Comparison of the relative merits for target recognition by ultra-wideband radar based on emitted impulse or step-frequency wave

摘要

The feasibility of ultra-wideband (UWB) radar systems for extracting signature information useful for target recognition purposes has been demonstrated previously. An UWB radar system emits either an extremely short pulse, impulse, or a frequency modulated signal (e.g., sweep or step-frequency). The frequency content of the emitted signals is designed to match the size and kind of typical targets and environments. We study the performance of two different radar systems, each intended for use as a ground penetrating radar (GPR). These systems are an impulse radar and a stepped-frequency continuous-wave radar. The frequency content of the emitted pulses is about 300-3,000 MHz with both systems. The same antenna system consisting of two crossed dipoles (transmitting and receiving) is used with both radar systems and it is directed upward in an outdoor setup. The targets are metal spheres of two sizes an each of them is placed above the antenna system on a thick foam plate made of polystyrene, which is virtually transparent for microwaves. Backscattered echoes from each target are analyzed in the frequency domain using traditional Fourier transforms and in the joint time-frequency domain using Wigner distributions (WD). The measured and digitally processed waveforms are then compared with theoretical predictions and the relative merits of the two UWB radar systems are evaluated. The results of our investigation serve to assess the best choice of GPR system for extracting discriminating target signature information.