UHF synthetic aperture radar
First Claim
1. A method of penetrating foliage by a radar signal, comprising the steps of:
- generating a steerable RF output signal in the UHF frequency range,transmitting and receiving the RF output signal for mapping the location of a ground target with said RF output signal, said RF output signal generating transmit and receive antenna patterns having a front or mainlobe and a backlobe;
generating a null in the backlobe of at least one of the antenna patterns; and
steering the null in the backlobe so as to obtain directivity of the radar signal.
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Accused Products
Abstract
A synthetic aperture radar (SAR) which operates at UHF frequencies and which includes a two element antenna. The SAR generates a null in the backlobe of the antenna pattern at the location of a target which is steered rather than trying to obtain directivity in the mainlobe. Both analog and digital implementations are provided. In the analog approach, required phase shifts are performed at a frequency higher than the RF output frequency and the receive and transmit nulls are steered separately to increase the width of the null so as to allow for wider SAR swaths. The digital implementation involves steering the null only on receive and multiplying fast time samples by a complex phase correction similar to that used in the analog approach to form the beam. The phase correction is also performed prior to range resolution which employs "stretch" processing, so as to achieve high range resolution.
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Citations
14 Claims
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1. A method of penetrating foliage by a radar signal, comprising the steps of:
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generating a steerable RF output signal in the UHF frequency range, transmitting and receiving the RF output signal for mapping the location of a ground target with said RF output signal, said RF output signal generating transmit and receive antenna patterns having a front or mainlobe and a backlobe; generating a null in the backlobe of at least one of the antenna patterns; and steering the null in the backlobe so as to obtain directivity of the radar signal. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A synthetic aperture radar system for penetrating foliage, comprising:
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an exciter circuit for generating an RF radar output signal in the UHF frequency range, a phased array antenna for transmitting and receiving said radar output signal for mapping the location of a ground target, said radar signal having a transmit antenna pattern and a receive antenna pattern, each said pattern including a front or mainlobe and a backlobe; circuit means generating a null in the backlobe of at least one of the antenna patterns; and
,circuit means steering the null in the backlobe so as to obtain directivity. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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Specification