JP4840189B2 - Mobile communication terminal - Google Patents

Description

  The present invention relates to a portable communication terminal having a wireless communication function, and more particularly to a portable communication terminal including a matching circuit for adjusting an impedance characteristic of an antenna.

  In a small-sized mobile communication terminal such as a mobile phone, an electrical component mounted around the antenna may be placed in a state of protruding from the GND of the substrate. In this case, the electric capacitance generated between the electric component and the antenna element may affect the input impedance and radiation characteristics of the antenna. Such influence will be specifically described with reference to the drawings.

  FIG. 6 shows an overview of a general folding mobile phone. A cellular phone 100 includes a camera 1, a receiver 2, an LCD 3 as a display unit, an input key 4 for input operation, a microphone 5, and the like.

  FIG. 7 simply shows a state where the housing case of the mobile phone 100 is removed. The antenna 6 is of a type that is mounted inside a housing case that has become common today, and its feeding point 7 is connected to the upper substrate GND10. The electrical component 8 refers to, for example, the camera 1, the receiver 2, the microphone 5, the vibrator, the speaker, and the like described above, but is not limited to a component having a specific function. Target all parts.

  The lead wire 19 of the electrical component 8 is connected to an audio input / output signal or a control signal input / output terminal. Also, one or more other lines extending from the electrical component 8 are grounded. In the illustrated example, a lead wire 9 separate from the lead wire (signal line) 19 is connected to the upper substrate GND 10. The upper substrate GND10 and the lower substrate GND11 are generally connected using a flexible cable, but in this description, these two substrates (10, 11) are assumed to be one substrate. Considered to be fully electrically connected.

  In the configuration shown in FIG. 7, the electrical component 8 mounted in the vicinity of the antenna 6 is regarded as a GND having a shape protruding from the end of the board because the lead wire 9 on one side is grounded to the GND (10). Can do. As described above, since the impedance of the antenna 6 decreases due to the proximity of the electrical component 8 to the antenna 6, the presence of the electrical component 8 causes a deterioration in the bandwidth and radiation characteristics of the input impedance of the antenna 6.

  FIG. 8 shows a conventional configuration example for improving antenna characteristics. In the illustrated mobile communication terminal 100 ′, an electrical component 8 such as a microphone or a speaker is connected to a substrate GND by a lead wire 9, and is connected by a lead wire 19 to a circuit of a control unit 15 that controls the operation of the terminal. In this configuration, an antenna matching circuit 17 for matching the impedances is inserted between the radio unit 16 and the antenna 6.

  By the way, the influence of the deterioration of the antenna characteristics due to the arrangement of the electric parts is more likely to appear when the electric parts are connected to the GND. As one of the improvement measures, there is a method of inserting a matching circuit composed of a series coil or the like into a connection line between the electrical component and the substrate GND as proposed in Patent Document 1 described later, for example. is there. By inserting a matching circuit and making the impedance high in terms of high frequency, it is possible to realize a wide band of radiation efficiency of the antenna.

  Further, the influence of the electric component (8) protruding from the board GND is likely to appear even when the terminal casing is closed. FIG. 9 shows a front view of the cellular phone 100 shown in FIGS. 6 and 7 with the housing closed. FIG. 10 is a side view thereof. As shown in FIGS. 9 and 10, in the closed state of the housing, the upper substrate GND10 to which the electrical component 8 is connected comes closer to the lower substrate GND11 than in the open state. As a result, when the impedance of the electrical component 8 varies, the input impedance and radiation characteristics of the antenna 6 also vary.

  In general, in the case of a λ / 2 type antenna, the antenna current distribution is 0 on the side opposite to the grounding portion of the antenna, so that the impedance is open. Therefore, in the case of the λ / 2 system, the radiation pattern of the antenna is hardly affected by the size and length of the metal shield housing.

On the other hand, in the case of a λ / 4 type antenna, the housing GND contributes to the radiation of the antenna as an image plate, so that a large amount of current also flows to the housing side. Therefore, since the length and shape of the casing (substrate) greatly affect the radiation pattern of the antenna, the casing (substrate) of the λ / 4 antenna can be regarded as a part of the antenna. Therefore, the length of the electrical component protruding from the end of the board GND and the ground GND line tends to affect the antenna characteristics.
JP 2002-009521 A (Patent No. 3671859)

  As described above with reference to FIGS. 9 and 10, in the case of a foldable mobile phone, the GND line (9) of the electrical component 8, the substrate GND (11), and The positional relationship is different. Therefore, the impedance of the electrical component 8 changes by opening and closing the housing.

  However, in the above-described method described in Patent Document 1, the circuit constant of the matching circuit configured by the series coil is fixed. Therefore, it is difficult to cope with the above-mentioned method that the electrical component affects the input impedance of the antenna every time the casing is opened and closed. This is because even if a matching circuit having a fixed constant is used, a frequency band in which the input impedance characteristic of the antenna is improved can be obtained, but a deteriorated frequency may be generated.

  Conventionally, a technique for obtaining input impedance characteristics and radiation characteristics in a desired band by preparing a plurality of antenna matching circuits (17) as shown in FIG. 8 and switching them is known. For this purpose, it is necessary to add another antenna matching circuit and switching circuit between the antenna (6) and the radio unit (16), but the wiring pattern between the antenna (6) and the radio unit (16) increases. That leads to transmission loss. Therefore, the method of switching a plurality of antenna matching circuits is not actually desirable.

  The present invention has been made in view of the above problems, and an object thereof is to provide a technique for maintaining stable antenna performance regardless of the operating state of a mobile communication terminal.

A portable communication terminal according to the present invention includes an antenna, an impedance matching circuit provided between the antenna and a radio unit that transmits and receives a radio signal via the antenna, and first and second antennas configured to be openable and closable. A portable communication terminal in which a feeding point of the antenna is connected to a GND of a substrate of one of the first and second casings. A detection means for detecting opening and closing of the housing of 2 and a conductive electronic component mounted on a substrate to which the feeding point of the antenna is connected, and between the GND terminal of the electronic component and the GND of the substrate A plurality of matching circuits for switching the impedance of the electronic component provided, and the impedance of the electronic component is input to the antenna according to the opening and closing of the first and second casings detected by the detection means I And having a switch circuit for switching the plurality of matching circuits so as to correspond to the impedance.

  According to the present invention, it is possible to prevent the impedance of a component connected to the ground of the substrate from fluctuating due to a change in the operating state of the terminal and affecting the input impedance of the antenna. Thereby, since the deterioration of the radiation characteristic of the antenna is avoided, the antenna characteristic can be stabilized.

  FIG. 1 shows the configuration of an embodiment of the present invention. The mobile communication terminal 101 is provided with an antenna matching circuit 17 between the radio unit 16 and the antenna 6 for matching their impedances. In addition, an electrical component 8 that is an arbitrary conductive component such as a microphone, a camera, a speaker, and a vibrator is connected to the circuit of the control unit 15 by a lead wire (signal line) 19. The electrical component 8 is electrically connected to the GND of the substrate (not shown) by a lead wire (GND side) 9.

  The electrical component 8 is mounted on the terminal at a location where the input impedance characteristic of the antenna 6 is likely to be affected by deterioration. This location is a location where the mounted electrical component 8 protrudes from the GND of the board as shown in FIG. 7, for example. The type and shape of the antenna 6 are not particularly limited, but a small antenna that can be built into a terminal, such as a λ / 2 type or a λ / 4 type, is an object.

  In addition to the above configuration, the mobile communication terminal 101 of the present embodiment includes a matching circuit 110 inserted in a line between the electrical component 8 and the GND, and a state change detection unit 18 that detects a change in the operating state of the terminal itself. .

  As shown in FIG. 1, the matching circuit 110 has one end connected to the lead wire (GND side) 9 of the electrical component 8 and the other end grounded. The matching circuit 110 has a circuit configuration that operates so that the impedance of the electrical component 8 corresponds to the input impedance of the antenna 6 in accordance with a change in the operating state of the terminal itself.

  The state change detection unit 18 has a function of detecting a change in a state set in advance with respect to the operation of the mobile communication terminal 101. The control unit 15 sends an operation switching command to the matching circuit 110 through the switching control line 20 every time the change in the operation state is detected by the state change detection unit 18.

  FIG. 2 shows the configuration of the first embodiment relating to the portable communication terminal 101 (FIG. 1). This embodiment is suitable for a terminal of a folding type, a sliding type, a turning type or the like that can open and close the casing of the terminal.

  As shown in FIG. 2, the mobile communication terminal 101A includes an open / close detection unit 18A that detects a change in the open / close state of the housing as the state change detection unit 18 (FIG. 1). The open / close detection unit 18A can be configured by a Hall IC having a function of detecting the open / closed state of the housing.

  Here, the open state of the housing refers to a state where the housing is unfolded as shown in FIGS. 6 and 7, for example. In addition, the closed state refers to a state in which the impedance of the electrical component 8 changes from the open state by overlapping the substrate GND of the housing as shown in FIGS. 9 and 10.

  As shown in FIG. 2, the matching circuit 110A of the mobile communication terminal 101A includes two matching circuits 13A and 14A, and a matching circuit (13A, 14A) according to a command sent from the control unit 15 through the switch control line 20A. And a switch 12 for switching. The switch 12 is connected to the lead wire (GND side) 9 of the electrical component 8. Each of the matching circuit 13A and the matching circuit 14A has one end connected to the switch 12 and the other end grounded.

  The matching circuit 13A corresponds to the open state of the housing, and the other matching circuit 14A corresponds to the closed state. In this embodiment, the matching circuit 13A is a circuit constant that optimizes the input impedance characteristics of the antenna matching circuit 17 in the open state of the casing, that is, in order to make the impedance of the electrical component 8 correspond to the input impedance of the antenna 6 in the open state. Circuit constants. The matching circuit 14A has a circuit constant that optimizes the input impedance characteristic of the antenna matching circuit 17 in the closed state of the housing.

  FIG. 3 shows a flowchart regarding the operation of the mobile communication terminal 101A. When the open / close detection unit 18A detects a change in the open / close state of the housing in the standby state or communication state of the mobile communication terminal 101A (step S1), the information is recognized by the control unit 15. When the recognized information indicates a change from the closed state to the open state of the housing (step S2: Yes), the control unit 15 instructs the switch 12A to switch from the matching circuit 14A to the matching circuit 13A (step S2). S3). When the change from the open state to the closed state is indicated (step S2: No), the switch 12A is instructed to switch from the matching circuit 13A to the matching circuit 14A (step S4).

  According to the mobile communication terminal 101A of the first embodiment, since the constant of the matching circuit 110A is switched in accordance with the change in the open / close state of the housing, the input impedance of the antenna 6 due to the fluctuation of the impedance of the electrical component 8 is increased. Can prevent the influence.

FIG. 4 shows the configuration of the second embodiment relating to the portable communication terminal 101 (FIG. 1). This embodiment is suitable for a so-called broadband frequency compatible terminal having a plurality of types of wireless communication means.

  The mobile communication terminal 101B according to the present embodiment includes a wireless switching detection unit 18B that recognizes a change in the form of wireless communication performed by the terminal as the state change detection unit 18 (FIG. 1). The wireless switching detection unit 18B only needs to be provided with at least a function for recognizing a change in wireless format, and does not need to have a function for determining which wireless format should be applied.

  Here, the wireless communication format is a frequency band selectable by the terminal (101B), for example, 62ch of 900 MHz band by GSM (Global System for Mobile communications) or 698ch of 1800 MHz band by DCS (Digital Communication System). And a combination of channels.

  Further, the change in the wireless format detected by the wireless switching detection unit 18B is associated with the change in the open / close state of the housing. For example, the relationship between the radio format and the open / closed state is such that the terminal is used in the open state in the Y channel wireless communication in the frequency X band and is used in the closed state in the N channel wireless communication in the frequency M band. Are predefined.

As shown in FIG. 4 , the portable communication terminal 101B of the present embodiment includes two systems of matching circuits 13B and matching circuits 14B corresponding to two types of wireless communication. The matching circuit 13B has a circuit constant that optimizes the input impedance characteristic of the antenna matching circuit 17 in wireless communication using the Y channel in the frequency X band. The matching circuit 14B has a circuit constant that optimizes the input impedance characteristic of the antenna matching circuit 17 in wireless communication using N channels in the frequency M band.

  The operation of the mobile communication terminal 101B is in accordance with the operation of the mobile communication terminal 101A described above with reference to FIG. In the present embodiment, the switch 12B is switched to the matching circuit 13B or the matching circuit 14B in accordance with the change in the wireless format detected by the wireless switching detection unit 18B.

  According to the mobile communication terminal 101B of the second embodiment, the constant of the matching circuit 110B can be switched without directly detecting the open / closed state of the housing. As a result, for example, a terminal in which the determination of the open / close state is not easy, such as a terminal in which a casing portion provided with the electrical component 8 is freely swung, or a terminal in which the operation state is difficult to define in two ways are dealt with. be able to.

  Each matching circuit (13A / 14A, 13B / 14B) in each of the above embodiments can be appropriately configured according to circuit constants required for the matching circuit. As an example, as shown in FIG. 5, a matching circuit can be configured by a π type using three elements (21, 22, 23) such as a chip coil and a capacitor. Further, as long as the configuration has a required constant, the circuit is not limited to the π type using three elements as shown in FIG. 5, and may be another circuit configuration using one element, two elements, or four or more elements. Further, the matching circuits (13A / 14A, 13B / 14B) may be different from each other.

  The mobile communication terminal 101 (FIG. 1) shown as an embodiment of the present invention recognizes two systems of operating states, but in implementing the present invention, there are only two operating states defined for the terminal. It is good also as three or more. Even if three or more operating states are defined, the present invention can be implemented by inserting a matching circuit (110) capable of coping with these operating states into a path from the electrical component (8) to the GND.

  The configuration of the matching circuit 110 is not limited to those of the embodiments shown in FIGS. 2 and 4 and may be other configurations.

  The operation state of the terminal that is the detection target of the state change detection unit (18) is not limited to the open / close state of the casing and the wireless format described in the above embodiments. For example, an event in which the impedance of the electrical component 8 of the terminal may change may be detected, such as whether a card as a recording medium or a communication medium is attached or detached, or an external input / output terminal is attached or detached.

It is a block diagram which shows the structure of embodiment of this invention. It is a block diagram which shows the structure of Example 1 of embodiment. 3 is a flowchart showing the operation of the first embodiment. It is a block diagram which shows the structure of Example 2 of embodiment. It is a block diagram which shows the structural example of the matching circuit in embodiment. It is a general-view figure of the conventional foldable mobile phone. It is a general-view figure which shows the internal structure in the open state of the conventional foldable mobile telephone. It is a block diagram which shows the structure of the conventional portable communication terminal. It is a general-view figure which shows the internal structure in the closed state of the conventional foldable mobile telephone. It is a general-view figure which shows the side surface in the closed state of the conventional foldable mobile telephone.

Explanation of symbols

101,101A, 101B Mobile communication terminal
110,110A, 110B matching circuit
6 Antenna
8 Electrical components
9,19 Lead wire
12,12A, 12B switch
13/14, 13A / 14A, 13B / 14B matching circuit
15 Control unit
16 Radio section
17 Antenna matching circuit
18 State change detector
18A Open / close detector
18B wireless switching detector
20 Switching control line
20A, 20B switch control line
21,22,23 elements

Claims (4)

An antenna,
An impedance matching circuit provided between the antenna and a radio unit that transmits and receives radio signals via the antenna;
And first and second housings configured to be openable and closable,
A portable communication terminal in which a feeding point of the antenna is connected to GND of a substrate of one of the first and second casings,
Detecting means for detecting opening and closing of the first and second housings;
A conductive electronic component is mounted on a substrate connected to the feeding point of the antenna, and is provided between the GND terminal of the electronic component and the GND of the substrate for switching the impedance of the electronic component. Multiple matching circuits;
A switch circuit that switches the plurality of matching circuits so that the impedance of the electronic component corresponds to the input impedance of the antenna in response to the opening and closing of the first and second housings detected by the detection means;
A mobile communication terminal characterized by comprising: The portable communication terminal performs wireless communication by switching between a plurality of different wireless communication formats, the plurality of wireless communication formats are associated with opening and closing of the first and second housings, and the detecting means is configured to The portable communication terminal according to claim 1 , wherein opening / closing of the second casing is detected by a change in the wireless communication format . The portable communication terminal according to claim 1 or 2, characterized in that it is configured to form π according to at least one of 3 elements of the plurality of matching circuits. 4. The mobile communication terminal according to claim 1 , wherein the electronic component is one of a microphone, a camera, a speaker, and a vibrator. 5.

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