Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
1998-10-26
2001-04-03
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S895000
Reexamination Certificate
active
06211826
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an antenna device and a portable radio incorporating the antenna device and more particularly aims at reducing the size of a portable radio by simplifying the circuit configuration of an antenna device.
Radiation characteristics during a call in the antenna device of a typical conventional portable radio are strongly affected by the human body (of a user). In such a conventional portable radio, a diversity antenna for switching a plurality of antennas from one to another is used for improving the radiation gain of the antenna.
FIG. 4
shows an antenna device in a conventional portable radio. The antenna device comprises an antenna element
1
projecting outward from the casing
2
of the portable radio, an internal antenna element
8
provided inside the casing
2
, a joint
4
which is electrically connected to the feeding point
3
of the antenna element
1
, a matching circuit unit
5
for matching the input impedance of the antenna element
1
with the radio circuit unit
6
of the portable radio, a switch
7
for selecting the antenna element
1
or the internal antenna element
8
, and a control unit
9
for controlling the switching of the switch
7
by comparing the levels of the electric power received by the antenna element
1
and the internal antenna element
8
.
While the switch
7
selects the antenna element
1
in this system, the power received by the antenna element
1
is transmitted to the radio circuit unit
6
via the joint
4
and the matching circuit unit
5
. The level of the power thus transmitted to the radio circuit unit
6
is stored in the control unit
9
. Then, the control unit
9
sets the switch
7
so as to connect the internal antenna element
8
and the radio circuit unit
6
. The power received by the internal antenna element
8
is transmitted to the radio circuit unit
6
and the then power level is stored in the control unit
9
.
The control unit
9
compares the levels of the power respectively received by the antenna element
1
and the internal antenna element
8
and changes the switch
7
over to the antenna element that has received the higher power level. The signal transmitted from the radio circuit unit
6
is radiated through the antenna element selected by the control unit
9
.
One of the antenna elements is selected in accordance with the level of the power thus received. Therefore, even when the radiation is restrained because one of the antenna elements is situated closer to the human body, the radiation can be given off through the antenna element where the restraint of radiation is lower, whereby the influence of the human body on the radiation characteristics of the antenna can be reduced.
However, there still exists a problem arising from causing the circuitry to be complicated in the conventional antenna device because the switch and the control unit are required to switch antenna elements from one to the other. Another problem lies in the fact that the portable radio can hardly be reduced in size because the number of parts tends to increase.
SUMMARY OF THE INVENTION
An object of the present invention intended to solve the foregoing problems is to provide an antenna device capable of preventing the gain of an antenna from deteriorating during a call with a simplified circuit arrangement. Further, it is provided a small-sized portable radio by the use of such an antenna device.
Accordingly, an antenna device according to the present invention has an antenna element with a feeding point which is provided in the casing of a portable radio, wherein a conductor element is provided in the casing, supplied with power from the same feeding point as what is connected to the antenna element and excited in phase with the antenna element and in the positive polarity.
In consequence, the antenna element and the conductor element both function as antennas and even when radiation from the antenna element is restrained because the antenna element is situated close to or brought into contact with the human body, the radiation from the conductor element is made possible, whereby the gain of the antenna is prevented from deteriorating. Furthermore, the circuit configuration of this antenna device can be simplified as the number of parts is reducible.
Moreover, a small-sized portable radio incorporating the antenna device can be provided.
Furthermore, according to the present invention, the conductor element is formed of a plate-like or linear conductor and its length is adjusted to set a predetermined antenna characteristics.
Moreover, according to the present invention, the conductor element is bent a plurality of times in any position in the casing, so that the antenna device is made compact by reducing the conductor element in size.
Still further, according to the present invention, the conductor element is made to resonate at a frequency slightly deviated from the resonance frequency of the antenna element, whereby it functions as a double-resonance antenna to ensure that broad-band antenna characteristics are obtained.
Still furthermore, according to the present invention, the length of the antenna element set at an electrical length with a wavelength of 0.65 and that of the conductor element is set at an electrical length with a wavelength of approximately 0.4, so that the function of the double-resonance antenna is fulfilled.
Moreover, according to the present invention, a portable radio can be made small-sized by incorporating the above-mentioned antenna device.
REFERENCES:
patent: 5561437 (1996-10-01), Phillips et al.
patent: 5703602 (1997-12-01), Casebolt
patent: 5854606 (1998-12-01), Kawahata et al.
patent: 5870066 (1999-02-01), Asakura et al.
Le Hoang-anh
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
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