High Efficiency 5 Watt S-Band Telemetry Transmitter Using Gallium Arsenide Field Effect Transistors

Abstract

A 5-Watt S-Band telemetry transmitter is often the biggest power drain on an airborne telemetry system's power supply. Furthermore, operation is typically limited to supply voltages of 24 Volts or higher. This is because the traditional telemetry transmitter uses a series regulator power supply and silicon bipolar amplifiers. In this paper we describe the design philosophy of a high efficiency telemetry transmitter that uses Gallium Arsenide Field Effect Transistors (GaAs FETs) as the power output stages. The GaAs FETs provide efficiency levels not achievable with silicon bipolar technology. In addition, the power supply uses a switching regulator which provides for constant power drain as a function of input voltage and allows operation down to an input voltage of 18 Volts. Overall, the transmitter can reduce the system's power drain by 30%.