Pseudo real time receive signal sampling for ground penetrating radar

• US 8,884,807 B1
• Filed: 05/09/2012
• Issued: 11/11/2014
• Est. Priority Date: 05/09/2012
• Status: Active Grant

• Current Assignee: Mal Geoscience USA
• Original Assignee: Mal Geoscience USA
• Inventors: Johansson, Bernth A. T., Friborg, Johan Gustaf
• Primary Examiner(s): GREGORY, BERNARR E
• Application Number:
  US13/467,486
• Time in Patent Office: 916 Days
• Field of Search: 342/21, 342/22, 342/27, 342/28, 342/73, 342/82, 342 88-103, 342/175, 342/176, 342/179, 342/189, 342192-197
• US Class Current: 342/22
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 7/28 Details of pulse systems
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

A system and method for pseudo real time collection of receive signal data in a single- or multi-channel ground penetrating radar. Each channel transmits electromagnetic impulses into a medium under test during each of a plurality of runs over the medium. Run receive signals are received in response to the transmitted impulses. Each run receive signal is sampled multiple times at a run sample rate. The sample points of each run are delayed by delay sequences with respect to the sample points of the other runs. The sample points of the individual runs are stored as a composite set of sample points representative of a receive signal sampled at an effective sample rate equal to a multiple of the run sample rate where the multiple is the number of runs.

Claims

1. A method for operating a ground penetrating radar channel, comprising:

generating a trigger signal for each one of a plurality of data collection runs, wherein the trigger signals are configured to trigger the transmission of ground penetrating electromagnetic waves;

receiving at an A/D converter a run receive signal in response to each ground penetrating electromagnetic wave;

A/D sampling each run receive signal at a sampling rate to produce a run set of sample points, including sampling each run receive signal at a different delay sequence with respect to a beginning of the run receive signal; and

storing the run sets of sample points as a composite set of sample points representative of a signal sampled with an effective sampling rate that is greater than the sampling rate at which the run receive signals were sampled.

2. The method of claim 1 wherein generating the trigger signals includes delaying the generation of the trigger signals by the delay sequences with respect to the A/D sampling.

3. The method of claim 1 wherein A/D sampling includes delaying the A/D sampling by the delay sequences with respect to the trigger signals.

4. The method of claim 1 using at least two runs and run sets of sample points for each composite set of sample points.

5. A method for synchronizing multiple ground penetrating radar channels of the type operated in accordance with the method of claim 1, comprising:

generating a common channel synchronization signal and providing the synchronization signal to each channel;

setting a time slot of the trigger signals of each channel to the channel synchronization signal, wherein the trigger signals of each channel are set to a different and non-overlapping time slot; and

synchronizing the trigger signals of each channel within the set time slot to the channel synchronization signal.

6. The method of claim 5 wherein generating the channel synchronization signal includes generating a channel synchronization signal having a substantially lower frequency than a frequency of the trigger signals.

7. The method of claim 6 wherein generating the channel synchronization signal includes generating an asynchronous channel synchronization signal.

8. The method of claim 7 wherein synchronizing the trigger signals of each channel includes immediately synchronizing the trigger signals of the channel to the channel synchronization signal if a run receive signal is not being A/D sampled by the channel upon assertion of the channel synchronization signal.

9. The method of claim 8 wherein synchronizing the trigger signals of each channel includes delaying the synchronization of the trigger signals of the channel to the channel synchronization signal if a run receive signal is being A/D sampled by the channel upon assertion of the channel synchronization signal.

10. The method of claim 7 wherein synchronizing the trigger signals of each channel includes delaying the synchronization of the trigger signals of the channel to the channel synchronization signal if a run receive signal is being A/D sampled by the channel upon assertion of the channel synchronization signal.

11. The method of claim 5 wherein synchronizing the trigger signals of each channel includes immediately synchronizing the trigger signals of the channel to the channel synchronization signal if a run receive signal is not being A/D sampled by the channel upon assertion of the channel synchronization signal.

12. The method of claim 11 wherein synchronizing the trigger signals of each channel includes delaying the synchronization of the trigger signals of the channel to the channel synchronization signal if a run receive signal is being A/D sampled by the channel upon assertion of the channel synchronization signal.

13. The method of claim 5 wherein synchronizing the trigger signals of each channel includes delaying the synchronization of the trigger signals of the channel to the channel synchronization signal if a run receive signal is being A/D sampled by the channel upon assertion of the channel synchronization signal.

14. The method of claim 1 wherein generating a trigger signal includes generating a trigger signal having a relatively constant repetition rate.

15. The method of claim 1 and further including varying the rate of the trigger signals, including lowering the trigger signal rate.

16. A system for collecting receive signal data in a ground penetrating radar channel, comprising:

a trigger generator to generate trigger signals for each one of a plurality of dates collection runs, wherein the trigger signals are configured to trigger the transmission of ground penetrating electromagnetic waves;

an A/D converter to receive run receive signals in response to the electromagnetic waves and to sample the run receive signals at a sampling rate and generate run sets of sample points;

a clock generator to provide a sample clock to the A/D converter;

a delay sequence control to cause the A/D converter to sample the run receive signals at different delay sequences with respect to beginnings of the run receive signals; and

memory to store the run sets of sample points having different delay sequences as a composite set of sample points representative of a signal sampled with an effective sampling rate that is greater than the sampling rate at which the run receive signals were sampled.

17. The system of claim 16 wherein the delay sequence control is coupled to the trigger generator and the clock generator, and causes the trigger generator to generate the trigger signals at different delay sequences with respect to the sample clock.

18. The system of claim 17 wherein the delay sequence control includes:

a programmable delay coupled to the trigger generator; and

a controller coupled to the programmable delay to load delay values in the programmable delay.

19. The system of claim 16 wherein the delay sequence control is coupled to the A/D converter and the trigger generator, and causes the A/D converter to generate the run sets of sample points at different delay sequences with respect to the trigger signals.

20. The system of claim 19 wherein the delay sequence control includes:

a programmable delay coupled to the A/D converter; and

a controller coupled to the programmable delay to load delay values in the programmable delay.

21. The system of claim 16 and further including:

a synchronization signal input to receive a channel synchronization signal; and

a synchronization control coupled to the synchronization signal input and the trigger generator, to set a time slot of the trigger signals to one a plurality of non-overlapping time slots and to synchronize the trigger signals within the time slot to the synchronization signal.

22. The system of claim 21 wherein the synchronization control immediately synchronizes the trigger signals to the channel synchronization signal if a run receive signal is not being A/D sampled upon assertion of the synchronization signal.

23. The system of claim 22 wherein the synchronization control delays the synchronization of the trigger signals if a run receive signal is being A/D sampled upon assertion of the synchronization signal.

24. The system of claim 23 wherein the gate generates trigger signals having a relatively constant repetition rate.

25. The system of claim 23 and further including a trigger control to control, including lower, the trigger signal rate.

26. The system of claim 21 wherein the synchronization control delays the synchronization of the trigger signals if a run receive signal is being A/D sampled upon assertion of the synchronization signal.

27. The system of claim 16 wherein the trigger generator generates trigger signals having a relatively constant repetition rate.

28. The system of claim 16 and further including a trigger signal control to control, including lower, the trigger signal rate.

29. A system for collecting multiple channels of receive signal data in a ground penetrating radar, comprising:

a channel synchronizer for generating a channel synchronization signal; and

a plurality of channels, each channel including;

a gate connected to receive trigger control signals and a trigger clock, wherein the trigger clock has a higher frequency than the trigger control signals and the gate gates the trigger clock as a function of the trigger control signal to generate a trigger signal during each of a plurality of data collection runs, wherein the trigger signals are configured to trigger the transmission of ground penetrating electromagnetic waves;

an A/D converter to receive run receive signals in response to the electromagnetic waves and to sample the run receive signals at a sampling rate and generate run sets of sample points;

a clock generator to provide a sample clock to the A/D converter and the trigger clock to the gate;

a programmable delay connected to received delay sequence control signals;

a programmed controller coupled to the channel synchronizer, the gate and the programmable delay, the programmed controller;

generating the delay sequence control signals to cause the A/D converter to sample each run receive signal at a different delay sequence with respect to a beginning of the run receive signal; and

generating the trigger control signals to set a time slot of the trigger signals to one a plurality of non-overlapping time slots and to synchronize the trigger signals within the time slot to the channel synchronization signal; and

memory to store the run sets of sample points having different delay sequences as a composite set of sample points representative of a signal sampled with an effective sampling rate that is greater than the sampling rate at which the run receive signals were sampled.

30. The system of claim 29 wherein the channel synchronizer generates an asynchronous channel synchronization signal.

31. The system of claim 30 wherein the channel synchronizer generates a channel synchronization signal having a substantially lower frequency than a frequency of the trigger signals.

32. The system of claim 29 wherein the programmable delay is coupled to the gate and delays the trigger signals.

33. The system of claim 29 wherein the programmable delay is coupled between the clock generator and the A/D converter and delays the sample clock.

34. The system of claim 29 wherein the programmed controller is a field programmable gate array.

35. The system of claim 29 wherein the programmed controller includes a counter to count trigger clock pulses and generates the trigger control signals as a function of the trigger clock pulse count.

36. The system of claim 29 wherein the programmed controller includes a sync register to store data relating to the timing relationship between an assertion of the channel synchronization signal and the set time slot for the trigger signals, and generates the trigger control signals as a function of the stored data in the sync register.

37. The system of claim 36 wherein the sync register stores a count value of the trigger clock when the channel synchronization signal is asserted.

38. The system of claim 37 wherein the programmed controller generates the trigger control signals immediately if a run receive signal is not being A/D sampled by the channel upon assertion of the channel synchronization signal, and delays generation of the trigger control signals if a run receive signal is being A/D sampled by the channel upon assertion of the channel synchronization signal.

39. The system of claim 29 wherein the programmed controller generates the trigger control signals immediately if a run receive signal is not being A/D sampled by the channel upon assertion of the channel synchronization signal, and delays generation of the trigger control signals if a run receive signal is being A/D sampled by the channel upon assertion of the channel synchronization signal.