Swept-step radar system and detection method using same
First Claim
1. A method of detecting an object, comprising:
- (a) transmitting a probe signal having a center frequency and a sweep bandwidth;
(b) receiving a return signal resulting from the probe signal;
(c) storing information corresponding to the object derived by using the return signal;
(d) shifting the center frequency;
(e) repeating steps (a) through (d) a number of times; and
(f) determining a range to the object using the stored information.
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Abstract
An apparatus and method for detecting an object and determining the range of the object is disclosed. A transmitter, coupled to an antenna, transmits a frequency-modulated probe signal at each of a number of center frequency intervals or steps. A receiver, coupled to the antenna when operating in a monostatic mode or, alternatively, to a separate antenna when operating in a bistatic mode, receives a return signal from a target object resulting from the probe signal. Magnitude and phase information corresponding to the object are measured and stored in a memory at each of the center frequency steps. The range to the object is determined using the magnitude and phase information stored in the memory. The present invention provides for high-resolution probing and object detection in short-range applications. The present invention has a wide range of applications including high- resolution probing of geophysical surfaces and ground- penetration applications. The invention may also be used to measure the relative permittivity of materials.
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Citations
34 Claims
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1. A method of detecting an object, comprising:
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(a) transmitting a probe signal having a center frequency and a sweep bandwidth;
(b) receiving a return signal resulting from the probe signal;
(c) storing information corresponding to the object derived by using the return signal;
(d) shifting the center frequency;
(e) repeating steps (a) through (d) a number of times; and
(f) determining a range to the object using the stored information. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
determining, with the antenna immersed in a first medium, a first input impedance of the antenna;
determining, with the antenna immersed in a second medium, a second input impedance of the antenna; and
determining a relative permattivity of the first medium using the first and second input impedances.
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12. The method of claim 1, wherein the first medium comprises substantially solid material, and the second medium comprises a fluid.
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13. The method of claim 1, further comprising producing a difference signal using the probe signal and the return signal, wherein storing the information further comprises storing information associated with the difference signal corresponding to the object.
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14. The method of claim 13, further comprising applying a window function to the difference signal, and range-gate filtering the windowed difference signal.
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15. A system for detecting an object, comprising:
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a transmitter, coupled to an antenna, that transmits a frequency-modulated probe signal having a center frequency and a sweep bandwidth;
a receiver, coupled to the antenna, that receives a return signal resulting from the probe signal;
a frequency selector that controls shifting of the probe signal center frequency to a number of center frequency values;
a memory that stores information of the return signal resulting from transmission of the probe signal at each of the center frequency values; and
a processor, coupled to the memory, that computes a range to the object using the information stored in the memory. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. A system for detecting an object, comprising:
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means for transmitting a probe signal having a center frequency and a sweep bandwidth;
means for receiving a return signal resulting from the probe signal;
means for shifting the center frequency to a number of center frequency values;
memory for storing information corresponding to the object derived by using the return signal at each of the center frequency values; and
means for computing a range to the object using the information stored in the memory. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
means for determining, with the antenna immersed in a first medium, a first input impedance of the antenna;
means for determining, with the antenna immersed in a second medium, a second input impedance of the antenna; and
means for determining a relative permittivity of the first medium using the first and second input impedances.
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32. The system of claim 31, wherein the first medium comprises substantially solid material, and the second medium comprises a fluid.
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33. The system of claim 22, further comprising means for producing a difference signal using the probe signal and the return signal, wherein the storing means comprises means for storing the information associated with the difference signal corresponding to the object.
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34. The system of claim 33, further comprising:
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means for applying a window function to the difference signal; and
means for range-gate filtering the windowed difference signal.
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Specification