Telecommunications – Receiver or analog modulated signal frequency converter – With wave collector
Reexamination Certificate
2002-02-04
2004-05-04
Vuong, Quochien B. (Department: 2685)
Telecommunications
Receiver or analog modulated signal frequency converter
With wave collector
C455S347000, C455S575700, C343S702000
Reexamination Certificate
active
06731920
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a portable telephone apparatus, and in particular, to a portable telephone apparatus for use in a portable telephone system and provided with at least two antennas.
BACKGROUND ART
A mobile communication system using a portable telephone set or the like has been rapidly developed in recent years. In general, a radio wave received by a mobile communication system is a multiple waves including a direct wave from a wave source and reflected waves from obstacles present in midway paths. In this case, the receiving sensitivity deteriorates due to fading. Therefore, a digital portable telephone system or the like performs diversity receiving in order to reduce the fading.
FIG. 19
is a block diagram showing a structure of a conventional portable telephone apparatus, and
FIG. 20
is a perspective view showing an analysis model for simulating the portable telephone apparatus shown in FIG.
19
.
Referring to
FIG. 19
, a whip antenna
202
of an external antenna extending upward from a feeding point
203
is provided on the top portion of the housing
201
of the portable telephone apparatus, the feeding point
203
of the whip antenna
202
is connected with a radio transmitter circuit
205
provided with a microphone
306
through a feeding cable
209
and the contact “a” of a transmitting and receiving switch
204
, and is connected with a receiving diversity circuit
207
through the feeding cable
209
and the contact “b” of the transmitting and receiving switch
204
. A planar inverted-F antenna
206
of an internal antenna built in the housing
201
and a radio receiver circuit
208
provided with a speaker
305
are connected with the receiving diversity circuit
207
.
Referring to
FIG. 20
, a speaker
212
close to an ear of a human body of a user is provided on an upper portion of a front surface
201
a
of the portable telephone apparatus, and a microphone
211
close to a mouth of the human body is provided on a lower portion of the front surface
201
a
. Moreover, the whip antenna
202
is provided in the vicinity of one of four corners on a top surface of the housing
201
located at the upper portion of the speaker
212
.
On the other hand, the planar inverted-F antenna
206
is provided in the housing
201
at an upper portion of a rear surface
201
b
which opposes to the front surface
201
a
. It is noted that since
FIG. 20
shows an analysis model for simulation, the planar inverted-F antenna
206
is located outside of the rear surface
201
b
of the housing
201
, however, in the case of an actual portable telephone apparatus, the planar inverted-F antenna
206
is provided so as to be located inside of the rear surface
201
b
of the housing
201
. This planar inverted-F antenna
206
is constituted by comprising a rectangular conductor plate
206
supported by a feeding pin
206
so as to be parallel to the rear surface of the housing
201
, a central portion of the upper side of the conductor plate
206
is connected with the receiving diversity circuit
207
illustrated in FIG.
19
through the feeding pin
206
, and the central portion of the conductor plate
206
is grounded through a short-circuit pin
206
c.
In the portable telephone apparatus constituted as described above, the transmitting and receiving switch
204
is switched over to the contact “a” side by a controller (not shown) of the portable telephone apparatus upon transmitting, and at this time, a radio signal modulated in accordance with an audio signal inputted to a microphone
306
is fed by being outputted to the whip antenna
202
from the radio transmitter circuit
205
through the transmitting and receiving switch
204
. On the other hand, upon receiving, the transmitting and receiving switch
204
is switched over to the contact “b” side by the controller, and at this time, a radio signal received by the whip antenna
202
is inputted to the receiving diversity circuit
207
through the contact “b” of the transmitting and receiving switch
204
, and a radio signal received by the planer inverted-F antenna
206
is inputted to the receiving diversity circuit
207
. The receiving diversity circuit
207
selects a radio signal having a higher level out of the radio signal received by the whip antenna
202
and the radio signal received by the planar inverted-F antenna
206
, and outputs the selected radio signal to the radio receiver circuit
208
. Thereafter, the radio receiver circuit
208
demodulates the received radio signal so as to generate and output an audio signal from the speaker
305
.
As described above, in the above-mentioned portable telephone apparatus, a radio signal having a higher level is selected out of signals received by two antennas
202
and
206
upon receiving, and only the whip antenna
202
is used upon transmitting.
In the analysis model of
FIG. 20
, the housing
201
had a rectangular-parallelepiped shape of 125 mm height, 35 mm width, and 20 mm depth, and at this time, the feeding point
203
of the whip antenna
202
was set to an origin of an XYZ coordinate system, and the longitudinal direction of the whip antenna
202
was set to the Z-axis direction. In this case, -X direction is a direction parallel to an audio (or voice)-radiating direction from the speaker
212
, and is a direction directed to the head of a human body, in particular, to an ear of the human body. X direction is a direction opposite to the audio-radiating direction from the speaker
212
.
FIGS. 21
,
22
, and
23
show radiating directivities on X-Y plane, X-Z plane, and Y-Z plane, respectively, in a free space of radio waves transmitted from the portable telephone apparatus shown in
FIGS. 19 and 20
.
In the above-mentioned simulation, a radiating directivity when exciting the whip antenna
202
by inputting a radio signal to the feeding point
203
was obtained by analyzing the directivity by the publicly-known moment method. In this case, the frequency of radio signals was set to 900 MHz, the housing
201
, the whip antenna
202
and the planar inverted-F antenna
203
were each made of an electrical conductor, and the analysis model was equivalently replaced with a wire grid in order to reduce the calculation time to perform a simulation (for example, See Prior art document 1 of Koichi Ogawa et al., “An Error Rate Performance of a &pgr;/4-shift QPSK Signal for a Handset Diversity Influenced by Head and Shoulder Effects”, Technical Report of IEICE (Institute of Electronics, Information and Communication Engineers in Japan), A-P 99-110, RC 88-107, October 1999”).
As apparent from
FIGS. 21
to
23
, it is found that the &thgr;-directional component E
&thgr;
of the electric field on X-Y plane is almost omni-directional.
As described above, for example, the whip antenna
202
or the like is used as an external antenna of a portable telephone apparatus, however, it is preferable that the directivity of the antenna
202
is isotropic (omni-directional on the horizontal plane) so as to be able to receive even a signal transmitted from any direction upon waiting for reception. However, since the whip antenna
202
exists adjacent to the speaker
212
, the directivity thereof is influenced by the human body such as an ear or a head thereof so that the directivity thereof deteriorates. Moreover, in this case, radio wave absorption by the head has been a large problem.
FIG. 24
is a side view showing a structure of a human body model carrying the portable telephone apparatus shown in
FIGS. 19 and 20
, and
FIG. 25
is a front view showing a structure of a human body model carrying the portable telephone apparatus shown in
FIGS. 19 and 20
.
Referring to
FIGS. 24 and 25
, the human body model for simulation is constituted by comprising a head portion
302
, a left shoulder portion
303
and a hand portion
304
in order to take into consideration the influence of the shoulder of the human body onto the radiating directivity of the antenna, and a half-length model constituted by integrating the head portion and the left shoulder portion is
Iwai Hiroshi
Koyanagi Yoshio
Ogawa Koichi
Yamada Ken'ichi
Matsushita Electric - Industrial Co., Ltd.
Vuong Quochien B.
Wenderoth , Lind & Ponack, L.L.P.
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