JP2010028521A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device capable of solving the problem, wherein increase in the number of frequencies available for communication cannot be attained, while suppressing expansion in apparatus scale. <P>SOLUTION: An antenna element 2 can be coupled with an antenna element 1 each other in a high-frequency manner. Furthermore, switching circuits 3 and 4 switch a short-circuited state and an open state regarding each of a plurality of predetermined switching points in the antenna element 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an antenna device that realizes multiband using a feeding element and a parasitic element.

  In recent years, in a wireless terminal such as a mobile wireless terminal, a response to a multi-band method in which a frequency band used for communication is switched from a plurality of frequency bands depending on a situation is progressing. For example, the wireless terminal switches the frequency band used for communication according to the situation such as indoors or outdoors.

  For example, when a linear antenna element is used as the antenna of the wireless terminal, a single resonance antenna having a frequency band corresponding to the length of the antenna element can be realized. Therefore, in order to configure a wireless communication device compatible with multiband, it is necessary to increase the number of antenna elements or to branch the antenna elements from the middle.

  However, when the number of antenna elements is increased or the antenna elements are branched from the middle, the apparatus becomes large. For this reason, it has been difficult to achieve both miniaturization and multi-band radio communication equipment.

  Patent Document 1 describes a multiband antenna capable of realizing multiband while suppressing an increase in size of the apparatus.

  This multiband antenna has a main element and a sub-element as antenna elements. The main element is a feeding element, and the sub-element is a parasitic element. The sub-element has a switch for connecting or disconnecting the base end portion of the sub-element and the ground conductor.

  In the first state in which the sub-element is electrically connected to the ground conductor, the sub-element and the main element are coupled at high frequency, and in the second state in which the sub-element is not electrically connected to the ground conductor, the sub-element is the main element. It acts as an element that does not have an electrical influence.

  As a result, in this multiband antenna, different frequency bands are communicated in each of the first state where the sub-element is electrically connected to the ground conductor and the second state where the sub-element is not electrically connected to the ground conductor. It becomes possible to use it.

Therefore, since it is possible to realize multiband without increasing the number of antenna elements, it is possible to suppress an increase in the size of the device.
Re-specialized WO2005 / 069439

  In the multiband antenna described in Patent Document 1, there are only two sub-element states, a first state and a second state. Further, when the sub element is in the first state where the sub element and the main element are coupled at a high frequency, only three frequency bands can be used for communication.

  For this reason, with one parasitic element, the number of frequency bands available for communication is limited. In order to increase the number of frequency bands that can be used for communication, it is conceivable to increase the number of sub-elements. However, increasing the number of sub-elements increases the size of the apparatus.

  For this reason, there has been a problem that the number of frequency bands available for communication cannot be increased while suppressing the increase in size of the apparatus.

  An object of the present invention is to provide an antenna device that solves the above-described problem that the number of frequency bands that can be used for communication cannot be increased while suppressing an increase in size of the device.

  An antenna device according to the present invention includes a feed element, a parasitic element that can be coupled to the feed element in high frequency, a substrate that generates an electric image of the feed element and the parasitic element, and the parasitic element. For each of the plurality of predetermined switching points, switching means for switching between a short-circuit state in which the switching point and the substrate are short-circuited and an open state in which the switching point is opened is included.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to increase the number of the frequency bands which can be utilized for communication, suppressing the enlargement of an apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram showing the configuration of the antenna device according to the first embodiment of the present invention.

  In FIG. 1, an antenna device 100 includes antenna elements 1 and 2 and a substrate 10. The substrate 10 includes switching circuits 3 and 4, control lines 5 and 6, a signal line 7, a wireless circuit 8, and a power feeding unit 9. The antenna device 100 is provided, for example, inside the housing of the mobile radio terminal.

  The antenna element 1 is an L-shaped linear power feeding element connected to the power feeding unit 9. One of the ends of the antenna element 1 is connected to the signal line 7 and the other is open.

  The antenna element 2 is a parasitic element having a half loop shape (specifically, a U-shaped linear shape). The antenna element 2 is provided at a position spaced apart from the antenna element 1 by a predetermined distance so that it can be coupled to the antenna element 1 at a high frequency. In the present embodiment, one of the bent portions of the antenna element 2 is provided at a position spaced apart from the open end of the antenna element 1 by a predetermined distance.

  The switching circuits 3 and 4 switch, for each of a plurality of predetermined switching points of the antenna element 2, either a short-circuit state in which the switching point is short-circuited with the substrate 10 or an open state in which the switching point is open. . In the present embodiment, the switching locations are the end portions 2 a and 2 b of the antenna element 2.

  The switching circuit 3 is provided between the end 2 a of the antenna element 2 and the substrate 10, and the switching circuit 4 is provided between the end 2 b of the antenna element 2 and the substrate 10. The switching circuit 3 switches between the short-circuit state in which the end 2a of the antenna element 2 is short-circuited to the substrate 10 and the open state in which the end 2a is opened. The switching circuit 4 switches between the short circuit state in which the end 2b of the antenna element 2 is short-circuited to the substrate 10 and the open state in which the end 2b is opened. The substrate 10 functions as a GND element (grounding element).

  The switching circuit 3 is connected to the control line 5, and the switching circuit 4 is connected to the control line 6.

  The radio circuit 8 is connected to the control lines 5 and 6 and the signal line 7.

  The radio circuit 8 transmits and receives an RF signal to and from the antenna element 1 via the signal line 7.

  The radio circuit 8 includes a switching control circuit 8a. The switching control circuit 8 a controls the switching circuits 3 and 4 via the control lines 5 and 6 according to the RF signal transmitted and received by the radio circuit 8 to individually switch the state of each end of the antenna element 2. In the present embodiment, the switching control circuit 8a places one of the end portions 2a and 2b of the antenna element 2 in a short circuit state and the other in an open state.

  The power feeding unit 9 feeds power to the antenna element 1.

  Substrate 10 has a larger area than antenna elements 1 and 2 so that an electric image of antenna elements 1 and 2 can be generated in substrate 10. Thereby, the antenna elements 1 and 2 and the substrate 10 can function as a plurality of loop-shaped antenna elements having different electrical lengths depending on the combination of the states of the end portions 2a and 2b of the antenna element 2. become.

  With the above configuration, the antenna device 100 has a plurality of different resonance frequencies for each antenna state determined according to the combination of the states of the end portions 2a and 2b.

  In addition, the antenna device 100 has two modes for each antenna state: a parasitic mode in which the antenna element 2 functions as a parasitic element of the antenna element 1 and a loop mode in which the antenna elements 1 and 2 function as loop-shaped antenna elements. Have The antenna device 100 has a plurality of different resonance frequencies for each mode.

  In the present embodiment, the antenna state includes two antenna states: an end 2a in an open state and an end 2b in a short-circuited state, and an antenna state in which the end 2a is short-circuited and an end 2b is in an open state. There are two antenna states. There are two modes for each antenna state. Therefore, the antenna device 100 has four resonance frequencies.

  Since the antenna device has these resonance frequencies and can use a frequency band having a predetermined bandwidth for communication, it can cope with multiband by switching these frequency bands as necessary. it can.

  Hereinafter, the operation of the antenna device 100 will be described.

  FIG. 2 is an explanatory diagram showing the input characteristics of the antenna device 100. In FIG. 2, the horizontal axis represents the frequency [GHz] and represents the input level [dB] of the RF signal of the antenna device 100.

  In FIG. 2, input characteristics 101 and 102 of the antenna device 100 are shown. The input characteristic 101 is the input characteristic of the antenna device 100 when the end 2a of the antenna element 2 controlled by the switching circuit 3 is in an open state and the end 2b of the antenna element 2 controlled by the switching circuit 3 is in a short-circuited state. Indicates. The input characteristic 102 is the input characteristic of the antenna device 100 when the end 2a of the antenna element 2 controlled by the switching circuit 3 is in a short circuit state and the end 2b of the antenna element 2 controlled by the switching circuit 3 is in an open state. Indicates.

  The antenna device 100 uses a frequency band having two resonance frequencies A and D with locally good reception sensitivity in the input characteristic 101 and resonance frequencies B and C with locally good reception sensitivity in the input characteristic 102 for communication. can do.

  At this time, the mode corresponding to the resonance frequencies A and B is the loop mode, and the mode corresponding to the resonance frequencies C and D is the parasitic mode.

  FIG. 3 is an explanatory diagram showing the direction of current flowing in the antenna elements 1 and 2 when communication is performed in a frequency band having the resonance frequencies A to D. FIG. In FIG. 3, the direction of current is indicated by an arrow.

  The current in the antenna element 1 flows from the power feeding unit 9 to the released end of the antenna element at all resonance frequencies. The feeding point from the feeding unit 9 is assumed to be in the vicinity of the end connected to the signal line 7.

  In the loop mode (resonance frequencies A and B), the current in the antenna element 2 flows in the direction from the open end to the shorted end. Further, in the loop mode corresponding to the resonance frequency A, the electric length of the loop antenna becomes long, and in the loop mode corresponding to the resonance frequency B, the electric length of the loop antenna becomes short.

  In the antenna element 2, the current flows in the direction from the short-circuited end to the open-ended end at the resonance frequencies C and D corresponding to the parasitic mode. For this reason, the antenna element 2 acts as a parasitic element of the antenna element 1.

  In the switching control circuit 8a, either one of the end portions of the antenna element 2 is in a short circuit state and the other is in an open state, but both end portions of the antenna element 2 may be open at the same time. In this case, the antenna element 2 acts as an element that does not electrically affect the antenna element 1.

  Next, the effect will be described.

  In the present embodiment, the antenna element 2 can be coupled to the antenna element 1 at a high frequency. The switching circuits 3 and 4 switch between a short-circuit state and an open state for each of a plurality of predetermined switching points of the antenna element 2.

  In this case, when one parasitic element and the feeding element are coupled at a high frequency, since each of the short circuit state and the open state has two resonance frequencies, at least four frequency bands can be used for communication. become. Therefore, the number of frequencies that can be used for communication with one parasitic element can be increased as compared with the antenna device of the prior art. Therefore, it is possible to increase the number of frequencies that can be used for communication while suppressing an increase in the size of the apparatus.

  Further, according to the combination of the states of the end portions 2a and 2b of the antenna element 2, it becomes possible to function as a plurality of loop-shaped antenna elements having different electrical lengths. For this reason, since it becomes possible to change the electrical length of an antenna element largely, it becomes possible to change the frequency characteristic of the antenna apparatus 100 largely. Therefore, it is possible to cope with a multiband covering a wide frequency range while suppressing an increase in size of the antenna device.

  Furthermore, since it is not necessary to connect a plurality of power feeding elements to the wireless circuit 8, it is possible to prevent the input / output of the wireless circuit 8 from becoming complicated.

  Next, a second embodiment will be described.

  The end portions 2a and 2b of the antenna element 2 have only two states of a short circuit state and an open state in the first embodiment, but there are three or more states in the present embodiment.

  FIG. 4 is a schematic diagram showing the antenna device of the present embodiment. In FIG. 4, antenna device 100 further includes changing elements 11 and 12 in addition to the configuration shown in FIG. 1.

  The change elements 11 and 12 are elements for generating the frequency characteristics of the antenna device 100, and are capacitive elements or inductive elements. Note that the antenna device 100 may include a plurality of changing elements having different capacities or inductances for each switching location.

  The switching circuit 3 switches the end 2a of the antenna element 2 to any one of open information, a short-circuit state, and a connection state in which the end 2a is short-circuited with the changing element. The switching circuit 4 switches the end 2b of the antenna element 2 to any one of open information, a short-circuit state, and a connection state in which the end 2b is short-circuited with the changing element.

  Next, the effect will be described.

  In the present embodiment, the state of the switching location further includes a connection state. In this case, since three or more states can be generated for one switching location, it is possible to further increase the number of frequency bands that can be used for communication while suppressing an increase in the size of the device.

  Next, another embodiment of the present invention will be described.

  In the first embodiment, the feeding element is an L-shaped linear antenna element 1 and the parasitic element is a U-shaped linear antenna element. However, the feeding element and the parasitic element are The shape is not limited to this, and can be changed as appropriate.

  For example, the feeder element and the parasitic element may be meander-shaped antenna elements shown in FIG. In this case, the switching locations are the two ends of the meandering parasitic element.

  Further, the feeding element and the parasitic element may be the plate-like antenna elements shown in FIGS. 6A and 6B.

  FIG. 6A shows a plate-like element (feed) 51 and a linear element 52 of the antenna device. The plate element (power supply) 51 is a plate-shaped power supply element. The linear element 52 is a U-shaped linear parasitic element.

  In FIG. 6B, a plate-like element (parasitic element) 53 and a linear element 54 of the antenna device are shown. The plate-like element (parasitic element) 53 is a plate-shaped parasitic element. The linear element 54 is an L-shaped linear power feeding element. In this case, the switching part may be an arbitrary part of the plate-like element (non-powered) 53.

  In addition, as the feed element and the parasitic element, the plate-like element (feed) 51 and the plate-like element (no-feed) 53 shown in FIGS. 6A and 6B may be slot antenna elements as shown in FIG.

  Furthermore, the feeding element and the parasitic element may be the loop antenna elements shown in FIGS. 8A and 8B.

  FIG. 8A shows a loop element (feeding) 61 and a linear element 62 of the antenna device. The loop element (power supply) 61 is an open loop power supply element. The linear element 62 is a U-shaped linear parasitic element.

  FIG. 8B shows a loop element (parasitic element) 63 and a linear element 64 of the antenna device. The loop element (parasitic element) 63 is an open loop parasitic element. The linear element 64 is an L-shaped linear feeding element. In this case, the switching points are two end portions of an open loop loop element (non-powered) 63.

  Moreover, the parasitic element may have three or more end points as shown in FIG.

  9 includes a feeding element 71, a parasitic element 72, and a switching circuit 73 of the antenna device.

  The feeding element 71 is an L-shaped linear antenna element. The parasitic element 72 is a multiple half-loop antenna element in which a plurality of half-loop antenna elements are connected. For this reason, the parasitic element 72 has three or more ends.

  The switching circuit 73 is provided for each end of the parasitic element 72 and switches the state of the end.

  In this case, since it is possible to generate more antenna states with one parasitic element, it is possible to further increase the number of frequency bands that can be used for communication.

  In each embodiment described above, the illustrated configuration is merely an example, and the present invention is not limited to the configuration.

  For example, the antenna device can be provided not only in a portable wireless device but also in a general wireless terminal.

It is the schematic diagram which showed the structure of the antenna device of 1st embodiment of this invention. It is explanatory drawing which showed the input characteristic of the antenna apparatus. It is explanatory drawing which showed the direction of the electric current which flows into an antenna element. It is the schematic diagram which showed the structure of the antenna device of 2nd embodiment of this invention. It is the schematic diagram which showed the meander-shaped antenna element. It is the schematic diagram which showed the plate-shaped electric power feeding element. It is the schematic diagram which showed the plate-shaped parasitic element. It is the schematic diagram which showed the slot-shaped antenna element. It is the schematic diagram which showed the loop-shaped electric power feeding element. It is the schematic diagram which showed the loop-shaped parasitic element. It is the schematic diagram which showed the parasitic element whose switching location is 3 or more.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Antenna element 3, 4 Switching circuit 5, 6 Control line 7 Signal line 8 Radio circuit 8a Switching control circuit 9 Feeding part 10 Substrate 11, 12 Change element

Claims (2)

A feeding element;
A parasitic element capable of being coupled with the feeding element at a high frequency, and
A substrate for generating an electrical image of the feeding element and the parasitic element;
For each of a plurality of predetermined switching points of the parasitic element, an antenna device including switching means for switching between a short circuit state in which the switching point and the substrate are short-circuited and an open state in which the switching point is opened . The antenna device according to claim 1,
The antenna device is configured to switch the short circuit state, the open state, and a connection state in which the switching portion and the capacitive element or the inductive element are short-circuited for each of the plurality of switching portions.

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