Multiplex communications – Communication over free space – Signaling for performing battery saving
Reexamination Certificate
1998-06-25
2001-08-07
Marcelo, Melvin (Department: 2733)
Multiplex communications
Communication over free space
Signaling for performing battery saving
C455S039000, C455S574000
Reexamination Certificate
active
06272116
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power saving device and, more particularly, to a power saving device applicable to a receiver of the type demodulating an FM (Frequency Modulation) signal.
It is a common practice with a portable telephone or similar miniature battery-powered portable electronic apparatus to use circuitry for reducing power consumption. A portable telephone, for example, is so constructed as to lower clock frequency while the telephone is in a stand-by state, as taught in Japanese Patent Laid-Open Publication No. 6-232797 by way of example.
However, even in the stand-by state, the above conventional telephone processes a control signal demodulated from a signal with a DSP (Digital Signal Processor). The DSP consumes substantial power even when the clock frequency is lowered, obstructing power saving in the stand-by state. In addition, a high frequency demodulation circuit used during conversation is used in the stand-by state also. Therefore, the demodulation circuit would aggravate power consumption in the stand-by state if provided with an quadrature detector and an AGC (Auto Gain Control) amplifier.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 4-120920, 5-130012, 6-252798, 7-95144, 8-56248, 8-172389, and 8-172672.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a power saving device capable of reducing power consumption in an FM signal waiting state.
It is another object of the present invention to provide a power saving device capable of reducing the power consumption of a receiver of the type receiving signals derived from a plurality of systems.
A power saving device of the present invention includes a first demodulation circuit for selectively demodulating modulated signals derived from at least two different systems. A second demodulation circuit demodulates only one of the modulated signals. A detection circuit detects a control signal out of any one of the modulated signals. A controller selects, based on the control signal detected by the detection circuit, either one of the first and second demodulation circuits while deactivating the other demodulation circuit.
REFERENCES:
patent: 61-240719 (1986-10-01), None
patent: 3-187622 (1991-08-01), None
patent: 4-120920 (1992-04-01), None
patent: 5-130012 (1993-05-01), None
patent: 6-232797 (1994-08-01), None
patent: 6-252798 (1994-09-01), None
patent: 6-276114 (1994-09-01), None
patent: 7-95144 (1995-04-01), None
patent: 8-56248 (1996-02-01), None
patent: 8-172389 (1996-07-01), None
patent: 8-172672 (1996-07-01), None
patent: 9-74384 (1997-03-01), None
Marcelo Melvin
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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