An experimental study of the effects of harmonic loading on microwave MESFET oscillators and amplifiers

This paper reports an extensive experimental investigation of the effects of second harmonic loading on the performance of microwave GaAs MESFET oscillators and strongly driven amplifiers. The measurement system used is an active load system based on six-port techniques. Harmonic load pull measurements were obtained for the NE72084 MESFET; the measurements show how the second harmonic load can influence the power gain and the power added efficiency in strongly driven amplifiers. The device line characterization technique was combined with the harmonic load pull technique; the measurement results illustrate how the output power and the DC to RF conversion efficiency of an oscillator depend on the choice of the second harmonic load. Amplifier and oscillator circuits have been designed using these measurements; the circuits have been constructed and measured. The results validate the experimental approach used and clearly illustrate the importance of properly selecting the second harmonic load in amplifier and oscillator circuits. Significant improvements in gain, output power and efficiency have been achieved by properly selecting the second harmonic load.

[1]  D. M. Snider,et al.  A theoretical analysis and experimental confirmation of the optimally loaded and overdriven RF power amplifier , 1967 .

[2]  K. Kurokawa,et al.  Some basic characteristics of broadband negative resistance oscillator circuits , 1969 .

[3]  S. Perlow,et al.  Automatic Load Contour Mapping for Microwave Power Transistors , 1974 .

[4]  Y. Takayama.  A New Load-Pull Characterization Method for Microwave Power Transistors , 1976 .

[5]  Wolfgang Wagner,et al.  Oscillator design by device line measurement , 1979 .

[6]  S.R. LeSage,et al.  Optimizing the power-added efficiency of a class B GaAs FET amplifier , 1988, 1988., IEEE MTT-S International Microwave Symposium Digest.

[7]  B. Kopp,et al.  High-efficiency 5-watt power amplifier with harmonic tuning , 1988, 1988., IEEE MTT-S International Microwave Symposium Digest.

[8]  W. S. Kopp,et al.  High efficiency power amplification for microwave and millimeter frequencies , 1989, IEEE MTT-S International Microwave Symposium Digest.

[9]  T. F. Brukiewa,et al.  Class-B power MMIC amplifiers with 70 percent power-added efficiency , 1989 .

[10]  Hua Quen Tserng,et al.  Harmonic tuning of power FETs at X-band , 1990, IEEE International Digest on Microwave Symposium.

[11]  Tatsuo Itoh,et al.  A periodic planar Gunn diode power combining oscillator , 1990 .

[12]  Kai Chang,et al.  Active integrated antenna elements , 1991 .

[13]  Robert M. Weikle,et al.  A 100-MESFET planar grid oscillator , 1991 .

[14]  Renato G. Bosisio,et al.  A new multiharmonic loading method for large-signal microwave and millimeter-wave transistor characterization , 1991 .

[15]  David B. Rutledge,et al.  Planar MESFET grid oscillators using gate feedback , 1992 .

[16]  Renato G. Bosisio,et al.  A novel approach for designing GaAs FET frequency multipliers with optimum conversion gain and power efficiency , 1992 .