Multiplex communications – Generalized orthogonal or special mathematical techniques – Quadrature carriers
Patent
1995-06-07
1997-11-11
Marcelo, Melvin
Multiplex communications
Generalized orthogonal or special mathematical techniques
Quadrature carriers
375224, 375235, H04L 2734
Patent
active
056871635
ABSTRACT:
An efficient method and apparatus for determining, recording, and analyzing the phase history of a Line-in signal. The Line-in signal is coupled to a conventional demodulator. I and Q components are output by the conventional demodulator and coupled to an IQ quantizer. The IQ quantizer determines a quadrant on an I/Q plot from the amplitude of each component. A histogram is generated which indicates in which quadrant the Line-in signal was for a first sample, and in which quadrant the Line-in signal was for a second sample, the second sample having been taken immediately after the first sample. From this histogram, the number of times the Line-in signal transitions from one quadrant to another over a predetermined period of time is known. If the number of times the input signal crosses one of the axis of the I/Q plot in a first direction is greater than the number of times the input signal crosses that axis in the opposite direction, then the frequency of the Line-in signal differs from the frequency of the In-phase reference signal and the Quadrature reference signal. The frequency of the Line-in signal is directly related to the difference between the number of times the signal crosses an axis of the I/Q plot in a first direction, minus the number of time the signal crosses that axis of the I/Q plot in the opposite direction. The present invention also determines whether the Line-in signal represents a particular signaling pattern, such as the well-known AA pattern defined in the V.32 standard.
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Fox Michael W.
Wang David T. K.
Cirrus Logic Inc.
Greenhaus Bruce W.
Jaquez Martin J.
Marcelo Melvin
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