Geophysical radar apparatus and method
First Claim
Patent Images
1. A pulse compression radar system for detecting objects or strata beneath ground including water or earth comprising:
- (a) a transmitter for generating a carrier signal;
(b) a modulator for modulating said carrier signal with a digital code word comprising a complementary code;
(c) antenna means for directing and transmitting said modulated signal toward the ground;
(d) receiver means for detecting and demodulating reflections of the modulated signal from reflectors on or beneath the ground to produce a received signal corresponding to the original code word but delayed in time by the time it takes for the transmitted signal to travel from the antenna to the reflectors and back and wherein the receiver means includes an in-phase channel and a quadrature channel wherein the received signal is respectively mixed with the carrier signal to produce an in-phase demodulated signal component I and a quadrature demodulated signal component Q which is 90°
out-of-phase with the in-phase component;
(e) correlator means for cross-correlating the demodulated received signal with the original digital code word to produce a higher resolution time compressed version of the received signal.
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Abstract
A ground probing radar is described for detecting radar reflections from underground objects. The radar is of the pulse compression type. A transmitter generates a biph
The U.S. Government has rights to this invention pursuant to Contract No. 536115 (DACA 89-81-K-0004) awarded by U.S. the Army Cold Regions Research and Engineering Laboratory.
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Citations
15 Claims
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1. A pulse compression radar system for detecting objects or strata beneath ground including water or earth comprising:
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(a) a transmitter for generating a carrier signal; (b) a modulator for modulating said carrier signal with a digital code word comprising a complementary code; (c) antenna means for directing and transmitting said modulated signal toward the ground; (d) receiver means for detecting and demodulating reflections of the modulated signal from reflectors on or beneath the ground to produce a received signal corresponding to the original code word but delayed in time by the time it takes for the transmitted signal to travel from the antenna to the reflectors and back and wherein the receiver means includes an in-phase channel and a quadrature channel wherein the received signal is respectively mixed with the carrier signal to produce an in-phase demodulated signal component I and a quadrature demodulated signal component Q which is 90°
out-of-phase with the in-phase component;(e) correlator means for cross-correlating the demodulated received signal with the original digital code word to produce a higher resolution time compressed version of the received signal. - View Dependent Claims (2, 3, 4, 5, 6, 8)
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7. A pulse compression system for airborne or ground probing of earth strata, including soil, bedrock, water, ice and the like, comprising:
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(a) source means for generating a carrier frequency signal; (b) modulator means for modulating said carrier signal with pairs of successive complementary code words; (c) antenna means for propagating said modulated carrier signal in the direction of said earth strata; (d) receiver means for detecting and demodulating reflections of said propagated signal and wherein the receiver means includes an in-phase channel and a quadrature channel wherein the received signal is respectively mixed with the carrier signal to produce an in-phase demodulated signal component I and a quadrature demodulated signal component Q which is 90°
out-of-phase with the in-phase component to produce received digital signals separated in time by the distance between reflecting objects;(e) correlator means for correlating said digital signals with said code words to identify the time delays and amplitudes of said reflections.
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9. The method of detecting reflecting objects, such as river beds, strata, buried pipes, and the like, located beneath the ground wherein the ground includes rock, soil, water, ice, or the like, comprising the steps of:
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(a) generating a carrier signal; (b) modulating said carrier signal with a digital complementary code word; (c) directing and transmitting said modulated signal toward the ground; (d) detecting and demodulating reflections of the modulated signal from reflections on or beneath the ground to produce an analog received signal corresponding to the original code word but delayed in time by the time it takes for the transmitted signal to travel from the antenna to the reflectors and back and wherein the demodulation includes mixing the received signal with the carrier signal to produce an in-phase demodulated signal component I and a quadrature demodulated signal component Q which is 90°
out-of-phase with the in-phase component I;(e) converting the received analog signal to a received digital signal; (f) correlating the received digital signal with the original digital code used to modulate the carrier signal to identify the time delays and amplitudes of the reflected signals. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method for airborne or ground probing of earth strata, including soil, bedrock, water, ice and the like, comprising:
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(a) generating a carrier frequency signal; (b) phase modulating said carrier signal with pairs of successive digital complementary code words; (c) propagating said modulated carrier signal in the direction of said earth strata; (d) detecting and demodulating reflections of said propagated signal to produce received digital signals separated in time by the distance between reflecting objects and wherein demodulating includes mixing the received signal with the carrier signal to produce an in-phase demodulated signal component I and a quadrature demodulated signal component Q which is 90°
out-of-phase with the in-phase component; and(e) correlating said digital signals with said code words to identify the time delays and amplitudes of the reflected signals.
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Specification