JP2014230028A - Antenna device and wireless communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute an antenna device in which loss due to an additional element, e.g., a matching circuit, is prevented in an antenna where applied frequency is switched using a switch, and to provide a wireless communication device including the same.SOLUTION: An antenna device includes a radiation electrode 10 having open first end 11e and second end 12e, power supply paths 13, 14, 15, 16 for supplying power to the power supply points FP1, FP2 of the radiation electrode 10, and a switch 30 performing power supply selectively via these power supply paths. A resonance mode of distributing an electromagnetic field of 1/4 wavelength and an electromagnetic field of 3/4 wavelength is generated by the radiation electrode from the power supply point FP1 to the first and second ends 11e, 12e, while a resonance mode of distributing an electromagnetic field of 1/4 wavelength and an electromagnetic field of 3/4 wavelength is generated by the radiation electrode from the power supply point FP2 to the first and second ends 11e, 12e, and these resonance modes are switched by switching the switch.

Description

  The present invention includes a small antenna used for a mobile communication device such as a mobile phone terminal and a GPS receiver, an electronic device having a short-range wireless communication function such as a wireless LAN and Bluetooth (registered trademark), and the antenna. The present invention relates to a wireless communication device.

  Patent Document 1 discloses a dual band antenna device including a single radiation electrode, first and second matching circuits, and a switch. FIG. 10 is a configuration diagram of the antenna device disclosed in Patent Document 1. In FIG. The antenna device includes a meander antenna 1 as an antenna element, first and second feeding units 2 and 3 at both ends of the meander antenna 1, one end connected to the feeding units 2 and 3, and the other end connected to a switch 6. The first and second matching circuits 4 and 5, the band changeover switch 6, and the radio circuit 7 for the antenna 1.

  First, when matching in the first frequency band is attempted, the switch 6 is connected to the first power feeding unit 2 side. Since the 2nd electric power feeding part 3 side is open | released at this time, the 1st electric power feeding part 2 becomes a feeding point of the antenna 1, the 2nd electric power feeding part 3 becomes an open end, and it operate | moves as an inverted L-shaped antenna.

  The first matching circuit 4 includes a series-connected inductor L1 and a shunt-connected inductor L2. When matching in the second frequency band is intended, the switch 6 is connected to the second power feeding unit 3 side. At this time, the second feeding unit 3 serves as a feeding point, and the first feeding unit 2 operates as an inverted L-shaped antenna in which the inductors L1 and L2 of the first matching circuit 4 are inserted.

JP 2006-310995 A

  As described above, the antenna device shown in FIG. 10 uses a switch to change the feeding point for one antenna element and to change the resonance frequency by changing the matching circuit.

  However, in the antenna apparatus shown in FIG. 10, since the antenna current flows through the matching circuit, a loss occurs in the matching circuit, causing a problem that the efficiency is lowered.

  An object of the present invention is to provide an antenna device that solves the problem of loss caused by an additional element such as a matching circuit in an antenna that switches an applied frequency using a switch, and a wireless communication device including the antenna device.

  The antenna device of the present invention is configured as follows.

(1) A radiation electrode formed on the dielectric element body or on the substrate, the first end and the second end being opened, and a plurality of power feeding points formed on the substrate to a plurality of feeding points of the radiation electrode. A power supply path and a switch that selectively supplies power through the plurality of power supply paths are provided.

  With the above configuration, the loss in the matching circuit can be suppressed compared to the configuration in which the frequency band is switched by the matching circuit as in the antenna device illustrated in FIG.

(2) It is preferable that the radiation electrode has a shape extending from the plurality of feeding points in different directions, and the first end and the second end face each other. According to this configuration, it acts as two independent radiation electrodes or a single radiation electrode depending on the frequency band, and can cope with multiband. Further, since the radiation electrode is arranged in a limited space, a small antenna device can be configured.

(3) A resonance mode in which an electromagnetic field having a quarter wavelength and an electromagnetic field having a quarter wavelength is distributed from the plurality of feeding points to the first end, and at least from the plurality of feeding points to the second end. A configuration in which a resonance mode in which an electromagnetic field having a quarter wavelength is distributed is preferable. With this configuration, it is possible to cope with further multiband.

(4) Preferably, a reactance element is connected to the shunt with respect to the plurality of feeding points.

  If both the low band and the high band are switched by the electrode length, a path other than the originally intended current path acts as a resonance line, and it may be difficult to perform matching due to the influence. Terminating with a reactance element, the resonant frequency of the resonant line can be shifted to a frequency that has no influence.

(5) In the above (4), the plurality of feeding points are two, and the reactance element connected to the one where the resonance frequency of the radiation electrode is lowered is an inductor, and the resonance frequency of the radiation electrode is The reactance element connected to the higher one is preferably a capacitor. With this configuration, it is possible to shift the resonance of paths other than the originally intended current path out of the necessary band in accordance with switching of the switch.

(6) The switch is a high-frequency switch IC whose path is switched by a control voltage with respect to the ground potential, and is preferably arranged in a ground electrode formation region on the substrate. With this configuration, since the ground electrode is not close to the radiation electrode compared to when the switch is disposed in the vicinity of the radiation electrode, it is possible to avoid deterioration of the antenna characteristics due to the layout of the switch.

(7) A wireless communication device according to the present invention includes the antenna device having the above-described configuration and a communication circuit connected to the antenna.

  According to the present invention, the loss in the matching circuit can be suppressed as compared with the antenna whose frequency band is switched by the matching circuit.

FIG. 1 is a plan view of a main part of an antenna device 101 according to the first embodiment. FIG. 2A is a diagram illustrating a current path in a state where the switch 30 is switched to the power feeding path 14 side. FIG. 2B is a diagram illustrating a current path in a state where the switch 30 is switched to the power feeding path 15 side. FIG. 3A and FIG. 3B are diagrams showing voltage distributions on the first radiation electrode and the second radiation electrode. FIG. 4 is a plan view of the main part of the antenna device 102 according to the second embodiment. FIG. 5A is a schematic diagram showing a current path CP1 of the first radiation electrode and a current path CP2 of the second radiation electrode in a state where the switch 30 is switched to the power feeding path 14 side. FIG. 5B is a schematic diagram showing the current path CP1 of the first radiation electrode and the current path CP2 of the second radiation electrode in a state where the switch 30 is switched to the power feeding path 15 side. FIG. 6 is a diagram showing voltage distributions on the first and second radiation electrodes when acting as an inverted L-type antenna. FIGS. 7A and 7B are diagrams showing voltage distributions on the first and second radiation electrodes when acting as an inverted F-type antenna. FIG. 8A is a diagram illustrating the frequency characteristics of the return loss (S11) of the antenna device 102 according to the second embodiment. FIG. 8B is a diagram showing the frequency characteristics of the return loss of the antenna device as a comparative example. FIG. 9 is a plan view of the main part of the antenna device 103 according to the third embodiment. FIG. 10 is a configuration diagram of the antenna device disclosed in Patent Document 1. In FIG.

  Hereinafter, some specific examples will be given to describe embodiments for carrying out the present invention. Each embodiment is an exemplification, and it is needless to say that still other embodiments can be obtained by partial replacement or combination of configurations shown in different embodiments.

<< First Embodiment >>
FIG. 1 is a plan view of a main part of the antenna device 101 according to the first embodiment. The antenna device 101 includes a radiation electrode 10 formed on the substrate 20 and a plurality of power supply paths 13, 14, 15, 16 and a switch (high-frequency switch IC) 30 that selectively supplies power via these power supply paths 13, 14, 15, and 16. The radiation electrode 10 extends in the opposite direction (left-right direction) from the two feeding points FP1 and FP2, and has a shape in which the first end 11e and the second end 12e face each other. The radiation electrode 10 includes a plurality of radiation electrode portions. That is, the radiation electrode portions 11a and 11b extend from the first feed point FP1, and the radiation electrode portions 12a, 12b, and 12c extend from the second feed point FP2. A ground electrode 21 is formed on the substrate 20, and the radiation electrode 10 and the feeding paths 13, 14, 15, and 16 are formed in a region where the ground electrode 21 is not formed. The control signal lines for the switch 30 are not shown.

  FIG. 2A is a diagram illustrating a current path in a state where the switch 30 is switched to the power feeding path 14 side (a state in which the power feeding path 14 side is selected). FIG. 2B is a diagram illustrating a current path in a state where the switch 30 is switched to the power feeding path 15 side (a state in which the power feeding path 15 side is selected). In the state shown in FIG. 2A, of the radiation electrode 10, the radiation electrode portions 11a and 11b act as the first radiation electrode, and the radiation electrode portions 12a, 12b, and 12c and the feeding path 16 are the second radiation. Acts as an electrode. A resonance mode (λ / 4 mode) in which an electromagnetic field of ¼ wavelength is distributed from the first feeding point FP1 to the first end 11e is generated in the first radiation electrode (11a, 11b). On the other hand, in the second radiation electrode (12a, 12b, 12c, 16), a resonance mode (λ / 4 mode resonance) in which an electromagnetic field of ¼ wavelength is distributed from the first feeding point FP1 to the second end 12e. And a resonance mode (resonance of 3λ / 4 mode) in which an electromagnetic field of 3/4 wavelength is distributed occurs.

  In the state shown in FIG. 2B, the radiation electrode portions 11a and 11b and the power feeding path 16 act as first radiation electrodes, and the radiation electrode portions 12a, 12b, and 12c act as second radiation electrodes. In the first radiation electrode (11a, 11b, 16), resonance of λ / 4 mode occurs from the second feeding point FP2 to the first end 11e. On the other hand, in the second radiation electrode (12a, 12b, 12c), λ / 4 mode resonance and 3λ / 4 mode resonance occur from the second feed point FP2 to the second end 12e.

  3A and 3B are diagrams showing voltage distributions on the first radiation electrode and the second radiation electrode. 3A shows the case of resonance in the λ / 4 mode, and FIG. 3B shows the case of resonance in the 3λ / 4 mode. As shown in FIGS. 3A and 3B, the feeding point FP1 or FP2 is a voltage node, and the tip (open end) 11e or 12e is a voltage antinode. In λ / 4 mode resonance, a standing wave having a quarter wavelength is generated at the resonance frequency. In the resonance of 3λ / 4 mode, a standing wave of 3/4 wavelength is generated at the resonance frequency. Note that the capacitance generated between the first end 11e and the second end 12e can particularly adjust the resonance frequency of the 3λ / 4 mode.

  In this manner, the electrical lengths of the first and second radiation electrodes are changed by switching the switch 30 shown in FIG. 1, so that the resonance frequencies of the λ / 4 mode and the 3λ / 4 mode by each radiation electrode are changed. Change.

<< Second Embodiment >>
FIG. 4 is a plan view of the main part of the antenna device 102 according to the second embodiment. The antenna device 102 includes a radiation electrode, a plurality of feed paths 13, 14, 15 that feed power to the two feed points FP 1, FP 2 of the radiation electrode, and the feed paths 13, 14, 15, and a switch 30 that selectively supplies power via 15. The radiation electrode has a shape in which the first end 11e and the second end 12e face each other. That is, the radiation electrode portions 11a, 11b, and 11c extend from the first feeding point FP1, and the radiation electrode portions 12a, 12b, and 12c extend from the second feeding point FP2. A ground electrode 21 is formed on the substrate 20, and the radiation electrode and the feeding paths 13, 14, 15 are formed in a region where the ground electrode 21 is not formed. A reactance element X1 is connected to the shunt in the vicinity of the first feeding point FP1. A reactance element X2 is connected to the shunt in the vicinity of the second feed point FP2. Here, the reactance element X1 is an inductor, and the reactance element X2 is a capacitor.

  FIG. 5A is a schematic diagram showing a current path CP1 of the first radiation electrode and a current path CP2 of the second radiation electrode in a state where the switch 30 is switched to the power feeding path 14 side. FIG. 5B is a schematic diagram showing the current path CP1 of the first radiation electrode and the current path CP2 of the second radiation electrode in a state where the switch 30 is switched to the power feeding path 15 side.

  In the state shown in FIG. 5A, the current path CP1 acts as a first radiation electrode by the radiation electrode portions (11a, 11b, 11c), and the current path CP2 acts as the radiation electrode portions (11b, 12a, 12b, 12c). ) Acts as a second radiation electrode.

  Here, if the second feeding point FP2 is not grounded via the reactance element X2 (capacitor), the current path CP3 is determined by the path formed by the feeding paths 14 and 15 and the radiation electrode portion 11b and the open-end capacitance of the switch 30. Thus, this current path CP3 acts as a resonance line. However, in the second embodiment, when the switch 30 selects the power supply path 14 side, the second power supply point FP2 is grounded via the reactance element X2 (capacitor). The current path CP3 due to the electrode part 11b does not occur. That is, the resonance frequency of the portion corresponding to the current path CP3 is greatly deviated from the use frequency band.

  In the state shown in FIG. 5A, the first radiation electrode and the second radiation electrode each function as an inverted L-type antenna.

  In the state shown in FIG. 5B, the current path CP1 acts as a first radiation electrode by the radiation electrode part (11b, 11c), and the current path CP2 is a second by the radiation electrode part (12a, 12b, 12c). Acts as a radiation electrode. When the switch 30 selects the power supply path 15 side, the first power supply point FP1 is grounded via the reactance element X1 (inductor). Therefore, the current path CP3 due to the power feeding paths 14 and 15 and the radiation electrode portion 11b does not occur. That is, the portion corresponding to the current path CP3 does not act as a resonance line (the resonance frequency greatly deviates from the use frequency band).

  In the state shown in FIG. 5B, the reactance element X1 (inductor) and the first radiation electrode act as an inverted F-type antenna, and the reactance element X1 (inductor) and the second radiation electrode have an inverse F Acts as a mold antenna.

  Thus, since the current path CP3 other than the originally intended current path does not act as a resonance line in the vicinity of the used frequency band, impedance matching between the original radiation electrode and the feeding circuit can be easily performed.

  FIG. 6 is a diagram showing voltage distribution on the first and second radiation electrodes when acting as the inverted L-type antenna. As shown in FIG. 6, the feeding point FP1 is a voltage node, and the tip (open end) 11e or 12e is a voltage antinode. In λ / 4 mode resonance, a standing wave having a quarter wavelength is generated at the resonance frequency. It should be noted that the resonance of the 3λ / 4 mode may be used in a state in which it acts as the inverted L-type antenna.

  FIGS. 7A and 7B are diagrams showing voltage distributions on the first and second radiation electrodes when acting as the inverted F-type antenna. FIG. 7A shows the case of resonance in the λ / 4 mode, and FIG. 7B shows the case of resonance in the 3λ / 4 mode. As shown in FIGS. 7A and 7B, the connection point (first feeding point FP1) of the reactance element X1 (inductor) is a voltage node, and the tip (open end) 11e or 12e is an antinode of the voltage. Become. In λ / 4 mode resonance, a standing wave having a quarter wavelength is generated at the resonance frequency. In the resonance of 3λ / 4 mode, a standing wave of 3/4 wavelength is generated at the resonance frequency.

  FIG. 8A is a diagram illustrating the frequency characteristics of the return loss (S11) of the antenna device 102 according to the second embodiment. FIG. 8B is a diagram showing the frequency characteristics of the return loss of the antenna device as a comparative example. The antenna device of this comparative example corresponds to a state where the reactance elements X1 and X2 are not provided in the antenna device shown in FIG. 8A and 8B, curve A shows the return loss of the antenna when the switch 30 is switched to the feeding path 14 side, and curve B switches the switch 30 to the feeding path 15 side. It shows the return loss of the antenna in the measured state.

  In the state where the switch 30 is switched to the power supply path 14 side, as shown in FIG. 8A, the λ / 4 mode resonance by the current path CP2 occurs at the frequency f11 (800 MHz), and the frequency f12 ( 1500 MHz), a λ / 4 mode resonance occurs due to the current path CP1. Further, in the state where the switch 30 is switched to the power feeding path 15 side, resonance in the λ / 4 mode by the current path CP2 occurs at the frequency f21 (900 MHz), and λ / by the current path CP1 occurs at the frequency f22 (1900 MHz). Four-mode resonance occurs. Further, a resonance of 3λ / 4 mode by the current path CP2 occurs at the frequency f23 (2400 MHz). In this example, in the state where the switch 30 is switched to the power supply path 14 side, the resonance in the 3λ / 4 mode by the current path CP2 is not matched due to the presence of the reactance element X2 (capacitor), and thus the return loss is Not appearing.

  In FIG. 4, when the reactance element X1 is not connected to the shunt in the vicinity of the first feed point FP1, and the reactance element X2 is not connected to the shunt in the vicinity of the second feed point FP2, as shown in FIG. It can be seen that the return loss at each resonance frequency is shallow and cannot be matched.

<< Third Embodiment >>
FIG. 9 is a plan view of the main part of the antenna device 103 according to the third embodiment. The antenna device 103 includes a radiation electrode 10 formed on a substrate 20, a plurality of feed paths 13, 14, 15, and 16 that feed power to two feed points FP 1 and FP 2 of the radiation electrode 10, and these feed paths. And a switch 30 that selectively supplies power via 13, 14, 15, and 16. The radiation electrode 10 has a shape in which the first end 11e and the second end 12e face each other. That is, the radiation electrode portions 11a and 11b extend from the first feed point FP1, and the radiation electrode portions 12a, 12b, and 12c extend from the second feed point FP2. A ground electrode 21 is formed on the substrate 20, and the radiation electrode 10 and the power feeding paths 13, 14, 15 are formed in a region where the ground electrode 21 is not formed. A reactance element X1 is connected to the shunt in the vicinity of the first feeding point FP1. A reactance element X2 is connected to the shunt in the vicinity of the second feed point FP2. Here, the reactance element X1 is an inductor, and the reactance element X2 is a capacitor.

  Unlike the antenna devices 101 and 102 shown in the first embodiment and the second embodiment, the switch 30 is arranged in the formation region of the ground electrode 21. A part of the power feeding paths 14 and 15 and the power feeding path 13 are coplanar lines. Other basic configurations and operations are the same as those of the antenna devices 101 and 102 shown in the first and second embodiments.

  Since the control signal of the switch 30 is a circuit that operates based on the ground potential, an electrode having the ground potential is disposed in the vicinity of the switch 30. When this ground potential electrode is close to the radiation electrode, the radiation characteristics of the antenna are adversely affected. If the switch 30 is disposed in the formation region of the ground electrode 21 as in this embodiment, the ground electrode is not close to the radiation electrode as compared with the case where the switch is disposed in the vicinity of the radiation electrode. Antenna characteristic deterioration can be avoided.

<< Other embodiments >>
In each of the embodiments described above, an example in which the radiation electrode is directly formed on the substrate 20 has been shown. However, an antenna in which the radiation electrode is formed on the dielectric body is configured, and this antenna may be mounted on the substrate. Good.

  Moreover, in each embodiment shown above, although the antenna apparatus provided with two feed points FP1 and FP2 was shown, you may make it switch the feed with respect to three or more feed points with a switch. As a result, further multi-banding can be achieved.

  In each of the embodiments described above, the reactance element X1 is an inductor and the reactance element X2 is a capacitor. However, the present invention is not limited to this. However, it is preferable that the reactance element shunt-connected to the root of the path whose length is increased by switching the switch is an inductor because the resonance frequency can be effectively lowered. If the reactance element to be shunt connected is an inductor, the equivalent line length starts from that position. Therefore, if both the reactance elements X1 and X2 are inductors, the change in the path length due to switching of the switches is reduced. End up. Further, if the reactance elements X1 and X2 are capacitors, the end of the unnecessary current path (CP3) cannot be completely shunt-connected (because the effect as a shunt connection element is low), so both of the reactance elements X1 and X2 If it is a capacitor, it is difficult to achieve desired matching in the high band. Therefore, it is preferable to shunt-connect the inductor to the root and to shunt-connect the capacitor to the opposite side, which has a longer path length by switching the switch.

  In each of the embodiments described above, the λ / 4 mode resonance and the 3λ / 4 mode resonance of the radiation electrode are used. However, one of the plurality of resonance modes resonates at the half wavelength with the entire radiation electrode open. The λ / 2 mode may be used.

CP1, CP2, CP3 ... current path FP1 ... first feeding point FP2 ... second feeding point X1, X2 ... reactance element 1 ... meander antenna 2 ... first feeding part 3 ... second feeding part 4 ... first matching circuit 5 ... 2nd matching circuit 6 ... switch 7 ... radio circuit 10 ... radiation electrode 11a, 11b, 11c ... radiation electrode part 11e ... 1st end 12a, 12b, 12c ... radiation electrode part 12e ... 2nd end 13, 14, 15, 16 ... Power supply path 20 ... Substrate 21 ... Ground electrode 30 ... Switch 101, 102, 103 ... Antenna device

Claims (7)

  A radiation electrode having a first end and a second end formed on the dielectric element body or on the substrate; and a plurality of power supply paths formed on the substrate for supplying power to a plurality of power supply points of the radiation electrode. An antenna device comprising: a switch that selectively supplies power through the plurality of power supply paths.   2. The antenna device according to claim 1, wherein the radiation electrode extends in a different direction from the plurality of feeding points, and has a shape in which the first end and the second end face each other.   A resonance mode in which an electromagnetic field of ¼ wavelength and an electromagnetic field of ¾ wavelength are distributed from the plurality of feeding points to the first end, and at least ¼ from the plurality of feeding points to the second end. The antenna device according to claim 1, wherein a resonance mode in which electromagnetic fields of wavelengths are distributed occurs.   The antenna device according to claim 1, wherein a reactance element is connected to a shunt with respect to the plurality of feeding points.   The plurality of feeding points are two, and the reactance element connected to the one where the resonance frequency of the radiation electrode is lowered is an inductor, and the reactance connected to the one where the resonance frequency of the radiation electrode is increased The antenna device according to claim 4, wherein the element is a capacitor.   The antenna device according to claim 1, wherein the switch is a high-frequency switch IC whose path is switched by a control voltage with respect to a ground potential, and is disposed in a ground electrode formation region on the substrate.   A wireless communication device comprising the antenna device according to claim 1 and a communication circuit connected to the antenna device.

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