An Adaptive Airborne VHF/UHF Transmitter System

Abstract

The impending 1970 change-over of telemetry RF links from VHF (215- 265 MHz) to UHF (1435-1545 and 2100-2200 MHz) requires a quantum jump in the state-of-the-art of solid-state transmitters. This problem is compounded by the fact that in certain instances, especially for spacecraft and special applications, there is still a need for transmitters at many different VHF and lower UHF frequencies between 136 MHz and 1 GHz. Therefore, the optimum RF product line is represented by a modular transmitter system composed of fundamental building blocks which will permit the assembly of transmitters capable of producing from 50 watts at 136 MHz to 1/2-watt at 5500 MHz with minimal variations in the over-all mechanical configuration. This adaptive transmitter system must also be able to provide optional features such as power-to-case ground isolation, modulation-to-power ground isolation, turn-on current limiting, either frequency of phase modulation remote turn-on capabilities, and internal telemetry functions of temperature, RF power, dc voltage. Additional design requirements for such a transmitter system are wideband frequency response and carrier deviation capabilities so that the transmitter may handle real-time video signal for use with television, radar and infra-red transmission systems. This paper describes the design alternatives and the conceptual approaches that were used in development of such an adaptive transmitter system. Performance data presented is typical of that achieved from L-band and S-band units.