US 4,742,566 AGranted

AM receiver

AssigneeU.S. Philips Corporation

InventorsErnst H. Nordholt, Hendrikus C. Nauta

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Abstract

AM receiver comprising a tuning oscillator (T0), a first phase detector (PD1) and a first loop filter (LP1) successively arranged in a first phase control loop. The tuning oscillator (T0) is synchronized with a reference oscillator (VCX0) coupled to the first phase detector (PD1) and applies a mixing frequency to a mixer stage (M) for conversion of a received AM signal into an IF-AM signal. The mixer stage (M) is coupled to an AM demodulator (SD) for demodulation of the base-band modulation signal. The reference oscillator (VCX0) is controllable and is disposed between a second loop filter (LP2) and a second phase detector (PD2) of a second phase control loop coupled to the mixer stage (M) for applying a local detection carrier synchronized with the IF-AM signal carrier to the AM demodulator (SD). The second loop filter (LP2) applies a control signal to the reference oscillator (VCX0) and is connected through a coupling circuit (C) to a control input of the tuning oscillator (T0) for a negative feedback of the control signal of the reference oscillator (VCX0) to the tuning oscillator (T0).

Claims6

Dependent claims

An AM receiver comprising:

a first phase control loop for establishing a tuning frequency including:
(a) a mixer stage for receiving a radio frequency signal and a tuning frequency signal, and producing an IF signal;
(b) a tuning frequency voltage controlled oscillator for providing said tuning frequency signal;
(c) a stable reference signal generator;
and
(d) a frequency control means for locking said tuning frequency signal in phase synchronism with said stable reference signal generator including a first loop filter for coupling a control voltage signal to a frequency control input of said voltage controlled tuning oscillator, and means for generating said control voltage as a function of the difference in phase between said stable reference frequency oscillator and said tuning frequency voltage controlled oscillator;
an AM baseband demodulator comprising a second phase control loop having a phase detector for receiving said mixer stage IF signal, and a signal from said reference signal generator, and a second loop filter for coupling an error signal from said phase detector to said reference signal generator, whereby said reference signal generator is phase locked with said IF signal;
and,
a coupling circuit for coupling said phase detector error signal to a frequency control input of said tuning frequency voltage controlled oscillator, whereby negative feedback from said reference signal generator to said voltage controlled oscillator results.

6 more elements

Dependencies are inferred from the claim text.