Paul E Armstrong

US Patent:

43331700, Jun 1, 1982

Filed:

Nov 21, 1977

Appl. No.:

5/853207

Inventors:

Lemuel P. Mathews - Rancho Palos Verdes CA
Charles A. Lohman - Fullerton CA
Paul R. Armstrong - Yorba Linda CA

Assignee:

Northrop Corporation - Los Angeles CA

International Classification:

G01S 380

US Classification:

367125

Abstract:

A plurality of acoustical transducers such as microphones are placed in appropriate array so that they are capable of detecting sonic energy emanating from an acoustical source such as an aircraft or a ground vehicle. The outputs of the transducers are sequentially sampled and multiplexed together, the time multiplexed signals then being converted from analog to digital form in an analog/digital converter. The output of the analog/digital converter is fed to a fast Fourier transformer (FFT), which transforms these signals to Fourier transform coefficients represented as real and imaginary (cosine and sine) components. The output of the fast Fourier transformer is fed to a digital processor. In this processor, the power and phase of each frequency bin for each microphone output is determined and the phase differences between signals received by pairs of microphones for each frequency bin of interest are determined. Each of these phase difference signals is divided by the frequency of their associated bin to provide a "phase difference slope" for each frequency bin and for each microphone pair.