Offset frequency homodyne ground penetrating radar

• US 9,348,020 B2
• Filed: 03/12/2013
• Issued: 05/24/2016
• Est. Priority Date: 03/12/2012
• Status: Active Grant

• Current Assignee: Vermeer Manufacturing Company
• Original Assignee: Vermeer Manufacturing Company
• Inventors: Wilson-Langman, Alan, Ryerson, Kenneth J., Rothe, Walter
• Primary Examiner(s): Sotomayor, John B
• Assistant Examiner(s): Windrich, Marcus
• Application Number:
  US13/797,929
• Publication Number:
  US 20130234879A1
• Time in Patent Office: 1,169 Days
• Field of Search: 342/22, 342/27, 342/191, 342/196
• US Class Current: 1/1
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 7/352 Receivers

Abstract

Systems and methods involve generating a baseband signal, up-converting the baseband signal to a radar signal frequency, filtering a lower sideband of the up-converted signal, and transmitting the filtered up-converted signal. Systems and methods also involve receiving a return signal, down-converting the return signal using a signal having a frequency offset from the up-converted signal, filtering the upper sideband of the down-converted return signal, and producing a baseband return signal.

Claims

1. A radar detection method, comprising:

generating a baseband signal;

up-converting the baseband signal to a radar signal frequency;

filtering a lower sideband of the up-converted signal;

transmitting the filtered up-converted signal, wherein generating, up-converting, filtering the lower sideband, and transmitting are implemented by a transmit section of a radar apparatus;

receiving a return signal;

down-converting the return signal using a signal having a frequency offset from the up-converted signal;

filtering the upper sideband of the down-converted return signal; and

producing a baseband return signal, wherein receiving, down-converting, filtering the upper sideband, and producing are implemented by a receive section of the radar apparatus;

wherein the frequency offset is a predetermined frequency related to a width of a sideband filter used for filtering the upper sideband of the down-converted return signal.

2. The method of claim 1, wherein the baseband signal is an arbitrary waveform.

3. The method of claim 1, wherein the baseband signal comprises a single frequency.

4. The method of claim 1, wherein the baseband signal comprises a plurality of disparate frequency components.

5. The method of claim 1, further comprising:

processing the baseband return signal to produce a time-domain signal; and

displaying the time-domain signal on a display.

6. The method of claim 1, wherein the predetermined frequency is a frequency greater than or equal to a width of a sideband filter configured for filtering the upper sideband of the mixed receive signal.

7. The method of claim 1, further comprising:

incrementing a frequency of a carrier signal used for up-converting the baseband signal to each of a plurality of disparate predetermined frequencies; and

repeating the method for each of the plurality of disparate predetermined frequencies.

8. The method of claim 1, wherein the method is performed underground and for detecting subsurface objects.

9. A radar detection method, comprising:

generating a baseband signal;

mixing the baseband signal with a transmit oscillator signal to produce a mixed transmit signal comprising a lower sideband and an upper sideband;

filtering the lower sideband of the mixed transmit signal;

transmitting the filtered mixed transmit signal, wherein generating the baseband signal, mixing the baseband signal, filtering the lower sideband, and transmitting are implemented by a transmit section of a radar apparatus;

receiving a return signal resulting from transmitting the filtered mixed transmit signal;

generating a receive oscillator signal having a frequency offset from that of the transmit signal by a predetermined frequency;

mixing the return signal with the receive oscillator signal to produce a mixed receive signal comprising a lower sideband and an upper sideband; and

filtering the upper sideband of the mixed receive signal to produce a baseband return signal, wherein receiving, generating the receive oscillator signal, mixing the return signal, and filtering the upper sideband are implemented by a receive section of the radar apparatus;

wherein the frequency offset is a predetermined frequency related to a width of a sideband filter used for filtering the upper sideband of the down-converted return signal.

10. The method of claim 9, wherein the baseband signal is an arbitrary waveform.

11. The method of claim 9, wherein the baseband signal comprises a single frequency.

12. The method of claim 9, wherein the baseband signal comprises a plurality of disparate frequency components.

13. The method of claim 9, further comprising:

processing the baseband return signal to produce a time-domain signal; and

displaying the time-domain signal on a display.

14. The method of claim 9, wherein the predetermined frequency is a frequency greater than or equal to a width of a sideband filter configured for filtering the upper sideband of the mixed receive signal.

15. The method of claim 9, wherein the method is performed underground and for detecting subsurface objects.

16. A radar apparatus, comprising:

an antenna arrangement;

a signal generator configured to generate a baseband signal;

a transmit section, coupled to the signal generator and the antenna arrangement, comprising a transmit oscillator operating at a predetermined frequency, the transmit section configured to;

generate a transmit signal comprising a mix of the baseband signal and a signal at the predetermined frequency; and

filter a lower sideband of the mixed transmit signal;

a receive section, coupled to the antenna arrangement, comprising a sideband filter and a receive oscillator configured to operate at a frequency differing from that of the transmit oscillator by a predetermined frequency offset related to a width of the sideband filter, the receive section configured to;

mix a return signal received by the antenna arrangement and a signal produced by the receive oscillator with the predetermined frequency offset to produce a mixed receive signal comprising a lower sideband and an upper sideband; and

filter the upper sideband of the mixed receive signal using the sideband filter to produce a baseband return signal.

17. The apparatus of claim 16, wherein the sideband filter comprises a Nyquist filter.

18. The apparatus of claim 16, wherein the radar apparatus is implemented as a ground penetrating radar.

19. The apparatus of claim 16, wherein the radar apparatus is implemented in a drill head of a horizontal directional drilling system.

20. The apparatus of claim 16, wherein the baseband signal is an arbitrary waveform.

21. The apparatus of claim 16, wherein the baseband signal comprises a single frequency.

22. The apparatus of claim 16, wherein the baseband signal comprises a plurality of disparate frequency components.

23. The apparatus of claim 16, further comprising:

a transform unit configured to transform the baseband return signal to a time-domain signal; and

a user interface comprising a display and configured to present the time-domain signal on the display.

24. The apparatus of claim 16, wherein the predetermined frequency offset is a frequency greater than or equal to a width of the sideband filter.