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Radio and Wireless Conference, 2003. RAWCON '03. Proceedings

Date 10-13 Aug. 2003

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Displaying Results 1 - 25 of 104
  • The evolution of UWB technology

    Publication Year: 2003 , Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB)  

    This talk will review the development of time domain electromagnetics by this writer and others over more than a 40-year period and show how the work contributed to the growth of ultra-wideband (UWB) radar and communications. It will also review some of the latest advancements made in the field of communications by investigators making presentations at this UWB session at RAWCON and attempt to put their work in perspective. Additionally, some remaining problem areas will be identified. View full abstract»

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  • Adaptive duplexer for multiband transreceiver

    Publication Year: 2003 , Page(s): 381 - 384
    Cited by:  Papers (23)  |  Patents (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    This paper proposes new adaptive duplexer architecture for multiband systems. It reduces the need for multiple switched duplexers. The propose new technique is based on two step isolation processes: (1) a wide-band circulator (20 dB isolation); and (2) an active double loop canvelling technique that leads to two s at the desired frequency and the transmitted frequency. This solution is based on multiband direct conversion receiver. In a direct conversion receiver a simple synchronous detector at the duplex offset frequency provides a convenient feedback signal. Using this approach it was possible to achieve 66 dB total isolation between the transmit signal and the receive signal and 37 dB total transmitter noise cancellation at the receiver band. Adaptive duplexing eliminates many external components in multiband transceiver front end. The described scheme is simple, uses a relatively low frequency error signals and has low computational complexity. View full abstract»

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  • A new miniaturized patch antenna for wireless systems

    Publication Year: 2003 , Page(s): 257 - 260
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (359 KB) |  | HTML iconHTML  

    This paper presents a design procedure of a new miniaturized patch antenna fed by an L-probe, which can be used for mobile handset applications. To examine the performance of this antenna, a prototype was designed, fabricated and measured at 2 GHz. The bandwidth and far-field radiation patterns of the proposed antenna are discussed theoretically and experimentally. The measured cross-polarization and the front-to-back ratio are also examined. View full abstract»

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  • Wideband predistortion linearization system for RF power amplifiers using an envelope modulation technique

    Publication Year: 2003 , Page(s): 401 - 404
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (361 KB) |  | HTML iconHTML  

    This paper proposes a wideband adaptive predistortion linearization system based on high-speed RF envelope modulation applied to the input signal of an RF power amplifier. An FPGA-based look-up table, fed by a digitized envelope power signal, controls the envelope modulation performed by an RF vector modulator. The advantages of this predistortion architecture over conventional baseband digital approaches are a wider bandwidth, and the elimination of the need for digital baseband I/Q streams. The predistortion system was implemented as a testbed. Using 3-carrier CDMA2000 and multi-tone signals, the linearization performances for a 0.5 W GaAs HFET and a 90 W peak envelope power (PEP) LDMOS power amplifier were examined on the testbed. In the third-order intermodulation distortion (IMD) region, the wideband multi-tone testing showed IMD suppressions of 9 to 13 dB over 63 MHz bandwidth and a range of 7 to 8 dB backoff. For the 90 W power amplifier, the system achieved adjacent channel power ratio (ACPR) improvement of 13 dB output power backoff. View full abstract»

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  • QoS-based adaptive modulation under rainfall environment in gigabit millimeter-wave broadband wireless access system

    Publication Year: 2003 , Page(s): 19 - 22
    Cited by:  Papers (1)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB) |  | HTML iconHTML  

    In the gigabit millimeter-wave broadband wireless access (Gb MMW BWA) system. Quality of MMW is strongly affected by rainfall hence the MMW link may fall down in the case of heavy rainfall. The making of route detour to avoid that heavy rain zone is expected to improve the quality. For that matter, however, it may be not sufficient to provide the high-traffic demands. Therefore, in this paper, we propose the QoS-based adaptive modulation scheme to compensate for rain attenuation, and thus to improve the spectrum efficiency of system. View full abstract»

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  • A rapid carrier recovery loop for direct conversion receivers

    Publication Year: 2003 , Page(s): 159 - 162
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (435 KB) |  | HTML iconHTML  

    Direct conversion receiver (DCR) is an alternative wireless architecture to the well established super-heterodyne, particularly for low-power and low-cost terminals [A. A. Abidi, December 1995]. A new Ka-band high-speed direct conversion wideband six-port receiver was designed for wireless communications. This QPSK six-port receiver operates using analog signal processing (ASP). The QPSK DCR consists of a receiver front-end, a QPSK demodulator and a carrier recovery module. A reverse modulation loop (RML) was used to provide a rapid carrier recovery. The maximum bit rate, around 120 MB/s, is limited by the speed of the base-band circuits. The new hardware receiver is proposed for use in wide Ka-band wireless mass-market QPSK communications such as LMDS services. Bit error rate (BER) results versus the noise and reference signal phase shift are presented. View full abstract»

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  • Review of the thin film resonator technology

    Publication Year: 2003 , Page(s): 333 - 336
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB) |  | HTML iconHTML  

    The thin film resonator technology has been under the development for over forty years in one form or another. Although the basic approach is derived from the desire to reach higher frequencies than those readily achieved by thinning bulk crystals, there have always been competing technologies for fundamental material or processing problems that have impeded the development. Finally, a point was reached in the wireless market wherein competing technologies appeared unable to meet the demands of modern wireless applications and thin film approaches began to receive some emphasis. This paper is a review of the thin film resonator technology. View full abstract»

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  • Design and evaluation of energy detection algorithms for IEEE 802.11a systems

    Publication Year: 2003 , Page(s): 63 - 66
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB) |  | HTML iconHTML  

    This paper presented signal detection algorithms for IEEE 802.11a orthogonal frequency division multiplexing (OFDM) systems. Signal detection is to detect the arrival of the OFDM packets. Due to the burst transmission characteristics, a simple and robust signal detection algorithm is required for practical hardware implementation. In this paper, we designed and compared three signal detection algorithms, which were based on the short training sequence transmitted in front of each OFDM packet. Computer simulations were conducted to evaluate the performance of these three signal detection algorithms. View full abstract»

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  • Software IQ sample estimation for multi-antenna systems

    Publication Year: 2003 , Page(s): 175 - 178
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB) |  | HTML iconHTML  

    Multi-antenna systems provide the option to enhance the data rates and to improve the overall system performance as long as high transmitter signal accuracy for all signal branches can be guaranteed. At the same time the analog front-end should provide low power consumption and a low cost solution. Hence a direct-conversion transmitter analog front-end architecture for an OFDM multi-antenna system will be proposed including the drawback of possible imperfect analog IQ signals. The expected analog imperfections will be compensated via software-based algorithms. The compensation techniques require IQ sample estimates from the transmitter envelope signal at the antenna input port. This paper provides a mathematical description of the software-based IQ estimation and provides simulation results in conjunction with a filter pre-equalization and quadrature compensation. View full abstract»

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  • A high-efficiency multistage Doherty power amplifier for WCDMA

    Publication Year: 2003 , Page(s): 397 - 400
    Cited by:  Papers (7)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (307 KB) |  | HTML iconHTML  

    A comprehensive analysis of multistage Doherty amplifier, which can be used to achieve higher efficiency at great back-off compared to the classical Doherty amplifier, is presented. A novel set of design equations for a generalized N-stage Doherty amplifier is introduced. For the first time, this technique is applied to the design of a WCDMA power amplifier (PA). The designed PA meets WCDMA requirements, and exhibit a power-added efficiency (PAE) of 34.5% at 6 dB back-off and 16.9% at 12 dB back-off. These PAEs are 2 times and 4 times better, respectively, than that of a single stage linear PA at the same back-off levels. The PA is capable of delivering up to 28.6 dBm of output power, and has a maximum adjacent channel power leakage ratio of -38 dBc and -51 DBc at 5 and 10 MHz offset, respectively. To the best of the author's knowledge, these represent the best reported results of a Doherty amplifier for WCDMA application in the 1.95 GHz band, to date. View full abstract»

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  • A new scalable SPICE model for spiral inductors in substrate with buried layer

    Publication Year: 2003 , Page(s): 345 - 348
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (297 KB) |  | HTML iconHTML  

    In the radio frequency application field, the needs to use inductor models whose intrinsic characteristics are correctly represented on the basis of the various working frequencies often arise. Several publications have treated modeling of integrated inductors based on a more or less resistive substrate. Undoubtedly the most interesting approaches are those based on distributed models of turns synthesize as ladder network. The main disadvantage of these innovative models is their intrinsic complexity and therefore the difficulty to implement them as SPICE device models to be easily used in circuit simulation tools. Researchers have mainly focused their attention on the modeling of inductors based on CLOS substrate but there is no work on distributed inductor model made on the substrate with little resistive buried layer. At present, technologies that deal with such profiles are integrated in STMicroelectronics for analog and digital designs. In this paper, our aim is, firstly, to describe an innovative distributed inductor model integrated on substrate with buried layer and, secondly, to show an innovative automatic methodology which allows synthesizing, through an optimization procedure, a usable SPICE model based on the new model described above. View full abstract»

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  • An efficient MAC protocol with direction finding scheme in wireless ad hoc network using directional antenna

    Publication Year: 2003 , Page(s): 233 - 236
    Cited by:  Papers (4)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (361 KB) |  | HTML iconHTML  

    In this paper, we propose an efficient directional MAC protocol with direction finding scheme for wireless ad hoc network. This efficient directional MAC protocol uses the receiver-oriented direction-finding scheme, where each node n periodically collects its neighborhood directional information and forms an angle-signal table (AST). Directional DATA/ACK packets are transmitted, after the omni-directional RTS/CTS which not only inform the hidden nodes of on-going communication status and but also are especially effective for the string topology in ITS (Intelligent Transportation System). This omni-directional RTS/CTS can be issued without disturbing the neighbors' on-going communication, by the utilization of DNAV (directional network allocation vector) with the angle information from AST. Simulation results in highway traffic scenarios show the performance improvements by this proposed directional MAC scheme conjunct with the equalized receiver sensitivity and receiver threshold. View full abstract»

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  • MIMO systems with antenna selection - an overview

    Publication Year: 2003 , Page(s): 167 - 170
    Cited by:  Papers (32)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (386 KB) |  | HTML iconHTML  

    We consider multiple-input - multiple-output (MIMO) systems with reduced complexity. Either one, or both, link ends chose the "best" L out of N available antennas. This implies that only L instead of N transceiver chains have to be built, and also the signal processing can be simplified. We show that in ideal channels, full diversity can be achieved, and also the number of independent data streams for spatial multiplexing can be maintained if certain conditions on L are fulfilled. We then discuss the impact of system nonidealities, like noisy channel estimation, correlations of the received signals, etc. View full abstract»

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  • A single-chip 2.4GHz low-power CMOS receiver and transmitter for WPAN applications

    Publication Year: 2003 , Page(s): 163 - 166
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    A single ship 2.4 GHz low power CMOS receiver and transmitter for WPAN applications are implemented and measured. The receiver uses a low-IF architecture with a poly-phase filter and transistor linearization technique to improve linearity per power, and the transmitter adopts a ROM based direct-conversion architecture for low power consumption and high integrated density. Experimental results show -79 dBm of sensitivity, 13 dB of receiver NF, -4.5dBm of receiver IIP3, and -4dBm of transmitter output power. The power consumption is 9 mW in receiver and 17 mW in transmitter at 1.8 V, respectively. View full abstract»

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  • Analysis of optimized input and output harmonic termination on the linearity of 5 GHz CMOS radio frequency amplifiers

    Publication Year: 2003 , Page(s): 293 - 296
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB) |  | HTML iconHTML  

    The high-frequency nonlinear distortion of a small-signal CMOS common-source amplifier stage is analyzed as a function of bias, source and load termination impedance, and harmonics at 5 GHz using a Volterra analysis. The predictions closely match measurements over bias, and source and load impedances. The results can be applied to low-power wireless RF circuit design applications. View full abstract»

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  • A look ahead scheme for adaptive spectrum utilization

    Publication Year: 2003 , Page(s): 83 - 86
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (362 KB) |  | HTML iconHTML  

    With the proliferation of wireless multimedia terminals and services, the demand for spectrum has been growing. Yet, there is widespread perception that the spectrum that has been assigned by the FCC for the various commercial and military applications is not being efficiently utilized. As a result there is several efforts underway that are dealing with the sensing of unused spectrum at a given time, and utilizing it for voice and/or data communications. In this paper, we consider spectrum opportunistic systems where the currently assigned spectrum is monitored in real time for idle bands and propose a new method to use any unutilized spectral opportunities, thereby enhancing the spectrum reuse efficiency. This new approach assigns packets to the sensed spectrum opportunities in the downlink of a cellular network. View full abstract»

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  • Optimization of Yagi array by hierarchical genetic algorithms

    Publication Year: 2003 , Page(s): 91 - 94
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB) |  | HTML iconHTML  

    A method of hierarchical genetic algorithms (HGA) is used for optimizing the element spacing and lengths of Yagi-Uda antennas. This scheme has the ability of handling multiobjective functions as well as the discrete constraints in the numerical optimizing process. Together with the technique of Pareto ranking scheme, more than one possible solution can be obtained. It has been found that the number of dipoles of the antenna can be minimally identified with multi-facet design criteria as well as the imposed stringent constraints on the antenna design. Furthermore, this added feature also enables a design tradeoff between cost and performance without extra computational effort. View full abstract»

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  • A common power-stage cellular/PCS/W-CDMA triple-band MMIC power amplifier

    Publication Year: 2003 , Page(s): 285 - 288
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (318 KB) |  | HTML iconHTML  

    This paper describes the design and experimental results of an InGaP/GaAs hetero-junction bipolar transistor (HBT) monolithic microwave integrated circuit (MMIC) power amplifier for cellular (850 MHz)/PCS(1750 MHz)/W-CDMA (1950 MHz) triple-band mobile terminal applications. This two-stage power amplifier has only one power-stage in common for the triple bands to achieve a small chip and module size for low manufacturing cost. In order to reduce quiescent current for cellular band, the band selecting circuit to control bias current is used to the power-stage amplifier. This power amplifier has the power gain of 30 dB (26 dB, 25 dB) for cellular (PCS, W-CDMA) band and power-added efficiency (PAE) of 43% at the output of 28 dBm for cellular band under 3.4 V operation voltage. View full abstract»

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  • Wireless local positioning - concepts, solutions, applications

    Publication Year: 2003 , Page(s): 219 - 224
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (561 KB) |  | HTML iconHTML  

    Local positioning will be one of the most exciting features of the next generation of wireless system. With this technique a mobile device can either gather the information about its position or can be localized from elsewhere. Completely new concepts and features in wireless data transmission and transponder systems is enabled by this. Self-organizing sensor networks, ubiquitous computing, location service billing, context dependent information services, tracking and guiding are only some of the numerous possible application areas. This paper gives an overview over existing wireless positioning solutions and attempts to structure different techniques and applications. Furthermore two novel positioning systems currently developed by Siemens are featured as system examples. First a neural cellular positioning system NCPS is introduced. This system is designed for positioning solutions for industrial, medical and consumer scenarios and is based on existing wireless voice and data infrastructure. Second the Siemens local positioning radar (LPR) is presented. This system is designed for cm-precision and realtime positioning in the area of industrial logistics, control and automation. The application examples are completed by an application in the field of augmented reality computing. View full abstract»

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  • ICI cancellation based channel estimation for OFDM systems

    Publication Year: 2003 , Page(s): 111 - 114
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (349 KB) |  | HTML iconHTML  

    Orthogonal frequency division multiplexing (OFDM), which is a multicarrier modulation scheme, splits high data rate information symbols into lower rate parallel data streams and transmits this parallel information on different orthogonal carriers. The loss of orthogonality among subcarriers causes inter-carrier interference (ICI), which affects both channel estimation and detection of OFDM data symbols. Channel estimation error degrades the performance of coherent receiver limiting capacity, data rate and performance of the overall OFDM system. This paper proposes a novel frequency-domain channel estimator, which mitigates the effects of ICI by jointly finding the frequency offset and channel frequency response (CFR). Unlike conventional channel estimation techniques, where ICI is treated as part of the noise, the proposed approach considers the effect of frequency offset in estimation of CFR. A binary search algorithm is used to find the present frequency offset and CFR jointly. Variance of the frequency offset estimator and mean-square error (MSE) performances for conventional least-squares (LS) estimator and the proposed method are obtained using computer simulations. The variance of the jointly estimated frequency offset is found to be very close to the Cramer-Rao lower bound. It is shown that the proposed method outperforms LS channel estimator especially in ICI dominated situations. View full abstract»

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  • Design and implementation of a ferroelectric smart antenna system for 802.11b WLANs

    Publication Year: 2003 , Page(s): 135 - 138
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB) |  | HTML iconHTML  

    This paper focuses on the design and implementation of an IEEE 802.11b WLAN smart antenna system for use in 802.11b WLAN network interface cards. The 2.4 GHz ferroelectric phase shifter is the key component for a two-element beam forming network (BFN). The smart antenna system is controlled by software that automatically adjusts the beam pattern to interference, and maximize the signal power. More than three orders of magnitude improvement in receive bit-error rate (BER) were measured when steering the antenna to the optimum position. View full abstract»

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  • A design of QAM modulator for multicode WCDMA

    Publication Year: 2003 , Page(s): 187 - 190
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (306 KB) |  | HTML iconHTML  

    A QAM modulator using multiple four-output FIR filters based on look-up table (LUT) is proposed for downlink of wideband CDMA systems, and its functions are verified by stand-alone tests by means of the test equipment that achieves the functions of a QAM receiver system. Because a modulator employs the multicode modulation and M-QAM unlike QPSK modulation, the FIR filter for pulse shaping requires the multi-bit input word. So we propose the filter structure with multi-bit input word, which consists of multiple four-output FIR filter and bit-weighted accumulators. It is easy to extend the filter structure as increase of input bit word without higher clock frequency. We measure the spectrum of the implemented modulator by using a spectrum analyzer. Also, the demodulated signal constellation is obtained in the case of 16, 64 and 256-QAM as increase of multicode number. View full abstract»

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  • Overcoming co-channel interference in TDMA systems using SOM equalizer

    Publication Year: 2003 , Page(s): 123 - 126
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (335 KB) |  | HTML iconHTML  

    This paper studies the co-channel interference (CCI) problem for time-division-multiple-access (TDMA) cellular mobile communication system with burst transmission. We present a method using self-organizing-map (SOM) to overcome CCI for such a system. The SOM is realized as a classification equalizer with a decision feedback adaptive filter. An extremely small number of unique words (UWs) are utilized to initialize the SOM equalizer. Simulation results show that the bit error rate (BER) of our proposed method is much better than that of the recently proposed nearest neighbor classification equalizer. View full abstract»

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  • 3D compact radiation analyzer for rapid testing of wireless terminals

    Publication Year: 2003 , Page(s): 139 - 142
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB) |  | HTML iconHTML  

    Rapid characterization and pre-qualification measurements are becoming more and more important for the ever-growing number of small antennas, mobile phones and Bluetooth devices. There is a need driven by the wireless industries for a smart test set-up with reduced dimensions and capable of measuring radiating devices for production pass/fail purpose almost in real time. Satimo has developed a compact and cost-effective measurement platform, which is able to perform rapid 3D testing of the pattern radiated by wireless devices. The 3D radiation analyzer called StarProd is derived from the well-established Satimo spherical test facilities based on multi-sensors technology. This paper describes in detail the 3D radiation analyzer and its different configurations for power, spurious, vector and active measurements. The achieved measurement accuracies are also presented. Measurements performed with the StarProd platform are displayed and illustrate the capabilities of the system. View full abstract»

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  • Design and implementation of RF subsystems with multiple embedded passives in multi-layer organic substrates

    Publication Year: 2003 , Page(s): 325 - 328
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (370 KB) |  | HTML iconHTML  

    Recent development in the design of high-Q passives embedded in low cost IC packages has made single-package integration of RF front-ends feasible. This paper analyses the effects of ground return in the performance of active circuits, while using multiple embedded devices in the package. The return-current path layout has been modeled using both electromagnetic field solvers as well as a circuit-based modeling methodology based on coupled line theory. Low noise amplifiers (LNAs) using discrete and embedded components have been designed and fabricated as test vehicles, and the modeled results have been verified with measurements. View full abstract»

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