Portable telephone capable of decreasing noise

Details Portable telephone capable of decreasing noise Portable telephone capable of decreasing noise

1997-07-11

1999-08-03

Hudspeth, David R.

Telecommunications

Receiver or analog modulated signal frequency converter

Noise or interference elimination

455222, 455266, 455220, 455307, 455310, H04B 126

Patent

active

059337699

ABSTRACT:
In a portable telephone, a voice filter is connected to an antenna through a receiving circuit. A filter is connected to the voice filter through a switching circuit and filters the voice signal from the voice filter to produce a filtered voice signal. The filter has a first cut-off frequency when the filter is supplied with a first clock signal. The filter has a second cut-off frequency smaller than the first cut-off frequency when the filter is supplied with a second clock signal. A telephone receiver is connected to the filter through an amplifier. A clock generating circuit is connected to the filter and generates the first clock signal when is supplied with a first frequency control signal. The clock generating circuit generates the second clock signal when is supplied with a second frequency control signal. A control circuit supplies the first frequency control signal to the clock generating circuit when a receiving field intensity from the receiving circuit is greater than a first predetermined field intensity. The control circuit supplies the second frequency control signal to the clock generating circuit when the receiving field intensity is between the first predetermined field intensity and a second predetermined field intensity smaller than the first predetermined field intensity. The control circuit supplies a switch control signal to the switching circuit when the receiving field intensity is smaller than the second predetermined field intensity. The switching circuit is off when is supplied with the switch control signal.

REFERENCES:
patent: 4527187 (1985-07-01), Ohta
patent: 4716407 (1987-12-01), Borras et al.
patent: 5214790 (1993-05-01), Kozlowski et al.
patent: 5257416 (1993-10-01), Cannon
patent: 5498998 (1996-03-01), Gehrke et al.
patent: 5806002 (1998-09-01), Wiatrowski et al.
patent: 5852772 (1998-12-01), Lampe et al.
patent: 5862466 (1999-01-01), Erickson
patent: 5870513 (1999-02-01), Williams
patent: 5884181 (1999-03-01), Arnold et al.

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