Digital FSK demodulator with offset cancellation

U.S. Patent Number: 5394109

Abstract: A digital FSK demodulator includes a quadrature phase detector for detecting space and mark tones used in FSK signals. Due to its inherent characteristics, a telephone loop in which the demodulator is used produces unequal amplitudes in detected mark and space tones. The inequality or offset must be cancelled so that a proper timing signal can be recovered from the FSK signal. The demodulator includes a digital compensation circuit for off-hook and on-hook offset cancellation.

Inventors: Simard; Frederic J. M. A. (Hull, CA)

Assignee: Northern Telecom Limited (Montreal, CA)

Application Number: 08/197,912

Issued: 1995-02-28

Expired: 2007-02-28

Classes: 329/300 ; 375/317

Field of search: 329/300,301,302,303 375/80,82,88,76

Click the image above to view patent images at uspto.gov within a frame.

Click here for the fulltext page on uspto.gov within a frame.