Antenna for portable radio device

Communications: radio wave antennas – Antennas – Slot type

Reexamination Certificate

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Details

C343S718000

Reexamination Certificate

active

06281854

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims benefit of priority of Japanese Patent Applications No. Hei-11-150447 filed on May 28, 1999 and No. 2000-112436 filed on April 13, 2000, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna for a portable radio device such as a finger-ring-type radio device which transmits signals concerning physical data of a person who wears the finger-ring-type radio device.
2. Description of Related Art
A wristwatch-type portable radio device carrying a slot antenna on its band is known. Such a slot antenna is described, for example, in the book titled “Analysis and Design of Antenna for Mobile Communication Device” (Authors: Ito, Matsuzawa and Naito; Section 5.2, Chapter 2; published in 1995 by Trikepps). However, the efficiency of such an antenna is not sufficiently high, and further improvement of such an antenna has been desired.
SUMMARY OF THE INVENTION
The present invention has been made to improve efficiency of an antenna mounted on a radio device such as a finger-ring-type radio device. The finger-ring-type radio device of the present invention is composed of a finger ring on which a slot antenna is mounted and a flat plate connected to the finger ring on which a patterned antenna and a transmission circuit for generating high frequency signals representing human physical data such as blood pressure or pulsation data are mounted.
The patterned antenna mounted on the flat plate is an antenna substantially radiating an electric-field-mode wave which has a main polarization component parallel to the surface of the plate. On the other hand, the slot antenna mounted on the finger ring is an antenna substantially radiating a magnetic-field-mode wave which has a main polarization component perpendicular to the surface of the plate. The slot antenna has a high efficiency at a position closer to a human body, while the patterned antenna has a high efficiency at a position apart from a human body. Since both the slot antenna and the patterned antenna are combined in the radio device, a high radiation efficiency is obtained at either position, close to or apart from the human body. Further, two antennas having different directivity patterns are combined, a high radiation efficiency is secured irrespective of the finger r ring directions.
To obtain a sufficient length of the slot corresponding to a frequency of a radio wave to be used, the slot may be formed in a zigzag shape. The slot antenna patterns and the feeder line patterns may be printed on both surfaces of a flexible substrate which is rounded and mounted on the finger ring. In this case, a feeder line on the front surface is preferably formed at a position overlapping another feeder line on the rear surface in order to eliminate feeder line impedance fluctuation. Further, only the feeder line portion may be extended so that the feeder lines are easily connected to the transmission circuit mounted on the flat plate.
In place of the patterned antenna mounted on the flat plate as the electric-field-mode antenna, a ground surface of the transmission circuit may be utilized. In this case, an electric-field-mode component included in the slot antenna is strengthened and coupled with the ground surface. To strengthen the electric-field-mode component in the slot antenna, the slot width is made much larger than the slot length, and unbalanced current is intentionally fed to the slot antenna.
According to the present invention, the antenna efficiency of the finger-ring-type radio device is greatly improved without making its structure complex.


REFERENCES:
patent: 3825833 (1974-07-01), Bogue
patent: 5589840 (1996-12-01), Fujisawa
patent: 5677698 (1997-10-01), Snowdon
patent: 5754143 (1998-05-01), Warnagiris et al.
patent: 5-288869 (1993-11-01), None
patent: 7-231217 (1995-08-01), None
patent: 8-32331 (1996-02-01), None
patent: 8-80288 (1996-03-01), None
Ito et al., Analysis and Design of Antenna for Mobile Communication Device, Chapter 2, §5.2 (1995, Trikepps).
Fujisawa et al., A Study on Small Slot Antenna for Wrist Watch Type Portable Radio Equipment, Abstract, p. 37 (1993, Institute of Electronics, Information and Communication Engineers).
Kuboyama et al., Slot Dipole Antenna, pp. 1-81 (1984, Institute of Applied Physics, University of Tsukuba).

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