Radio receiver apparatus of orthogonal detection type comprising

Details Radio receiver apparatus of orthogonal detection type comprising Radio receiver apparatus of orthogonal detection type comprising

1995-01-19

1996-08-20

Chin, Stephen

Pulse or digital communications

Receivers

Automatic frequency control

4551922, 455209, H04L 2706

Patent

active

055486193

ABSTRACT:
In a radio receiver apparatus of an orthogonal detection type, a voltage controlled first local oscillator generates a first local oscillation signal, and mixers mix an inputted reception signal with the first local oscillation signal and a 90.degree. shifted signal thereof, respectively, the mixed signals respectively being passed through first and second band-pass filters to obtain desired first intermediate frequency signals. Further, a second local oscillator generates a second local oscillation signal. Further mixers mixes the first intermediate frequency signals from the first and second band-pass filters with the second local oscillation signal and a 90.degree. shifted signal thereof, respectively. Then there is calculated either one of a sum of and a difference between the resulting mixed signals, the calculated signal being passed through a third band-pass filter to obtain a second intermediate frequency signal to be demodulated. Furthermore, an average frequency detector detects an average frequency of the second intermediate frequency signal for a predetermined time interval, and a frequency correction circuit controls the first local oscillation frequency of the first local oscillation signal based on the detected average frequency.

REFERENCES:
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patent: 4814715 (1989-03-01), Kasperkovitz
patent: 4837853 (1989-06-01), Heck
patent: 4878029 (1989-10-01), Saulnier et al.
patent: 5253097 (1993-10-01), Naito et al.
patent: 5396521 (1995-03-01), Minami
patent: 5416805 (1995-05-01), Tonello et al.

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