A nanosecond pulse generator based on avalanche transistor

Ultra-wideband (UWB) pulse generators based on an avalanche transistor are widely used in time domain ground penetrating radar(GPR). For shallow subsurface detection, it is essential to increase the pulse amplitude while maintaining the pulse width in order to improve the spatial resolution of GPR. Eliminating pulse trailing is also necessary to improve GPR performance. In this paper, a simple nanosecond generator was designed based on an avalanche transistor. The generator consists of a trigger circuit and a two-stage MARX circuit. The trigger signal is produced by the avalanche transistor in the trigger circuit. Resistors between the base and emitter of the transistor (Rbe) in the MARX circuit are optimized to improve the performance of the output pulse. The output characteristics of the generator are studied for different Rbe and charging capacitor. The results prove that optimizing resistors and charging capacitors decreases the width of the pulse and eliminates the pulse trail. A pulse with width of 900 ps and an amplitude of 25.2V was achieved. The RMS time jitter value of the pulse generator was found to be less than 400 ps.