JP5507935B2 - Antenna structure, radio communication apparatus, and antenna control method - Google Patents

Antenna structure, radio communication apparatus, and antenna control method Download PDF

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JP5507935B2
JP5507935B2 JP2009212079A JP2009212079A JP5507935B2 JP 5507935 B2 JP5507935 B2 JP 5507935B2 JP 2009212079 A JP2009212079 A JP 2009212079A JP 2009212079 A JP2009212079 A JP 2009212079A JP 5507935 B2 JP5507935 B2 JP 5507935B2
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frequency band
antenna element
antenna
current
circuit
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JP2011061712A (en
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亮 伊藤
淳 内田
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日本電気株式会社
Necアクセステクニカ株式会社
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Description

  The present invention relates to an antenna structure, a wireless communication apparatus, and an antenna control method capable of wireless communication in a plurality of different frequency bands.

  FIG. 11 schematically shows an example of an antenna structure (see Patent Document 1). The antenna structure 100 includes a first antenna element 101, a second antenna element 102, a first blocking means 103, and a second blocking means 104.

  In the antenna structure 100, one end sides of the first antenna element 101 and the second antenna element 102 are connected to each other. A connection portion X between the first antenna element 101 and the second antenna element 102 is electrically connected to a wireless circuit (feeding point) 106 of the wireless communication apparatus through a matching circuit 105. The first antenna element 101 resonates in a predetermined first frequency band, and this resonance enables transmission and reception of radio waves in the first frequency band. That is, when the first antenna element 101 is in conduction with the radio circuit 106 and the current in the first frequency band is supplied from the radio circuit 106, the first antenna element 101 resonates by the power supply and generates radio waves in the first frequency band. Wireless transmission. When radio waves in the first frequency band arrive, the first antenna element 101 resonates and receives the radio waves, and the received signal is transmitted to the radio circuit 106.

  The second antenna element 102 resonates in a predetermined second frequency band higher than the first frequency band, and this resonance enables transmission and reception of radio waves in the second frequency band. That is, the second antenna element 102 operates in the same manner as the first antenna element 101 and transmits and receives radio waves in the second frequency band, although the resonance frequency is different from that of the first antenna element 101.

  The first blocking means 103 has a function of blocking conduction between the wireless circuit 106 and the first antenna element 101. The second blocking means 104 has a function of blocking conduction between the wireless circuit 106 and the second antenna element 102. The operations of the first blocking means 103 and the second blocking means 104 are controlled as follows by a control circuit (not shown) of the wireless communication apparatus.

  That is, when the wireless communication apparatus performs wireless communication in the first frequency band, the control circuit causes the second cutoff unit 104 to perform the conduction cutoff operation, and the first cutoff unit 103 does not perform the conduction cutoff operation. For this reason, since the first antenna element 101 and the wireless circuit 106 are in a conductive state, the first antenna element 101 is in a state capable of wireless communication. On the other hand, since the second antenna element 102 and the wireless circuit 106 are in a conduction cut-off state, the second antenna element 102 is in a state where wireless communication is not possible.

  When the wireless communication apparatus performs wireless communication in the second frequency band, the first cutoff unit 103 performs a conduction cutoff operation and the second cutoff unit 104 does not perform a conduction cutoff operation by the control circuit. For this reason, since the second antenna element 102 and the wireless circuit 106 are in a conductive state, the second antenna element 102 is in a state in which wireless communication is possible. On the other hand, since the first antenna element 101 and the wireless circuit 106 are in the conduction cut-off state, the first antenna element 101 cannot wirelessly communicate.

  As described above, the antenna structure 100 can perform wireless communication in the two frequency bands of the first frequency band and the second frequency band, and the wireless communication is performed by the operations of the first blocking unit 103 and the second blocking unit 104. The communication frequency band is switched.

JP 2006-311246 A

  By the way, a plurality of frequency bands such as an 800 MHz band and a 2 GHz band are set as radio communication frequency bands of the mobile phone. There is a movement to increase the frequency band. With such movement, an antenna capable of supporting radio communication in a larger frequency band has been demanded. Patent Document 1 also proposes an antenna structure that can support wireless communication in three frequency bands. As shown in FIG. 12, the proposed antenna structure 110 is an application of the antenna structure 100 shown in FIG. That is, the antenna structure 110 further includes the third antenna element 111 and the third blocking means 112 in addition to the configuration of the antenna structure 100. One end side of the third antenna element 111 is connected to the connection portion X, and is electrically connected to the radio circuit 106 through the matching circuit 105 in the same manner as the first and second antenna elements 101 and 102. The third antenna element 111 resonates in a predetermined third frequency band and can transmit and receive radio waves in the third frequency band. The third blocking means 112 has a function of blocking conduction between the third antenna element 111 and the radio circuit 106.

  In the proposed antenna structure 110, wireless communication in three frequency bands is possible. However, in the proposed antenna structure 110, the third antenna element 111 is further provided in addition to the configuration of the antenna structure 100 as described above. The antenna element has a length corresponding to the radio wave wavelength in the corresponding frequency band, and is larger than circuit components such as the blocking means 103. For this reason, the antenna structure 110 becomes considerably larger than the antenna structure 100 because the third antenna element 111 must be provided.

  As described above, in the configuration of Patent Document 1, if an attempt is made to increase the frequency band in which wireless communication is possible, antenna elements must be added by the number of the increased frequency band, and an increase in size is inevitable. There is a problem. Wireless communication devices such as portable telephones tend to be miniaturized, and there is a demand for miniaturization of the antenna. Therefore, it is not preferable to enlarge the antenna structure.

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide an antenna structure, a wireless communication apparatus, and an antenna control method that can easily increase the frequency band that can be used for wireless communication without increasing the size.

The antenna structure of the present invention is
A first antenna element that resonates in a predetermined first frequency band;
A second antenna element that resonates in a predetermined second frequency band different from the first frequency band;
A short-circuit portion connected to a predetermined branch portion of the first antenna element and guiding a current in a predetermined third frequency band different from the first frequency band and the second frequency band from the branch portion to the ground; ,
The partial area between the predetermined open end of the first antenna element and the branch portion, and the second antenna element are disposed adjacent to each other,
The current in the third frequency band is transmitted from the second antenna element to the partial region of the first antenna element by electromagnetic coupling, and the current in the third frequency band is further transmitted from the first antenna element. The short-circuited portion is energized through the partial region, and the current energization causes the partial region and the short-circuited portion of the second antenna element and the first antenna element to resonate in the third frequency band as one antenna. Function.

  The wireless communication apparatus of the present invention includes the antenna structure.

The antenna control method of the present invention includes:
A first antenna element that resonates in a predetermined first frequency band, a second antenna element that resonates in a predetermined second frequency band different from the first frequency band, and a predetermined branch portion in the first antenna element And a short-circuit part for guiding a current in a predetermined third frequency band different from the first frequency band and the second frequency band from the branch part to the ground, and further from the second antenna element to the first antenna. Wireless communication in the first frequency band in an antenna structure having a configuration in which current in the third frequency band is transmitted by electromagnetic coupling to a partial region between a predetermined open end of the element and the branching portion In the case of performing the above, the current of the first frequency band is supplied to the first antenna element,
In the case where the antenna structure performs wireless communication in the second frequency band, a current in the second frequency band is supplied to the second antenna element,
When the antenna structure performs wireless communication in the third frequency band, the current in the third frequency band is supplied to the second antenna element, and the current is electromagnetically coupled from the second antenna element. , Transmitting to the partial area of the first antenna element, further energizing the short-circuit portion from the branch portion of the first antenna element, the partial area of the second antenna element and the first antenna element and the The short-circuit portion is resonated in the third frequency band to function as one antenna.

  ADVANTAGE OF THE INVENTION According to this invention, the increase in the frequency band which can respond to radio | wireless communication becomes easy, without enlarging an antenna structure.

It is a figure for demonstrating 1st Embodiment. It is a figure for demonstrating the antenna structure of 2nd Embodiment. It is a model figure showing an example of the radio | wireless communication apparatus with which the antenna structure of 2nd Embodiment is integrated. It is a figure for demonstrating an example of the resonant circuit used with the antenna structure of 2nd Embodiment. It is a figure showing the impedance characteristic and return loss characteristic of the antenna structure of 2nd Embodiment. It is a graph showing the relationship between return loss and loss. It is a figure showing the impedance characteristic and return loss characteristic of the antenna structure for comparing with the antenna structure of 2nd Embodiment. It is a figure for demonstrating the antenna structure of 3rd Embodiment. It is a figure showing the structural example of the switch circuit used for the antenna structure of 3rd Embodiment. It is a figure for demonstrating other embodiment. It is a figure for demonstrating one of the antenna structures shown by patent document 1. FIG. It is a figure for demonstrating another antenna structure shown by patent document 1. FIG.

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

(First embodiment)
FIG. 1A schematically shows the antenna structure of the first embodiment. The antenna structure 1 includes a first antenna element 2, a second antenna element 3, and a short-circuit portion 4. The first antenna element 2 resonates in a predetermined first frequency band. The second antenna element 3 resonates in a predetermined second frequency band different from the first frequency band. The short-circuit portion 4 is connected to a predetermined branch portion 5 of the first antenna element 2. The short-circuit unit 4 has a function of guiding a current in a predetermined third frequency band different from the first frequency band and the second frequency band from the branch unit 5 to the ground G.

  Furthermore, in this antenna structure 1, the partial region 7 between the predetermined open end 6 of the first antenna element 2 and the branching portion 5 and the second antenna element 3 are disposed adjacent to each other. Accordingly, the antenna structure 1 has a configuration in which the current I in the third frequency band is transmitted from the second antenna element 3 to the partial region 7 of the first antenna element 2 by electromagnetic coupling. Further, the current I in the third frequency band is supplied from the partial region 7 of the first antenna element 2 to the short-circuit portion 4 through the branch portion 5. By energization of this current I, the second antenna element 3, the partial region 7 of the first antenna element 2 and the short-circuit portion 4 resonate in the third frequency band and function as one antenna.

  When performing wireless communication using the antenna structure 1 of the first embodiment, the following control is performed. For example, when it is desired to perform wireless communication in the first frequency band, a current in the first frequency band is supplied to the first antenna element 2. Thereby, the first antenna element 2 resonates in the first frequency band, and wireless communication in the first frequency band is performed by the resonance. When radio communication in the second frequency band is desired, current in the second frequency band is supplied to the second antenna element 3. Accordingly, the second antenna element 3 resonates in the second frequency band, and wireless communication in the second frequency band is performed by the resonance. Further, when it is desired to perform wireless communication in the third frequency band, the current I in the third frequency band is supplied to the second antenna element 3. The current I in the third frequency band is energized not only to the second antenna element 3 but also to the partial region 7 of the first antenna element 2 by electromagnetic coupling, and further to the short-circuit portion 4. Thereby, the partial region 7 and the short-circuit portion 4 of the second antenna element 3 and the first antenna element 2 resonate in the third frequency band, and wireless communication in the third frequency band is performed by this resonance.

  In the antenna structure 1 of the first embodiment, as described above, each of the two antenna elements 2 and 3 can independently perform a resonance operation, and each can perform wireless communication in different frequency bands. . In addition, the second antenna element 3, the partial region 7 of the first antenna element 2, and the short-circuit portion 4 resonate like one antenna in the third frequency band, Wireless communication can also be performed. Thus, in this antenna structure 1, not only the individual resonances of the antenna elements 2 and 3 but also the resonance involving the antenna elements 2 and 3 can be performed, so that the number of antenna elements is not increased. The frequency band in which wireless communication can be performed can be increased. In other words, the antenna structure 1 of the first embodiment can easily increase the frequency band in which wireless communication is possible without increasing the size.

  The antenna structure 1 as described above is incorporated in the wireless communication device 10 as shown in FIG. By incorporating the antenna structure 1, the wireless communication device 10 can increase the frequency band of wireless communication without significantly increasing the installation space for the antenna element.

(Second Embodiment)
The second embodiment will be described below.

  As shown in FIG. 2, the antenna structure 20 of the second embodiment includes a first antenna element 21, a second antenna element 22, a short-circuit portion 23, and an impedance matching circuit 24. In the second embodiment, the antenna structure 20 is incorporated into a foldable (clamshell type) portable telephone 11 as shown in FIG. 3, for example, and transmits and receives radio waves.

  Here, the mobile phone 11 of FIG. 3 will be briefly described. The mobile phone 11 includes a first housing 12, a second housing 13, and a hinge part 14. The first housing 12 is provided with screen display means 15 such as a liquid crystal screen. The second housing 13 is provided with an operation unit 16 including numeric keys and a determination key. Further, a circuit board 17 is built in the second housing 13. For example, the circuit board 17 is formed with a wireless circuit (feeding point) for performing wireless communication, a ground pattern that functions as an electrical ground, a control circuit that controls the operation of the mobile phone 11, and the like. Yes. The hinge portion 14 is configured to connect the first housing 12 and the second housing 13 with the hinge portion 14 as a center so as to freely rotate and displace.

In the antenna structure 20 of the second embodiment, the first antenna element 21 has a configuration that resonates in a predetermined first frequency band (for example, 800 MHz band). That is, one end side Q 21 of the first antenna element 21 is the feeding end, the other end K 21 is an open end. Feeding end Q 21 of the first antenna element 21, through an impedance matching circuit 24 is electrically connected to the radio circuit 18 of the portable telephone 11. The physical length from the feeding end Q 21 to the open end K 21 of the first antenna element 21 is an electrical length (electric length) determined in advance for the first antenna element 21 to resonate in the first frequency band. ) Is set based on.

  In the second embodiment, a branch antenna element 31 described later is connected to the first antenna element 21.

  The second antenna element 22 has a configuration that resonates in a predetermined second frequency band. In the second embodiment, the second frequency band is a higher frequency band than the first frequency band, for example, the 2 GHz band.

One end Q 22 of the second antenna element 22 is the feeding end, the other end K 22 is an open end. Feeding end Q 22 of the second antenna element 22, through an impedance matching circuit 24 is electrically connected to the radio circuit 18 of the portable telephone 11. The physical length from the feeding end Q 22 to the open end K 22 of the second antenna element 22 is the electrical length (electric length) determined in advance for the second antenna element 22 to resonate in the second frequency band. ) Is set based on.

In the second embodiment, the open end K 22 of the second antenna element 22 is disposed so as to face the open end K 21 of the first antenna element 21.

  The first antenna element 21, the second antenna element 22, and the branch antenna element 31 as described above are disposed inside the hinge portion 14 of the mobile phone 11, for example, in a state of being hardened inside the plastic resin 29. .

  The impedance matching circuit 24 includes a common impedance matching circuit 25, a low band impedance matching circuit 26, and a high band impedance matching circuit 27. The impedance matching circuit 24 is mounted on the circuit board 17 of the mobile phone 11, for example.

  The common impedance matching circuit 25 is electrically connected to the radio circuit 18 of the mobile phone 11, and the first and second antenna elements 21 and 22 are connected to the common impedance matching circuit 25 through the impedance matching circuits 26 and 27, respectively. Are commonly connected. The common impedance matching circuit 25 has a circuit configuration for impedance matching between the radio circuit 18 and the antenna elements 21 and 22 side. There are various circuit configurations for impedance matching, and any of these circuit configurations may be adopted here, and the description thereof is omitted.

Low-band impedance matching circuit 26 is provided in the first antenna element 21 of the feeding end Q 21 and the common impedance circuit 25 electrically connected to the first on conduction path provided to the antenna element dedicated for. The low-band impedance matching circuit 26 is a circuit having a function of adjusting the electrical length of the first antenna element 21. That is, it is preferable that the first antenna element 21 has the set electrical length required to resonate in the first frequency band, but there are many cases where the set electrical length cannot be accurately obtained due to various factors. For this reason, in the second embodiment, the low-band impedance matching circuit 26 adjusts the electrical length so that the electrical length of the first antenna element 21 viewed from the radio circuit 18 side becomes the electrical length set above. It is carried out. The low-band impedance matching circuit 26 has the following circuit configuration. For example, when it is desired to adjust the electrical length in the direction of increasing, a coil is provided as the low-band impedance matching circuit 26. Further, when it is desired to adjust the electrical length in the direction of shortening, a capacitor is provided as the low-band impedance matching circuit 26. In the second embodiment, the first antenna element impedance matching section is configured by the conduction path dedicated to the first antenna element and the low-band impedance matching circuit 26.

High-band impedance matching circuit 27 is provided on a conductive path provided on the second antenna element dedicated for common impedance circuit 25 and the feeding end Q 22 of the second antenna element 22 in order to electrically connect. The high-band impedance matching circuit 27 is a circuit having a function of adjusting the electrical length of the second antenna element 22. That is, the high-band impedance matching circuit 27 is electrically connected so that the electrical length of the second antenna element 22 viewed from the radio circuit 18 side becomes the electrical length set to be required to resonate at the second resonance frequency. This is a circuit for adjusting the length. Similar to the low-band impedance matching circuit 26, for example, a coil is provided as the high-band impedance matching circuit 27 when it is desired to adjust the electrical length in a longer direction. Further, when it is desired to adjust the electrical length in the direction of shortening, a capacitor is provided as the high-band impedance matching circuit 27. In the second embodiment, the second antenna element impedance matching section is configured by the conduction path dedicated to the second antenna element and the high-band impedance matching circuit 27.

  In the second embodiment, the electrical lengths of the first and second antenna elements 21 and 22 can be individually adjusted by the impedance matching circuits 26 and 27, respectively. As described above, since the electrical lengths of the antenna elements 21 and 22 can be individually adjusted, the following effects can be obtained. That is, when it is desired to adjust the electrical length of the first and second antenna elements 21 and 22, the physical length from the feeding end to the open end of the first and second antenna elements 21 and 22 is adjusted. Therefore, it is conceivable to adjust the electrical length. However, due to various factors, it is often difficult to change the physical length of the antenna element for adjusting the electrical length. In such a case, electrical electrical length adjustment using a lumped constant is performed. Assume that the impedance matching circuits 26 and 27 are not provided when the first and second antenna elements 21 and 22 are connected to the common radio circuit 18. In this case, if a lumped constant for adjusting the electrical length is provided in the common impedance matching circuit 25, the following problem occurs. That is, when the lumped constant of the common impedance matching circuit 25 is set so that the first antenna element 21 can have a set electrical length, the electrical length of the second antenna element 22 is set due to the lumped constant. Deviation from electrical length. Conversely, when the lumped constant of the common impedance matching circuit 25 is set so that the second antenna element 22 can have a set electrical length, the electrical length of the first antenna element 21 is set due to the lumped constant. It will deviate from the electrical length. Thus, in the electrical length adjustment using the lumped constant of the common impedance matching circuit 25, the electrical length on the other side also fluctuates due to the electrical length adjustment of one of the antenna elements 21 and 22, and the electrical length is There arises a problem that it deviates from the set electrical length. In contrast, in the second embodiment, as described above, the configuration in which the electrical lengths of the antenna elements 21 and 22 can be individually adjusted is provided, so that occurrence of such a problem can be avoided. Thereby, it becomes easy to give both the antenna elements 21 and 22 the set electrical length with high accuracy. That is, the first antenna element 21 can accurately have an electrical length set to resonate in the first frequency band, and the second antenna element 22 also has an electrical length set to resonate in the second frequency band. Can be held with high accuracy.

  The short-circuit portion 23 is connected to a branch portion 33 whose position is determined in the first antenna element 21 as described later, and has a function of guiding a current in a predetermined third frequency band from the branch portion 33 to the ground. In the second embodiment, the third frequency band is a frequency band that is higher than the first frequency band and lower than the second frequency band. For example, the third frequency band is a 1.5 GHz band.

  In the second embodiment, the short-circuit unit 23 includes a branch antenna element 31 and an impedance matching circuit 32. The branch antenna element 31 is for connecting the branch portion 33 of the first antenna element 21 and the impedance matching circuit 32.

For example, the impedance matching circuit 32 is provided on the circuit board 17 of the mobile phone 11 and is electrically connected to the ground pattern G of the circuit board 17. In the second embodiment, the impedance matching circuit 32 is constituted by a resonance circuit. The resonant circuit is configured such that when the impedance matching circuit 32 side is viewed from the branching portion 33, the circuit is configured to be open in the first frequency band and to be short-circuited in the third frequency band. Yes. FIG. 4A shows an example of the circuit configuration of the resonance circuit. The resonance circuit 32a of FIG. 4A has a circuit configuration in which a coil 37 is connected in series to a parallel resonance circuit 38 of a capacitor 35 and a coil 36. In the resonance circuit 32a, the circuit constants are set so that the capacitor 35 and the coil 36 of the parallel resonance circuit 38 resonate in parallel in the first frequency band (800 MHz band) and appear open. Further, the circuit constant of the coil 37 is set so that the coil 37 and the parallel resonant circuit 38 are in series resonance in the third frequency band (1.5 GHz band) and appear to be short-circuited. For this reason, the resonance circuit 32a can have an impedance characteristic as shown by the solid line A in FIG. That is, the solid line A in FIG. 4B represents how the impedance of the resonance circuit 32a changes with a frequency change from 830 MHz to 2.17 GHz using a Smith chart. The solid line A extends from the point a 1 (corresponding to 830 MHz) along the outermost circle of the Smith chart, passes through the point a 2 (corresponding to 1.5 GHz), and goes to the point a 3 (corresponding to 2.17 GHz). Has reached. As indicated by the impedance characteristic of the solid line A, the resonance circuit 32a is open (open) in the first frequency band (800 MHz band) and short-circuited (short) in the third frequency band (1.5 GHz band). Can do.

Since the short-circuit portion 23 includes the impedance matching circuit 32 as described above, when the current flowing through the branch portion 33 of the first antenna element 21 is the current I 3 in the third frequency band (1.5 GHz band). The current I 3 is supplied from the branch portion 33 to the short-circuit portion 23. On the other hand, when the current flowing through the branch portion 33 of the first antenna element 21 is a current in the first frequency band (800 MHz), since the short circuit portion 23 is not visible for the current, the current is The short circuit part 23 is not energized.

In the antenna structure 20 of the second embodiment, as described above, the open ends K 21 and K 22 of the first and second antenna elements 21 and 22 face each other and are arranged close to each other. Thus, the current I 3 of the third frequency band supplied to the second antenna element 22, the electromagnetic coupling is transmitted from the open end K 22 of the second antenna element 22 to the open end K 21 of the first antenna element 21 The Current I 3 of the third frequency band, energized toward the branch portion 33 from the open end K 21 of the first antenna element 21, as described above, energizing the short-circuit section 23 from the branching portion 33. Such a second antenna element 22, and the partial region to the branch portion 33 from the open end K 21 of the first antenna element 21, the energization current I 3 of the third frequency band between the short circuit portion 23, the third The position of the branch portion 33 is set so that resonance in the frequency band occurs.

In the second embodiment, the open ends K 21 and K 22 of the first and second antenna elements 21 and 22 are arranged facing each other, and electromagnetic coupling between the open ends K 21 and K 22 is used. The current I 3 in the third frequency band is transmitted. Since the open ends K 21 and K 22 are the portions where the electric field distribution in the antenna element is the largest, the loss can be suppressed by transmitting the current I 3 using the open ends K 21 and K 22 .

In the second embodiment, the short circuit portion 23 includes the impedance matching circuit (resonance circuit) 32. For this reason, the conduction of the current I 3 in the third frequency band to the short-circuit portion 23 and the conduction interruption of the current in the first frequency band in the short-circuit portion 23 can be achieved only by appropriately setting the resonance circuit 32.

Since the antenna structure 20 of the second embodiment has the above-described configuration, the mobile phone 11 can perform wireless communication using the antenna structure 20 as follows. For example, when it is desired to perform wireless communication in the first frequency band, the mobile phone 11 uses the control circuit 19 to convert the current for wireless communication output from the wireless circuit 18 to the antenna structure 20 into the current in the first frequency band. And As a result, the current in the first frequency band reaches the power feeding section Q 21 of the first antenna element 21 from the radio circuit 18 through the common impedance matching circuit 25 and the low band impedance matching circuit 26. As described above, since the current in the first frequency band is equivalent to the absence of the short-circuit portion 23, the current in the first frequency band is opened from the power feeding portion Q21 of the first antenna element 21 to the open end. It is energized toward the K 21. Accordingly, the first antenna element 21 resonates in the first frequency band and communicates radio waves in the first frequency band.

When it is desired to perform wireless communication in the second frequency band, the mobile phone 11 uses the control circuit 19 to convert the current for wireless communication output from the wireless circuit 18 to the antenna structure 20 as the current in the second frequency band. To do. The current in the second frequency band passes from the wireless circuit 18 through the common impedance matching circuit 25 and the high-band impedance matching circuit 27 to the power feeding part Q 22 of the second antenna element 22. Then, the current in the second frequency band is energized from the feeding part Q 22 of the second antenna element 22 toward the open end K 22 . Accordingly, the second antenna element 22 resonates in the second frequency band and communicates radio waves in the second frequency band.

When it is desired to perform wireless communication in the third frequency band, the portable telephone 11 uses the control circuit 19 to convert the current for wireless communication output from the wireless circuit 18 to the antenna structure 20 by the current I in the third frequency band. 3 The current I 3 in the third frequency band passes from the radio circuit 18 through the common impedance matching circuit 25 and the high band impedance matching circuit 27 to the power feeding part Q 22 of the second antenna element 22. Then, the current I 3 of the third frequency band, after energized toward the open end K 22 from the feeding portion Q 22 of the second antenna element 22, as described above, by electromagnetic coupling, the first antenna element 22 It is transmitted to the open end K 21. Further, the current I 3 in the third frequency band is energized from the branch portion 33 of the first antenna element 21 to the short-circuit portion 23. Thus, the second antenna element 22, and the partial region to the branch portion 33 from the open end K 21 of the first antenna element 21, and a short circuit portion 23, acting like a single antenna element, the third frequency band Resonates and communicates radio waves in the third frequency band.

  In the antenna structure 20 of the second embodiment, as described above, not only the antenna elements 21 and 22 resonate independently, but also another resonance operation can be performed by combining the antenna elements 21 and 22. I made it. For this reason, the frequency band which can respond to radio | wireless communication can be increased, without increasing an antenna element. This has been confirmed by experiments. That is, in the experiment, the impedance characteristics and return loss of the antenna structure (comparative example) having the same configuration as the antenna structure 20 and the antenna structure 20 of the second embodiment except that the short-circuit portion 23 is omitted. The characteristics were investigated.

The impedance characteristic of the antenna structure 20 obtained by the experiment is represented by a solid line B in the Smith chart of FIG. The return loss characteristic is represented by a solid line C in the graph of FIG. Note that points b 1 to b 10 in the diagram of FIG. 5A indicate impedances corresponding to the frequencies of the points b 1 to b 10 indicated on the horizontal axis of the graph of FIG. 5B, respectively. ing.

  Looking at the return loss characteristic of FIG. 5B, the antenna structure 20 shows three resonances. That is, resonance in the 800 MHz band based on the resonance operation of the first frequency band of the first antenna element 21 is observed. In addition, resonance in the 2 GHz band based on the resonance operation of the second frequency band of the second antenna element 22 is also observed. Further, resonance in the 1.5 GHz band based on the resonance operation in the third frequency band in which both the first and second antenna elements 21 and 22 are involved is observed.

By the way, as frequency bands for wireless communication of the mobile phone, a frequency band S A (800 MHz band), a frequency band S C (1.7 GHz band), a frequency band S D (2 GHz) shown in FIG. Band) is set. Furthermore, as described above, there is a movement to add the frequency band S B (1.5 GHz band). Further, in order to obtain predetermined good radio communication based on the relationship between the return loss of the antenna structure and the loss that adversely affects the radio communication state as shown in FIG. It is considered to be preferably 5 dB or less.

Looking at the return loss characteristics of FIG. 5B, the antenna structure 20 has a return loss of −5 dB or less in any of the four frequency bands S A to S D for the mobile phone, and is wireless. Communication is possible.

The impedance characteristic of the comparative example obtained by the experiment is represented by a solid line D in the Smith chart of FIG. The return loss characteristic of the comparative example is indicated by a solid line E in the graph of FIG. Points b 1 to b 10 in FIGS. 7A and 7B are the same as points b 1 to b 10 shown in FIGS. 5A and 5B, respectively.

  In the comparative example, when looking at the return loss characteristic of FIG. 7B, two resonances are observed. That is, in the comparative example, resonance based on the resonance operation of the first frequency band of the first antenna element 21 and resonance based on the resonance operation of the second antenna element 22 in the second frequency band are seen.

When the return loss characteristic of FIG. 7B of this comparative example is compared with the return loss characteristic of FIG. 5B of the antenna structure 20 of the second embodiment, the antenna structure 20 is more resonant than the comparative example. It can be seen that increases. Further, it can be seen that the antenna structure 20 has an expanded frequency range capable of supporting wireless communication with a return loss of −5 dB or less as compared with the comparative example. For this reason, in the comparative example, the antenna structure 20 can cope with all the frequency bands S A to S D , while it can cope with the frequency bands S A , S C , and S D but cannot cope with the frequency band S B. is there. That is, it has been confirmed through experiments that the antenna structure 20 can increase the frequency band that can be used for wireless communication without increasing the number of antenna elements.

(Third embodiment)
The third embodiment will be described below.

  In the third embodiment, instead of the impedance matching circuit 32 of the short-circuit portion 23 shown in the second embodiment, the short-circuit portion 23 is provided with a switch circuit 40 as shown in FIG. Other configurations of the third embodiment are the same as those of the second embodiment. In the third embodiment, the description of the same part as the description of the second embodiment is omitted.

The switch circuit 40 is portable so that the current I 3 in the third frequency band is conducted to the short-circuit portion 23 (on state) and is otherwise cut off (off state). It is controlled by the control circuit 19 of the type telephone 11. 9A and 9B show specific circuit configuration examples of the switch circuit 40. FIG.

  The switch circuit 40 (40a) in FIG. 9A uses a diode. That is, the switch circuit 40 a includes a pin (p-intrinsic-n) diode 42, a coil 43, and a resistance unit 44. The cathode side of the pin diode 42 is electrically connected to the ground pattern G, and the anode side of the pin diode 42 is electrically connected to the branch portion 33 of the first antenna element 21 through the branch antenna element 31. Furthermore, one end side of a series connection circuit of the coil 43 and the resistor unit 44 is connected to the anode side of the pin diode 42. The other end of the series connection circuit of the coil 43 and the resistance unit 44 is connected to the control circuit 19.

  The coil 43 is provided for high-frequency cutting, and the coil 43 makes the control circuit 19 invisible from the antenna side so that the influence of the control circuit 19 does not reach the antenna. The resistor unit 44 limits the current so that the current value supplied from the control circuit 19 to the pin diode 42 is suitable for the pin diode 42.

  For example, either a low signal having a voltage value of zero or a high signal having a predetermined voltage value greater than zero is applied from the control circuit 19 to the switch circuit 40a. When a low signal is output from the control circuit 19 to the switch circuit 40a, the voltage applied to the pin diode 42 is substantially zero, and the pin diode 42 is turned off. In this case, the conduction state is cut off between the branch portion 33 of the first antenna element 21 and the ground pattern G by the pin diode 42 in the off state. On the other hand, when a high signal is output from the control circuit 19 to the switch circuit 40a, the voltage applied to the pin diode 42 becomes the forward voltage drop of the pin diode 42, and the pin diode 42 is turned on. In this case, the pin diode 42 in the ON state is in a conductive state between the branch portion 33 of the first antenna element 21 and the ground pattern G, and the branch portion 33 is short-circuited to the ground pattern G.

  The switch circuit 40 (40b) in FIG. 9B uses a transistor. That is, the switch circuit 40 b includes a field effect transistor (FET) 46 and a coil 47. The source side of the FET 46 is connected to the ground pattern G, and the drain side of the FET 46 is electrically connected to the branch portion 33 of the first antenna element 21 through the branch antenna element 31. One end side of the coil 47 is connected to the gate side of the FET 46, and the other end side of the coil 47 is connected to the control circuit 19.

  The coil 47 is provided for high frequency cut similarly to the coil 43 of the switch circuit 40a. The coil 47 makes the control circuit 19 invisible from the antenna side, and the influence of the control circuit 19 does not reach the antenna. I am doing so.

  As for the switch circuit 40b, the switching operation is controlled based on the signal output from the control circuit 19 as in the switch circuit 40a. That is, when a low signal is output from the control circuit 19 to the switch circuit 40b, the FET 46 is in an off state in which no current flows between the source and the drain. In this case, the FET 46 in the off state is in a conduction cut-off state between the branch portion 33 of the first antenna element 21 and the ground pattern G. On the other hand, when a high signal is output from the control circuit 19 to the switch circuit 40b, the FET 46 is in an ON state in which current flows between the source and the drain. In this case, the ON-state FET 46 is in a conductive state between the branch portion 33 of the first antenna element 21 and the ground pattern G, and the branch portion 33 is short-circuited to the ground pattern G.

  As described above, the antenna structure of the third embodiment is controlled so that the switch circuit 40 (40a, 40b) is turned on, so that the antenna elements 21, 22 are both in the same manner as in the second embodiment. Resonant operation is performed in the third frequency band involved. Thereby, also in this 3rd Embodiment, the effect similar to 2nd Embodiment can be acquired. That is, the frequency band for wireless communication can be increased without increasing the number of antenna elements, as compared with the case where the two antenna elements 21 and 22 only resonate independently.

(Other embodiments)
In addition, this invention is not limited to the 1st-3rd embodiment, Various embodiment can be taken. For example, in each of the first to third embodiments, one short-circuit portion 4, 23 is connected to the first antenna element 2, 21. In contrast, for example, as illustrated in FIG. 10, the first antenna element 21 may be connected to short-circuit portions 23 a, 23 b, and 23 c at a plurality of different locations. In this case, the antenna structure 50 including the configuration of FIG. 10 can resonate in the fourth frequency band and the fifth frequency band in addition to the first to third frequency bands. For example, the antenna structure 50 resonates in a first frequency band (for example, 800 MHz band) by the first antenna element 21 and a second frequency band (for example, 2.4 GHz band) by the second antenna element 22. Further, the antenna structure 50 has a third frequency band (for example, 1.5 GHz band) including the second antenna element 22, a partial region from the open end K21 of the first antenna element 21 to the branching portion 33b, and the short-circuit portion 23b. Resonates at. Further, the antenna structure 50 resonates in a fourth frequency band (for example, 2 GHz band) by the second antenna element 22, the partial region from the open end K21 of the first antenna element 21 to the branching portion 33a, and the short-circuit portion 23a. To do. Furthermore, the antenna structure 50 has a fifth frequency band (for example, 1.2 GHz band) including the second antenna element 22, a partial region from the open end K21 of the first antenna element 21 to the branching portion 33c, and the short-circuit portion 23c. Resonates at. In such a case, the interval between the resonance frequency bands becomes narrow, which may make frequency separation using an impedance matching circuit difficult. In such a case, it is preferable to provide the short circuit 23 with the switch circuit 40 as shown in the third embodiment.

  Furthermore, in the second and third embodiments, the first antenna element 21, the second antenna element 22, and the branch element 31 are fixed inside the plastic resin 29, and the hinge portion 14 of the mobile phone 11. Was housed inside. Instead of this, the first antenna element 21, the second antenna element 22, and the branch element 31 may be provided on a dielectric substrate such as ceramics. The dielectric substrate is mounted on the circuit board 17, for example. Furthermore, the first antenna element 21, the second antenna element 22, and the branch element 31 may be provided directly on the circuit board 17. Thus, the aspect in which the first antenna element 21, the second antenna element 22, and the branch element 31 are incorporated in the wireless communication apparatus is not limited to the second and third embodiments.

  Furthermore, the shape of the first antenna element 21 or the second antenna element 22 is not limited to the shape shown in FIG. 2, and may be other shapes such as a meander shape.

Further, in the second and third embodiments, the first antenna element 21 and the second antenna element 22 are arranged with the open ends K 21 and K 22 facing each other. Instead, the arrangement of the first antenna element 21 and the second antenna element 22 considers the problem of interference between antennas, the efficiency of current transmission in the third frequency band, the size of the antenna installation space, and the like. Thus, other appropriate arrangement modes can be adopted.

  Furthermore, in the second and third embodiments, the first antenna element 21 and the second antenna element 22 are electrically connected to the common radio circuit 18. On the other hand, the first antenna element 21 and the second antenna element 22 may be connected to different radio circuits, respectively. In this case, for example, the radio circuit connected to the first antenna element 21 serves as a power supply for a current in a predetermined first frequency band (for example, 800 MHz band). The wireless circuit connected to the second antenna element 22 serves as a power supply for current in a predetermined second frequency band (for example, 2 GHz band) and a predetermined third frequency band (for example, 1.5 GHz band). Other configurations are the same as those of the second and third embodiments, and in such a case, the same effects as the second and third embodiments, that is, without increasing the antenna elements, The effect that the frequency band which can respond to radio | wireless communication can be increased can be acquired. When each antenna element is connected to a separate radio circuit, the common impedance matching circuit is omitted.

  Furthermore, in the second and third embodiments, the mobile phone 11 is shown as an example of a wireless communication device in which the antenna structure 20 is incorporated. However, the wireless communication device including the antenna structure of the present invention is a mobile phone. It is not limited to 11. For example, as other examples of the wireless communication device provided with the antenna structure of the present invention, a portable phone other than a foldable type, a portable information terminal such as a PDA (Personal-Digital-Assistant), or an installation type wireless There are communication devices.

DESCRIPTION OF SYMBOLS 1,20,50 Antenna structure 2,21 1st antenna element 3,22 2nd antenna element 4,23 Short-circuit part 5,33 Branch part 32 Impedance matching circuit 40 Switch circuit

Claims (9)

  1. A first antenna element that resonates in the first frequency band by supplying a current in the first frequency band through a feeding end to which current is supplied ;
    A second antenna element resonating at the second frequency band by the current current of the second frequency band that is different from the through feeding end supplied the first frequency band is supplied,
    And a short-circuit portion for guiding the current of the third frequency band that is different from the connected first frequency band and the second frequency band to a predetermined branch portion to the ground from the branch portion of the first antenna element, further,
    The partial area between the electrical open end of the first antenna element and the branch portion, and the second antenna element are disposed adjacent to each other,
    The current in the third frequency band supplied to the feeding end of the second antenna element passes through the second antenna element and is transmitted from the second antenna element to the partial region of the first antenna element by electromagnetic coupling. is reached, in the et, supplying an electric current to the short-circuit portion through said partial region of said first antenna element, wherein the partial region and the short portion of the second antenna element and the first antenna element by the current supply is An antenna structure that functions as one antenna by resonating in the third frequency band.
  2.   The short-circuit portion is short-circuited with respect to the current in the third frequency band when the short-circuit portion side is viewed from the branch portion of the first antenna element, and the current in the first frequency band is 2. The antenna structure according to claim 1, further comprising an open impedance matching circuit.
  3.   The antenna structure according to claim 1, wherein the short-circuit part includes a switch circuit that switches between conduction and interruption of the branch part of the first antenna element and the ground.
  4. A common impedance matching circuit electrically connected to a power supply that feeds each current of the first frequency band, the second frequency band, and the third frequency band;
    An impedance matching section for a first antenna element that electrically connects the common impedance matching circuit and the first antenna element and adjusts an electrical length of the first antenna element;
    The impedance matching part for 2nd antenna elements which adjusts the electrical length of a 2nd antenna element while electrically connecting the said common impedance matching circuit and the said 2nd antenna element is further provided. The antenna structure according to claim 2 or 3.
  5. The second frequency band is higher than the first frequency band;
    The antenna structure according to any one of claims 1 to 4, wherein the third frequency band is higher than the first frequency band and lower than the second peripheral frequency band.
  6.   The antenna structure according to any one of claims 1 to 5, wherein the open end of the first antenna element and a predetermined open end of the second antenna element face each other.
  7.   7. The first antenna element is further provided with at least one short-circuit portion that guides a current in a predetermined frequency band to the ground separately from the short-circuit portion. 8. Antenna structure.
  8.   A wireless communication apparatus comprising the antenna structure according to any one of claims 1 to 7.
  9. A first antenna element through the feeding end current is supplied a current of a first frequency band resonates at the first frequency band by supplying said first frequency through a feeding end current is supplied a second antenna element a second frequency band of the current that is different from the band resonant at the second frequency band by supplying, the first connected to a predetermined branch portion of the antenna element the first frequency band and the current of the third frequency band that is different from said second frequency band and a short-circuit portion for guiding the ground from the branch portion, further, from the second antenna element, and electrical open ends of said first antenna element The antenna structure having a configuration in which the current of the third frequency band is transmitted to the partial region between the branch part by electromagnetic coupling, and the first frequency band When to perform the wireless communication, the said feeding end of said first antenna element, supplying a current of the first frequency band,
    When allowing the antenna structure to perform wireless communication in the second frequency band, supply a current in the second frequency band to the feeding end of the second antenna element;
    When the antenna structure performs wireless communication in the third frequency band, the current in the third frequency band is supplied by supplying the current in the third frequency band to the feeding end of the second antenna element. The second antenna element is transmitted from the second antenna element to the partial region of the first antenna element by electromagnetic coupling, and further, the short-circuit portion is energized from the branch portion of the first antenna element. An antenna control method for causing the second antenna element and the partial region of the first antenna element and the short-circuit portion to resonate in the third frequency band to function as one antenna.

JP2009212079A 2009-09-14 2009-09-14 Antenna structure, radio communication apparatus, and antenna control method Expired - Fee Related JP5507935B2 (en)

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JP5590060B2 (en) * 2012-03-28 2014-09-17 株式会社村田製作所 Multiband antenna device design method
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JP5700055B2 (en) 2013-01-17 2015-04-15 株式会社村田製作所 Antenna device
US9374126B2 (en) * 2013-11-27 2016-06-21 Nokia Technologies Oy Multiband on ground antenna with a dual radiator arrangement
WO2016076605A2 (en) * 2014-11-11 2016-05-19 주식회사 이엠따블유 Antenna device of portable terminal and portable terminal including same
KR101691081B1 (en) * 2014-11-11 2016-12-30 주식회사 이엠따블유 Antena for use in a portable terminal and a portable terminal including same

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KR20050086733A (en) * 2002-11-18 2005-08-30 가부시키가이샤 요코오 Antenna for plurality of bands
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