Communications: radio wave antennas – Antennas – Spiral or helical type
Reexamination Certificate
2001-06-28
2003-06-24
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Spiral or helical type
C343S702000
Reexamination Certificate
active
06583769
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to chip antennas, and in particular relates to a chip antenna for mobile communication units such as portable telephone terminals and pagers and a chip antenna for local area networks (LANs).
2. Description of the Related Art
It is important for antennas for use in mobile communication units and LANs to be small-sized. As one of the antennas satisfying such a demand, a helical-type chip antenna is known.
An example of a conventional helical-type chip antenna is shown in
FIGS. 9 and 10
. A chip antenna
100
comprises a rectangular-solid dielectric base body
121
, an antenna line
130
disposed in the dielectric base body
121
, a feed terminal
110
, and a fixing terminal
111
. One end
134
of the antenna line
130
is electrically connected to the feed terminal
110
and the other end
135
is unconnected.
The antenna line
130
is formed by alternately connecting a conductor pattern
131
and a via hole
132
in series. The antenna line
130
has a helical structure having a uniform width and height (or diameter) and the pitch P, and is wound about a straight axis CL in the horizontal direction (direction of arrow X in the drawing).
In order to enable a chip antenna also to be used at low frequencies, the chip antenna is generally required to reduce the resonance frequency. One of the methods for reducing the resonance frequency of the chip antenna is to decrease the spiral pitch of the antenna line.
However, since in the conventional chip antenna
100
, adjacent via holes
132
are close to each other, there is a problem that the spiral pitch of the antenna line
130
cannot be reduced much due to limitation in manufacturing.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a chip antenna capable of reducing the spiral pitch of an antenna line so that it is smaller than that of a conventional chip antenna.
In order to achieve the above-mentioned object, in accordance with a first aspect of the present invention, a chip antenna comprises a base body, an antenna line disposed in the base body and being spirally wound, and a feed terminal disposed on a surface of the base body and being electrically connected to one end of the antenna line, wherein the antenna line has a winding axis which curves in a zigzag manner.
In accordance with a second aspect of the present invention, a chip antenna comprises a base body, an antenna line disposed in the base body and being spirally wound, and a feed terminal disposed on a surface of the base body and being electrically connected to one end of the antenna line, wherein the antenna line has a substantially straight winding axis, and adjacent wound portions have a different width or diameter.
More specifically, the antenna line may be formed by electrically connecting a plurality of conductor patterns disposed in the base body in series by via holes which are arranged in the base body in a staggered arrangement.
By the structures described above, the minimum spiral pitch of the antenna line can be smaller than that of a conventional antenna, thereby enabling the resonance frequency of the chip antenna to be reduced to less than that of a conventional chip antenna.
A chip antenna according to the present invention may further comprise an opposing conductor for adjusting the resonance frequency, wherein the opposing conductor opposes at least one of the plurality of conductor patterns forming the antenna line and is electrically connected to part of the plurality of conductor patterns. Thereby, when the area of the opposing conductor for adjusting the resonance frequency is changed, the resonance frequency of the chip antenna can be adjusted without changing the number of winding turns of the antenna line.
REFERENCES:
patent: 4644366 (1987-02-01), Scholz
patent: 5541610 (1996-07-01), Imanishi et al.
patent: 0863570 (1998-09-01), None
patent: 2702091 (1994-09-01), None
patent: 4242911 (1992-08-01), None
patent: 8316725 (1996-11-01), None
Patent Abstracts of Japan vol. 2000, No. 04, Aug. 31, 2000 & JP 2000 013132 A (TDK Corp), Jan. 14, 2000.
Patent Abstracts of Japan vol. 1998, No. 08, Jun. 30, 1998 & JP 10 084216 (Saitama Nippon Denki KK), Mar. 31, 1998.
Cardosa et al. “A Spherial Helical Antenna” Antennas and Propagation Society International Symposium, 1993. AP-S. Digest Ann Arbor, MI, USA Jun. 28-Jul. 2 1993, New York, NY IEEE, Jun. 28, 1993 pp. 1558-1561.
Asakura Kenji
Shiroki Koji
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Wimer Michael C.
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