Abstract: A Two-Stage Hybrid algorithm offers significant improvement in the false alarm rate and detection performance of Space-Time Adaptive Processing in non-homogeneous environments for both radar and digital communications. The first stage analyzes data from a range cell of interest by direct data domain processing, suppressing discrete interferers within the range cell of interest. The second stage implements a purely statistical STAP algorithm, preferably an enhanced version of the Joint-Domain Localized (“JDL”) statistical algorithm. For radar this second stage estimates the interference within the range cell of interest from the surrounding range cells. For a communications system, the second stage estimates the covariance matrix of the interference from the entire data block. For both radar and communications, an adaptive filter that suppresses the interference is generated from the estimate by second-order statistics.

Abstract: Spatial-temporal waveform diversity methods vary or modulate the far-field radiated waveform of a radar and/or communication antenna as a function of look direction (sidelobe structure). Radar detection performance and angle of arrival estimation are enhanced to deny a coherent reference to non-cooperative bistatic radars and coherent repeater jammer systems. In the most general case, the spatial-temporal modulated waveform varies as a function of angle, based upon the principles of multi-dimensional Fourier synthesis. Spatial-temporal denial is achieved with as few as two auxiliary antennas bracketing a main antenna. The same methods for spatial-temporal waveform diversity can also embed communications signals into the transmitted radar waveform for one-way simulcast of both waveform types. These same directionally dependent simulcast waveforms can incorporate navigation signals for enhanced precision engagement.

Abstract: A signal processing system applies space-time adaptive processing ("STAP") to an airborne surveillance Doppler radar comprised of a single-channel, rotating antenna. The STAP substantially improves signal-to-interference-plus-noise ratio ("SINR"), thereby improving the detection of weak targets.

Abstract: Apparatus and method for improving detection of targets in a radar system that employs adaptive filtering. A nonhomogeneity detector eliminates nonhomogeneous signals from the population of signals received. An adaptive filter weight controller estimates covariance matrices from only homogenous signals. Thus the apparatus and method improves the probability of detecting the presence or absence of a target at the same time that it decreases the probability of a false alarm by improving the performance of an adaptive filter. Though developed for airborne radar, the apparatus and method may be applied to the processing of any image.

Abstract: Range-Doppler ambiguity is eliminated from an ultra-wideband radar system by transmitting an ultra-wideband chirped pulse towards a moving target, and mixing it with the doppler-shifted chirped pulse which is received as a target echo return signal. Multioctave radar tracing systems can potentiality track stealth aircraft without ambiguity since pulses containing many frequencies can defeat narrow-band radar absorbing material coatings. The unambiguous range-doppler signal processing method mixes the chirped pulse to yield an instantaneous Doppler frequency (which indicates target velocity) and a rate of change in the instantaneous Doppler frequency (which indicates target acceleration).

Abstract: An artificial intelligence system improves radar signal processor performance by increasing target probability of detection and reducing probability of false alarms in a severe radar clutter environment. This utilizes advances in artificial intelligence and expert systems technology for the development of data analysis and information (signal) processors used in conjunction with conventional (deterministic) data analysis algorithms to combine radar measurement data (including observed target tracks and radar clutter returns from terrain, sea, atmospheric effects, etc.) with topographic data, weather information, and similar information to formulate optimum filter coefficients and threshold tests. Present fielded radar systems use one CFAR algorithm for signal processing over the entire surveillance volume. However, radar experiments have shown that certain CFAR algorithms outperform others in different environments.

Abstract: A radar system that includes an ultra wideband radar signal processor for electronically scanned arrays that utilizes frequency offset generation (FOG) to achieve beam steering as compared with phase shift and time delay techniques of conventional radars. The device comprises a transmit antenna, a chirp generator connected to the transmit antenna and a first summing circuit, a receiver antenna connected to the first summing circuit, a Doppler de-ramping chirp circuit connected to a second summing circuit, the output of the second summing circuit connected to an amplitude and weighting circuit and the output of the amplitude circuit connected to a spectrum analyzer of a Fast Fourier Transform (FFT) circuit. The signal processing consists of mixing the target returns with the transmitted signal to obtain a video beat note signal. This video beat note signal is mixed with a Doppler de-ramping chirp waveform which is matched to the desired target velocity.

Abstract: A broadband multi-element antenna having desirable phase, standing wave and polarization characteristics is disclosed. The antenna is arranged as a plurality of airfoil shaped elements located in radial planes about a central axis with the element peripheries collectively defining a horn shaped surface--centrally disposed of which is a ground plane member of preferably truncated conical shape which includes electrical feeding arrangements having in phase and out of phase element coupling. The antenna is suitable for radar, satellite, and other precision uses including military applications.

Abstract: A system is disclosed for use with radar systems so as to reduce the dynamic range requirement of the analog to digital converter through analog clutter cancellation prior to digitization. Clutter return estimates are formulated via modern digital signal processing techniques, converted to analog representation, and subtracted from the received waveform. Typically, the MTI cancellation is performed on the quadrature components of the received signal. The complex residue is then processed for target detection. This quadrature processing is not illustrated in the figures. In practice, sampling the received waveform prior to baseband down conversion, at an intermediate frequency, is also feasible. Digital synchronous detection and coherent MTI processing are then implemented in the digital signal processor. Rather than employ a radar signal processor which is either all analog or all digital it is beneficial to utilize hybrid schemes which capitalize on the advantages of both.

Abstract: A multi-octave bandwidth antenna is disclosed which radiates with variable polarizations using: a metal ground plane, first and second blade antenna elements, first and second coaxial transmission line feeds, and a 180.degree. hybrid coupler. The two blade antenna elements are fixed above the metal ground plane in proximity with each other, and fed respectively by the central conductors of the first and second coaxial transmission line feeds. The 180.degree. hybrid coupler has a sum and difference port to control the polarization of waveforms of the antenna.

Abstract: A Bi-Blade Antenna is disclosed which will radiate and receive multi-octave electromagnetic waveforms with century bandwidth (i.e. 100 to 1) using two blade antenna elements and a coaxial transmission line feed. The blade antenna elements each have a comparatively narrow throat, a mid-section called a mouth, and a tip. The two throats are fixed in proximity to each other and are fed by the coaxial line feed. The central conductor of the feed is connected to one throat while the outer coaxial conductor is connected to the second throat. The mouth is formed by an arc of constant radius to result in a low voltage standing wave ratio of about 1.19 to 1.