ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

4aUW11. Asymptotic behavior of the matched-phase noise filter in the limit of low signal-to-noise ratio.

B. Edward McDonald

Gregory J. Orris

Naval Res. Lab., Washington, DC 20375-5000

It has been shown elsewhere that information about the shape of the noise spectrum with no phase knowledge can be used to construct a noise rejection algorithm which we call the matched-phase filter. Here, it is demonstrated that to first order in the signal-to-noise ratio (SNR), the matched-phase filter is capable of improving an arbitrarily low SNR (<<1) to order unity when the spectrum of the noise is known exactly. This analysis accounts for properties of numerical results with computer-generated signal and noise, with SNR values below -100 dB. Since computers have dynamic ranges far in excess of audio equipment, these results in an actual experiment would be limited by the dynamic ranges of the equipment used. Also shown are examples illustrating the performance of the algorithm when the noise spectrum is known only approximately.