US 5,396,521 A · Receiver capable of reducing power consumption in a PLL circuit

Abstract

In a receiver for use in demodulating a modulated wave modulated by a digital data signal arranged within a preselected channel to produce a reproduced data signal by the use of a local frequency signal of a local frequency, a VCO and a PLL circuit are intermittently put into active states with reference to an offset frequency between a channel frequency and the local frequency. The PLL circuit is put into the active state for a time interval determined by the offset frequency before reception of the preselected channel while the VCO is put into the active state during the active state of the PLL circuit and during reception of the preselected channel. A duration of the active state in the PLL circuit becomes long when the offset frequency does not fall within a predetermined range determined by predetermined offset frequencies and, otherwise, the duration of the active state in the PLL circuit becomes short. The offset frequency is detected by a frequency detector which produces a control signal appearing only when the offset frequency is present outside of the predetermined range. The control signal is sent to a control circuit for controlling battery saving operations of the VCO and the PLL circuit.

Claims8

Dependent claims

A receiver that responds to a modulated signal, which is subjected to modulation by a baseband digital signal and which has a channel frequency, wherein said receiver comprises:

demodulating means, wherein said demodulating means is supplied with said modulated signal and a local frequency signal of a local frequency, for carrying out demodulation of said modulated signal by using said local frequency signal to demodulate said baseband digital signal into a demodulated signal;
local signal supplying means, which has a phase locked loop selectively put into an inactive state and an active state, for supplying said local frequency signal to said demodulating means;
frequency difference detecting means coupled to said demodulating means for detecting a frequency difference between said channel frequency and said local frequency to determine whether or not said frequency difference falls within a predetermined range and to produce a control signal when said frequency difference exceeds said predetermined range;
and
controlling means coupled to said frequency difference detecting means and said local signal supplying means for controlling said local signal supplying means to put said phase locked loop of said local signal supplying means into said active state in a presence of said control signal so as to keep said local frequency under control of said phase locked loop and to put said phase locked loop into said inactive state in an absence of said control signal so as to keep said local frequency with said phase locked loop kept inactive.

2 more elements

A receiver that responds to a modulated signal which is modulated by a data signal and a local frequency signal of a local frequency by producing a desired baseband signal which carries said data signal with reference to said modulated signal and said local frequency signal and by demodulating said desired baseband signal into a reproduced data signal representative of said data signal, said desired baseband signal having a reference value, wherein said receiver comprises:

offset detecting means supplied with said desired baseband signal for detecting an offset amount from said reference value to determine whether or not said offset amount falls within a predetermined range and to produce a control signal only when said offset amount does not fall within said predetermined range;
local oscillation frequency generating means for generating said local frequency signal before reception of said desired baseband signal to keep said local frequency signal during said reception of said desired baseband signal, wherein said local oscillation frequency generating means carries out a phase locked operation in response to an operation control signal by carrying out said phase locked operation before said reception of said desired baseband signal;
and
operation control means for producing said operation control signal in response to said control signal and said reproduced data signal.

1 more element

Dependencies are inferred from the claim text.

Receiver capable of reducing power consumption in a PLL circuit

Life of this patent

Receiver capable of reducing power consumption in a PLL circuit

Life of this patent

Abstract

Claims8