Use Of Bistatic Allofrequency Antennas In Ground-Penetrating Radar (Gpr) Investigations

Shielded monostatic transducers used in ground-penetrating radar investigations<br>(GPR) provide good results in probing subsurface features. Use of bistatic (paired) isofrequency<br>transducers can improve survey results. Bistatic antennas transmitting and receiving<br>at the same center frequency (iso-) can reduce ‘ringing” produced by initial contact<br>of a vertically incident radar pulse with highly conductive surface material. Selection<br>of a suitable antenna separation can improve capture of reflected pulses that would<br>be lost using a monostatic system. What is reported here is the use of a pair of antennas<br>having different center frequencies (allo-), with the higher frequency receiver serving as<br>a filter for the lower frequency transmitter. Impulse radar units transmit and receive<br>broad bandwidth pulses. Lower frequency antennas usually transmit pulses with higher<br>power, allowing specific frequencies to penetrate deeper into geologic media. In the<br>zone of frequency overlap, sufficient energy will be reflected back to the higher<br>frequency receiver to permit higher resolution of targets at greater depth.