USA As Represented by Secretary of the Navy

George M Dillard

Henry F Taylor

Barry R Hunt

The present invention is digital open-loop sidelobe canceller for decorreing signals by removing correlated components. The invention has inputs for receiving n pairs of digital sample values representing the digitized in-phase components and quadrature-phase components of the output of the main radar receiver and also of at least one auxiliary radar receiver. These data samples are stored in memory for later processing and are also furnished to computation networks which calculate weighting coefficients which are processed as real numbers. These real number weighting coefficients are utilized to subtract calculated real number values from the sample values representing the digitized in-phase and quadrature-phase components of the output of the main radar receiver.

Digital sidelobe canceller with real weights

Magnetic drum storage for the track before detect system

A fiber optic delay line filter receives light energy input signals repretative of any form of temporally varying signals such as electrical or acoustical, for example. A plurality of fiber optic light paths each having a determinably variant optical propagation delay, receives and transmits the light energy signals. A photo responsive means receives the delayed output light energy signals transmitted by the plurality of fiber optic light paths and produces a single electrical output signal as a function of the sum of the delayed output light energy signals, thus performing a filtering or correlation function. In a preferred embodiment, an injection laser or light emitting diode may be employed as the means for converting the temporally varying input signals to commensurate light energy signals. In a variant embodiment, a single fiber optic light path, having a partially reflective surface at each end, gives effect to multiple reflective transmissions along the length of the fiber optic light path which are then detected by a photo responsive device, providing a narrowband filter output as a function of the length and number of multiple reflective transmissions.

Fiber optic delay line filter

An apparatus for estimating the mean level of a stochastic process such as ould be observed at the output of a radar, communications, or sonar receiver and for using the mean level to provide a threshold with which possible signal samples are compared to determine the presence or absence of the signal. The estimated mean level is used in lieu of a priori information when it is unreasonable to assume that the characteristics of the stochastic process are known. A first order recursive filter receives signal samples and provides an output which is proportional to the mean of the stochastic process. The output of the first order recursive filter Y.sub.n is multiplied by the factor T such that the product TY.sub.n is a threshold quantity which is compared with the input signal samples X.sub.n. When X.sub.n exceeds TY.sub.n an output is indicated.

Recursive filter mean-level detector

A wholly digital system for computing the discrete Fourier transform of sequentially received data in a recursive fashion. Two parallel shift registers store and shift the real and imaginary components of the complex number X.sub.k + iY.sub.k. The data in the parallel registers are successively shifted one bit per strobe in response to receipt of new data. Additional logic operates recursively on successive data inputs to compute the discrete Fourier transform.

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San Diego, CA, United States of America

George M Dillard