Automatic antenna tuning method and apparatus

• US 5,301,358 A
• Filed: 08/03/1992
• Issued: 04/05/1994
• Est. Priority Date: 12/05/1988
• Status: Expired due to Term

• Current Assignee: Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Corporation (Seiko Group), Seiko Epson Corporation (Seiko Group)
• Inventors: Mukai, Larry H., Gaskill, Garold B.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): KEOUGH, TIMOTHY
• Application Number:
  US07/924,266
• Time in Patent Office: 610 Days
• Field of Search: 455/193.1, 455/193.2, 455/193.3, 455/226.2, 455/234.2, 455/289, 455/290, 455/291, 455/71, 455/94.1, 455/56.1, 340/825.44
• US Class Current: 455/193.2
• CPC Class Codes: H01Q 1/27 Adaptation for use in or on movable bodies H01Q1/08, H01Q1/12, H01Q1/18 take precedence
• CPC Class Codes: H03J 1/0033 for voltage synthesis with a D/A converter
• CPC Class Codes: H03J 7/28 using counters or frequency dividers

Abstract

A wristwatch paging receiver is provided with an antenna matching network that automatically retunes the network at the beginning of a listening interval. During the retuning operation, a control signal is applied to a variable tuning element in the matching network, such as a varactor diode, and is swept from a minimum value to a maximum value. This sweeping is desirably performed in discrete voltage steps that correspond to unit increments of varactor capacitance. A feedback signal from the receiver, such as an AGC signal, is monitored during this operation to note which varactor bias signal yields the maximum AGC signal. After the sweep is concluded, the apparatus applies to the varactor the bias voltage that yielded the maximum AGC signal during the sweeping operation. This bias voltage is maintained through the end of the listening interval. At the beginning of the next listening interval, the process may be repeated.

Claims

1. A periodically active antenna for periodically receiving packets of information, comprising:

an antenna tuning element coupled to said antenna for tuning said antenna;

means coupled to said antenna for producing a first signal which indicates the strength of a signal received by said antenna;

sweep means for sweeping said antenna tuning element through a range of values,

detection means for detecting when said first signal has a maximum signal value as said sweep means sweeps said antenna tuning element through a range of values,

means responsive to said detection means for setting said tuning element to the value that produces said maximum signal value;

means for automatically activating said tuning means when said antenna is activated and prior to the receipt of said packet of information;

whereby said antenna is automatically tuned to the value that produces the maximum first signal prior to the time that said antenna receives information and whereby said antenna thereby reliably and accurately receives said packets of information.

2. In combination,

an antenna for generating a first periodic signal in response to periodically transmitted signals, said antenna generating a maximum value of said periodic signal when said antenna is tuned to the frequency of said transmitted signals;

antenna tuning means coupled to the antenna for tuning said antenna;

means for periodically activating said antenna tuning means prior to receipt of said periodically transmitted signal whereby said antenna is tuned when said periodic signal is transmitted, and

means for deactivating said tuning means during the transmission of said periodically transmitted signal.

3. In a method of operating an antenna system that is operative during recurrent time slots to receive a paging signal, said antenna system including an antenna tuning circuit,

the improvement comprising the step of:

activating said antenna circuit prior to each time slot to optimize reception of said paging signal and for deactivating said tuning circuit during the receipt of said periodically transmitted signal whereby said periodically transmitted signal can be received with optimum tuning of said antenna.