Design and Development of a High-Power Pulse Transmitter for Underground Environmental Perception

Abstract

This article represents a design for a high-power pulse transmitter for high-depth imaging applications. The pulse transmitter consists of an avalanche transistor-based pulse-shaping network, an improved step recovery diode (SRD)-based configuration, and a pulse-shifting circuit with a broadband combiner to generate a first derivative Gaussian pulse for high-power applications. The output pulse of the transistor-based circuit is fed to a balun, which produces two opposite polarity pulses and then feeds two parallel SRD pulse-shaping circuits that produce ultrashort pulses. The SRD-based part of the circuit was developed to have a high amplitude output pulse. Moreover, using a technique based on pulse shifting, a higher power monopulse was achieved without using a balun and a differentiator. This design achieved a monopulse of 169-ps pulsewidth with a peak power of <inline-formula> <tex-math notation="LaTeX">$P =5.78$ </tex-math></inline-formula> W. In order to check the validity of the transmitter for imaging applications, several experiments for buried objects in the sand are conducted, including metal objects, water pipe, rock, and copper veins. All reconstructed 3-D images clearly represent the target shape and dimension, confirming the functionality of the designed transmitter for sensing and imaging applications.