Radar system having quadrature phase detector compensator
AssigneeRaytheon Company
InventorsFrederick E. Churchill, George W. Ogar, Bernard J. Thompson
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Abstract
Method and apparatus are disclosed for correcting amplitude and phase imbalances between the "in phase" and "quadrature" channels of a digital signal processor by determining a correction coefficient from a test signal periodically introduced into the quadrature phase detector of a radar system. The frequency spectrum of the signal at the output of the phase detector in response to each such test signal is utilized to produce a correction coefficient for application to radar return signals passing through the phase detector during normal radar operation, thereby providing true quadrature radar return signals for digital processing.
Claims4
A method for correcting unbalances between "in phase" and "quadrature" channels of a quadrature phase detector in a digital signal processing radar system comprising the steps of:
- a. periodically impressing a test signal having a frequency component f.sub.D on the quadrature phase detector;
- b. converting signals produced at the output of the quadrature phase detector in response to such test signal into a set of N complex digital words, such signals being converted at a rate M where M is an integral multiple of f.sub.D and N is equal to the ratio of the rate M to the frequency component f.sub.D ;
- c. determining the frequency spectrum described by the set of N complex digital words;
- d. deriving correction coefficients in accordance with the determined frequency spectrum;
- and,
- e. applying such correction coefficients to signals produced at the output of the quadrature phase detector in response to radar return signals.
In a digital processing radar system wherein a quadrature phase detector is provided to demodulate radar return signals, such demodulated radar signals then being sampled and converted into a set of complex digital words, at a predetermined rate M, an improved apparatus for correcting imbalances between channels of such quadrature phase detector, comprising:
- a. means for periodically impressing a test signal having a frequency component f.sub.D on the quadrature phase detector, the frequency f.sub.D being an integral submultiple of M, such phase detector producing an output signal in response thereto;
- and
- b. a compensator responsive to the set of complex digital words and the output signal for deriving correction coefficients.
Dependencies are inferred from the claim text.