METHODS AND APPARATUS FOR DETERMINATION OF A FILTER CENTER FREQUENCY
First Claim
1. A method for calculating a center frequency and a bandwidth for a radar doppler filter, the center frequency and bandwidth calculated to provide radar performance over varying terrain and aircraft altitude, pitch, and roll by keeping a doppler swath centered in an antenna beam, said method comprising:
- receiving an antenna mounting angle, a slant range, and velocity vectors in body coordinates;
calculating a range swath doppler velocity, and a track and phase swath bandwidth using the antenna mounting angle, slant range, and velocity vectors;
calculating a phase swath doppler velocity based at least in part on the range swath doppler velocity and the track and phase swath bandwidth;
calculating a range swath center frequency based on the range swath doppler velocity;
calculating a phase swath center frequency based on the phase swath doppler velocity; and
calculating a level and verify swath bandwidth based upon the track and phase swath bandwidth.
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Abstract
A method for calculating a center frequency and a bandwidth for a radar doppler filter is herein described. The center frequency and bandwidth are calculated to provide radar performance over varying terrain and aircraft altitude, pitch, and roll. The method includes receiving an antenna mounting angle, a slant range, and velocity vectors in body coordinates, calculating a range swath doppler velocity, a track and phase swath bandwidth, and a phase swath doppler velocity. The method continues by calculating a range swath center frequency based on the range swath doppler velocity, calculating a phase swath center frequency based on the phase swath doppler velocity, and calculating a level and verify swath bandwidth based upon the track and phase swath bandwidth.
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Citations
23 Claims
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1. A method for calculating a center frequency and a bandwidth for a radar doppler filter, the center frequency and bandwidth calculated to provide radar performance over varying terrain and aircraft altitude, pitch, and roll by keeping a doppler swath centered in an antenna beam, said method comprising:
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receiving an antenna mounting angle, a slant range, and velocity vectors in body coordinates;
calculating a range swath doppler velocity, and a track and phase swath bandwidth using the antenna mounting angle, slant range, and velocity vectors;
calculating a phase swath doppler velocity based at least in part on the range swath doppler velocity and the track and phase swath bandwidth;
calculating a range swath center frequency based on the range swath doppler velocity;
calculating a phase swath center frequency based on the phase swath doppler velocity; and
calculating a level and verify swath bandwidth based upon the track and phase swath bandwidth. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A processor configured to:
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receive an antenna mounting angle, a slant range, and velocity vectors in body coordinates;
calculate a range swath doppler velocity, and a track and phase swath bandwidth using the antenna mounting angle, slant range, and velocity vectors;
calculate a phase swath doppler velocity based at least in part on the range swath doppler velocity and the track and phase swath bandwidth;
calculate a range swath center frequency based on the range swath doppler velocity;
calculate a phase swath center frequency based on the phase swath doppler velocity; and
calculate a level and verify swath bandwidth based upon the track and phase swath bandwidth.
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11. A swath band pass filter, said filter comprising a first order filter, said filter configured to center on a doppler frequency and operate according to Eo=(A0/B0)×
- En−
(A0/B0)×
En×
Z−
2−
(B1/B0)×
Eo×
Z−
1(B2/B0)×
Eo×
Z−
2, where En is an input signal, A0 is 2×
Fs×
Wb, B0 is (4×
Fs2)+(2×
Fs×
Wb)+(Wl×
Wu), B1 is (2×
Wl×
Wu)−
(8×
Fs2), and B2=(4×
Fs2)−
(2×
Fs×
Wb)+(Wl×
Wu), and Wb=2π
B, a bandwidth in radians, Wu=2π
×
(Fc+B/2), an upper 3 db point of said filter in radians, and Wl=2π
×
(Fc−
B/2), a lower 3 db point of said filter in radians.
- En−
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12. A radar signal processing circuit comprising:
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a radar gate correlation circuit configured sample radar data at a sampling rate;
a correlation bass pass filter configured to filter non-zero gated radar return samples and ignore zero amplitude samples;
a mixer configured to down sample an in-phase component and a quadrature component of the filtered signal to a doppler frequency;
a band pass filter centered on the doppler frequency; and
a processor configured to determine a center frequency for said band pass filter. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for centering a doppler swath within an antenna beam, said method comprising:
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controlling a swath filter center frequency based on aircraft velocity; and
controlling swath filter bandwidth based on aircraft velocity such that a charge time for the filter is equal to the time that the aircraft takes to fly across the doppler swath. - View Dependent Claims (22, 23)
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Specification