Offset frequency homodyne ground penetrating radar

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.