Self-calibrating interferometric synthetic aperture radar altimeter
First Claim
1. (original) a method of remotely sensing terrain elevation, comprising the steps of:
- sampling returns from radar scatterers associated with the terrain along multiple lanes using first and second channels that overlap to form a cross-shaped antenna pattern; and
analyzing the returns to determine the elevation according to one or more of the following modalities;
phase monopulse (PM), amplitude monopulse (AM), and time delay response (TDR).
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Abstract
A synthetic aperture radar system uses RF bandwidth and Doppler beam sharpening principles to develop fine altitude and along-track resolutions. To achieve accurate cross-track position measurements the system and method exploit a combination of modes based on a novel antenna pattern combination. The unique arrangement of the antenna patterns allows the radar to process terrain elevation measurements in three independent modes, namely, time-delay response (TDR), amplitude monopulse (AM) and phase monopulse (PM). The additional modes address the interfering scatter problem and the calibration issues required for practical and cost effective operation. The approach also maximizes the number of terrain measurements made per look, thereby reducing the impact of errors and noise through averaging and “voting” (i.e., the comparison of measurements and discarding of “outliers”).
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Citations
20 Claims
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1. (original) a method of remotely sensing terrain elevation, comprising the steps of:
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sampling returns from radar scatterers associated with the terrain along multiple lanes using first and second channels that overlap to form a cross-shaped antenna pattern; and
analyzing the returns to determine the elevation according to one or more of the following modalities;
phase monopulse (PM), amplitude monopulse (AM), and time delay response (TDR). - View Dependent Claims (2, 3, 4, 5)
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6. In an interferometric synthetic aperture radar (IFSAR) system utilizing dual receive antennas, the improvement comprising:
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overlapping the antenna patterns to form a cross-shaped footprint enabling simultaneous terrain elevation measurement using one or more of the following modalities;
phase monopulse (PM), amplitude monopulse (AM), and time delay response (TDR).
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7. A method of remotely sensing terrain elevation, comprising the steps of:
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sampling returns from radar scatterers associated with the terrain along multiple lanes A, B, and C using first and second channels that form a cross-shaped antenna pattern that substantially overlaps in lane B; and
analyzing the returns to determine the elevation according to one or more of the following modalities;
phase monopulse (PM) using interferometric Doppler beam-sharpening, amplitude monopulse (AM) using an amplitude ratio variation as a function of cross-track position in the sampling lanes, and time delay response (TDR) using the first and second channels to determine the time delay of a scatterer in one of the lanes. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A multi-mode altimeter system for use on a platform that moves relative to a terrain of interest, the system comprising:
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a multi-channel antenna operative to generate overlapping antenna patterns on a terrain partitioned into a plurality of sampling lanes; and
a processor to perform elevation measurements of the terrain, including time-delay-response (TDR), amplitude-monopulse (AM) and phase-monopulse (PM) operational modes. - View Dependent Claims (14, 15, 16)
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17. A multi-mode altimeter system for use on a platform that moves relative to a terrain of interest, the system comprising:
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a multi-channel antenna operative to generate an overlapping, cross-shaped pattern defining a first channel and a second channel; and
a Doppler processor using selective timing and filtering to perform elevation measurements along three sampling lanes A, B and C on the terrain covered by the cross-shaped channel pattern in accordance with time-delay response (TDR), amplitude monopulse (AM) and phase monopulse (PM) modes of operation. - View Dependent Claims (18, 19, 20)
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Specification