Polarization detector
First Claim
1. A radar polarization detector comprising:
- means adapted to receive electromagnetic signals having a plurality of signal components each having nonidentical predetermined polarizations for providing signals representative of said received signal components;
means coupled to said receiving means for processing said representative signals to establish time averages corresponding to said polarization of said signals and for providing signals representative of said time averages; and
means coupled to said processor means for comparing said parameter representative signals to predetermined threshold signals and for providing signals indicative of said time average representative signals having a signal level greater than said threshold signal.
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Abstract
An apparatus and method for detecting the polarization of signals reflected from targets immersed in clutter. Signals reflected from targets illuminated with quasimonochromatic electromagnetic signals such as FMCW radar are received by antennas responsive to orthogonally polarized components of the reflected signals. These received orthogonal signal components are then analyzed in a processor which detects the polarization of the reflected signal by estimating the Stokes parameters for the reflected signal. The estimated Stokes parameters may then be used to generate detection criteria that are compared to a predetermined threshold level. The presence of the target is indicated when the detection criteria level exceeds the level of the predetermined threshold.
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Citations
13 Claims
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1. A radar polarization detector comprising:
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means adapted to receive electromagnetic signals having a plurality of signal components each having nonidentical predetermined polarizations for providing signals representative of said received signal components; means coupled to said receiving means for processing said representative signals to establish time averages corresponding to said polarization of said signals and for providing signals representative of said time averages; and means coupled to said processor means for comparing said parameter representative signals to predetermined threshold signals and for providing signals indicative of said time average representative signals having a signal level greater than said threshold signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for detecting the presence of a radar target immersed in clutter comprising the steps of:
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illuminating said radar target with electromagnetic radiation to provide a signal reflected from said target; receiving electromagnetic radiation signal components of said reflected signal having predetermined non-identical polarizations; providing a signal representative of said signal components; processing said representative signals to establish time averages corresponding to the polarization of said signal components and provide signals representative of said time averages; and comparing said time average representative signals to predetermined threshold signals to provide signals indicative of said time average representative signals having a signal level greater than said threshold signals. - View Dependent Claims (10, 11, 12)
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13. A method as recited in claim 13 wherein the step of processing comprises the steps of:
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detecting the amplitude Av (t) of said first representative signal; detecting the amplitude Ah (t) of said second representative signal; squaring said first and second amplitude detected signal to provide first and second squared signals; subtracting said second squared signal from said first squared signal to determine the signal Ah2 (t)-Av2 (t); adding said first and second squared signal to determine the signal Ah2 (t)+Av2 (t); phase shifting said second representative signal by 90 degrees; multiplying said phase shifted signal by said first representative signal; filtering the product of said first representative signal and said phase shifted signal to select the term of the product corresponding to the sine of the phase difference of the first and second signal components; amplifying said sine term by a factor of four whereby the signal Ah (t)Av (t) sin (φ
h (t)-φ
v (t)) is determined;multiplying the first and second representative signals; filtering the product of said first and second representative signals to select the term of the product corresponding to the cosine of the phase difference of the first and second signal; amplifying said cosine term by a factor of four, whereby the signal Ah (t)Av (t) cos (φ
h (t)-φ
v (t)) is determined; andintegrating the signals Ah2 (t)+Av2 (t), Ah2 (t)-Av2 (t), Ah (t)Av (t) cos (φ
h (t)-φ
v (t)), and Ah (t)Av (t) sin (φ
h (t)-φ
v (t)) to obtain estimates of the Stokes parameters s0, S1, S2, and s3, respectively.
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Specification