Pulse or digital communications – Systems using alternating or pulsating current – Angle modulation
Patent
1996-08-14
1999-02-02
Chin, Stephen
Pulse or digital communications
Systems using alternating or pulsating current
Angle modulation
375326, 375329, 370445, 370910, H04L 12413, H04L 2718
Patent
active
058675337
ABSTRACT:
An apparatus and a method for detecting a carrier signal of a phase shift keyed modulated signal. A first counter circuit generates a plurality of counts, with each count being a number of cycles of a reference frequency signal occurring between two consecutive rising edges of an intermediate frequency signal. A comparison circuit compares a first count of reference frequency cycles to a second count of reference frequency cycles when a difference between an initial count of reference frequency cycles and a first predetermined number is less than a second predetermined number. The first predetermined number represents a time period of one cycle of the nominal center frequency, and the first count and the second count respectively represent time periods of first and second cycles of a pair of consecutive cycles of the intermediate frequency signal. The comparison circuit generates a difference signal when a difference between the first count and the second count is less than a third predetermined number. A second counter circuit counts cycles of the intermediate frequency signal and generates a carrier detect signal when a count of the intermediate frequency signal cycles equals a fourth predetermined number.
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Bracco Michael J.
Camp, Jr. William O.
Fleek Arthur E.
Chin Stephen
Flynn John D.
Gluck Jeffrey W.
International Business Machines - Corporation
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