Wideband ground penetrating radar system and method
An improved Ground Penetrating Radar (GPR) system is provided. The system advantageously employs full waveform digitization of a returning signal to significantly reduce the number of launch signals and allowing the amount of radiation emitted to stay within the limit set by the Federal Communications Commission (FCC), while producing a robust information detection signal. In addition, intermittent large latent-duty-cycle sampling employs a less expensive digitizer typically used in prior art GPRs. The system is scalable at low-cost to accommodate multi-antenna multi-static testing for subsurface tomographic imaging.
1. An impulse ground penetrating radar (iGPR) system, the iGPR system comprising:
a source comprising:
a source pulser for transmitting a pulse having period T pulse ;
an initiating trigger source for generating a trigger signal to the source pulser for initiating the pulse transmission
a receiver comprising:
a real-time waveform sampler for portion sampling a reflected pulse;
and wherein the reflected pulse is real-time sampled for a period T win , where T win <T pulse ;
wherein the initiating trigger source is connectable to the real-time pulse sampler for initiating sampling the reflected pulse; and
an adjustable delayer for delaying the trigger signal to the real-time waveform sampler.
2. The iGPR as in claim 1 wherein the adjustable delayer comprises a transmission cable.
3. The iGPR as in claim 1 further comprising a trigger circuit connectable to the real-time pulse sampler for initiating a sampling trigger for sampling the reflected pulse.
4. The iGPR as in claim 3 wherein the trigger circuit derives the sampling trigger from the reflected pulse.
5. The iGPR as in claim 1 further comprising a trigger circuit connectable to the real-time pulse sampler for initiating a sampling trigger for sampling the reflected interrogatory pulse.
6. The iGPR as in claim 5 further comprising a direct coupling signal between the source and the receiver.
7. The iGPR as in claim 1 wherein the real-time waveform sampler comprises:
a plurality of sequentially connected delay elements for generating a plurality of sequentially delayed write strobe signals;
a write clock connectable to at least one of the plurality of sequentially connected delay elements, wherein the write clock generates a clock signal at a predetermined frequency f write to at least one of the sequentially connected delay elements, wherein each of the sequentially connected delay elements delays the clock signal (1/f write )/K, where K=the plurality of sequentially connected delay elements;
a plurality of sampling switches, each of the plurality of sampling switches corresponding to an output of the plurality of delay elements;
a plurality of sampling charge storage elements corresponding to the plurality of sampling switches, and wherein the plurality of sampling charge storage elements sequentially sample a portion of the reflected pulse;
and wherein T win =1/f write .
8. The iGPR as in claim 7 wherein the plurality of sampling charge storage elements further comprises a corresponding plurality of charge capacitors.
9. The iGPR as in claim 7 further comprising an Analog-Digital Convener (ADC) connected to each of the plurality of sampling charge storage elements.
10. The iGPR as in claim 9 further comprising:
a data register connected to the ADC;
a readout controller connected to the data register; and
a decoder connected to the data register.
11. A method for operating a ground penetrating radar, the method comprising:
pulsing a transmitter to emit a radar frequency electromagnetic wave;
providing a receiver for receiving a reflected signal of the emitted wave, wherein the reflected signal comprises an information segment and a no-information segment;
digitally sampling the information segment; and
not digitally sampling the no-information segment;
wherein digitally sampling the information segment further comprises digitally sampling the information segment with a Giga Samples per Second (GSPS) sampling receiver.
12. The method as in claim 11 wherein digitally sampling the information segment comprises intermittently sampling the information segment.
13. The method as in claim 11 wherein digitally sampling the information segment further comprises continuously sampling the information segment.
14. The method as in claim 11 further comprising synchronizing the pulsing of the transmitter and the digital sampling of the information segment.
15. The method as in claim 14 further comprising providing a direct coupling signal between the transmitter and the receiver for synchronizing the pulsing of the transmitter and the digital sampling of the information segment.
16. An impulse ground penetrating radar (GPR) system, the GPR system comprising:
a transmitter antenna for transmitting radar signal pulses;
a pulses for pulsing the transmitter;
a receiver antenna for receiving the reflected transmitted signal pulses;
a sampling receiver for digitally sampling an information portion of the reflected signal pulse, wherein the sampling receiver comprises:
a Giga Samples per Second (GSPS) sampling receiver;
a signal generator for synchronizing the pulser and the sampling receiver; and
wherein the transmitter antenna and the receiver antenna comprise a pair of Good Impedance Match Antennas (GIMA);
wherein the sampling receiver comprises a continuous sampler.
17. The system as in claim 16 wherein the sampling receiver comprises an intermittent sampler.