Complementary-sequence pulse radar with matched filtering and Doppler tolerant sidelobe suppression preceding Doppler filtering

A radar apparatus for detecting targets, comprising:

• code generating means for generating first and other complementary code sequences, said complementary code sequences being selected so their autocorrelations have main lobes of the same polarity, and sidelobes which, when summed with the corresponding sidelobes of others of said complementary code sequences, tend to cancel;
• transmitting means coupled to said code generating means for transmitting electromagnetic pulses modulated by said complementary code sequences;
• receiving means for receiving echoes of said pulses reflected from a target, for producing a sequence of range values of received first and succeeding pulse sets, said received first pulse set being modulated by said first code sequence, and said received succeeding pulse sets being modulated by said other code sequences;
• matched filtering means coupled to said receiving means, for selectively matched filtering said code sequences to thereby produce compressed pulses, respectively;
• summing means coupled to said matched filtering means for summing together said compressed pulses, whereby the main lobes of said compressed pulses add, and the sidelobes tend to cancel, thereby producing range-sidelobe suppressed range pulses;
• and
• Doppler filtering means including a plurality of Doppler channels, said Doppler filtering means being coupled to said summing means, for filtering said received range-sidelobe-suppressed range pulses 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-sidelobe suppressed range values.

An apparatus, comprising:

• a code generator for generating complementary codes, said codes being selected so that their autocorrelation functions have main lobes of the same polarity, and so that their sidelobes tend to cancel;
• a transmitter coupled to said code generator for transmitting signals modulated by said codes;
• a receiver for receiving echoes of said signals reflected from an anomaly, for producing a sequence of range values of received signal sets, said received first signal set being modulated by said first code, and said received succeeding signal set being modulated by said succeeding codes;
• a plurality of mixers and coupled oscillators for removing Doppler phase shift along the range dimension to which are coupled said received first code set and succeeding code sets;
• a plurality of single pole, multiple throw switches coupling the said received code sets to a corresponding plurality of matched filters for matched filtering said code sets to produce a corresponding plurality of time compressed pulses;
• a plurality of delay and summing means to align such time compressed pulses so that their main lobes add and so that their sidelobes tend to cancel;
• a pulse-to-pulse Doppler filter bank including a plurality of pulse-to-pulse Doppler channels;
• coupling means whereby each of the plurality of said time compressed, delayed and summed pulses is coupled to the corresponding channel of said pulse-to-pulse Doppler filter bank, said filter bank Doppler channels filtering signal sets into a like plurality of frequency components, each of said frequency components being associated with one of said Doppler channels, for producing, if the anomaly radial velocity is appropriate, a sequence of range values in at least one of said Doppler channels.