DESIGN OF A HIGH PERFORMANCE HIGH POWER RADAR TRANSMITTER

Abstract

In Radar systems there have always been attempts to improve the performance of the Transmitter. This paper describes the design of a highly stable and reliable transmitter that has been fabricated and tested. The system is based on a grid pulsed, coupled cavity Travelling Wave Tube Amplifier(TWTA) which delivers the system requirement of 80 kw peak power and 2 kw average power. In order to meet the phase stability of RF output and purity of its spectrum, the high voltage power supplies of the TWTA are made highly stable. For the Radar system requirement (high Moving Target Indicator improvement factor) stability of 5V in 40 KV is required and this had been achieved. Protection and control circuits with appropriate interlocks are provided and the transmitter is in operation in a Radar System. Amplitude spectrum of the output RF pulse measured 100 Hz away from the carrier is better than -60 dBc/Hz. The article discusses design of the Transmitter with emphasis on the high power inverter, the grid modulator and regulation scheme. It also covers depressed collector mode of TWT operation. Results presented are supply regulation and spectral purity of the transmitter.