MTT-17 Technical Coordinating Committee on HF-VHF-UHF technology. The wideband balun was designed to deliver a 4:1 impedance transformation, converting a balanced 100 Ω source to an unbalanced 25 Ω load. It was constructed using a multiaperture ferrite core and a pair of bifilar wires with four parallel turns. View full abstract»

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  • 25. RF MEMS-CMOS Device Integration: An Overview of the Potential for RF Researchers

    Publication Year: 2013 , Page(s): 39 - 56
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5257 KB) |  | HTML iconHTML  

    Over the past decades, a great deal of progress has been made in the development of semiconductor manufacturing processes. This in turn has made possible the monolithic integration of microelectromechanical systems (MEMS) devices with driving, controlling, and signal processing CMOS electronics [1][4]. There have been several successful well known commercial examples of integrated MEMS-CMOS devices, including the Analog Devices ADXL accelerometers [5], the Texas Instruments digital micromirror device (DMD) [6], the STMicroelectronics accelerometers and gyroscopes [6], and SiTime vacuum-encapsulated resonators [7]. More recently, Cavendish Kinetic [8] and WiSpry [9] launched their RF MEMS switches fabricated through MEMS-CMOS integration. While several techniques for MEMS-CMOS integrations have been widely employed for sensor and accelerometer applications, most of the work reported in literatures on RF MEMS has focused on devices fabricated using conventional surface micromachining techniques. It is the objective of this article to provide RF researchers with an overview of the potential of integrating MEMS with CMOS for RF MEMS applications. View full abstract»

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  • 26. The next challenge for cellular networks: backhaul

    Publication Year: 2009 , Page(s): 54 - 66
    Cited by:  Papers (21)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3554 KB) |  | HTML iconHTML  

    Growth in the number of mobile users, coupled with the strong uptake of wireless broadband services, is driving high transport capacity requirements among cellular networks. However, revenues are not scaling linearly with increases in traffic. Demand for optimizing the cost efficiency of backhaul is becoming as critical as investment in the radio infrastructure. As a result, new transmission technologies, topologies, and network architectures are emerging in an attempt to ease the backhaul cost and capacity crunch. View full abstract»

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  • 27. Advancements at the Lower End: Advances in HF, VHF, and UHF Systems and Technology

    Publication Year: 2015 , Page(s): 28 - 49
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    In the March 2002 issue of IEEE Transactions on Microwave Theory and Techniques (T-MTT), Frederick Raab, chair and founder of the highfrequency (HF), very high frequency (VHF), ultrahigh frequency (UHF) technology technical committee of the IEEE Microwave Theory and Techniques Society (Technical Committee 17), organized an extensive overview paper "HF, VHF, and UHF Systems and Technology" [1]. The paper started with the early-20th-century notion that frequencies above approximately 1.5 MHz (200 m and down) were useless for communications, a fact soon discovered to be incorrect as experimenters and amateur radio enthusiasts showed the utility of the higher frequencies. The paper reviewed HF through UHF communication techniques and technologies, various propagation modes, and a number of systems and applications below 1,000 MHz. There have been many advances in this frequency range in the intervening years, some of them quite striking, as well as new applications and other applications not mentioned in the paper; updating the paper on HF, VHF, and UHF technology is the major focus of this article. In addition to updates on some of the material in the original paper, new technologies and/or a better understanding of electromagnetic (EM) behavior have occurred, and these are included in this article. View full abstract»

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  • 28. CMOS Differential Ring Oscillators: Review of the Performance of CMOS ROs in Communication Systems

    Publication Year: 2013 , Page(s): 97 - 109
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4372 KB) |  | HTML iconHTML  

    The integrated differential ring oscillator (DRO) in complementary metal oxide semiconductor (CMOS) technology has been used in numerous products for a long time. Its presence has been extended to high-speed clock and data recovery (CDR) circuits for optical communication, analog and digitally controlled oscillators, frequency dividers of high-frequency synthesizers, clock generators of digital circuits, analog-to-digital converters (ADCs), and many more applications [1]-[5]. Implementations of these ring oscillators are seen in emerging technologies such as ultrawideband (UWB) and radio frequency identification (RFID) as well as wireless sensor networks (WSNs) and short-range communication devices [6], [7]. The DRO is a good design choice for integrated circuit (IC)designers because of its continued use in different bulk CMOS technologies. This article presents implementation techniques and performance comparisons of the DRO as a CMOS voltage-controlled oscillator (VCO) in low radio frequency (RF) bands, along with presentation and discussion of a number of circuit approaches. View full abstract»

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  • 29. Linear Doherty PA at 5 GHz

    Publication Year: 2015 , Page(s): 89 - 93
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    At the 2014 International Microwave Symposium (IMS2014) in Tampa, Florida, the power amplifier (PA) design competition celebrated its tenth anniversary. Back in 2004, it was the first student design competition that the IEEE Microwave Theory and Techniques Society (MTT-S) organized and, since then, the only one that has been held regularly every year. We started to participate in this competition in 2012, which also happened to be the year when a significant change in the competition rules was adopted. Starting in 2012, the power-added efficiency (PAE) in the figure of merit (FOM) that is used to evaluate the PAs, FOM = PAE/4?f, was measured at a power level at which the intermodulation distortion (IMD) that the PA produces from a two-tone excitation first exceeds 30 dBc. With that new rule, not only did linearity start to play a major role but also the test signal changed from continuous wave (CW) to a modulated signal with a peak to average ratio of 3 dB. View full abstract»

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  • 30. Wireless Data Center Management: Sensor Network Applications and Challenges

    Publication Year: 2014 , Page(s): S45 - S60
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    The modern data centers (DCs) are essential to fulfilling ever-evolving computational demands around cloud computing, big data, and IT infrastructure. These DCs are facilities (Figure 1) that house computer systems and associated components such as networking and storage systems. To operate a DC, power supplies, network connections, environmental controls (e.g., air conditioning, humidity), and security infrastructure are needed. Technology and business challenges such as virtualization, load consolidation, real-time troubleshooting, and service-level guarantees require a robust and adaptive server management plan for enterprise. The majority of DC issues are related to overutilization of resources, application failures, data security, power usage effectiveness (PUE), and infrastructure costs. This requires proactive solutions that are business intelligent and built over a network of sense points that are guaranteed to deliver reliable trends and measurements in a reliable and timely fashion. Since it is expensive to build new DCs, the best option is to improve usage of an existing facility through lower infrastructure overhead to deliver better resource management. An optimal sensor network would perform real-time sensor-data collection and deliver a) improved server rack utilization, b) improved DC cooling, and c) improved loadbalancing through dynamic capping of thermally constrained systems. View full abstract»

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  • 31. Too Much Pressure: Wireless Intracranial Pressure Monitoring and Its Application in Traumatic Brain Injuries

    Publication Year: 2015 , Page(s): 39 - 53
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    Intracranial pressure (ICP) is the pressure exerted by the components of the cranial vault, which are the brain, cerebrospinal fluid (CSF), and blood. An elevation of ICP results in a reduction of blood flow to the brain [1]. The brain can cope with intracranial hypertension (ICH) to a certain extent, after which a slight increase in the cerebral volume results in a rapid rise of ICP [2]. A significant reason for death and long-term disability due to head injuries and pathological conditions is an elevation in ICP. An ICP > 20 mmHg is considered a significant threshold and demands an immediate control measure [3]. ICP monitoring can assist in the management of patients with a variety of brain diseases and injuries. The technique has proven valuable, indeed often lifesaving, in the acute care of traumatic brain injury (TBI) [4], hydrocephalus [5], drowning [6], inflammatory and related cerebral diseases such as Reye?s syndrome [7], intracranial hemorrhage [8], and postoperative suboccipital brain tumors [9]. Most patients have headaches and other symptoms suggestive (but not always indicative) of raised ICP; continuous access to ICP levels would greatly facilitate their management. There is a conspicuous need for a wireless implantable ICP-monitoring system as several chronic diseases are associated with ICH. Accurate monitoring of the ICP following a neurosurgical procedure is a basic requirement for adequate treatment [10]?[12]. Since the intracranial contents exist within a rigid vault (the skull), direct ICP measurements require neurosurgical intervention, with its attendant risks. An implant placed during surgery, for the underlying cause of neural disorder, would be a useful adjunct to patient care. View full abstract»

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  • 32. Accurate Linearization with Low-Complexity Models Using Cascaded Digital Predistortion Systems

    Publication Year: 2015 , Page(s): 94 - 103
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3578 KB)  

    Power efficiency is one of the main concerns in modern radio frequency (RF) power amplifier (PA) design. However, efficiency-driven designs typically impose operation of these devices in a compressed mode [1]. When operating in this region, the amplifiers will behave nonlinearly and produce a distorted output signal [1]. This distortion produces new spectral components at the PAs' output that are outside the bandwidth of the input signal, so the distorted output signal has a wider bandwidth than the input signal. This bandwidth enlargement effect, called "spectral regrowth," is undesired in RF transmitters due to wireless systems' spectral mask regulations [2]. View full abstract»

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  • 33. Low-Noise Amplifier for Statistical Multiband and Multistandard Applications

    Publication Year: 2015 , Page(s): 116 - 121
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    The Low-Noise Amplifier (LNA) Student Design Competition has continuously evolved since its inception. Each year, students have been challenged to design an LNA with an increased emphasis on ruggedness, linearity, and broadband performance [1]-[5]. The 2014 IEEE Microwave Theory and Techniques Society (MTT-S) International Microwave Symposium (IMS2014) continued this trend by requiring students to design an LNA receiver module for statistical multiband and multistandard applications in an effort to raise awareness about the complexity and nondeterministic nature of the topic. For the first time in competition history, the measurement frequencies were not predetermined and were decided on the day of the competition by two rolls of a six-sided die, with each side representing a frequency in gigahertz. This requirement prevented students from optimizing a design for a particular set of frequencies and instead called for a design possessing linear broadband performance from 1 to 6 GHz. View full abstract»

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  • 34. Space solar power programs and microwave wireless power transmission technology

    Publication Year: 2002 , Page(s): 46 - 57
    Cited by:  Papers (82)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1429 KB) |  | HTML iconHTML  

    Future large-scale space solar power (SSP) will form a very complex integrated system of systems requiring numerous significant advances in current technology and capabilities. Ongoing technology developments have narrowed many of the gaps, but major technical, regulatory, and conceptual hurdles remain. Continuing systems concept studies and analyses will be critical to success, as will following a clear strategic R&T road map. This road map must assure both an incremental and evolutionary approach to developing needed technologies and systems is followed, with significant and broadly applicable advances with each increment. In particular, the technologies and systems needed for SPS must support highly leveraged applicability to needs in space science, robotic and human exploration, and the development of space. Considerable progress has been made in the critical area of microwave power transmission. At 5.8 GHz, DC-RF converters with efficiencies over 80% are achievable today. Rectennas developed at 5.8 GHz have also been measured with efficiencies greater than 80%. With optimized components in both the transmitter and rectenna, an SPS system has the potential of a DC-to-DC efficiency of 45%. View full abstract»

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  • 35. Mach-Zehnder: A Review of Bias Control Techniques for Mach-Zehnder Modulators in Photonic Analog Links

    Publication Year: 2013 , Page(s): 102 - 107
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2016 KB) |  | HTML iconHTML  

    The Mach-Zehnder modulator (MZM) has been widely used for broadband photonic analog links and high-speed digital optical fiber communication systems because it possesses large modulation bandwidth, low driving voltage, and low chirp. The MZM is a very important optical modulator for photonic applications. In an MZM, the input light is split into two paths, each of which is modulated by an electrical signal. Then the two arms are combined to generate an intensity-modulated light or a phase-modulated light at the output of the MZM. An MZM can be made of lithium niobate (LiNbO3), gallium arsenide (GaAs), or indium phosphide (InP), materials that exhibit some anisotropy in their dielectric properties. Theoretically, the relation of output optical field and driving voltage is a cosine function, i.e., nonlinear transfer function. For RF photonics, the MZM has typically two applications: optical harmonic generation for optical frequency multiplication and optical subcarrier modulation for optical signal modulation. For optical frequency multiplication, high transfer-function nonlinearity is preferred. In contrast, high transfer-function linearity is preferred for optical subcarrier modulation. It is well known that a cosine transfer function can present high or low nonlinearity dependent on operation voltage. Specifically, bias voltages determine the degree of nonlinearity or linearity of the MZM transfer function. For optical frequency multiplication such as millimeter-wave generation, the MZM should be biased at some specific bias points, such as minimum transmission, maximum transmission, and quadrature bias points, to enhance nonlinearity [1]?[2]. For optical subcarrier modulation, biasing an MZM in its linear region such as quadrature bias points allows transmitting broadband RF signals with multioctave bandwidth and improves spurious free dynamic range (SFDR). Therefore, care must be taken to maintain and control the MZM bias point for a specific applicat- on. View full abstract»

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  • 36. Transistor Model Building for a Microwave Power Heterojunction Bipolar Transistor

    Publication Year: 2015 , Page(s): 85 - 92
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    This article describes the detailed development of a large-signal transistor model for a microwave power heterojunction bipolar transistor (HBT). Based on the neurospace-mapping (Neuro-SM) technique, this model uses neural networks to map a coarse model space represented by the existing model simulations onto the fine model space represented by device measurements. This article tied for first place in the Microwave Transistor Modeling Student Design Competition at the 2014 IEEE International Microwave Symposium (IMS2014) held in Tampa, Florida. View full abstract»

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  • 37. Flexible Filters: Reconfigurable-Bandwidth Bandpass Planar Filters with Ultralarge Tuning Ratio

    Publication Year: 2014 , Page(s): 43 - 54
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    The objective of this overview article is to report the latest research findings in the research into RF/ microwave reconfigurable-bandwidth bandpass planar filters with ultralarge passbandwidth tuning ratio. This means filtering devices with much higher flexibility, showing reconfigurable bandwidths between narrow/moderate-band and ultrawideband states. Specifically, two different solutions we recently proposed are described, with emphasis on their operating principles and achieved electrical performances. They consist of 1) transversal signal-interference switchable-bandwidth bandpass filters and 2) tune-all bandpass filters simultaneously exploiting MMRs and quality-factor control to achieve unprecedented reconfiguration levels in terms of center frequency and instantaneous passbandwidth. Some other modern filtering topologies proposed by other authors, which have clear interest to attain very high levels of bandwidth variation, are also expounded. View full abstract»

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  • 38. Submillimeter-Wave Radar: Solid-State System Design and Applications

    Publication Year: 2014 , Page(s): 51 - 67
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    For decades, the principal role of microwave engineering techniques in the submillimeter (submm)-wave, or terahertz (THz), regime, spanning about 300 GHz-3 THz, has been to optimize the performance of components and systems used in molecular spectroscopy measurements for astronomy, earth science, and plasma diagnostics [1]. THz applications beyond spectroscopy have been much slower to develop. Ultrahigh bandwidth communication at THz frequencies may have the most powerful market forces to support it, but no systems have been deployed beyond the prototype stage, likely because of the unavailability of commercial submm-wave components, challenges with integrating them with existing communications hardware, and the often severe atmospheric attenuation. View full abstract»

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  • 39. Transversal Signal Interaction: Overview of High-Performance Wideband Bandpass Filters

    Publication Year: 2014 , Page(s): 84 - 96
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4234 KB) |  | HTML iconHTML  

    This article presents an introduction of recently wideband bandpass filters based on transversal signal interaction concepts. Different resonant structures are reported on, including branch-line coupler/ring resonator, interdigital coupled lines, DSPSL 180° phase-shifting structure, Marchand balun, open/shorted coupled lines, T-shaped structures, and open/shorted stubs. Detailed comparisons of out-of-band transmission zeros, effective circuit size, 3-dB bandwidth, upper stopband, and group delay for the wideband/UWB filters discussed in this article are presented. Different bandwidth of wideband bandpass filters can be realized based on transversal signal interaction concepts, branch-line coupler/ring resonator can be easy to realize wide bandwidth with narrow upper stopbands due to their harmonic response. The filter structures using different 180° phase-shifting structures such as DSPSL, shorted coupled lines, and Marchand balun can meet UWB bandwidth/band demand, and the circuit size can be further reduced, while the selectivity and upper stopband should be further improved. The integrated applications of shorted/open coupled lines and shorted/open stubs can increase the numbers of the transmission zeros out-of-band, besides the circuit size reduction, the upper stopband can be also extended to over 4.7 f0 . Moreover, the transversal signal-interaction concepts have been also extended to the design of differential wideband//UWB balanced bandpass filters with broadband common-mode suppression in our former works. View full abstract»

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  • 40. Design of 1:4 Ultrawideband Hybrid Transmission-Line Balun

    Publication Year: 2015 , Page(s): 122 - 126
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    This article presents the 1:4 wideband balun based on transmission lines that was awarded the first prize in the Wideband Baluns Student Design Competition. The competition was held during the 2014 IEEE Microwave Theory and Techniques Society (MTT-S) International Microwave Symposium (IMS2014). It was initiated in 2011 and is sponsored by the MTT-17 Technical Coordinating Committee. The winner must implement and measure a wideband balun of his or her own design and achieve the highest possible operational frequency from at least 1 MHz (or below) while meeting the following conditions: ? female subminiature version A (SMA) connectors are used to terminate all ports ? a minimum impedance transformation ratio of two ? a maximum voltage standing wave ratio (VSWR) of 2:1 at all ports ? an insertion loss of less than 1 dB ? a common-mode rejection ratio (CMRR) of more than 25 dB ? imbalance of less than 1 dB and 2.5?. View full abstract»

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  • 41. A Dual-Frequency Ultralow-Power Efficient 0.5-g Rectenna

    Publication Year: 2014 , Page(s): 109 - 114
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1174 KB) |  | HTML iconHTML  

    The second annual Student Wireless Energy Harvesting (WEH) Design Competition was held during the 2013 IEEE Microwave Theory and Techniques Society (MTT_S) International Microwave Symposium (IMS2013) in Seattle, Washington, United States. This year, the competition parameters were modified from those of last year [1], and a new figure of merit (FoM) was established. The overall goal of the competition was to demonstrate low-mass hardware that can efficiently receive and rectify extremely low-incident power densities at two frequencies, with a fixed dc load. As the radio-frequency (RF) environment gets more saturated with spurious power, designs from this competition will become a feasible way to energize ultralow-powered or low-duty-cycle hard-to-reach sensors. Concepts such as Internet-of-Things, in which small ubiquitous devices and sensors will log data and send it to the cloud, could benefit from wireless energy harvesters. These sensors will not have convenient ways to stay powered unless power harvesting circuits are used for the sensor hardware. View full abstract»

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  • 42. Highly Efficient Compact Rectenna for Wireless Energy Harvesting Application

    Publication Year: 2013 , Page(s): 117 - 122
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1294 KB) |  | HTML iconHTML  

    In this article, the design procedure of the winning WEH device in the IMS2012 Student Design Competition is presented. The designed WEH circuit is a rectenna consisting of a rectifier in voltage doubler structure and a folded dipole antenna. The design steps of the rectifier circuit and the antenna are explained in detail, and simulation and measurement results are shown. View full abstract»

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  • 43. Substrate Integrated Waveguide Filters: Practical Aspects and Design Considerations

    Publication Year: 2014 , Page(s): 75 - 83
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    In the current literature, the majority of research work reported on substrate integrated waveguide (SIW) filters has focused on the development of physical topologies as well as design and realization techniques for filter specifications and electrical parameters. The practical and successful implementation of SIW filters requires special consideration of mechanical and thermal properties during the design and processing stages. These properties include the effects of ambient operating environment, average, and peak power-handling capabilities as well as design and production economics, including labor costs, skilled labor availability, mass-production issues, and projected production delivery rates [1]. Bandpass filters are more concerned with those practical aspects as their in-band and out-of-band performance are much more sensitive than other types of filters to those mechanical and thermal issues. View full abstract»

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  • 44. High-Q Tunable Filters: Challenges and Potential

    Publication Year: 2014 , Page(s): 70 - 82
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6399 KB)  

    High-Q tunable filters are in demand in both wireless and satellite applications. The need for tunability and configurability in wireless systems arises when deploying different systems that coexist geographically. Such deployments take place regularly when an operator has already installed a network and needs to add a new-generation network, for example, to add a long-term evolution (LTE) network to an existing third-generation (3G) network. The availability of tunable/reconfigurable hardware will also provide the network operator the means for efficiently managing hardware resources, while accommodating multistandards requirements and achieving network traffic/capacity optimization. Wireless systems can also benefit from tunable filter technologies in other areas; for example, installing wireless infrastructure equipment, such as a remote radio unit (RRU) on top of a 15-story high communication tower, is a very costly task. By using tunable filters, one installation can serve many years since if there is a need to change the frequency or bandwidth, it can be done through remote electronic tuning, rather than installing a new filter. Additionally, in urban areas, there is a very limited space for wireless service providers to install their base stations due to expensive real estate and/or maximum weight loading constrains on certain installation locations such as light poles or power lines. Therefore, once an installation site is acquired, it is natural for wireless service providers to use tunable filters to pack many functions, such as multistandards and multibands, into one site. View full abstract»

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  • 45. The Doherty power amplifier

    Publication Year: 2006 , Page(s): 42 - 50
    Cited by:  Papers (84)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1873 KB) |  | HTML iconHTML  

    In this article, we show that the Doherty amplifier is capable of delivering the stringent requirements of the base station power amplifiers. We explain the operation principles, including both linearity and efficiency improvements, and the basic circuit configuration of the amplifier. Advanced design methods to operate across wide bandwidth and improve the linearity are also described. For verification, the Doherty amplifier is implemented using laterally diffused metal oxide semiconductor (LDMOS) transistors and measured using a WCDMA 4FA signal. These results show that the Doherty amplifier is a promising candidate for base station power amplifiers with wide bandwidth, high efficiency, and linearity View full abstract»

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  • 46. Envelope Tracking or Polar—Which Is It? [Microwave Bytes]

    Publication Year: 2012 , Page(s): 34 - 56
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (13620 KB) |  | HTML iconHTML  

    The terms “envelope tracking” (ET), “evelope elimination and restoration” (EER), and “polar” are generally used interchangeably in the literature for any transmitter circuit built using a dynamic power supply (DPS) architecture on the RF power amplifier (PA). Indeed, these are sometimes combined together into the same category and called EER/ET or ET/EER [1]. It is my experience from more than 15 years working with these technologies that there are very distinct and major differences between these techniques. Establishing simple and clear definitions as to which is which helps us clearly understand the differences between them. More importantly, this allows much less ambiguity as the literature expands regarding these important transmitter techniques. View full abstract»

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  • 47. Planar antennas

    Publication Year: 2006 , Page(s): 63 - 73
    Cited by:  Papers (54)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1806 KB) |  | HTML iconHTML  

    This article reviews the state of the art in broadband antennas for emerging UWB applications and addresses the important issues of the broadband antenna design for UWB applications. First, a variety of planar monopoles with finite ground planes are reviewed. Next, the roll antennas with enhanced radiation performance are outlined. After that, the planar antennas printed on PCBs are described. A directional antipodal Vivaldi antenna is also presented for UWB applications. Last, a UWB antenna for wearable applications is exemplified View full abstract»

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  • 48. Behavioral modeling and predistortion

    Publication Year: 2009 , Page(s): 52 - 64
    Cited by:  Papers (73)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3570 KB) |  | HTML iconHTML  

    In this article, a thorough overview of behavioral modeling and predistortion of dynamic nonlinearities in RF PAs and transmitters was presented. The sensitivity of the DUT behavior to the characteristics of the stimulus was reviewed to ensure appropriate conditions for accurate observation. Nearly all state-of-the-art behavioral models were described and their relative performance and complexity discussed. Similarities and specifics of behavioral modeling and digital predistortion were presented. Thereby, digital predistortion can be seen as a behavioral modeling problem for which performance assessment is much more straightforward. For DUT behavioral modeling, there is no comprehensive metric that allows the model performance evaluation while taking into account the model accuracy in predicting all the three components of the DUT behavior (in-band distortion, static nonlinearity and memory effects). Finally, a software digital predistortion solution that enables closed-loop wideband linearization was briefly presented with excellent linearization capabilities when amplifying a 12-carrier 60-MHZ wide WCDMA signal. View full abstract»

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  • 49. Beyond the Smith Chart: A Universal Graphical Tool for Impedance Matching Using Transformers

    Publication Year: 2014 , Page(s): 100 - 109
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1911 KB)  

    The topic of impedance transformation and matching is one of the well-established and essential aspects of microwave engineering. A few decades ago, when discrete radio-frequency (RF) design was dominant, impedance matching was mainly performed using transmission-lines techniques that were practical due to the relatively large design size. As microwave design became possible using integrated on-chip components, area constraints made L-C section matching (using lumped passive elements) more practical than transmission line matching. Both techniques are conveniently visualized and accomplished using the well-known graphical tool, the Smith chart. View full abstract»

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  • 50. A Mircostrip Circuit Tool Kit App with FDTD Analysis Including Lumped Elements

    Publication Year: 2015 , Page(s): 74 - 80
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2621 KB)  

    At the 2014 IEEE Microwave Theory and Techniques Society (MTT-S) International Microwave Symposium (IMS2014), the Apps for MTT Student Design Contest was held,sponsored by the Microwave Field Theory (MTT-15) Technical Committee. One objective of the design contest is to take advantage of the growing computing capacity of smart handheld and mobile devices to promote their use for the computer-aided analysis and design of microwave components and circuits. With the rapid development of recent iOS and Android smart phones or pads, some advanced scientific computation programs can now be executed on these portable devices. These handy devices can also deal with microwave circuit calculations if the applications (apps) are well designed. Since these devices are always accessible, it may be more convenient for engineers and students to analyze and design microwave circuits on the phones or pads directly. Note that full-wave, three-dimensional (3-D) simulations for complicated microwave circuits usually require a large amount of memory and a central processing unit with high performance, so it may be difficult to run full-wave 3-D simulations on portable smart devices. View full abstract»

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IEEE Microwave Magazine is intended to serve primarily as a source of information of interest to professionals in the field of microwave theory and techniques.

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