Detectors

Details Detectors Detectors

1994-07-11

1997-03-18

Chin, Stephen

Pulse or digital communications

Receivers

Angle modulation

375326, 375334, 375344, 327 43, 329302, 329303, H03D 300

Patent

active

056129769

ABSTRACT:
A direct conversion Binary FSK radio receiver has an AFC loop comprising an Exclusive-Or phase detector 104 responsive to the I.sub.3 and Q.sub.3 signals. I and Q filters 100, 101 are not identical but have different frequency-phase characteristics such that their phase shifts are identical when the local oscillator 102 is correctly tuned and differ when the local oscillator is off-tune. Detector 104 detects the change of phase and applies a control signal to local oscillator 102 such as to return the local oscillator frequency to the correct value. Alternatively, identical filters may be used in the I and Q channels, circuits having different phase shifts being coupled between the I.sub.3 and Q.sub.3 signals and the inputs of the phase detector 104.

REFERENCES:
patent: 5042052 (1991-08-01), Roberts et al.
patent: 5249204 (1993-09-01), Funderburk et al.
patent: 5301210 (1994-04-01), Vandamme et al.
patent: 5438594 (1995-08-01), Podolak

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