A Compact 112 ps Step Recovery Diode Based Pulse Generator for Medical Applications

This paper presents the design of an ultra-wideband (UWB) sub-nanosecond pulse generator. It has been developed as a part of a novel silent speech radar application working at frequencies between 500MHz and 5 GHz. The proposed circuit is based on a step recovery diode (SRD) and generates a Gaussian pulse with an amplitude of 4V and a bandwidth of 4.85 GHz. The circuit has been simulated, a PCB fabricated, optimized and tested. A 3.3V or 5V CMOS clock of more than 25 MHz repetition rate with moderate requirements on rise and fall times can be used to trigger the pulse. The output is designed to match to 50Ohm loads which allows to feed antenna structures directly. Measurement results are presented and show Gaussian pulses with a pulse duration of 112 ps Full-Wave at Half-Maximum (FWHM).