Radio receiver frequency control system

• US 5,029,237 A
• Filed: 08/01/1989
• Issued: 07/02/1991
• Est. Priority Date: 06/30/1988
• Status: Expired due to Term

• Current Assignee: Protocol-ip.com, LLC, Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: AT&T, Inc.
• Inventors: Ragan, Lawrence H.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Charouel, Lisa
• Application Number:
  US07/388,228
• Time in Patent Office: 700 Days
• Field of Search: 455/182, 455/183, 455/192, 455/207, 455/209, 455/226, 455/228, 455/343, 455/314, 455/315, 455/260, 455/262
• US Class Current: 455/182.2
• CPC Class Codes: G08B 5/22 using electric transmission; using electromagnetic transmission
• CPC Class Codes: G08B 5/228 combined with other devices having a different main function, e.g. watches
• CPC Class Codes: H03J 7/065 the counter or frequency divider being used in a phase locked loop
• CPC Class Codes: H04B 1/16 Circuits
• CPC Class Codes: H04B 1/18 Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H

Abstract

Frequency control in a miniature receiver is effected by a synthesizer that is operated briefly to provide a tuning voltage to a voltage controlled local oscillator. A capacitor is shunted across the output of the synthesizer and is charged to the level of the tuning voltage. After the capacitor is charged, the synthesizer is deenergized and the diminishing voltage provided to the oscillator by the discharging capacitor is correspondingly supplemented by an AFC voltage that tracks drift of the received signal in the IF passband. The deenergizing of the synthesizer eliminates synthesizer noise and reduces the receiver'"'"'s power consumption.

Claims

1. A method of operating a receiver comprising repetitively:

digitally generating a first frequency control voltage for a first time period;

storing said first frequency control voltage in a capacitor;

applying a voltage across the capacitor to a voltage responsive tuning element to thereby tune the receiver to a first channel;

discontinuing generation of the first frequency control voltage at the end of the first time period, thereby permitting the voltage applied by the capacitor to the voltage responsive tuning element to diminish during a second time period following the first;

processing an output signal produced by the receiver to generate a second frequency control voltage; and

applying said second frequency control signal to augment the voltage of the voltage responsive tuning element during the second time period so as to compensate for the diminishing voltage applied thereby by the capacitor;

applying said first frequency control voltage to a first terminal of the capacitor during the first time period; and

applying said second frequency control voltage to a second terminal of the capacitor during the second time period.