Improvement of Intermodulation Distortion Asymmetry Characteristics With Wideband Microwave Signals in High Power Amplifiers

This paper presents the improvement techniques of intermodulation-distortion asymmetries with wide carrier-spacing signals in L/S-band high power amplifiers. We proposed a novel circuit technique to directly connect LC series resonant circuits to the gate and drain electrodes of the transistor die in a package for baseband terminations with a wide frequency range. By applying this circuit technique to a 28-V operation 200-W GaAs heterojunction field-effect transistor (HJFET) amplifier, the third-order intermodulation distortion (IMD3) asymmetries were improved even if the two-tone carrier spacing (Deltaf) exceeds 100 MHz. In addition, we analyzed the IMD3 asymmetries of a Doherty amplifier through the IMD3 vector combination of the main and peak amplifiers. A newly developed 28-V operation 200-W GaAs HJFET Doherty amplifier with source and load baseband terminations also delivered flat IMD3 characteristics against the Deltaf over 50 MHz.     

Design of a high-gain FET amplifier operating at 4.4-5.0 GHz

Described here is the design and the electrical performance of a MESFET amplifier featuring an output power of 1 W with a gain of 34 dB over the frequency range from 4.4 to 5.0 GHz. The key elements that allowed the achievement of this performance were: high-gain power MESFET's, a circuit design technique based on power characterization of the MESFET's, and a low-parasitics integrated microstrip construction. The amplifier is intended to replace a medium power TWT in a telecommunication system. When compared with a typical 1-W TWT this solid-state amplifier not only requires a much simpler power supply, is lighter and has perhaps higher reliability, but also has some better electrical performances; this should result in better system performance.     

GaAs MESFET Small-Signal X-Band Amplifiers

This paper describes several techniques used to design and realize small-signal amplifiers at X band using Plessey 1-mu m gate-length GaAs MESFET's. Noise figures of 3 dB or better at 8 GHz with associated gains of 5.5 dB have been produced. The mounting of GaAs MESFET's on 25-mil-thick alumina substrates and their S-parameter characterization is described. Owing to some uncertainties in these measurements, four parallel approaches were used to realize amplifiers. The "designed," "semidesigned," "semituned," and "tuned" methods are described and results are presented for each case. A semidesigned single-stage amplifier has a gain of 8 /spl plusmn/ 0.6 dB from 8.5 to 9.5 GHz and a minimum noise figure of 4.4 dB. A semituned amplifier can be tuned from 8 to 10 GHz with VSWR's less than 2:1 over any 600-MHz bandwidth in that range.     

A 25-W 5-GHz GaAs FET Amplifier for a Microwave Landing System

A 25-W 29-dB gain 5-GHz GaAs FET amplifier has been developed which can be used for a transmitter in the Microwave Landing System. By using 10-W class practical internally matched GaAs FET's hermetically sealed in ceramic packages, the four-stage amplifier has been constructed simply. The amplifier provides 30-W power output with 18.5 percent power efficiency at 17-dBm power input level. It also exhibited an exceffent AM/PM conversion of approximately 1°/dB, compared to 6°/dB for TWT amplifiers.     

Broad-Band Internal Matching of Microwave Power GaAs MESFET's

Broad-band internal matching techniques for high-power GaAS MESFET's at C band have been developed adopting novel circuit configurations and large-signal characterizations in the circuit design. The lumped-element two-section input matching network is formed on a single ceramic plate with a high dielectric constant. The semidistributed single-section output circuit is formed in microstrip pattern on an alumina plate. The internally matched GaAs FET with 11200-mu m total gate width developed has a 2.5-W power output at 1-dB gain compression and a 4.4-W saturated power output with 5.5-dB linear gain from 4.2 to 7.2 GHz without external matching. The FET internally matched from 4.5 to 6.5 GHz exhibited 5-W saturated power output with 6-dB linear gain.     

High frequency divider circuits using ion-implanted GaAs MESFET's

A single clock master-slave frequency divider circuit was designed and fabricated using GaAs MESFET's in the direct-coupled FET logic (DCFL) circuit architecture. At room temperature, the maximum operating frequency was 6.2 GHz at a power consumption of 3.5 mW/gate. The complete divider circuit and buffer amplifier was realized in a 65 × 165 µm²area. The MESFET's were fabricated using Si ion implantion directly into GaAs wafers and used a self-aligned recessed gate. The nominal gatelength was 0.6 µm. Corresponding fabricated ring oscillator circuits showed minimum gate delays of 18.5 ps at 3.1 mW/gate for fan-out of one at 300 K and 15.2 ps at 3.5 mW/gate at 77 K.     

K-Band High-Power GaAs FET Amplifiers

Lumped-element internal matching techniques were successfully adopted for K-band power GaAs FET amplifiers. The developed 18-GHz band two-stage amplifier provides 1.05-W power output at 1-dB gain compression and 1.26-W saturated power output with 8.1-dB small-signal gain. The 20-GHz band single-stage amplifier has 1.04-W power output with 3-dB associated gain. Lumped-element internal matching circuit design as well as amplifier fabrication are described. Intermodulation distortion and AM-to-PM conversion characteristics are also presented.     

A 6-GHz 80-W GaAs FET Amplifier with a TM-Mode Cavity Power Combiner

A novel 8-way divider/combiner using TM/sub 010/- and TM/sub 020/ -mode cavities was developed. This divider/combiner has an insertion loss of 0.2 dB and a bandwidth of 600 MHz in the 6-GHz communications band. For broadening the operating bandwidth of the divider/combiner, two techniques of double cavities and tight coupling are described. Degradation of power-combining efficiency is also discussed when input signals into a power combiner have variations in amplitude and phase. By using this divider/combiner, an experimental 6-GHz 80-W GaAs FET amplifier with a combining efficiency of 85 percent was demonstrated to investigate the feasibility of a solid-state high-power amplifier.     

A high-transconductance self-aligned GaAs MESFET fabricated by through-AIN implantation

This paper describes a new technique for the fabrication of high-transconductance GaAs MESFET's. Tungsten-silicide gate, self-aligned GaAs MESFET's were fabricated on extremely thin channel layers formed by implantation through AlN layers on semi-insulating GaAs substrates. Transconductance of the through-implanted MESFET's showed 30- to 50-percent increase as compared with that of conventional self-aligned MESFET's and reached its maximum value at 300 mS/mm for 1-µm gate-length FET's. The uniformity of the threshold voltage across a 2-in wafer was also excellent with a standard deviation of 44 mV. Circuit simulation indicates that the advantage of these FET's becomes more crucial when used in a very large-scale integrated circuit (VLSI).     

High-gain gaas mesfet op amp

A gain enhancement technique for GaAs MESFET op amps is presented. It uses positive feedback to cancel the output conductance between the driver and active load transistors in a common-source amplifier configuration. An op amp using this technique was implemented in a 1-µm non-self-aligned GaAs MESFET process. The op amp exhibited a dc gain of 60 dB and a unity-gain frequency of 840 MHz.Please address all correspondence to C.A.T. Salama.     

Design and performance of compact low noise GaAs MESFET amplifiers for UHF operation

The design considerations and experimental results of compact low noise GaAs MESFET Amplifiers for UHF operation are described in this paper. The miniaturized and optimized circuits are obtained by means of special matching network and CAD technique. Both a two-stage unit at 700 MHz and a three-stage unit at 1000 MHz are fabricated on a 50×60 mm² alumina substrate, and power gain of 29 dB and 30 dB, noise figure of 0.8 and 1.2 dB and bandwidth of 40 MHz (3 dB) and 100 MHz (1 dB) are obtained respectively. The satellite direct broadcasting TV receiver fabricated with a 700 MHz GaAs MESFET amplifier has clear pictures and good sound.     

GaAs FET's with a flicker-noise corner below 1 MHz

GaAs MESFET's with significantly reduced low-frequency noise are demonstrated through application of an understanding that the dominant noise source is generation-recombination (g-r) noise from deep level traps in the gate and backside depletion layers. A 1/f noise spectrum measured from 100 Hz to 10 MHz is modeled as the sum of Lorentzian noise spectra from a few traps subject to the temperature distribution inherent in a GaAs MESFET. The noise associated with a single mid-bandgap trapping level does not appear as an ideal Lorentzian, but rather as 1/f over nearly a decade frequency range by virtue of a time constant that is a strong function of temperature ( exp[Ea/ kT]) and an estimated temperature distribution of 22°C across the active region. The major g-r trap was characterized as having an activation energy of 0.75 eV. By reducing the g-r noise, flicker noise was decreased by more than 15 dB compared to our conventional GaAs MESFET's and the noise corner was reduced to less than 1 MHz from a typical 40 MHz. This significant reduction was achieved by using MBE layers designed to have lower trap concentrations and high channel doping. These results are within 10 dB of the estimated 1/f noise limit due to the quantum mechanics of carrier scattering [5], [14].     

Bias dependence of GaAs and InP MESFET parameters

A comparative analysis of the bias dependence of critical RF parameters in GaAs and InP metal-semiconductor field-effect transistors (MESFET's) led to the following conclusions. 1) The drain-gate feedback capacitance in GaAs MESFET's is lower than in InP MESFET's, because of a stronger tendency in GaAs to form stationary Gunn domains at the typical drain bias levels employed. 2) The drain-source output resistance in InP MESFET's is lower than in GaAs MESFET's mainly for high drain current units, a fact which is linked to a substrate related softer pinch-off behavior in InP. 3) The current-gain cutoff frequency fT, in the current saturation range of the GaAs MESFET decreases strongly with drain bias as a result of the formation of the stationary Gunn domain. In the InP MESFET, this effect is weaker. At the optimum bias, fT is only 10-20 percent higher in InP MESFET's than in GaAs ones.     

A 6-GHz Four-Stage GaAs MESFET Power Amplifier (Short Papers)

A 6-GHz GaAs MESFET power amplifier with 1-W output power, 26dB gain, and 8-dB noise figure is described. It is a fully integrated four-stage amplifier with an efficiency of 22 percent. The third-order intermodulation product is 31.5 dB below the carrier at an output power of 1 W.     

小型超高频低噪声FET放大器的设计和性能

本文报道了UHF频段小型低噪声GaAs MESFET放大器的设计考虑、射频性能和试验结果。采用特殊的匹配网络和CAD技术使电路达到小型化和最佳化。设计的二级700MHz和三级1000MHz放大器均制作在50600.8mm3的陶瓷基片上。其射频性能分别为:功率增益GP为25dB(最佳29dB)和30dB,噪声系数NF低于1.1dB(最佳0.8dB)和1.2dB,带宽W约为40MHz(3dB)和100MHz(1dB)。用700MHz放大器装成的卫星直播电视接收机,接收图像清晰,伴音音质良好。     

A Single Supply, High Linearity 2-W PA MMIC for WLAN Applications Using Quasi-Enhancement Mode PHEMTs

A fully matched, 2-W high linearity amplifier monolithic microwave integrated circuit, by using quasi-enhancement mode technology of AlGaAs/InGaAs/ GaAs pseudomorphic high electron mobility transistors, is demonstrated for wireless local area network applications. At Vgs= 0 V, V_ds= 5 V, this power amplifier has achieved 14-dB small-signal gain, 33-dBm output power at 1-dB gain compression point, and 34.5-dBm saturated output power with 35% power added efficiency at 5.8 GHz. Moreover, high-linearity with 45.2-dBm third-order intercept point is also achieved     

Self-pumped parametric amplification with GaAs transferred-electron devices

The letter reports experimental results obtained with a non-degenerate-type self-pumped parametric amplifier using GaAs transferred-electron devices. Gains of as much as 30dB, noise figures as low as 18dB, and instantaneous gain-bandwidth products of about 50MHz have been obtained at Xband signal frequencies with the amplifier using GaAs transferred-electron devices oscillating at Q band frequencies.     

0.2 Micron length T-shaped gate fabrication using angle evaporation

A new technique has been developed to generate sub-half-micron T-shaped gates in GaAs MESFET's. The technique uses a single-level resist and an angle evaporation process. By using this technique, T-shaped gates with lengths as short as 0.2 µm near the Schottky interface have been fabricated. Measured gate resistance from this structure was 6.1 Ω/mm gate width which is the lowest value ever reported for gates of equal length. GaAs single- and dual-gate MESFET's with 0.3 µm long T-shaped gates have also been fabricated. At 18 GHz, maximum available gain of 9.5 dB in the single-gate FET and maximum stable gain of 19.5 dB in the dual-gate device have been measured.     

Low-noise HEMT using MOCVD

Low-noise HEMT AlGaAs/GaAs heterostructure devices have been developed using metal organic chemical vapor deposition (MOCVD). The HEMT's with 0.5-µm-long and 200-µm-wide gates have shown a minimum noise figure of 0.83 dB with an associated gain of 12.5 dB at 12 GHz at room temperature. Measurements have confirmed calculations on the effect of the number of gate bonding pads On the noise figure for different gate Widths. Substantial noise figure improvement was observed Under low-temperature operation, especially compared to conventional GaAs MESFET's. A two-stage amplifier designed for DBS reception using the HEMT in the first stage has displayed a noise figure under 2.0 dB from 11.7 to 12.2 GHz.     

A pile-up masking technique for the fabrication of sub-half-micron gate length GaAs MESFET's

A pile-up masking technique, using conventional optical lithography and a two-step evaporation process, has been developed to produce sub-half-micron gates of controllable dimensions. The new approach allows a high-yield production of self-aligned and deep-recess gates with multi-layered metallization systems. By using this technique, GaAs single-gate and dual-gate MESFET's with Cr/Au gates 0.2 µm long and 0.9 µm thick (i.e., an aspect-ratio of 4.5) have been fabricated. The technique can be applied to the production of high-frequency low-noise MESFET's.