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Microwave Theory and Techniques, IEEE Transactions on

Issue 6  Part 2 • Date June 2001

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Displaying Results 1 - 12 of 12
  • Editorial

    Publication Year: 2001 , Page(s): 1145 - 1147
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  • Efficient transmission-power-control scheme for Ku-band high-power amplifiers in portable user earth terminals

    Publication Year: 2001 , Page(s): 1167 - 1173
    Cited by:  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB) |  | HTML iconHTML  

    A novel power-amplifier scheme is presented in this paper that realizes highly efficient transmission power control (TPC). The output power is controlled without sacrificing high power-added efficiency by combining multiple amplifiers with different power levels. Unique switching and impedance matching techniques make it possible to eliminate RF switching circuits and their associated power losses. This direct coupled architecture is called the “switchless amplifier-switching scheme.” The requirements for realizing the novel power amplifiers used in this scheme are estimated, and Ku-band amplifier monolithic microwave integrated circuits (MMICs) that follow this scheme are fabricated. The capabilities of the scheme are confirmed by testing these MMICs. Finally, a novel power amplifier incorporating the developed MMICs is constructed to demonstrate its performance. Experimental results show that the amplifier can achieve a significant reduction in DC power at low output power levels under TPC View full abstract»

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  • A highly efficient linearized wide-band CDMA handset power amplifier based on predistortion under various bias conditions

    Publication Year: 2001 , Page(s): 1194 - 1201
    Cited by:  Papers (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB) |  | HTML iconHTML  

    This paper investigates the use of amplifier linearization for performance improvement on a power amplifier developed for a wide-band CDMA (W-CDMA) system. A predistortion technique was chosen due to its compact size, which is suitable to implement in handsets. A predistorter (PD) monolithic-microwave integrated-circuit based on a heterojunction FET (HJFET) was designed and fabricated. Depending on the control voltage, the PD achieves both gain expansion and compression characteristics, which is shown to be important for compensating various amplifier nonlinearities. The power performances of an HJFET amplifier with and without a PD are compared. Due to the variation of the amplifier's responses under high and low quiescent current levels, the PD response required for optimum distortion cancellation in each case is examined. The linearized amplifier demonstrates a state-of-the-art power-added efficiency (PAE) of 57.4% under W-CDMA criteria, resulting from a 5-dB reduction in adjacent channel leakage power ratio. In addition, the use of power control in a W-CDMA system requires amplifiers with good efficiency over a wide range of output power. By combining a bias control scheme with predistortion, it is shown that a high PAE of over 40% can also be achieved for a 20 dB output power range. The improvements achieved are attributed to the alleviation of amplifier's nonlinearities after linearization View full abstract»

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  • Linearity of X-band class-F power amplifiers in high-efficiency transmitters

    Publication Year: 2001 , Page(s): 1174 - 1179
    Cited by:  Papers (20)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB) |  | HTML iconHTML  

    Modern communication signals have time-varying envelopes with significant peak-to-average ratios, resulting in low average efficiency when amplified by commonly used linear power amplifiers (PAs). For linear amplification with increased average efficiency, the Kahn envelope-elimination-and-restoration method uses a highly efficient saturated PA. In this paper, an 8.4 GHz class-F PA with 55% maximum instantaneous efficiency at 610 mW output power, is experimentally characterized in several different biasing modes. Operated in linear mode with constant drain bias, this PA has 10% average efficiency. The suppression of two-tone intermodulation products is 27 dBc when operated at about 0.7 times the peak output power. For the same PA operated in a modified Kahn mode with drive and bias control, a comparable linearity (27.7 dBc) can be obtained at peak output power. Furthermore, the average efficiency increased to 44%, a factor of 4.4 over the linear fixed bias mode View full abstract»

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  • A second harmonic class-F power amplifier in standard CMOS technology

    Publication Year: 2001 , Page(s): 1216 - 1220
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB) |  | HTML iconHTML  

    For personal communications systems, the highest possible integration on monolithic technology of all RF functions is desirable. The most difficult component to be monolithically integrated with all other functions is the output power amplifier. This paper describes the design and test of an integrated class-F power amplifier with 200-mW output power at 1.9 GHz and a 3 V power supply based on a 0.6 μm CMOS standard technology. A theoretical study of class-F operation that highlights the influence of nonideal active devices and output network topology on the circuit behavior was performed to have guidelines for amplifier optimization View full abstract»

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  • A phenomenologically based transient SPICE model for digitally modulated RF performance characteristics of GaAs MESFETs

    Publication Year: 2001 , Page(s): 1180 - 1186
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB) |  | HTML iconHTML  

    A phenomenologically based transient SPICE model was developed for GaAs MESFETs. The model accounts for both trapping and detrapping effects; hence, it can simultaneously simulate low-frequency dispersion and gate-lag characteristics. This is different from conventional models, which can simulate either effect, but not both. The present model has been used to describe both surface- and substrate-related trapping phenomena in epitaxial or ion-implanted MESFETs. The model was experimentally verified in terms of pulsed I-V characteristics and pulsed AC response View full abstract»

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  • Improvement of third-order intermodulation product of RF and microwave amplifiers by injection

    Publication Year: 2001 , Page(s): 1148 - 1154
    Cited by:  Papers (40)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    This paper discusses the improvement in the third-order intermodulation product (IM3) performance obtainable from RF and microwave amplifiers by two alternative injection techniques. The first is the addition to the amplifier input of the second harmonics of the input spectrum and the second is the addition to the amplifier input of the difference frequencies between the spectral components of the input signal. Both techniques are considered in theory, by simulation and in practice. Both techniques give useful improvements in two-tone IM3 performance. The second harmonic technique reduced the IM3 level by 43 dB in an amplifier at 835 MHz. The difference-frequency technique gave a reduction of 48 dB in an amplifier at 880 MHz. The difference-frequency technique also gives a greater improvement for complex spectra signals View full abstract»

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  • Maximum efficiency and output of class-F power amplifiers

    Publication Year: 2001 , Page(s): 1162 - 1166
    Cited by:  Papers (89)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (76 KB) |  | HTML iconHTML  

    A class-F power amplifier (PA) improves efficiency and power-output capability (over that of class A) by using selected harmonics to shape its drain-voltage and drain-current waveforms. Typically, one waveform (e.g., voltage) approximates a square wave, while the other (e.g., current) approximates a half sine wave. The output power and efficiency of an ideal class-F PA can be related to the Fourier coefficients of the waveforms, and Fourier coefficients for maximally flat waveforms have been determined. This paper extends that theory by determining the coefficients for the maximum power and efficiency possible in a class-F PA with a given set of controlled harmonics View full abstract»

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  • Millimeter-wave monolithic power amplifier for mobile broad-band systems

    Publication Year: 2001 , Page(s): 1211 - 1215
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB) |  | HTML iconHTML  

    For personal communication systems, the highest possible integration into monolithic technology of all RF functions are desirable. A frequency band around 60 GHz is assigned for future mobile communication fourth-generation systems (i.e., mobile broad-band systems concept). In this paper, the design and test of two monolithic class-A power amplifiers with 0.15 μm pseudomorphic heterojunction FET (PMHFET) technology is presented. One of the amplifiers is a three-stage cascade 50 Ω amplifier and the second is a balanced amplifier based on the previous one, but matched for integration on a waveguide carrier. A study on the accuracy of the passive elements and discontinuities models at 60 GHz was performed. Models for the microstrip discontinuities were obtained from electromagnetic simulation. In order to choose the best FET bias, a nonlinear model for the PMHFETs devices, based on continuous DC and AC measurements, were derived. For comparison purposes, the FET simulation results with a nonlinear model based on pulsed measurements are also presented. To avoid stability problems, at the device level an RC feedback network was introduced. A 1-dB compression point of 18 dBm was measured on-wafer for both amplifiers at 62 GHz with VDSbias=3.5 V. The three-stage and balanced amplifiers chip sizes are 3 mm×1.5 mm and 3 mm×4 mm, respectively View full abstract»

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  • A novel configuration for 1:N multiport power dividers using series/parallel transmission-line division and a polyimide/alumina-ceramic structure for HPA module implementation

    Publication Year: 2001 , Page(s): 1187 - 1193
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    A novel configuration for 1:N multiport power dividers using series and parallel division of the transmission lines with a polyimide/alumina-ceramic structure is proposed and successfully demonstrated. Since these circuits need only line divisions and mode transitions to function as power dividers, they inherently possess an extremely flat frequency response. The polyimide/alumina-ceramic substrate suits the three-dimensional arrangement of various kinds of transmission lines and their transitions. It is also useful in implementing high power amplifier multichip modules because the alumina substrate can hold all active devices or monolithic microwave integrated circuits and provides convenient interfaces between them and the power dividers. The line divisions and mode transitions are analyzed by a commercial electromagnetic simulator. Two types of 1:4 power dividers, which are series/parallel and parallel/series configurations, are fabricated. No peculiar resonance was observed over the frequency range of 1-8 GHz. The amplitude deviation over this range was less than 3.2 dB View full abstract»

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  • High-efficiency push-pull power amplifier integrated with quasi-Yagi antenna

    Publication Year: 2001 , Page(s): 1155 - 1161
    Cited by:  Papers (10)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB) |  | HTML iconHTML  

    This paper presents a C-band push-pull power amplifier integrated with a modified uniplanar quasi-Yagi antenna. In this circuit, corrugation is added to the truncated ground plane of the antenna so that it can be used for both out-of-phase power combining and second harmonic tuning. By using the active integrated antenna concept, this novel circuit eliminates the usage of an ordinary 180° hybrid at the power-amplifier output stage, therefore eliminating the losses associated with the hybrid, resulting in a compact and high-efficiency power-amplifier design with intrinsic second harmonic suppression. At an operating frequency of 4.15 GHz, a maximum measured power-added efficiency (PAE) of 60.9% at an output power of 28.2 dBm has been achieved. The measured PAE is above 50% over a 260-MHz bandwidth. Additionally, the second harmonic radiation is found to be 30 dB below the fundamental in both E- and H-planes. When the circuit is subjected to a two-tone test, the measured third-order intercept point is 37 dBm, about 10 dB above the P1 dB point View full abstract»

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  • Transmission-line load-network topology for class-E power amplifiers

    Publication Year: 2001 , Page(s): 1202 - 1210
    Cited by:  Papers (37)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    Class-E amplifiers are a type of switching amplifier offering very high efficiency approaching 100%. In this paper, a topology and design methodology, which could be used for a transmission-line implementation of a class-E power amplifier, is presented. A simple transmission-line class-E load network is proposed that offers combined transformation of the load resistance down to a suitable level, as well as simultaneous suppression of harmonics in the load. The load network was developed and tested with the aid of a time-domain simulator (i.e., SPICE). A microstrip layout was designed and a first prototype was built operating at 1 GHz utilizing a field-effect transistor as the switching device. A drain efficiency of 72% was measured for our prototype after tuning, although better performance can be expected with an improved switching transistor and careful tuning of the load network View full abstract»

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Aims & Scope

The IEEE Transactions on Microwave Theory and Techniques focuses on that part of engineering and theory associated with microwave/millimeter-wave components, devices, circuits, and systems involving the generation, modulation, demodulation, control, transmission, and detection of microwave signals. This includes scientific, technical, and industrial, activities. Microwave theory and techniques relates to electromagnetic waves usually in the frequency region between a few MHz and a THz; other spectral regions and wave types are included within the scope of the Society whenever basic microwave theory and techniques can yield useful results. Generally, this occurs in the theory of wave propagation in structures with dimensions comparable to a wavelength, and in the related techniques for analysis and design..

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Meet Our Editors

Editor-in-Chief
Dominique Schreurs
Dominique.Schreurs@ieee.org

Editor-in-Chief
Jenshan Lin
jenshan@ieee.org