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Microwaves, Antennas & Propagation, IET

Issue 8 • Date June 6 2011

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Displaying Results 1 - 22 of 22
  • Special Issue on RF/Microwave Communication Subsystems for Emerging Wireless Technologies [Guest Editorial]

    Page(s): 861 - 863
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (84 KB)  

    This paper covers selected topics related to active components are included. An integrated voltage controlled oscillator; low loss microelectromechanical systems (MEMS) switches and switch networks integrated with GaAs monolithic microwave integrated circuits (MMIC), low-noise amplifiers (LNA) are then presented. The next paper presents a two stage class-AB CMOS power amplifier with improved stability for enhanced data rates for GSM evolution (GSM-EDGE) applications, which additionally includes a study on the efficiency improvement obtained by implementing an envelope tracking architecture. Finally, the section concludes with a paper on the application of digital signal processing techniques in transmitter architectures such as polar, envelope tracking and linear amplification with nonlinear components (LINC), aiming to guarantee increased efficiency. View full abstract»

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  • Laser prototyping of multilayer LTCC microwave components for system-in-package applications

    Page(s): 864 - 869
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (641 KB)  

    This study describes the fabrication of multilayer microwave components in low temperature co-fired ceramic (LTCC) technology using a laser prototyping method that requires no masks or photolithographic steps. Multilevel inductors, metal-insulator-metal capacitors and substrate integrated waveguides (SIWs) have been demonstrated. Optimisation of the laser machining parameters for the fabrication of microvias and micro-channels for the components is investigated. Using a 1064-nm IR laser, vias and channels with widths smaller than the thickness of the substrate have been achieved using the proposed multi-step process. Microvias with a diameter and separation of 75 and 50--m, respectively, have been realised by optimising the laser fluence and processing cycles. Micro-channels having widths of 30-100--m have also been demonstrated and used as the side walls for SIWs. The proposed fabrication technique offers a useful method for the rapid prototyping of multilayer LTCC modules. View full abstract»

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  • Recent results on compact broad-band and multi-band low-temperature co-fired ceramic components for radio frequency front-ends

    Page(s): 870 - 876
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (669 KB)  

    Compact components for radio frequency (RF) front-ends realised in low-temperature co-fired ceramics (LTCC) are presented. The aim of this study was to highlight recent advances in realisation of different components for modern RF/microwave subsystems, stressing such attributes as compactness, wide bandwidth and operation in multiple bands. Two key components of every RF front-end are filters and couplers. To illustrate the feasibility of using LTCC technology to realise these components, several designs of filters and couplers are presented. Very compact LTCC ridge waveguide filter covering the whole US ultra-wide band is first discussed, followed by a dual-band LTCC ridge waveguide filter. Two types of wide-band couplers are shown: ridge waveguide couplers realised in LTCC and empty metallic waveguide and also a strip-line LTCC coupler. A common characteristic that will be shown is that the presented components by the authors are modelled using computer-aided design tools based on modal analysis for waveguides as well as commercially available finite-element tools. The shown examples have simulation results compared by different methods as well as some experimental results in LTCC and empty metallic waveguide, used to demonstrate the proposed approach. View full abstract»

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  • Compact coplanar waveguide filter for integration in ultra wideband medical sensors

    Page(s): 877 - 881
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (277 KB)  

    In this study a novel compact filter structure for ultra-wideband (UWB) applications is presented. The filter is realised with coplanar waveguide technology and it is optimised for the European UWB regulation. It presents a transfer function with sharp transitional bands and low variation of the group delay time in the passband. The filter also has good time-domain behaviour and it introduces only low distortion on the transmitted pulse. The compactness of the presented filter structure and its good time-domain and frequency-domain properties allow its integration in small-size UWB sensors for medical applications, where low size and low distortion are required. View full abstract»

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  • Wideband planar Goubau line integrated circuit components at millimetre waves

    Page(s): 882 - 885
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (318 KB)  

    This study provides the design, fabrication and test results of passive planar Goubau line (PGL) components compatible with active micro-strip circuits, in millimeter(mm)-wave frequency range (40-60 GHz). Such wideband passive components are of interest in designing wideband digital wireless communication equipment. Basic passive components of this study include: two PGLs with conductor strip widths of 50 and 260 μm, respectively, transitions from chosen PGLs to 50 Ω micro-strip circuit, PGL loads and PGL power divider/combiners. Active components such as planar micro-strip circuits can be placed in tandem with passive PGLs using above transitions to design wide band circuits from microwaves to mm waves. PGL is formed by a planar conductor deposited on a standard 0.254 mm (10 mil) planar alumina substrate (ceramic) as opposed to the standard Goubau line made with a circular conductor and a circular dielectric. Passive PGL components are designed, simulated, fabricated and measured with an automatic network analyser (ANA) and test fixture. Simulation and test data support PGL component designs. PGL components operate well over a wide frequency range (from 40 to about 60 GHz). Similar results are expected with PGL at other mm-wave frequencies (below 40 GHz and above 60 GHz) and at terahertz frequencies (above 100 GHz). View full abstract»

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  • Complete network characterisation of stratified planar circuits using the method of moments technique: an integrated approach to lumped and wave ports

    Page(s): 886 - 894
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    This study gives a full treatment of the network characterisation of multi-port planar circuits embedded in shielded stratified media with an integrated approach to lumped ports and wave ports. The details of the mathematical formulation for the retrieval of scattering parameters are given in three cases: networks possessing only lumped ports, networks possessing only wave ports and networks with a combination of both types. A detailed description of the computer algorithm is presented to help the reader easily reproduce our results. The implementation of combined ports in the framework of planar multi-layered structures is particularly useful in analysing systems that have waveguide connections and planar circuitries in their structure, such as cavity-backed antennas and their associated feeding systems, dielectric resonator antennas or compound microwave filters. In such structures one can divide the system into the waveguide structure and the planar circuitries and analyse each part separately with an appropriate and efficient numerical technique. Network characterisations will be consequently communicated at the port interfaces. This strategy enhances the total performance of the computational scheme to a great extent, while not affecting the accuracy of the full-wave analysis. View full abstract»

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  • Coupling matrix synthesis of dissipative microwave filters

    Page(s): 895 - 900
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    This study reviews the coupling matrix synthesis of dissipative microwave filters. It compares it to the synthesis of lossless transfer functions and shows that by correctly interpreting the mathematical operations in the lossless case, that is especially the matrix product of vectors and matrices, the same procedure can be adopted for the case including losses. Beyond this, necessary and sufficient conditions are provided guaranteeing that a proper coupling matrix, that is which is symmetric, is obtained at the end. Two examples show the application of the procedure and demonstrate that the correct filter transfer functions are indeed obtained. View full abstract»

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  • Adaptive prototype for fixed length and dual-band waveguide H-plane filters

    Page(s): 901 - 908
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    An algorithm for the design of waveguide filters with prescribed length is presented. The technique is based on the concept of adaptive prototype, providing a one-to-one correspondence between the circuit and the physical structure, as for classical Cohn's direct-coupled cavity filters. In addition, two fixed length filters can be joined together to construct a dual-band filter. Examples of application of the method are discussed. View full abstract»

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  • Review of substrate-integrated waveguide circuits and antennas

    Page(s): 909 - 920
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    Substrate-integrated waveguide (SIW) technology represents an emerging and very promising candidate for the development of circuits and components operating in the microwave and millimetre-wave region. SIW structures are generally fabricated by using two rows of conducting cylinders or slots embedded in a dielectric substrate that connects two parallel metal plates, and permit the implementation of classical rectangular waveguide components in planar form, along with printed circuitry, active devices and antennas. This study aims to provide an overview of the recent advances in the modelling, design and technological implementation of SIW structures and components. View full abstract»

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  • Low insertion loss substrate integrated waveguide quasi-elliptic filters for V-band wireless personal area network applications

    Page(s): 921 - 927
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (812 KB)  

    Novel V-band substrate integrated waveguide (SIW) filters have been presented. Design procedures for the filters synthesis and mechanisms providing quasi-elliptic response have been explained. The insertion loss of the filters has been measured below 2 dB with microstrip-to-SIW transitions being included. View full abstract»

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  • Substrate integrated waveguide predistorted filter at 20 GHz

    Page(s): 928 - 933
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (371 KB)  

    This work presents the synthesis, design and testing of a fourth-order Chebyshev predistorted filter centred at 20 GHz and with 300 MHz bandwidth, implemented in substrate integrated waveguide (SIW) technology. Although the dielectric material adopted in this work allows for obtaining SIW resonators with a quality factor Q=500, the use of predistortion permits to realise a filter response with an in-band flatness equivalent to a filter with Q=2000, not achievable otherwise with the adopted material in SIW technology. Additionally, this work presents the design and testing of a conventional SIW filter (without predistortion) implemented with the same dielectric material. Comparison of the measured filter responses demonstrates the benefits of using predistortion technique in SIW technology for achieving improved performance at high frequency. View full abstract»

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  • 60 GHz wide tuning range SiGe bipolar voltage controlled oscillator for high definition multimedia interface and wireless docking applications

    Page(s): 934 - 939
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (499 KB)  

    A wide tuning range voltage controlled oscillator (VCO) with novel architecture is proposed in this work. The entire circuit consists of a VCO core, a summing circuit, a single-ended to differential (STD) converter and a buffer amplifier. The VCO core oscillates at half the desired frequency and the second harmonic of the VCO core is extracted by the summing circuit, which is then converted to a differential pair by the STD. The entire VCO circuit operates from 58.85 to 70.85 GHz with 20% frequency tuning range. The measured VCO gain is less than 1.6 GHz/V. The measured phase noise at 3 MHz offset is less than -78 dBc/Hz across the entire tuning range. The differential phase error of the output signals is measured by down converting the VCO output signals to low gigahertz frequency using an on-chip mixer. The measured differential phase error is less than 8°. The VCO circuit, which is constructed using 0.35 μm SiGe technology, occupies 770 × 550 μm2 die area and consumes 62 mA under 3.5 V supply. View full abstract»

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  • Non-reciprocal coupling network for beam-steering coupled oscillator arrays

    Page(s): 940 - 947
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (650 KB)  

    A non-reciprocal coupling network for beam-steering coupled oscillator arrays (COAs) is investigated. It is shown that this non-ferrite circuit based on the non-reciprocal behaviour of microwave transistor amplifiers generates explementary phases between adjacent coupled oscillators. Thus, this coupling network can be used to increase the array stability while extending the achievable scanning range. Numerical simulations of a multistage coupling network have shown the possibility of obtaining non-reciprocal coupling phases up to ±180° with transmission coefficients better than -2 dB. The circuit is also useful for compensating the reciprocal coupling effect between the antenna elements. It has been shown numerically that a multistage coupling network leads to non-reciprocal coupling phases up to ±180° with transmission coefficients better than -7.5 dB for a weakly COA of patch antennas at 10 GHz. A single-stage circuit with non-reciprocal coupling phases of ±175° was designed, fabricated and tested. Numerical simulations of the circuit show non-reciprocal coupling phases of ± 179.5° and -175.1° at 10 GHz, while measured results show non-reciprocal coupling phases of ±172.7° and -168.6° at 9.920 GHz. View full abstract»

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  • Wide-band radio frequency micro electro-mechanical systems switches and switching networks using a gallium arsenide monolithic microwave-integrated circuits foundry process technology

    Page(s): 948 - 955
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (733 KB)  

    In this study, the authors present the designs and experimental results of radio frequency (RF) micro electro-mechanical systems (MEMS) switches and switching circuits for gallium arsenide (GaAs)-based monolithic microwave-integrated circuits (MMIC). The switches and switching networks [single-pole single throw (SPST), single-pole double throw and double-pole double throw] are fabricated using OMMIC's GaAs MMIC foundry process technology. Measured results for a wide-band SPST switch design show isolation better than 20 dB up to 80 GHz with impedance matching better than -15 dB and insertion loss below 1.6 dB. Such low-loss GaAs-based RF MEMS switches are also capable of sustaining a power level of more than 10 W (up to 41 dBm) at 1 and 4 GHz, respectively, during cold-switching cycling conditions. Finally, to highlight the possibilities and benefits of monolithic integration of such MEMS switches and active RF devices on the same GaAs substrate, we present the experimental results of a wide-band (i.e. more than 10-40 GHz) GaAs MEMS-enabled switched low-noise amplifier circuit. View full abstract»

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  • Complementary metal oxide semiconductor class-AB amplifier for global system for mobile communications-enhanced data rates for GSM evolution Tx

    Page(s): 956 - 962
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (730 KB)  

    In this work a two-stage class-AB complementary metal oxide semiconductor radio frequency (CMOS RF) power amplifier is designed and tested according to global system for mobile communications-enhanced data rates for GSM evolution (GSM-EDGE) requirements. The amplifier efficiency is improved by using a DC-DC converter that lets the power supply voltage track the envelope of the input signal. The amplifier stability is improved by implementing an on-chip ground separation technique. The ground separation technique is based on separating the grounds of the amplifier stages on the chip and thus any parasitic feedback paths are removed. Simulation and experimental results show that the technique makes the amplifier less sensitive to bondwire inductance, and consequently improves the stability and performance. View full abstract»

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  • Digital processing compensation mechanisms for highly efficient transmitter architectures

    Page(s): 963 - 974
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1277 KB)  

    This article presents the design and final field programmable gate array (FPGA) integration of the necessary baseband (BB) signal processing for some of the emergent highly efficient amplification architectures. Following the software-design radio concept, this design is aimed at generating, monitoring and correcting BB and intermediate frequency signals for operating in highly efficient power amplifier (PA) architectures, such as envelope tracking PAs, envelope elimination and restoration or polar transmitter and linear amplification with non-linear components. The closed-loop nature of this FPGA design allows introducing control strategies to overcome or mitigate the unwanted distortion arising from maladjustments in the aforementioned efficient transmitter architectures. In addition to the signal generation blocks, three key blocks are included in the design to significantly contribute to the performance of these power-efficient architectures. These three blocks are a fractional delay filter block, a block that generates a slower (or slew-rate-limited) version of the envelope of the signal and a digital adaptive predistortion block. Experimental results presented in this article show the importance of including these blocks to provide these efficient transmitter architectures with correcting capabilities to guarantee power efficiency and linear amplification at RF. View full abstract»

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  • Adaptive reactance-controlled antenna systems for multi-input multi-output applications

    Page(s): 975 - 984
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (549 KB)  

    The study addresses the limited performance of multi-input multi-output (MIMO) systems under the real-life effects of spatial correlation and antenna mutual coupling. For this reason, an adaptive antenna system (AAS) capable of changing its transmission parameters via passive radiators attached to tunable loads, according to the structure of the RF propagation channel is described. The multi-active multi-passive array structure is tractably analysed using the active element response vector (instead of the classical steering vector) and the active element current vector (all being functions of the variable loading). The AAS targets at maximising tight MIMO ergodic and outage rate bounds, relying on partial channel knowledge when tuning to a different loading state for optimising the rate of communication. The proposed AAS can be limited to practical dimensions whereas the passive antennas require no extra RF hardware, thus meeting the cost, space and power constrains of the users' mobile terminals. The simulation results show that the AAS, thanks to its 'adaptivity', is able to achieve satisfactory performance even in poor scattering environments whereas a significant part of the mutual information that is lost owing to the spatial correlation and the electromagnetic coupling is successfully retrieved. View full abstract»

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  • Reconfigurable front-end antennas for cognitive radio applications

    Page(s): 985 - 992
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (579 KB)  

    This study presents new antenna schemes suitable for cognitive radio communications. The antenna structures consist of a ultra wide band (UWB) sensing antenna, and a frequency reconfigurable communicating antenna both incorporated into the same substrate. Two different techniques to achieve the required frequency agility are proposed. The first one is based on a rotational motion of the radiating patch whereas the second is based on optical switching. The importance of these techniques is that no bias lines are needed as is seen in the case of RF MEMs, PIN diodes and lumped elements. Prototype antennas were fabricated and a good agreement was observed between the simulated and the measured data. View full abstract»

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  • Design and fabrication of ultra-low cost radio frequency identification antennas and tags exploiting paper substrates and inkjet printing technology

    Page(s): 993 - 1001
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (653 KB)  

    This work deals with the design and fabrication of antennas for radio frequency identification (RFID) tag devices operating in the low microwave frequency range. Paper substrate material and inkjet printing process have been used to guarantee mechanical flexibility and ultra-low production costs of the antenna. A new antenna design methodology has been developed with the purpose to minimise the amount of both substrate material and conductive ink. The first goal is achieved by reducing, for a given frequency, the antenna size. The second goal, instead, is pursued by studying the surface current density distribution along the antenna and removing the metal material where such a current density is negligible. The above methodology has been applied to several antennas designs ranging from a windshield sticker tag to an RFID-SAW antenna. Moreover a 3.5 GHz crossed-dipole tag, based on the frequency-doubling mechanism, is reported along with a possible modification to enable wireless sensing. The experimental characterisation of these prototypes validates the proposed design methodology opening, in the mean time, the possibility for ultra-low cost mass production of RFID tag devices based on paper materials. View full abstract»

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  • Software tools for efficient generation, modelling and optimisation of fractal radiating structures

    Page(s): 1002 - 1007
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (691 KB)  

    This study describes in-house developed software tools for designing micro-strip patch fractal antennas. As the fractal geometry is quite complex, IFSMaker application was developed purposely for an easy definition and maintaining of planar fractal structures. In the next step, the authors use the cavity model technique for modal analysis of internal fields of the patch. This simplified model is reasonably fast, so that the optimisation loop may be employed in order to reduce the fundamental mode resonant frequency. This is accomplished with the EvalInFEM, PSOoptimizer and IFSLimiter applications. The theory of characteristic modes is then used to refine the results and finally the antenna is simulated with a full-wave CST simulator, built and measured. View full abstract»

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  • Development of passive microwave antenna-feed systems for wide-band dual-polarisation receivers

    Page(s): 1008 - 1015
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (749 KB)  

    This study presents the design and experimental results of a wide-band passive antenna-feed system developed for the C-band dual-circular-polarisation receiver of the Sardinia radio telescope (SRT). The latter is a 64 m diameter shaped radio-telescope under construction designed to operate with high efficiency from 300 MHz to over 100 GHz. The developed C-band antenna-feed system exhibits very high performances in a 30 band centred at 6.7 GHz, for example the return loss at all electrical ports is higher than 30 dB and the cross-coupling between the two polarisations is lower than 34 dB. The design solutions of all the feed-system components such as marker injector, polariser, transitions and the ortho-mode transducer (OMT) are reported in the study. In particular, the novel architecture of the OMT that provides an isolation between the two rectangular ports better than 70 dB is described in close detail. Computed and experimental results regarding both the complete system and its sub-assemblies are reported and discussed. View full abstract»

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  • Optimal configurations for integrated antenna feeders with linear dual-polarisation and multiple frequency bands

    Page(s): 1016 - 1022
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    Different configurations for the antenna feeder of advanced microwave subsystems are introduced, working in several schemes which combine multiple frequency bands with two linear orthogonal polarisations. The aim of this study is to highlight state-of-art research results on different waveguide components for modern radio frequency (RF)/microwave subsystems, stressing the impact of the selected architecture in the whole system in both the electrical performance and the volume and size of the feeder. Two are the key components of this type of RF/microwave feeder: the ortho-mode transducer for polarisation discrimination and the multiplexers for separating the frequency bands. It will be shown that a careful study of the whole feeder architecture can simplify in some cases the individual components, with the consequent benefit in electric performance and size reduction. The computer-aided design of the presented architectures is outlined, showing examples for different applications and comparing numerical simulations by different methods with experimental results. View full abstract»

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IET Microwaves, Antennas & Propagation covers all aspects of microwave and antenna engineering and propagation.

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