Communications: directive radio wave systems and devices (e.g. – Testing or calibrating of radar system – By monitoring
Patent
1989-11-09
1990-11-06
Tarcza, Thomas H.
Communications: directive radio wave systems and devices (e.g.,
Testing or calibrating of radar system
By monitoring
342128, H04B 102
Patent
active
049689681
ABSTRACT:
A system is disclosed for measuring and correcting for waveform modulation errors in a radar system employing FM signals and a digitally controlled waveform generator. The system relies on the assumption that the transmitter and other waveform phase and amplitude error contributions are slowly varying with respect to the radar mode data collection time and that instantaneous pulse-by-pulse correction is not necessary. During a calibration mode, a small portion of the transmitter output is input into the receiver and mixed with the waveform generator signal, with the waveform modulation being removed from the mixer signal, such that the mixer signal is at a constant IF but with phase and amplitude variations that result from the distortions. The radar digital processor measures these distortions, and during normal radar operation predistorts the waveform generator signal with phase distortions in antiphase with the measured distortions to compensate for the measured distortions. Amplitude distortions are compensated by control of a variable attenuator device. As a result, the system compensates for the exciter and transmitter distortions as well as distortions introduced by the receiver input circuitry.
REFERENCES:
patent: 4160958 (1979-07-01), Mims et al.
patent: 4359779 (1982-11-01), Levine
patent: 4584710 (1986-04-01), Hansen
patent: 4692766 (1987-09-01), Rolfs
"Digital Generation of Wideband Linear FM Waveforms", R. W. Hopwood, R. A. Tracy, Westinghouse Electric Corporation, pp. 111-113.
"A Direct Digitally Synthesized Exciter Achieving Near Theoretical Performance for an Operation SAR System", W. D. Gallaway et al., Environmental Research Institute of Michigan.
Alkov Leonard A.
Denson-Low Wanda K.
Hellner Mark
Hughes Aircraft Company
Tarcza Thomas H.
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