Direct conversion receiver

Details Direct conversion receiver Direct conversion receiver

1995-11-09

1997-06-17

Chin, Stephen

Pulse or digital communications

Receivers

Angle modulation

375328, H03D 300, H04L 2714

Patent

active

056404280

ABSTRACT:
In a first direct conversion receiver for demodulating I and Q signals, having a quadrature relation therebetween, obtained from a received FSK signal through a direct conversion, a first D FF latches a level of the I signal when a sign condition of I and Q signals moves from the same to different sign conditions, a second D FF latches a level of the Q signal when the sign condition of the I and Q signals moves from the different to same sign condition and EXCLUSIVE OR operations are made among the I and Q signals and the outputs of the first and second D FFs to provide a frequent data judgement to improve a receiving sensitivity of an FSK signal having a relative low modulation index. In a second direct conversion receiver, a sign change in the Q signal is detected by a first edge detection circuit 17, a first D FF holds the level of the I signal, and an EXCLUSIVE OR circuit provides a first demodulation result. A sign change in the I signal is detected by a second edge detection circuit 17, a second D FF holds the level of the Q signal, an EXCLUSIVE OR circuit provides a second demodulation result and a subtracting circuit combines the first and second demodulation results. An earlier change detection circuit also combines the first and second demodulation results with a delay in the first and second demodulation results reduced.

REFERENCES:
patent: 4475219 (1984-10-01), Puckette
patent: 4651107 (1987-03-01), Akaiwa
patent: 4752742 (1988-06-01), Akaiwa
patent: 5309113 (1994-05-01), Mimura et al.
patent: 5345187 (1994-09-01), McGuire
patent: 5446762 (1995-08-01), Ohba et al.
patent: 5485108 (1996-01-01), Kojima

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