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To improve the power handling capability at ground stations of a 5.8-GHz solar space power satellite using microwave power transmission, a power charge-pump meta-semiconductor field-effect transistor (MESFET)-based rectifier is presented in this article. Unlike conventional microwave Schottky diodes, diode-connected MESFETs, whose nonlinear characteristics help them to have a unique current–voltage (I-V) curve that overcomes the limitations of a Schottky diode. Thus, the maximum input power of the proposed rectifier is extended up to 251.2 mW by replacing a Schottky diode with a diode-connected MESFET. Additionally, a class F harmonic processing network is introduced to control the voltage and current waveform at the load of the rectifier. Consequently, the RF-dc conversion efficiency is increased since the power dissipation is limited at the junction resistance of both the drain and the source of the MESFET. Owing to the abnormal characteristics of the diode-connected MESFET, the measured conversion efficiency of our rectifier is approximately 73.2% at 126 mW, and the input power range for rectifier efficiency higher than 50% is between 16 and 224 mW. The proposed rectifier for the space solar power satellite application is demonstrated and verified using a microwave wireless power transmission system. [ABSTRACT FROM AUTHOR]

A novel backgate modulation technique alleviating limitations associated with supply-regulated polar transmitters is proposed. The backgate of a partially depleted silicon-on-insulator metal–semiconductor field-effect transistor with a breakdown voltage of 15 V is used to modulate the gain and output power of an RF power amplifier (PA). The high-impedance backgate provides high-efficiency and wide-dynamic-range modulation of PA gain. Measured results at 1.8 GHz demonstrate 16% power-added efficiency improvement at 6-dB backed-off output power, compared with the same RF PA without backgate modulation. [ABSTRACT FROM AUTHOR]

In this paper, a consistent gate charge model for GaAs MESFETs based upon charge conservation is proposed for monolithic microwave integrated circuit power amplifier designs. This new model is capable of accurately modeling the transistor under various biasing conditions. The conventional approaches for charge modeling of GaAs MESFETs usually adopt analytical equations to fit nonlinear gate capacitors separately, which might be difficult to implement in circuit simulators whose capacitance is always the derivative of an internal state variable (charge). Moreover, compared with the conventional diode and Statz model, the performance prediction in the linear region, saturation knee region, and subthreshold region is greatly improved. Measured and modeled results of a 2\,\times\,150 \mu\ m GaAs MESFET are compared and good agreement has been obtained. Comparisons between the proposed model, diode junction model, and Statz model are also presented in this paper. In addition, a class-AB Ku-band power amplifier using a 0.18-\mu\ m GaAs MESFET process was designed with the new model for verification of the new model accuracy. [ABSTRACT FROM PUBLISHER]

A comprehensive analysis of a multistage Doherty amplifier, which can be used to achieve higher efficiency at a lower output power level compared to the classical Doherty amplifier, is presented. Generalized design equations that explain the operation of a three-stage Doherty amplifier, which can be easily extended to an N-stage Doherty amplifier, are derived. In addition, the optimum device periphery, which minimizes AM-AM distortion for perfect Doherty amplifier operation, is analyzed. For the first time, a multistage Doherty power amplifier that meets wide-band code-division multiple-access (WCDMA) requirements is demonstrated. The designed power amplifier exhibits a power-added efficiency (PAE) of 42% at 6-dB output power backoff and 27% at 12-dR output power backoff. These PAEs are more than 2× and 7× better, respectively, than that of a single-stage linear power amplifier at the same output power backoff levels. The power amplifier is capable of delivering up to 33 dBm of output power, and has a maximum adjacent channel power leakage ratio of -35 and -47 dBc at 5- and 10-MHz offset, respectively. To the best of the authors' knowledge, these represent the best reported results of a Doherty amplifier for WCDMA application in the 1.95-GHz band to date. [ABSTRACT FROM AUTHOR]

This paper describes a miniaturized monolithic-microwave integrated-circuit (MMIC) analog phase shifter using two quarter-wave-length transmission lines. A conventional analog phase shifter employs an analog phase-shifter topology using a 3-dB 90° branch-line hybrid requiring four quarter-wave-length transmission lines. Thus, in the first stage of our study, we present a new analog phase-shifter topology using only two quarter-wave-length transmission lines. The phase shifter here has only one-half as many transmission tines as a conventional analog phase shifter using a 3-dB 90° branch-line hybrid, and the circuit can be miniaturized to less than one-fourth as compared to the conventional analog phase shifter. Furthermore, we show that the operating frequency range of the phase shifter is very wide and can obtain large phase variation with small capacitance variation. Next, an experimental Ku-band MMIC analog phase shifter is presented. A phase shift of more than 180° and an insertion loss of 3.6±1.1 dB are obtained at the frequency range from 12 to 14 GHz. The chip size of the experimental MMIC phase shifter is less than 3.0 mm2 [ABSTRACT FROM PUBLISHER]

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 [ABSTRACT FROM PUBLISHER]