A 300W S-band solid-state transmitter

This paper describes the structure and the performance of a 300 W compact solid-state transmitter operating over 2.9 to 3.1 GHz, for radar and medical applications. The transmitter consists of three major parts: PLL-DDS synthesizer, pulse shaping circuit and multi-stage class-C amplifier. A 300 W peak power with a pulse width up to 50 μs and 5% duty cycle was achieved by combining two 160 W amplifiers with Si-BJT using a balanced configuration. The output power level is controlled in 6 dB dynamic range by means of a DC supply block. The power droop during RF-pulse is less than 0.2 dB for 5% duty operation in the whole output power dynamic range. The synthesized VCO achieves more than 10^-7 long-term stability including pulling effect and -75 dBc/Hz@1 kHz phase noise. In addition the spectrum requirements are also satisfied.