JP2007067512A - Antenna assembly, portable information terminal, program, recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna assembly in which directivity is controlled such that high performance and miniaturization can be attained while reducing SAR and ensuring communication performance. <P>SOLUTION: The antenna assembly comprises a feeding section 100 arranged in the center of a housing B, a power supply element 600 for outputting a radio wave or capturing a radio wave, two parasitic elements 200 and 300 arranged substantially in parallel on the opposite sides of the power supply element 600, and element control circuits 400 and 500 for switching the matching of the parasitic elements 200 and 300 wherein matching by the element control circuits 400 and 500 is switched depending on the communication state and directivity of the antenna is altered. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an antenna device, a portable information terminal, a program, and a recording medium that ensure communication performance, and particularly to an antenna device of a portable information terminal having a foldable casing.

  When a telephone call or data communication is performed using a mobile phone that is one of the portable information terminals, a method of controlling the directivity of the antenna device is employed in order to maintain the communication state. At this time, it is necessary to reduce the specific absorption rate (SAR) to the human head of the person using the mobile phone as much as possible.

  Specifically, a plurality of antenna devices having different properties are mounted on a single mobile phone, and the directivity is controlled by switching the antenna device according to a use state such as a call or data communication and a radio wave environment. Further, as in the planar antenna disclosed in Patent Document 1, the position of the λ / 2 antenna parasitic element arranged in parallel with the λ / 2 antenna feeder is appropriately changed to improve directivity. There is also a method.

For the following reasons, it is desirable that there are a plurality (a plurality of types) of antenna devices used for the mobile phone. That is, first, to relax the position of the low-impedance part that cannot be communicated at all, so-called “null point”, and second, the case changes like a foldable mobile phone. The reason is to cope with a change in antenna characteristics accompanying the above, and the third reason is to use reception diversity.
JP-A-11-27030

  In a conventional mobile phone, when a plurality of antenna devices are designed, there is a high possibility that any one of the antenna devices will radiate strongly to the human head. Therefore, in order to reduce the SAR, a control method has been adopted in which the antenna device is switched and fixed so as not to strongly radiate the human head according to the use state, the radio wave environment, and the like. However, in this method, the significance of using a plurality of antennas is lost for the first to third reasons.

  In the first place, it is necessary to use a plurality of antenna devices for the above first to third reasons, but it cannot be said that it can meet the recent demand for higher functionality and smaller size in portable information terminals.

  The planar antenna of Patent Document 1 requires a structure and space for changing the position of the λ / 2 antenna parasitic element, and it is difficult to meet the demand for higher functionality and smaller size.

  In view of the above circumstances, an object of the present invention is to provide an antenna device and the like that controls directivity so that SAR can be reduced and communication performance can be ensured while achieving high functionality and downsizing.

  An aspect of the present invention that solves the above problems includes a power feeding unit disposed in a central portion of the housing, a power feeding element that outputs or captures radio waves, and two power supplies that are disposed substantially in parallel with the power feeding element interposed therebetween. An antenna device comprising: a parasitic element; and an element control circuit that switches matching of the parasitic element; switching matching by the element control circuit according to a communication state; and changing antenna directivity It is about.

  Here, the element control circuit makes the parasitic element function as a reflector or a radiator by switching matching of the parasitic element, or invalidates the parasitic element. In particular, when the communication state is a call, the parasitic element is made to function as a reflector or a radiator in switching of matching by the element control circuit.

  Another aspect of the present invention relates to a portable information terminal equipped with the antenna device. Another aspect of the present invention relates to a program that causes a computer of the portable information terminal to function as the antenna device. Another aspect of the present invention relates to a recording medium storing the program.

  Since the antenna device of the present invention has a plurality of types of antenna characteristics and is controlled so as to change the directivity as appropriate, the SAR can be reduced, and communication performance can be ensured while achieving high functionality and miniaturization.

  Hereinafter, the best mode for carrying out the antenna device of the present invention will be described. In the description, the drawings submitted at the same time as this specification will be referred to as appropriate.

  FIG. 1 is an external view of a foldable mobile phone 10 that is a portable information terminal. This mobile phone 10 has a housing U and a housing B, and both the housing can be rotated at the hinge portion 13 to form an open state as shown in the figure and a folded state when folded. it can. The housing U is provided with a speaker 11 for outputting the voice of the other party and a liquid crystal screen 12 for displaying image data. The housing B is provided with an operation unit 14 for inputting numbers, letters such as alphabets, on-hook, off-hook, and the like, and a microphone 15 for inputting user's voice.

  FIG. 2 illustrates components constituting the antenna device in the internal structure of the housing B. FIG. The antenna device of the cellular phone 10 includes a power feeding unit 100, two parasitic elements 200 and 300, two element control circuits 400 and 500, and a power feeding element 600. Although not shown, the cellular phone 10 has a central processing unit (CPU) for central processing control of the processing operations of the components constituting the antenna device and the processing operations of the components taken up in FIG. Further, a ROM (Read Only Memory) storing a program for executing central processing control and a RAM (Random Access Memory) for temporarily storing data such as telephone number data and image data are provided.

  The power feeding unit 100 is an element that supplies power to the antenna device, and is located in the central portion of the housing B. By arranging the power feeding unit 100 in such a position, power is supplied so that communication performance can be maintained depending on the use state, radio wave environment, etc., regardless of where the other parts are located inside the housing B. can do. That is, it becomes advantageous in designing the antenna device. Unlike the conventional method of controlling the directivity by switching the antenna, since the power feeding unit is only required at one place, a radio frequency switch or the like is unnecessary. As a result, the cost can be reduced, and the loss of transmission power closely related to the call time and the loss of reception power related to the reception sensitivity can be greatly reduced, resulting in longer call time and improved reception sensitivity. It becomes.

  The parasitic elements 200 and 300 are metal bars that are arranged substantially in parallel with the feeding element 600 and mainly function as a reflector or radiator of the Yagi antenna. Which of these functions depends on the action of element control circuits 400 and 500 described later. The parasitic element 200 is arranged at the upper part of the casing B substantially perpendicular to the longitudinal direction of the mobile phone 10, and the parasitic element 300 is arranged at the lower part of the casing B substantially perpendicular to the longitudinal direction of the cellular phone 10. Has been.

  The element control circuits 400 and 500 have matching circuits that perform impedance matching of the parasitic elements 200 and 300, respectively. By switching matching by the matching circuit, the state of the parasitic elements 200 and 300 can be determined, and the characteristics of the antenna device can be changed.

  The power feeding element 600 is a metal rod that is disposed inside the housing B substantially perpendicular to the longitudinal direction of the mobile phone 10 and mainly functions as a radiator of the Yagi antenna. When making a call or data communication, radio waves can be emitted to the outside, or radio waves can be taken in from outside.

  As shown in FIG. 2, by disposing the parasitic elements 200 and 300 apart from each other, the positions of the null points change greatly, and the other null point can be covered. And since the electric power feeding part 100 is located in the center part of the housing | casing B, it can maintain communication performance as mentioned above, and becomes advantageous in design.

  In a foldable portable information terminal such as the mobile phone 10, a flexible cable for passing control signals through the housing U and the housing B is essential. Therefore, in order to design the components on the board so as to reduce the loss on the wiring, it is preferable to arrange them in the vicinity of the folding portion. In that case, a large part that is not directly related to communication such as a personal information card such as USIM or an external storage device such as an SD card is preferably placed in the lower part of the casing because the part is placed near the folding part.

  When the parasitic elements 200 and 300 corresponding to the element control circuits 400 and 500 respectively function as a reflector of the Yagi antenna, the matching may be switched by the matching circuit to make the line length electrically longer than that of the feeder element 600. This action of the element control circuit is called “element reflection”. Conversely, when functioning as a radiator of a Yagi antenna, the matching may be switched by a matching circuit to make the line length electrically shorter than that of the feed element 600. This operation of the element control circuit is called “element radiatorization”. The directivity of the antenna device can be changed by switching the element to a reflector and the element to a radiator.

  In addition, the element control circuits 400 and 500 lose the function as a reflector or radiator by switching the parasitic elements 200 and 300 to matching that matches a short state with the casing B, and are equivalent to the casing B. Can be in a state. Such an operation of the element control circuit is called “element invalidation”.

  FIG. 3 illustrates the directivity that can be realized by the antenna device of this embodiment by the action of the element control circuits 400 and 500. A state when the user is making a call with the cellular phone 10 opened is depicted. The casing U is positioned so that the speaker 11 is applied to the user's ear, and the casing B is positioned so that the microphone 15 approaches the user's mouth. At this time, in order to reduce the SAR to the human head, the directivity of the antenna device provided in the housing B needs to be set to directivity A and directivity B on the XY plane. If the antenna device is provided in the lower part of the mobile phone 10, it is easy to realize such directivity. The direction, scale, strength, and the like of the directivity A and directivity B can be appropriately controlled by the operation of the element control circuits 400 and 500. In this case, of course, it should be noted that control is performed while reducing SAR.

  By disabling both the parasitic elements 200 and 300, the feeding element 600 can be used as a dipole antenna. Moreover, it can be used as a Yagi antenna by making one of the parasitic elements 200 and 300 a reflector and making the other a radiator. Furthermore, it can be used as a beam antenna by invalidating any one of the parasitic elements 200 and 300. Therefore, the antenna device of this embodiment can realize the usage method of five types of antennas by the above action of the element control circuit.

Antenna (1): Both parasitic elements 200 and 300 are invalidated and used as a dipole antenna (in this case, omnidirectional)
Antenna (2): The parasitic element 200 is used as a radiator, and the parasitic element 300 is used as a reflector and used as a Yagi antenna (at this time, the directivity A is large and the directivity B is small).
Antenna (3): Parasitic element 200 is made a reflector and parasitic element 300 is made a radiator and used as a Yagi antenna (At this time, directivity A is small and directivity B is large).
Antenna (4): The parasitic element 200 is made into a radiator and the parasitic element 300 is invalidated and used as a beam antenna (at this time, the directivity A is large and the directivity B is normal).
Antenna (5): Parasitic element 200 is made a reflector, and parasitic element 300 is invalidated and used as a beam antenna (At this time, directivity A is normal and directivity B is large).

  By selecting the optimal antenna for the usage situation, it is possible to secure communication performance and improve the null point. Further, since the dipole antenna of the antenna (1) is non-directional, it should not be used to suppress radiation to the head due to a call, but should be used when performing data communication such as packet communication. With this in mind, the method of using the antenna device of this embodiment is as shown in the flowchart in FIG.

  When using the mobile phone 10, the user determines whether to perform a call or to perform packet communication (or standby state) as data communication (S01). When making a call, under the control of the element control circuit, the antenna (2) to (5) having the best communication performance is selected (S02). The omnidirectional antenna (1) is not used to reduce SAR. When performing packet communication (or standby state), the antenna (1) to (5) having the best communication performance is selected under the control of the element control circuit (S03). Whether the communication performance is good or bad is determined based on the communication quality in RSSI, RSCP, BER, etc. Thereafter, the matching is switched so as to switch to the selected antenna (S04). These steps are repeated so that the communication performance can be maintained.

  From the above description, the antenna device of this embodiment can select the optimum antenna from among the five types of antennas according to the usage state and radio wave environment, etc., so ensuring communication performance after taking SAR countermeasures Is possible. In particular, it is better not to select an omnidirectional antenna during a call. Furthermore, since the power feeding portion of the antenna device is arranged in the central portion of the housing, it is superior in design, and loss of antenna characteristics can be suppressed.

  In addition, although the form mentioned above is the best thing for implementing the antenna apparatus etc. of this invention, it is not the meaning limited to this. Therefore, various modifications can be made without departing from the scope of the present invention.

1 is an external view of a foldable mobile phone 10 that is a mobile information terminal. FIG. Of the internal structure of the housing B, the components constituting the antenna device are shown. The directivity which can be realized by the antenna device of this embodiment is illustrated. It is a flowchart which shows the usage method of the antenna apparatus of this form.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Feed part 200 Parasitic element 300 Parasitic element 400 Element control circuit 500 Element control circuit 600 Feeding element

Claims (6)

A power feeding unit arranged in the central part of the housing;
A power feeding element that outputs or captures radio waves;
Two parasitic elements arranged substantially in parallel with the feeding element interposed therebetween;
An element control circuit for switching matching of the parasitic element;
An antenna device, wherein the antenna directivity is changed by switching matching by the element control circuit according to a communication state.   The element control circuit makes the parasitic element function as a reflector or a radiator by switching matching of the parasitic element, or invalidates the parasitic element. The antenna device described.   3. The antenna device according to claim 2, wherein when the communication state is a call, the parasitic element is caused to function as a reflector or a radiator in switching of matching by the element control circuit.   A portable information terminal equipped with the antenna device according to claim 1.   A program for causing a computer of the portable information terminal according to claim 4 to function as the antenna device.   A recording medium storing the program according to claim 5.

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