UHF Integrated Power Amplifiers

This paper describes the development of integrated UHF power amplifiers using thin-film lumped elements and UHF power-transistor chips. Single-stage hybrid amplifier modules capable of delivering output powers up to 20 watts CW in the frequency range of 225-400 MHz are reported. In addition, broad-band hybrid amplifiers are discussed with 1-dB bandwidths of up to 40 percent in the same 225-400 MHz band. These amplifiers are presently housed in a three-terminal stud-mounted module, 0.8-inch high, 0.65-inch wide, and 0.35-inch deep. The module has a 50-ohm-impedance input lead, a 50-ohm-impedance output lead, and a dc lead (grounding is through the stud). Gain and output powers significantly greater than those available from a single module are obtained by cascading and/or paralleling individual modules at their 50-ohm terminals, either directly or by means of power combiners and power dividers. By use of the latter approach, a 76-watt amplitier having a gain of 15.8 dB at an operating frequency of 350 MHz has been constructed.