Design of an Absorptive High-Power PIN Diode Switch for an Ultra-Wideband Radar

This paper details the development of a low-loss, PIN diode single-pole double-throw (SPDT) absorptive switch for an ultra-wideband radar. The fabricated switch operates with a peak power of 200 watts at a 10% duty cycle. It has an insertion loss of less than 0.8 dB, a return loss greater than 19 dB, and isolates the transmitter and receiver beyond 37 dB over the frequency band (170 MHz-470 MHz) for sensitive radar measurements. An external RF limiter and a low-power CMOS switch at the receiving end are used to reduce video leakage from the PIN diode switch and enhance the isolation up to 80 dB. In addition, a fast-switching MOSFET-based PIN diode driver circuit is designed with a dead-time control circuit to minimize the cross-conduction currents for the PIN diode switch. The rise and fall times for the PIN diode switch are less than 200 ns. The switch-driver includes integrated low-noise power supplies that generate −50 V, 15 V, and 5 V from a common rail 50 V input source.