Ultra-fast Pulse Transmitter for UWB Microwave Radar

Design and measurement results on formation of ultra short pulses for the transmitter of an ultra wideband (UWB) microwave radar is presented in this paper. Ultra-fast transmitter pulses were generated by avalanche pulse generator and successively sharpened using step recovery diode (SRD) based pulse sharpener circuit. The SRD diode was auto-biased from the input pulses of amplitude +7V. Present method reduces parasitic in the circuit arising from the bias network, which results in less distortion of the output pulses, and facilitates broadband matching with the transmitter antenna. Using double stage SRD diodes, rise time of the output pulses were down to 50 ps of amplitude 1.1V in a 50 ohm system. Experimental results from single stage and double stage pulse forming networks were compared. The impulse generator has been used for the transmitter of an UWB mono-static microwave radar system. Time domain measurement results of the UWB radar shows improved accuracy (±0.75 cm at a distance of 1m) in distance measurement.