Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2002-01-23
2003-10-14
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S841000
Reexamination Certificate
active
06633262
ABSTRACT:
TECHNICAL FIELD
The present invention relates to portable radio terminals, particularly to a portable telephone as the portable radio terminal.
BACKGROUND ART
A portable telephone generally includes an antenna element to transmit and receive electromagnetic waves, and a radio transmitter-receiver provided in the portable telephone to apply energy to the antenna element. Since the impedance of the antenna element differs from the impedance of the radio transmitter-receiver, the impedance must be matched. Therefore, a matching circuit is provided between the radio transmitter-receiver and the antenna element in a conventional portable telephone for impedance matching.
FIG. 15
shows a structure of a conventional portable telephone. Referring to
FIG. 15
, a conventional portable telephone
401
includes a main unit case
410
, a metal substrate
411
, a feed unit
412
, a matching circuit
413
, a shield box
414
, and a monopole antenna
421
.
Metal substrate
411
is housed in main unit case
410
. Shield box
414
is disposed at the surface of metal substrate
411
, and matching circuit
413
constituting feed unit
412
is provided in the proximity of shield box
414
. Monopole antenna
421
is connected to matching circuit
413
.
Main unit case
410
is of a hollow configuration with metal substrate
411
located therein. Metal substrate
411
includes an epoxy glass material and a conductor layer
441
a
formed of copper at the surface thereof. Metal substrate
411
is of a rectangular configuration and has long sides and short sides.
Shield box
414
is provided at the upper portion of metal substrate
411
. A radio transmitter-receiver is provided in shield box
414
to extract the information included in the wave received by monopole antenna
421
and to apply a predetermined energy to monopole antenna
421
to radiate waves. The radio transmitter-receiver is covered with shield box
414
to be shielded electromagnetically. Shield box
414
is configured, for example, by a layered body of copper and nickel with a nickel layer formed at the surface of copper.
Matching circuit
413
configuring feed unit
412
is provided so as to face a portion of shield box
414
. Matching circuit
413
is formed of a lumped constant element such as coils and capacitors. Matching circuit
413
has a portion connected to the radio transmitter-receiver in shield box
414
. The remaining portion of matching circuit
413
is connected to monopole antenna
421
.
Monopole antenna
421
is attached to matching circuit
413
so as to extend in a predetermined direction. Monopole antenna
421
extends along the longitudinal direction of metal substrate
411
and main unit case
410
. The electrical length of monopole antenna
421
is mainly set to &lgr;/4 or &lgr;/2.
The problem induced by such a conventional portable telephone
401
will be described hereinafter.
In general, when monopole antenna
421
receives a wave, a current flow is conducted from feed unit
412
to the radio transmitter-receiver in shield box
414
. However, a current that flows at the surface of shield box
414
as shown by arrow
430
is also present. There is also a current that bypasses the surface of metal substrate
411
to flow to the radio transmitter-receiver. Since the conductivity of metal substrate
411
and shield box
414
is poor with respect to the antenna conductor, heat is generated at this area to result in signal loss.
The present invention is directed to solve such a problem. An object of the present invention is to provide a portable radio terminal that has a high antenna efficiency and improved in gain.
DISCLOSURE OF THE INVENTION
A portable radio terminal according to an aspect of the present invention includes a substrate, a shield member, an antenna element, and a feed unit. The substrate includes a portion having a conductive surface. The shield member covers a radio transmitter-receiver provided on the substrate to shield the radio transmitter-receiver electromagnetically, and has conductivity. The antenna element has an electrical length of (&lgr;/2)×N (N is an integer), and extends in a predetermined direction. The feed unit is provided at the substrate so as to be apart from the shield member in an extending direction of the antenna element, and includes a matching circuit connected to the antenna element.
In the portable radio terminal of the above structure, the feed unit is provided at the substrate so as to be apart from the shield member in the extending direction of the antenna element. Since the feed unit is apart from the shield member in the extending direction of the antenna element, the current flowing to the shield member can be reduced to prevent occurrence of a loss in electric signals. Thus, a portable radio terminal of high antenna efficiency and improved in gain can be provided.
Preferably, the end portion of the substrate is dielectric at the surface. The feed unit is provided at the portion of the substrate that is dielectric. Since there is no conductive portion where the feed unit is located, the current flowing to the conductive portion can be reduced. As a result, a loss in the electric signal can be prevented. Thus, a portable radio terminal of high antenna efficiency and improved in gain can be provided.
Also preferably, the end portion of the substrate has a protruding portion where the feed unit is provided. Since the feed unit provided at the protruding portion is immune to the effect of the shield member, a loss in electrical signals can further be prevented effectively.
Preferably, the shield member, feed unit and antenna element are provided sequentially so as to be distant from the substrate along the extending direction of the antenna element. Since the feed unit is provided apart from the substrate, the current flowing to the conductive portion can be reduced. As a result, a loss in the electric signal can be prevented. Thus, a portable radio terminal of high antenna efficiency and improved in gain can be provided.
A portable radio terminal according to another aspect of the present invention includes a substrate, a shield member, a dielectric, a feed unit, and an antenna element. The surface of the substrate is conductive. The shield member covers a radio transmitter-receiver provided on the substrate to shield the radio transmitter-receiver electromagnetically, and has conductivity. The dielectric is provided on the substrate. The feed unit is provided on the dielectric so as to be apart from the surface of the substrate in the thickness direction of the substrate, and includes a matching circuit. The antenna element has an electrical length of (&lgr;/2)×N (N is an integer), and is connected to the feed unit.
In the portable radio terminal of the above structure, the feed unit is provided on the dielectric so as to be apart in the thickness direction of the substrate's surface. Since the feed unit is provided apart in the direction perpendicular to the surface of the substrate, the current flowing from the feed unit to the shield member or to the surface of the substrate can be reduced. As a result, a loss in electric signals can be prevented. Thus, a portable radio terminal of high antenna efficiency and improved in gain can be provided.
REFERENCES:
patent: 5335366 (1994-08-01), Daniels
patent: 5874920 (1999-02-01), Araki et al.
patent: 5986608 (1999-11-01), Korisch et al.
patent: 6285327 (2001-09-01), See
patent: 6295462 (2001-09-01), Kudoh
patent: 6-152221 (1994-05-01), None
patent: 6-291711 (1994-10-01), None
patent: 7-038316 (1995-02-01), None
patent: 7-273688 (1995-10-01), None
patent: 7-283631 (1995-10-01), None
patent: 08-222927 (1996-08-01), None
patent: 9-018215 (1997-01-01), None
patent: 11-088209 (1999-03-01), None
Fukasawa Toru
Imanishi Yasuhito
Ohmine Hiroyuki
Shoji Hideaki
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