Double-sideband suppressed-carrier radar to null near-field reflections from a first interface between media layers
First Claim
1. An earth-penetrating radar for guiding mining machinery, comprising:
- a software defined radio transceiver with program software to implement a radar transmitter and radar receiver, wherein a software programming enables a switch in operational modes between near-field and far-field signal detection;
wherein, said radar transmitter provides for launching pairs of separated and coherent continuous waves in a double-sideband suppressed-carrier modulation through the air;
a radar receiving antenna for placement proximate to an air interface with a first layer of material, and having impedance characteristics that depend on a surrounding natural medium adjacent to the antenna and an operating frequency;
wherein, said radar receiver includes coherent demodulation for suppressing a first reflection of radio signals emitted by the radar transmitter from an air interface with a first layer of material and received by the radar receiving antenna;
a receiver processor for determining any electrical parameters of a natural medium adjacent to the antenna from stored a priori data and impedance measurements of the radar receiving antenna; and
a radar processor for calculating the depth of an interface between said first layer of material and a second deeper layer of material, by measuring a signal delay of a second reflection of radio signals emitted by the radar transmitter from said first and second material interface which was received by the radar receiving antenna.
1 Assignment
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Accused Products
Abstract
A ground-penetrating radar comprises a software-definable transmitter for launching pairs of widely separated and coherent continuous waves. Each pair is separated by a constant or variable different amount double-sideband suppressed carrier modulation such as 10 MHz, 20 MHz, and 30 MHz Processing suppresses the larger first interface reflection and emphasizes the smaller second, third, etc. reflections. Processing determines the electrical parameter of the natural medium adjacent to the antenna.
The modulation process may be the variable or constant frequency difference between pairs of frequencies. If a variable frequency is used in modulation, pairs of tunable resonant microstrip patch antennas (resonant microstrip patch antenna) can be used in the antenna design. If a constant frequency difference is used in the software-defined transceiver, a wide-bandwidth antenna design is used featuring a swept or stepped-frequency continuous-wave (SFCW) radar design.
The received modulation signal has a phase range that starts at 0-degrees at the transmitter antenna, which is near the first interface surface. After coherent demodulation, the first reflection is suppressed. The pair of antennas may increase suppression. Then the modulation signal phase is changed by 90-degrees and the first interface signal is measured to determine the in situ electrical parameters of the natural medium.
Deep reflections at 90-degrees and 270-degrees create maximum reflection and will be illuminated with modulation signal peaks. Quadrature detection, mixing, and down-conversion result in 0-degree and 180-degree reflections effectively dropping out in demodulation.
46 Citations
15 Claims
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1. An earth-penetrating radar for guiding mining machinery, comprising:
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a software defined radio transceiver with program software to implement a radar transmitter and radar receiver, wherein a software programming enables a switch in operational modes between near-field and far-field signal detection; wherein, said radar transmitter provides for launching pairs of separated and coherent continuous waves in a double-sideband suppressed-carrier modulation through the air; a radar receiving antenna for placement proximate to an air interface with a first layer of material, and having impedance characteristics that depend on a surrounding natural medium adjacent to the antenna and an operating frequency; wherein, said radar receiver includes coherent demodulation for suppressing a first reflection of radio signals emitted by the radar transmitter from an air interface with a first layer of material and received by the radar receiving antenna; a receiver processor for determining any electrical parameters of a natural medium adjacent to the antenna from stored a priori data and impedance measurements of the radar receiving antenna; and a radar processor for calculating the depth of an interface between said first layer of material and a second deeper layer of material, by measuring a signal delay of a second reflection of radio signals emitted by the radar transmitter from said first and second material interface which was received by the radar receiving antenna. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An earth penetrating radar method, comprising:
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using a near measurement mode and a far measurement mode for predistortion and calibration of a transmitted waveform and a carrier suppression; setting a radar first to near measurement mode to measure near-antenna signals reflected from a first interface by setting a modulation signal phase θ
m to zero degrees during a calibration;processing a near measurement mode, wherein a first sideband is turned off and a magnitude and phase are a measurement of a second sideband alone; repeating a measurement for an opposite sideband; adjusting magnitudes of said sidebands to be equal in value and adjusting the phase θ
m to zero degrees;adjusting a carrier phase θ
c to zero degrees to compensate for a distorted frequency response in the radar and antennas;
then switching to a far measurement mode that sets
such that any first interface reflection is suppressed;using polarized antennas for any additional suppression; and using a software-defined transceiver for phase-coherent detection of the depth of said second interface reflection. - View Dependent Claims (10, 11, 12)
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13. An earth-penetrating radar, comprising:
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a radio frequency (RF) power amplifier and antenna for launching corrected versions of coherent pairs of first and second continuous wave frequencies into a geologic heterogeneous media with different constituent electrical parameters for causing first, second, and additional interface reflected waves to be received; a receiver and antenna for collecting signals reflected from a first interface and other signals reflected or scattered from buried objects and interfaces of material with contrasting electrical parameters; a down-converter and coherent demodulator for coherent demodulating of an in-phase I =cos(θ
m + ω
mτ
1)cos(θ
c+ω
cmτ
1)+cos(θ
m+ω
cmτ
2)cos(τ
c+ω
cτ
2)+ . . . , and Q=cos(θ
m+ω
mτ
1)sin(θ
c+ω
cmτ
1)+cos(θ
m+ω
mτ
2)sin(θ
c+ω
cmτ
2)+ . . . , where θ
m is a processor-controllable phase shift (π
/2, 0, 3π
/2, 2π
), . . . , and ω
m is a modulation frequency of a double-sideband suppressed carrier or phase-modulated signal, and θ
c is a carrier phase with a frequency of ω
c;a processor for determining the magnitude of each reflection as M=|cos(θ
m+ω
mτ
)| for each pair of transmitting continuous waves, wherein τ
=τ
1 represents the echo delay time occurring for reflections from the surface near the antenna and τ
=τ
2 represents the echo delay time occurring for more distant reflections from buried objects and interfaces; anda device for predistortion inserted before the RF power amplifier and antenna, and that has an inverse response of said power amplifier and antenna, wherein adaptive digital predistortion is controlled by a feedback loop for adapting to changes in response of the power amplifier and antenna; wherein, a determination of distance (R) to a second interface or boundary is discernable from a detected phase shift of a modulation and suppressed carrier waveform. - View Dependent Claims (14, 15)
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Specification