A Wideband UHF Transmitter for Space Applications

Abstract

This paper describes the design and performance of a frequency-modulated 10watt S-band transmitter. Analogue frequency response is in excess of 7 Mc and digital signals at rates up to 10 megabits per second are transmitted satisfactorily. This extra wideband transmitter, ruggedized for space applications, utilizes a solid state exciter for signal generation, a traveling wave tube amplifier for power amplification, and a solid state traveling wave tube power supply that will withstand critical atmospheric pressures. A detailed analysis of rf bandwidth requirements and the state of the semiconductor art at the time of transmitter design resulted in the exciter taking the form of a 70 Mc voltage controlled oscillator whose output is amplified and converted to the S-band output frequency by means of broadband varactor harmonic generators. Production versions of this transmitter have consistently demonstrated satisfactory orbital operation. Laboratory data has indicated a minimum rf power output of 10 watts at base-plate temperatures ranging from -35° to +75° Centigrade. Baseband response is from 10 cycles to more than 7 Mc at ±6 Mc frequency deviation.