Constant false alarm rate radar system and method of operating the same

In a radar which is operative to transmit signals comprising a train of sub-pulses with a predetermined phase-coded pattern and which derives the in-phase (I) and quadrature (Q) components of the received echo signals with respect to a local reference oscillator, said receiver utilizing phase discrimination constant false alarm rate (CFAR) techniques for detection of desired echo signals in the presence of undesired interference, the improvement being a system comprising:

• a phase angle sensor for measuring the phase angle of said received echo signal with respect to said local reference oscillator as one of at least eight predetermined phase angle representations based on the relative polarity and magnitude of the derived I and Q vector components of the received echo signals;
• means for sampling the measured phase angle representations of the received echo signals at times corresponding to the sub-pulse spacing of the phase-coded pattern of the transmitted signals;
• first means for deriving the difference in phase angle representations between that sampled and that transmitted for the corresponding sub-pulses of the phase-coded pattern of the transmitted signals;
• second means for deriving the sine and cosine values of the derived difference in phase angle representations for said sub-pulses of the phase-coded pattern;
• means for accumulating the derived sine values corresponding to the sub-pulses of the phase coded pattern and for accumulating the derived cosine values corresponding to the sub-pulses of the phase coded pattern;
• and
• third means for deriving a signal which is representative of a correlation of the measured phase pattern of the echo signal with the phase pattern transmitted based on a function of the accumulated derived sine and cosine values.