Adaptive matched filter

An adaptive matched filter which provides an output signal having an enhanced signal-to-noise ratio for varying noise power distributions for signals having known spectral content embedded in the noise, comprising:

• Fourier transform circuitry for providing signals representing the Fourier transform of signals applied thereto, said applied signals comprising noise signals and signals embedded therein having a known spectral content;
• means for providing an output signal indicative of the noise power of said Fourier transform representing signals;
• analog-to-digital conversion means for converting analog signals provided by said output signal providing means into digital signals;
• computer means which stores data indicative of said signals of known spectral content for receiving said digital signals and processing said digital signals in a predetermined manner to provide a signal indicative of the noise power spectral distribution of said signals, and further processing said noise power signals and said stored data to provide signals representing the transfer function of said adaptive matched filter;
• inverse Fourier transform circuitry for providing signals representing the inverse Fourier transform of signals representing said transfer function;
• and
• correlation means for combining the signals applied to the adaptive matched filter with signals representing said transfer function in a predetermined manner to provide an output signal which has an enhanced signal-to-noise power ratio.

A method of processing signals that enhances the signal-to-noise power ratio of the signals for varying noise power distributions, where the signals contain known signals and noise signals, the method comprising the steps of:

• (a) obtaining signals that represent the Fourier transform of the signals that contain known signals and noise signals;
• (b) estmating a power spectral density of the noise signals contained in the signals that contain known signals and noise signals;
• (c) calculating a transfer function by using both estimates of the power spectral density derived in step (b) and stored information that characterizes the known signals and providing signals that represent the transfer function;
• (d) performing an inverse Fourier transform upon the transfer function signals to produce impulse response signals;
• and
• (e) correlating the signals that contain known signals and noise signals with the impulse response signals to produce a filter output signal that has an enhanced signal-to-noise power ratio.