Antenna circuit and wrist radio instrument

• US 5,243,356 A
• Filed: 04/15/1992
• Issued: 09/07/1993
• Est. Priority Date: 08/05/1988
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Hama, Norio
• Primary Examiner(s): Hille, Rolf
• Assistant Examiner(s): BROWN, PETER T
• Application Number:
  US07/870,160
• Time in Patent Office: 510 Days
• Field of Search: 343/718, 343/720, 343/741, 343/744, 343/748, 343/866, 343/868, 455/344, 455/274, 455/289-291, 368/10
• US Class Current: 343/718
• CPC Class Codes: H01Q 1/273 Adaptation for carrying or wearing by persons or animals

Abstract

The antenna circuit and wrist radio instrument of the present invention compensates for slippage in the resonance frequency of antenna circuits caused by such as the wrist thickness of the person wearing them, and by being worn on the wrist and then not worn, and can always tune to a set frequency. Accordingly, the present invention is one that can automatically receive a set frequency signal stably and with a set sensitivity, with no need for special adjustments.

Claims

1. A wrist-mounted radio instrument including a radio receiver, comprising:

a) a wrist band having two portions;

b) a connector assembly having a first portion mounted on a first one of said two wrist band portions, and a second portion mounted on a second one of said two wrist band portions, said connector assembly operable to detachably connect said wrist band portions so that said wrist radio instrument may be removably attached to a human wrist;

c) a loop antenna embedded within said wrist band;

d) a means for detecting electrical connection of said wrist band portions;

e) a means, coupled to said wrist band, for automatically engaging a frequency correction circuit for a predetermined period of time, upon detection of the electrical connection of said wrist band portions;

f) a first variable capacity diode electrically coupled to said loop antenna; and

g) a first voltage generation circuit for generating a DC voltage connected to said variable capacity diode for changing the capacity of said variable capacity diode in correspondence with changes in the circumferential length of said loop antenna;

wherein said first voltage generation circuit comprises;

1) a voltage supply circuit having a positive terminal and a ground terminal;

2) a fixed resistor having first and second terminals; and

3) a variable resistor having first and second terminals;

said fixed resistor first terminal and said variable resistor first terminal being electrically connected in series so as to form a common node, said common node being connected to said first variable capacity diode, said positive terminal being electrically connected to said fixed resistor second terminal, and said variable resistor second terminal being electrically connected to said ground terminal.