JP2002152115A - Portable terminal equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide portable terminal equipment having an antenna system and capable of improving an SAR and securing satisfactory communication characteristics. SOLUTION: Two dipole antennas 21 and 22 are provided on a PCB of the main body of portable telephone set. Signal power transmitted from a transmitting/receiving circuit part 6 is distributed by a power distributor/ synthesizer 33, the unbalanced/balanced conversion of a transmitting mode is performed by baluns 36 and 37 through phasers 34 and 35 and the power is supplied through a power feeding terminal to the dipole antennas 21 and 22. By suitably controlling phases ϕ1 and ϕ2 of respective antenna currents from 0 to 180 deg. by the phasers 34 and 35, electromagnetic fields close to the head of a human body are mutually canceled and decreased so that the SAR can be reduced. Besides, by controlling the power distribution ratio of the power distributor/synthesizer 22 and the phase of the phasers 34 and 35, a radiation pattern and the SAR are optimized so that communication performance can become satisfactory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a portable telephone, a PH
For portable terminals such as S and PDA, in particular, SAR (Sp
The present invention relates to an improvement of an effective absorption rate.

[0002]

2. Description of the Related Art In recent years, with the spread of portable terminals, the influence of radio waves radiated from the terminal on the human body, particularly the influence on the user's human head (SAR), has been promoted. In the portable terminal, current concentrates on the abdomen of the antenna, and as a result, the electromagnetic field concentrates on the human head near the radiation source such as the antenna feeding point, and the SAR increases. Such S
Protection guidelines for improving AR are also being disclosed.

FIG. 5 shows an antenna structure of a monopole antenna system widely used in a conventional portable telephone and a current distribution and a voltage distribution during operation. In FIG. 5A, a PCB (printed wiring board) 1 of the telephone body includes:
A λλ monopole antenna 2 is mounted via a feed point 3. 5A and 5B, since the monopole antenna 1 resonates at a desired frequency by the antenna element and the antenna ground plane to form one antenna, the ground plane current using the PCB 1 as the ground plane according to the antenna current ia ie flows to PCB1 as shown.

FIG. 6A shows an antenna current ia at this time.
FIG. 4B shows a near-field distribution due to the ground plane current ie and FIG.
Indicates a near magnetic field distribution. In the figure, reference numeral 4 denotes a mobile phone main body, and reference numeral 5 denotes a user's human head.

[0005]

In the above configuration,
In order to reduce the SAR, it is sufficient to reduce the intensity of the near electromagnetic field in the direction of the head of the human body in an actual use state. From that viewpoint, the antenna structure of FIG. 5 has the following problem.

(1) In the 1 / 4λ monopole antenna system, since the PCB 1 of the telephone body 4 forms a ground plane,
The ground plane current ie flows through the PCB1. Since it is difficult to control the ground plane current ie flowing through the PCB, the near electromagnetic field cannot be controlled or reduced. (2) The antenna current ia flows in a concentrated manner near the feeding point 3 of the antenna. Usually, this current concentrated portion is a portion where the head 5 comes closest. (3) For this reason, a method has been proposed in which a shielding plate is separately provided on the head side to reduce power radiation in the head direction. However, in the monopole antenna method, the PCB and the shielding plate also have a ground plane current. Since the ie flows, the shielding effect of the shielding plate is small.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a portable terminal having an antenna system capable of improving SAR and securing good communication characteristics. .

[0008]

In order to achieve the above object, in a portable terminal according to the present invention, a plurality of dipole antennas for simultaneously performing the same communication are provided, and power is supplied to each of the dipole antennas. Phase control means for controlling the phase is provided.

Further, power distribution ratio adjusting means for adjusting the distribution ratio of the power supplied to each dipole antenna may be provided.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are configuration diagrams showing an antenna structure in a mobile phone as a mobile terminal according to an embodiment of the present invention, wherein FIG. 1A is a plan view and FIG. 1B is a side view.

In FIG. 1, reference numeral 1 denotes a PCB of a telephone body,
Reference numeral 21 denotes a first dipole antenna (balanced feeding type antenna) provided above the PCB1, and reference numeral 22 denotes a second dipole antenna provided above the PCB1. Reference numeral 31 denotes a power supply unit of the dipole antenna 21, and 32 denotes a dipole antenna.
This is a power supply unit of the antenna 22. Reference numeral 6 denotes a transmission / reception circuit unit provided below the PCB 1. Generally, in a mobile phone, as shown in FIG.
A transmission / reception circuit unit is provided below.

Reference numeral 7 denotes a coaxial cable (semi-rigid cable) that connects the power distribution / synthesis circuit formed on the upper part of the PCB 1 and the transmission / reception circuit 6. 8 is a speaker, PCB1
Is mounted on the surface (head side) opposite to the surface on which the dipole antenna is mounted. The dipole antenna 21 has an antenna current i having a phase of φ1.
a1 flows, and the phase of the dipole antenna 22 is φ
2 antenna current ia2 flows. The two dipole antennas 21 and 22 are used simultaneously for transmitting and receiving the same signal.

In the above example, the power from the transmission / reception circuit unit 6 is supplied through the coaxial cable 7 to the power supply unit 3 above the PCB.
After being led to the microstrip circuit of the power supply circuit section described later including the power supply circuits 1 and 32, the power is distributed by the power distributor described later to 2
The transmission and reception circuit unit 6 and the power supply unit 31 are connected by a coaxial cable 7, and the transmission and reception circuit unit 6 and the power supply unit 32 are connected by another coaxial cable. Alternatively, the power may be separately supplied to the two antennas.

FIG. 2 is a block diagram showing the configuration of the power supply circuit section 30 in which the power supply circuits 31 and 32 are formed. FIG.
, The power supply circuit section 30 includes a transmission / reception circuit section 6, a power distribution / combiner 33 connected by a coaxial cable 7, and a phase shifter 3 for controlling the phases of the antenna currents ia1 and ia2.
4 and 35, and a balun (Balun) which supplies unbalanced-balanced current to each antenna after phase-controlled current is supplied to each antenna.

Next, the operation of the above configuration will be described. FIGS. 3A, 3B and 3C are configuration diagrams schematically showing the relationship between the dipole antennas 21 and 22 and the phases φ1 and φ2 of the respective antenna currents and the head 5 of the user. 5 is a front view.

FIGS. 4 (a) and 4 (b) show the phases φ1 and φ2.
FIG. 4 is a configuration diagram illustrating a relationship between the head 5 and a near magnetic field, and is a diagram of the head 5 viewed from above.

In FIG. 2, the signal power transmitted from the transmission / reception circuit unit 6 is divided in half by a power distributor / combiner 33, and phase shifters 34 and 35 respectively provide desired phases φ1 and φ2.
Then, the transmission mode is unbalanced-balanced converted by the baluns 36 and 37 and supplied to the dipole antennas 21 and 22 via the feed terminals. The dipole antenna resonates by itself and functions as two dipole antennas.

At this time, the phases φ 1 and φ 2 of the antenna currents ia 1 and ia 2 are set to 0 to 18 by the phase shifters 34 and 35.
By appropriately adjusting the angle between 0 ° and, for example, adjusting the power supply phase difference to 180 ° as shown in FIG. 4, the magnetic fields near the head 5 can be reduced by canceling each other, SAR can be reduced.

At this time, the near magnetic field on the side opposite to the head 5 also decreases, and the antenna gain in that direction also decreases, but the power distribution ratio by the power distribution / combiner 33 and the phase shifters 34, 3
Radiation pattern and SAR by adjusting the phase of
Can be optimized to improve communication performance.

In this embodiment, the case where two dipole antennas are provided has been described. However, three or more dipole antennas are provided, and the power supply phase is adjusted and the power distribution ratio is adjusted. May be configured. In addition, the present invention is applicable to not only a mobile phone but also a
The present invention can be applied to other portable terminals such as S and PDA.

[0021]

As described above, according to the present invention, a plurality of dipole antennas are provided and used in common for transmitting and receiving the same signal, and the power supply phase to each dipole antenna is controlled. The PCB of the device
The SAR can be reduced by reducing the electromagnetic field in the vicinity of the user's head without flowing a ground plane current to the head.

Also, by configuring so that the power distribution ratio and phase to each dipole antenna can be adjusted,
Communication performance can be improved.

[Brief description of the drawings]

FIG. 1 is a front view and a side view showing an antenna structure of a mobile phone according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a power supply circuit unit.

FIG. 3 is a front view and a side view of a PCB schematically showing a relationship between a telephone body provided with two dipole antennas and a human head according to an embodiment of the present invention; It is a block diagram.

FIG. 4 is a plan view schematically showing a relationship between a feeding phase of two dipole antennas and a magnetic field near a human head according to the embodiment of the present invention.

FIG. 5 is a configuration diagram showing a mounting structure of a monopole antenna, a current distribution, and a voltage distribution in a conventional portable terminal.

FIG. 6 is a configuration diagram schematically showing a magnetic field near a head in a conventional portable terminal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PCB (printed wiring board) of telephone main body 21 1st dipole antenna 22 2nd dipole antenna 30 feeding circuit part 31, 32 feeding part 33 power distribution / combiner 34, 35 phaser 36, 37 balun 5 human body Head 6 Transmission / reception circuit 7 Coaxial cable

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J021 AA02 AA11 AB03 DB02 DB03 FA05 FA32 GA01 GA02 HA05 5J047 AA17 AB07 FD01 5K011 AA06 DA00 JA01 KA00 5K067 AA35 BB04 EE02 KK03

Claims (2)

[Claims] 1. A portable terminal device comprising: a plurality of dipole antennas for simultaneously performing the same communication; and a phase control means for controlling a power supply phase to each of the dipole antennas. 2. The portable terminal according to claim 1, further comprising power distribution ratio adjusting means for adjusting a distribution ratio of power supplied to each of said dipole antennas.