VIP doppler filter bank signal processor for pulse doppler radar
AssigneeWestinghouse Electric Corp.
InventorsJohn W. Taylor, Jr., Raymond G. Martin
Life of this patent
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Abstract
A low PRF pulse doppler radar system utilizing a VIP digital filter bank signal processor to suppress echoes from terrain, rain, and chaff, and pass echoes from aircraft moving at higher speeds is disclosed. Each of a plurality of VIP filters individually provides high attenuation to undesired signals over designated frequency bands, the width of which are a large fraction of 1/T.sub.av where T.sub.av is the average interpulse period. Little or no attenuation of desired signals having doppler frequencies greater than 1/T.sub.av occurs. The outputs of the plurality of filters are desensitized to prevent false alarm from clutter, and the presence of a desired radar pulse echo is determined by a comparison with a threshold level.
Claims10
In a pulse doppler radar system, the combination comprising:
- means for generating radar pulses at predetermined variable interpulse periods;
- means for receiving the echo pulses;
- means for converting the sampled pulses to digital words;
- a plurality of digital filters, each filter having I and Q components;
- said plurality of digital filters being operative to receive the digital words in sequence at the sample times, each of said filters being constituted to provide attenuation to pulse echoes from objects less than a predetermined velocity over a different predetermined doppler frequency band, each said filter having a single rejection notch, the width of which is a large fraction of the reciprocal of the average period between the sampled pulses, each said filters being constituted also to provide substantially no attenuation to pulse echoes having doppler frequencies greater than the reciprocal of said average period;
- means responsive to clutter interference in each filter to desensitize the outputs of the respective filter to prevent false alarms from clutter;
- and
- means to detect the output values of the desensitizing means.
In a pulse doppler radar system, the combination comprising:
- means for generating radar pulses at time intervals having variable interpulse periods;
- means for receiving the pulse echoes;
- means for converting the pulse echoes to digital words;
- a plurality of digital filters each having I and Q components, including a storing means operative to store a plurality of input digital words;
- each said filter having a single rejection notch, the width of which is a large fraction of the reciprocal of the average period between transmitted pulses to provide substantial attenuation to signals over predetermined doppler frequency bands having widths less than the reciprocal of the average period between transmitted pulses and substantially no attenuation to echo pulses having doppler frequencies greater than the reciprocal of the average period;
- means to store a set of weighting coefficients for each filter, each coefficient being selected to reject echo pulses of predetermined doppler frequencies when applied to a predetermined plurality of stored digital words;
- means to multiply a predetermined set of the stored weighting coefficients by the stored digital words the weighting coefficients being selected in accordance with the variable interpulse periods of transmission of the echo pulses corresponding to the time separation of the digital words in each filter;
- means to output the sum of the weighted words of each filter;
- means for each filter responsive to the weighted words representative of clutter interference to desensitize the filter output to prevent excessive clutter false alarm;
- means to integrate the outputs of the desensitizing means;
- and
- means to detect the integrated outputs above a predetermined threshold value.
Dependencies are inferred from the claim text.