Complementary-sequence pulse radar with matched filtering following doppler filtering

Claim 1

A method for detecting anomalies, comprising the steps of: transmitting toward an anomaly a first pulse set consisting of a predetermined plurality of first pulses, said pulses of said first set being dispersed in time pursuant to a predetermined phase code; transmitting toward said anomaly a second pulse set consisting of said predetermined plurality of second pulses, said pulses of said second set being dispersed in time pursuant to a second phase code selected to be complementary to said predetermined phase code in a manner such that, after pulse compression of said first and second pulses, the resulting range sidelobes are substantially equal in amplitude and opposite in sign; receiving echoes of said first and second pulses reflected from said anomaly to produce received first and second pulse sets; Doppler filtering said received first and second pulse sets into a plurality of frequency components to produce a sequence of range values for each frequency component, each of said sequence of range values including said first and second code sequences; for each said frequency components, matched filtering each of said first and second code sequences of range values to produce first and second compressed pulses; summing said first and second compressed pulses; and after said Doppler filtering step, converting at least some of said plurality of frequency components to a common frequency.

Claim 2

A method for detecting anomalies, comprising the steps of: transmitting toward an anomaly a first pulse set consisting of a predetermined plurality of first pulses, said pulses of said first set being dispersed in time pursuant to a predetermined phase code; transmitting toward said anomaly a second pulse set consisting of said predetermined plurality of second pulses, said pulses of said second set being dispersed in time pursuant to a second phase code selected to be complementary to said predetermined phase code in a manner such that, after pulse compression of said first and second pulses, the resulting range sidelobes are substantially equal in amplitude and opposite in sign; receiving echoes of said first and second pulses reflected from said anomaly to produce received first and second pulse sets; Doppler filtering said received first and second pulse sets into a plurality of frequency components to produce a sequence of range values for each frequency component, each of said sequence of range values including said first and second code sequences; for each said frequency components, matched filtering each of said first and second code sequences of range values to produce first and second compressed pulses; summing said first and second compressed pulses; and after said Doppler filtering step, converting at least some of said plurality of frequency components to a common frequency.

Claim 9

An apparatus for detecting targets, comprising: code generating means for generating first and second complementary code sequences, said first and second complementary codes being selected so their autocorrelations have main lobes of the same polarity, and sidelobes of the same amplitude and mutually opposite polarity; transmitting means coupled to said code generating means for transmitting electromagnetic pulses modulated by said first and second complementary codes; receiving means for receiving echoes of said pulses reflected from a target, for producing a sequence of range values of received first and second pulse sets, said received first pulse set being modulated by said first code sequence, and said received second pulse set being modulated by said second code sequence; Doppler filtering means including a plurality of Doppler channels, said Doppler filtering means being coupled to said receiving means, for filtering said received first and second pulse sets into a plurality of frequency components, each associated with one of said Doppler channels, for producing in at least one of said Doppler channels, if the radial velocity of said target is appropriate, a sequence of range values including said first and second code sequences; matched filtering means coupled to each of said Doppler channels, for selectively matched filtering said first and second code sequences to thereby produce first and second compressed pulses, respectively; summing means coupled to said matched filtering means for summing together said first and second compressed pulses, whereby the main lobes of said compressed pulses add, and the sidelobes tend to cancel; wherein said matched filtering means comprises single pole, double throw switch means coupled to each of said Doppler channels for selectively switching said sequence of range values including said first code sequence to a first path, and for selectively switching said sequence of range values including said second code sequence to a second path; first code matched filter means matched to said first code sequence coupled to said first path; and second code matched filter means matched to said second code sequence coupled to said second path.

Claim 10

An apparatus for detecting targets, comprising: code generating means for generating first and second complementary code sequences, said first and second complementary codes being selected so their autocorrelations have main lobes of the same polarity, and sidelobes of the same amplitude and mutually opposite polarity; transmitting means coupled to said code generating means for transmitting electromagnetic pulses modulated by said first and second complementary codes; receiving means for receiving echoes of said pulses reflected from a target, for producing a sequence of range values of received first and second pulse sets, said received first pulse set being modulated by said first code sequence, and said received second pulse set being modulated by said second code sequence; Doppler filtering means including a plurality of Doppler channels, said Doppler filtering means being coupled to said receiving means, for filtering said received first and second pulse sets into a plurality of frequency components, each associated with one of said Doppler channels, for producing in at least one of said Doppler channels, if the radial velocity of said target is appropriate, a sequence of range values including said first and second code sequences; matched filtering means coupled to each of said Doppler channels, for selectively matched filtering said first and second code sequences to thereby produce first and second compressed pulses, respectively; summing means coupled to said matched filtering means for summing together said first and second compressed pulses, whereby the main lobes of said compressed pulses add, and the sidelobes tend to cancel; wherein said matched filtering means comprises single pole, double throw switch means coupled to each of said Doppler channels for selectively switching said sequence of range values including said first code sequence to a first path, and for selectively switching said sequence of range values including said second code sequence to a second path; first code matched filter means matched to said first code sequence coupled to said first path; and second code matched filter means matched to said second code sequence coupled to said second path.