Brian M Mccarthy

US Patent:

56300166, May 13, 1997

Filed:

Mar 7, 1996

Appl. No.:

8/614777

Inventors:

Kumar Swaminathan - Gaithersburg MD
Brian M. McCarthy - Lafayette Hill PA

Assignee:

Hughes Electronics - Los Angeles CA

International Classification:

G10L 900

US Classification:

395 237

Abstract:

A digital discontinuous cellular communication system has a transmitter that transmits two frames of data following detection of voice inactivity. A receiver includes a comfort noise generator that uses the two frames of data to output noise to the speaker during period of voice inactivity. The comfort noise generator includes synthesis codebook with samples scaled by actual background noise and excitation codebook with samples filtered and scaled by the background noise that are combined to produce comfort noise having attributes and loudness level of the received background noise prior to interruption of transmission. The scaled signals are weighted to vary the loudness level and spectral attributes.

US Patent:

55375090, Jul 16, 1996

Filed:

May 28, 1992

Appl. No.:

7/890747

Inventors:

Kumar Swaminathan - Gaithersburg MD
Brian M. McCarthy - Lafayette Hill PA

Assignee:

Hughes Electronics - Los Angeles CA

International Classification:

G10L 900

US Classification:

395 237

Abstract:

A digital discontinuous cellular communication system has a transmitter that transmits two frames of data following detection of voice inactivity. A receiver includes a comfort noise generator that uses the two frames of data to output noise to the speaker during period of voice inactivity. The comfort noise generator includes synthesis codebook with samples scaled by actual background noise and excitation codebook with samples filtered and scaled by the background noise that are combined to produce comfort noise having attributes and loudness level of the received background noise prior to interruption of transmission. The scaled signals are weighted to vary the loudness level and spectral attributes.

US Patent:

53331915, Jul 26, 1994

Filed:

Apr 22, 1993

Appl. No.:

8/051189

Inventors:

Brian M. McCarthy - Lafayette Hill PA

Assignee:

InterDigital Technology Corporation - Wilmington DE

International Classification:

H04M 900

US Classification:

379386

Abstract:

A method of operating a digital signal processor to detect DTMF tones in a digital voice telephone system in which the digitally encoded signals appearing on the telephone channel are decimated to compress the spectrum to be monitored for the appearance of call signalling tones. The signals received in a decimated block are "correlated" or convolved with one another on a forward and backward time-shifted basis and each forward and backward correlation product is summed to form the elements of a 5. times. 5 modified covariance matrix. The modified covariance matrix exhibits the desirable property that its eigenvectors will be symmetric. Since all eigenvectors of the modified covariance matrix are orthogonal and the eigenvectors associated with the signal span the signal subspace, the signal subspace is orthogonal to the eigenvector associated with the noise. The dot product of the noise eigenvector with the signal subspace is set to zero. The roots of the resultant polynomial identify the frequencies of the DTMF tones, if in fact the same were present in the received signal.