UHF Field-Effect-Transistor Mixer of High Dynamic Range.
SYLVANIA ELECTRONIC SYSTEMS-WEST MOUNTAIN VIEW CALIF
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A study is presented of theoretical and experimental performance of a 90-degree-hybrid-coupled FET mixer covering 500-1000 MHz. The theoretical work completed includes methods for calculating FET mixer gain, noise figure, third-order intermodulation, and harmonic intermodulation products single-frequency spurious responses. A model suitable for use in mixer design is also described. Test data from the experimental model of the mixer, over the frequency range of 500 to 1000 MHz, indicated a noise figure of 10.9 to 13.3 dB, gain of 2.8 to 5.6 dB, and a 3-dB-gain-compression level of 6 dBm at the input. The intermediate frequency was 160 MHz, with a bandwidth of a 4 MHz. Good correlation between calculated and measured performance was obtained. In addition, there is described a computer program, written in FORTRAN IV for the IBM 1130 and automating the calculations required to estimate FET mixer performance, in which curvative effects up through the ninth order are included. Some comparison is made of the test results with typical hot-carrier diode mixers which, in the 500- to 1000-MHz range, are comparable except for their conversion losses.
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