Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2002-09-26
2004-01-27
Nguyen, Hoang V. (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S7000MS
Reexamination Certificate
active
06683578
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a built-in antenna for a portable wireless unit, which exhibits high radiation characteristics even under various use conditions of the wireless unit.
BACKGROUND ART
In the specification, the term “portable wireless unit” involves a wireless information terminal, such as a music distribution dedicated terminal not having the speech function, in addition to a portable telephone set and PHS (trade mark).
By convention, the portable wireless unit, e.g., portable telephone set or PHS, uses a whip antenna of the telescopic type or a planar inverted-F antenna for its antenna.
The antenna described in the specification of U.S. Pat. No. 5,204,687 may be enumerated for the whip antenna of the telescopic type, used for the portable telephone set. The telescopic type whip antenna is constructed such that an electrically insulated helical antenna is mounted on the tip of the monopole antenna. When it is extended, it serves as a monopole antenna, and when it is contracted and put within the housing of the portable telephone set, it functions as a helical antenna.
The planar inverted-F antenna is disclosed in Japanese Unexamined Patent Laid-Open No. 103406/1981. In the example described in this publication, the planar inverted-F antenna is expanded to have a planar structure, and the peripheral length of the planar element is the half wavelength, and small. When the planar inverted-F antenna is disposed at an end of a ground plate of the housing of the portable telephone set, the planar inverted-F antenna has a relatively broad band characteristic. Further, the planar inverted-F antenna has a structure, which presents an impedance matching function. Therefore, it is advantageous in that there is no need of providing an impedance matching circuit outside the housing.
A normal portable telephone set, as shown in
FIG. 12
, includes both of a whip antenna attached to the outside of the portable telephone set and a planar inverted-F antenna mounted in the housing. The signals received by those antennae are switched from one to the other and vice versa in a diversity manner. Exactly, the signals received by those antennae are compared in level, and the antenna of which the signal level is the higher of those signal levels is selected, and a communication is performed.
In the portable telephone set shown in
FIG. 12
, a monopole antenna
27
and a planar inverted-F antenna
30
operate independently, and those antennae do not operate as a called composite antenna. A radio frequency switch
33
selects the monopole antenna
27
or the planar inverted-F antenna
30
depending on the received signal levels, as mentioned above.
An impedance matching circuit
34
matches a feeding point impedance of the monopole antenna
27
to 50 &OHgr;. The planar inverted-F antenna
30
is a conductive plate of which the peripheral length is set to be about the half wavelength of the operating frequency. It is arranged in parallel with a ground plate
26
, while being spaced by 4 mm, for example. A feeding point
32
is provided at a point which is on one side of the planar inverted-F antenna
30
and spaced from a earthing portion
31
by a fixed distance, e.g., 3 mm. A radio frequency signal derived from the impedance matching circuit
34
of the monopole antenna
27
or a radio frequency signal derived from the feeding point
32
of the planar inverted-F antenna
30
is selected by the radio frequency switch
33
. In
FIG. 12
, a helical antenna
28
is connected through an insulating portion
29
to the tip of the monopole antenna
27
.
Directivity patterns of the antennae of
FIG. 12
are depicted in
FIGS. 13 and 14
by using the coordinates illustrated aside in FIG.
12
.
FIG. 13
shows a directivity pattern of the monopole antenna
27
when it is selected, and
FIG. 14
shows a directivity pattern of the planar inverted-F antenna
30
when it is selected. In
FIG. 13
, a solid line
35
indicates a vertically polarized wave component, and a broken line
36
indicates a horizontally polarized wave component. In
FIG. 14
, a solid line
37
indicates a vertically polarized wave component of the received radio wave, and a broken line
38
indicates a horizontally polarized wave component.
In the monopole antenna
27
shown in
FIG. 13
, an average level of the vertically polarized wave component
35
is higher than that of the horizontally polarized wave component
36
. The vertically polarized wave component
35
has a pattern resembling that of the directivity of an 8-shaped half wavelength dipole. In the planar inverted-F antenna
30
shown in
FIG. 14
, the horizontally polarized wave component
38
is relatively high, and the vertically polarized wave component
37
has a butterfly-shaped pattern directivity since the antenna current is distributed in the ground plate
26
.
A horizontal plane pattern average gain (referred to as PAG) is generally used for an evaluation index used for evaluating the antenna character of the portable telephone set. In a state that a human body equipped with a portable telephone antenna is positioned at the center of a spherical coordinate system, and the head of a human body is directed in the zenithal direction (Z direction), the PAG is given by
PAG
=
1
2
π
∫
0
2
π
[
G
θ
(
π
2
,
φ
)
+
1
XPR
G
φ
(
π
2
,
φ
)
]
ⅆ
φ
[
Formula
1
]
In the above equation, G&thgr; (&phgr;) and G&phgr; (&phgr;) are power directivities of a vertically polarized wave and a horizontally polarized wave in the X-Y plane.
A general cross-polarization power ratio XPR of a mobile communication unit in a multiple wave environment is expressed by a ratio of the vertically polarized wave component to the horizontally polarized wave component, and is 4 to 9 dB, as known. This ratio is calculated on the assumption that the vertically polarized wave component of an arriving wave is higher than the horizontally polarized wave component by 4 to 9 dB. Accordingly, in the radiation pattern of the antenna, the vertically polarized wave component is weighted by XPR. Substantially in the specification, description of the XPR will be given by using 9 dB as a general value in an urban area. Thus, in the antenna of the portable telephone set, a high PAG is obtained by increasing the vertically polarized wave component when it is in use.
The PAG is generally −7 dB when the portable telephone set is in a speech communication state and the whip antenna is extended, and this value is a target value of the performance of the main antenna contained.
Recently, it is demanded to completely build the main antenna into the portable telephone set, in place of the antenna being protruded outside, such as the whip antenna. In this case, the performance comparable with that of the external whip antenna is required for the built-in main antenna, as a matter of course.
In the conventional built-in type planar inverted-F antenna, however, in the speech communication state that the user grips the portable telephone set and moves it close to his ear, reduction of the radiation efficiency of the antenna is great since the distribution of the antenna current is present in the ground plate of the portable telephone set. For this reason, the PAG of the antenna is lower than that of the whip antenna being extended, approximately −11 dB. It is confirmed that when the portable telephone set is put close to a metal table, the antenna gain reduces, and the value of the PAG is lowered to about −16 dB.
When the portable telephone set is placed on the metal table, the conventional whip antenna is frequently stored in the housing. In this case, the helical antenna
28
shown in
FIG. 12
operates. The helical antenna
28
is close to the metal table, and its axial direction is parallel to the metal disk, and its gain is reduced through its electromagnetic interaction with the metal, and the PAG is about −18 dB.
One of the main use c
Aoki Kouta
Haruki Hiroshi
Nishikido Tomoaki
Saito Yutaka
Matsushita Electric - Industrial Co., Ltd.
Nguyen Hoang V.
Pearne & Gordon LLP
LandOfFree
Built-in antenna of portable radio apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Built-in antenna of portable radio apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Built-in antenna of portable radio apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3240906