Raytheon Company

Hughes Aircraft Company

Charles J Mott

Clifton Quan

Trung T Nguyen

Edmond E Griffin, Ii

A cancellation technique embodied in a system and a radar signal processing method that is employed to detect near-range targets. The present invention uses a frequency-modulation continuous-wave (FMCW) or stepped frequency waveform and is capable of detecting near-range targets that would normally be obscured by transmitter leakage and internal reflections. This cancellation technique works by transmitting one or more reference ramp signals and then subtracting the coherent average of the transmitted reference ramp signals from a group of succeeding transmitted and received ramp return -signals. The resulting group of FM ramp return signals is noncoherently integrated to achieve more stable target detection statistics. More particularly, the present technique implements the following processing steps. Generating a predetermined number of reference ramp signals. Coherently averaging target return signals corresponding to transmitted reference ramp signals to produce a reference average signal. Transmitting additional ramp signals. Subtracting the reference average signal from each ramp return signal to produce a cancelled ramp signal. Fourier transforming each cancelled ramp signal. Magnitude detecting the Fourier transform signal. Noncoherently integrating the magnitude detected signal. Thresholding the integrated signal. Centroiding the thresholded signal, wherein centroid position is indicative of the range to the nearest target. Displaying target data for a target-whose position is less than a predetermined cutoff range.

Near-range microwave detection for frequency-modulation continuous-wave and stepped frequency radar systems

Low frequency radiating elements are embedded in a flared notch array. The flared notch array forms a series of parallel troughs in which absorptive loads are placed to reduce the antenna radar cross section. The low frequency radiating elements are embedded in the array transverse to the troughs at or below the level of the absorptive loads, and excite several troughs. The absorptive load material is absorptive in the operating band of the flared notch array, but appears as a relatively low loss dielectric at the lower frequencies of operation of the low frequency radiating elements. The low frequency radiating elements can perform Identify Friend or Foe functions in the UHF and L-band regions of the spectrum, while the flared notch array operates at X-band.

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El Segundo, CA, United States of America

Charles J Mott