Automatic frequency control apparatus for FSK receiver and FSK r

Details Automatic frequency control apparatus for FSK receiver and FSK r Automatic frequency control apparatus for FSK receiver and FSK r

1994-12-21

1997-05-27

Chin, Wellington

Pulse or digital communications

Receivers

Automatic frequency control

375326, 375327, 375328, 375272, 329300, 329302, 329306, 329307, 4551822, 4551961, 455258, H04L 2714, H04L 2710, H04L 2706, H03D 318

Patent

active

056338988

ABSTRACT:
A first AFC apparatus receives and detects I and Q signals from a received first FSK signal with a local osc signal; demodulates the I and Q signals; F/V-converts I or/and Q signals into a voltage; compares it with a reference; and detects a frequency deviation direction of the local osc signal from the carrier signal according to the results of comparing and the demodulating. The local osc frequency is controlled by a given amount according to the result of the frequency deviation direction detection. A second AFC apparatus receives and detects I and Q signals using a first osc signal; FSK-modulates the I and Q signals with a second local osc signal having a lower frequency than the first local osc signal; and compares the frequency of the second FSK signal and the second local osc signal to supply a demodulation result. A frequency control for the first local osc signal is obtained by an averaging circuit averaging the modulation result. The F/V converter used in this apparatus has various modification and amplitude limiter may be provided as necessary. The averaging may be effected for a given data period of the first FSK signal. Power consumption can be reduced by selectively supplying a power with/without a holing circuit. FSK receivers use these automatic frequency control apparatus are also disclosed.

REFERENCES:
patent: 4103244 (1978-07-01), Tan
patent: 4485347 (1984-11-01), Hirasawa
patent: 4486715 (1984-12-01), Maas
patent: 5208835 (1993-05-01), Weeks
patent: 5309113 (1994-05-01), Mimura

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