Inventors:
William Rafferty - Pasadena CA
Gary J. Saulnier - Clifton Park NY
Assignee:
General Electric Company - Schenectady NY
International Classification:
H03D 300
Abstract:
A variable-delay, sine-cosine non-coherent demodulator recovers digital data angle-modulated upon a radio-frequency (RF) carrier signal, by frequency conversion of the carrier signal to a selected IF frequency, which is ideally equal to one-fourth of a sample frequency supplied to the demodulator. The IF signal is sampled at the sample frequency, and the samples are then sorted to provide a pair of baseband quadrature-phased I and Q signals. Each of the I and Q signals is delayed by a variable first delay T. sub. 1 to provide first-delayed in-phase I. sub. 1 and first-delayed quadrature-phased Q. sub. 1 signals. These signals are then delayed by a second delay T. sub. 2 to provide twice-delayed in-phase I. sub. 2 and twice-delay quadrature-phase Q. sub. 2 signals. The sum of the two delays is a constant related to the sample frequency, which itself is related to the data bit rate, but the first delay T. sub.