JP2013128248A - Dipole antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a dipole antenna capable of facilitating adjustment of impedance as well as miniaturization.SOLUTION: The dipole antenna 1 includes a first antenna element 21 that is connected to a ground line 13 and a second antenna element 22 that is connected to a signal line 11 and longer than the first antenna element 21. The second antenna element 22 includes a coupling section 22A that has capacity coupling from one end to the other end of the first antenna element 21.

Description

  The present invention relates to a dipole antenna capable of easily adjusting impedance while achieving downsizing.

  A dipole antenna incorporated in a small electronic device such as a cellular phone generally requires adjustment of impedance. A dipole antenna to which this adjustment pattern is connected has been proposed (see Patent Document 1).

JP 2004-104344 A

  However, since the dipole antenna of Patent Document 1 is provided with a pattern for impedance adjustment in addition to the antenna pattern, the dipole antenna itself tends to increase in size, contrary to the recent demand for miniaturization.

  The present invention has been made in consideration of the above points, and an object of the present invention is to propose a dipole antenna capable of easily adjusting the impedance while reducing the size.

  In order to solve such a problem, a dipole antenna of the present invention includes a first antenna element connected to a ground line, a second antenna element connected to a signal line and longer than the first antenna element, and the second antenna element. The antenna element is provided with a coupling portion that is close to one end to the other end of the first antenna element so as to be capacitively coupled.

  In such a dipole antenna, for example, if the tip of the first antenna element is shaved, not only can the electrical load of the shaved antenna element part be reduced, but also capacitive coupling with the coupling part in the part. Can be reduced. For this reason, compared with the case where the 2nd antenna element does not have the coupling part which carries out capacitive coupling from the other end of the 1st antenna element, the reduction amount of the electrical load per unit length can be enlarged. Therefore, it is possible to adjust the impedance without providing an impedance adjustment pattern separately from the antenna pattern and without forcing an operation such as increasing the distance between the first antenna element and the second antenna element. In this way, a dipole antenna that can easily adjust the impedance while reducing the size is provided.

  Moreover, it is preferable that at least a part of the second antenna element other than the coupling portion is capacitively coupled to the coupling portion.

  In this case, both the resonance frequency and the impedance can be adjusted by changing the length of the first antenna element, and the resonance frequency can be mainly adjusted by changing the length of the second antenna element. it can. This is confirmed from the experimental results of the present inventors.

  The coupling portion is disposed along the first antenna element, and the part is along the coupling portion on a side opposite to the side where the first antenna element is located with respect to the coupling portion. Preferably they are arranged.

  In this case, since the amount of capacitive coupling per unit length can be increased, the amount of adjustment of impedance can be increased by changing the length of the first antenna element.

  Moreover, you may make it further provide the coaxial cable by which an external conductor is electrically connected to the said 1st antenna element, and an internal conductor is electrically connected to the said 2nd antenna element. In the case of including such a coaxial cable, the first antenna element includes a connection portion to which the outer conductor is electrically connected, and a main body portion extending along the axis of the outer conductor connected to the connection portion. It is preferable to become.

  According to such a dipole antenna, the main body portion of the first antenna element and the coupling portion along the main body portion are arranged substantially in parallel with the coaxial cable, so that it is lower than the case where they are not arranged in parallel. Can be turned upside down.

  As described above, according to the present invention, there is provided a dipole antenna that can easily adjust the impedance while reducing the size.

It is the schematic which looked at the dipole antenna of 1st Embodiment from right above. It is a graph which shows the relationship between VSWR and frequency at the time of fixing the length of a 1st antenna element and changing the length of a 2nd antenna element. It is a graph which shows the relationship between VSWR and frequency when the length of the second antenna element is fixed and the length of the first antenna element is varied. It is the schematic which looked at the dipole antenna of 2nd Embodiment from right above. It is a graph which shows the measurement result regarding the radiation characteristic of the dipole antenna of 1st Embodiment in the use frequency band of wireless LAN. It is a graph which shows the measurement result regarding the radiation characteristic of the dipole antenna of 2nd Embodiment in the use frequency band of wireless LAN. It is the schematic which looked at the dipole antenna of 3rd Embodiment from right above. It is the schematic which looked at the dipole antenna of 4th Embodiment from right above.

  Hereinafter, a preferred embodiment of a dipole antenna according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic view of the dipole antenna according to the first embodiment viewed from directly above. As shown in FIG. 1, the dipole antenna 1 of the first embodiment includes a coaxial cable 10, a first antenna element 21, and a second antenna element 22 as main components.

  The coaxial cable 10 includes an inner conductor 11, an insulating member 12 that covers the outer peripheral surface of the inner conductor 11, an outer conductor 13 that covers the outer peripheral surface of the insulating member 12, and a jacket 14 that covers the outer conductor 13.

  The outer conductor 13 is exposed from the jacket 14 at one end of the coaxial cable 10, the insulating member 12 is exposed from the outer conductor 13, and the inner conductor 11 is exposed from the insulating member 12.

  The first antenna element 21 is, for example, a strip-shaped conductor foil, and has a pattern in which a connection portion 21A and a main line portion 21B, to which a ground line is electrically connected, are integrally connected.

  In the present embodiment, the outer conductor 13 of the coaxial cable 10 is electrically connected to the connecting portion 21A by soldering or the like. The main line portion 21B extends along the axis of the outer conductor 13 connected to the connection portion 21A, and is longer than the connection portion 21A. The end of the main line portion 21B is an open end.

  The second antenna element 22 is, for example, a strip-shaped conductor foil, similar to the first antenna element. The second antenna element 22 has a pattern in which a coupling portion 22A capacitively coupled from one end to the other end of the first antenna element 21 and an extension portion 22B extending from the coupling portion are integrally connected.

  In the case of the present embodiment, the coupling portion 22A is disposed along the first antenna element 21, and the first coupling portion 22Aa disposed along the connection portion 21A and the first coupling portion 22A disposed along the main line portion 21B. 2 binding sites 22Ab. The inner conductor 11 of the coaxial cable 10 is electrically connected as a signal line to the first coupling portion 22Aa.

  On the other hand, the extension 22B is arranged on the side opposite to the side where the first antenna element 21 is located with respect to the coupling portion 22A. Specifically, the extension portion 22B includes a first extension portion 22Ba disposed in a direction orthogonal to the joint portion 22A from the end portion of the joint portion 22A, and a second portion of the joint portion 22A from the end portion of the first extension portion 22Ba. It consists of 2nd extension site | part 22Bb arrange | positioned along binding site | part 22Ab.

  As described above, the dipole antenna 1 according to this embodiment includes the first antenna element 21 connected to the outer conductor 13 and the second antenna element 22 connected to the inner conductor 11 and longer than the first antenna element. Prepare as an element. The second antenna element 22 is provided with a coupling portion 22A that is capacitively coupled from one end of the first antenna element 21 to the other end.

  In such a dipole antenna 1, for example, if the end portion of the first antenna element 21 is cut, not only can the electrical load of the cut portion be reduced, but also capacitive coupling with the coupling portion 22A in the portion. Can also be reduced.

  For this reason, compared with the case where the 2nd antenna element 22 does not have 22 A of coupling parts, the reduction amount of the electrical load per unit length can be enlarged. Therefore, the impedance at the antenna input / output can be reduced without providing an impedance adjustment pattern separately from the antenna pattern and without forcing an operation such as increasing the distance between the first antenna element 21 and the second antenna element 22. Can be adjusted. In this way, a dipole antenna that can easily adjust the impedance while reducing the size is provided.

  In the case of the present embodiment, the extension 22B other than the coupling portion 22A in the second antenna element 22 is disposed on the side opposite to the side where the first antenna element 21 is located with respect to the coupling portion 22A. Further, the second extension part 22Bb, which is a part of the extension part 22B, is disposed along the second binding part 22Ab of the coupling part 22A and is capacitively coupled to the second binding part 22Ab.

  In this case, both the resonance frequency and the impedance are adjusted by changing the length of the first antenna element 21, and the resonance frequency is mainly adjusted by changing the length of the second antenna element 22. be able to.

  Here, FIG. 2 and FIG. 3 show the experimental results regarding the input characteristics of the dipole antenna 1 when one of the first antenna element 21 and the second antenna element 22 is fixed and the other is variable.

  FIG. 2 is a graph showing the relationship between VSWR (Voltage Standing Wave Ratio) and frequency when the length of the first antenna element 21 is fixed and the length of the second antenna element 22 is varied. Specifically, in FIG. 2, the width of the first antenna element 21 and the second antenna element 22 is 2 mm. On the other hand, the length of the connecting portion 21A in the first antenna element 21 is 4 mm, and the length of the main line portion 21B is 8 mm, which is fixed to 12 mm in total. On the other hand, the length of the coupling portion 22A in the second antenna element 22 is fixed to 22 mm, the length of the first extension portion 22Ba is fixed to 1 mm, and the length of the second extension portion 22Bb is variable to 15 mm, 13 mm, and 11 mm, respectively. It was done.

  As shown in FIG. 2, the resonance frequency is approximately 2150 MHz when the length of the second extension portion 22Bb of the second antenna element 22 is 15 mm, approximately 2250 MHz when 13 mm, and approximately 2350 MHz when 11 mm. It became. From this, it can be seen that as the length of the second antenna element 22 is shortened, the resonance frequency is shifted to the higher frequency side. On the other hand, the VSWR was about 1.2 even when the length of the second extension portion 22Bb of the second antenna element 22 was 15 mm, 13 mm, or 11 mm. From this, it can be seen that even if the length of the second antenna element 22 is variable, the impedance is approximately the same.

  On the other hand, FIG. 3 is a graph showing the relationship between the VSWR and the frequency when the length of the second antenna element 22 is fixed and the length of the first antenna element 21 is varied. Specifically, in FIG. 3, the widths of the first antenna element 21 and the second antenna element 22 are set to 2 mm as in the case of FIG. On the other hand, the length of the coupling portion 22A in the second antenna element 22 is fixed to 22 mm, the length of the first extension portion 22Ba is fixed to 1 mm, and the length of the second extension portion 22Bb is fixed to 13 mm. On the other hand, the length of the connecting portion 21A in the first antenna element 21 is fixed to 4 mm, and the length of the main line portion 21B is changed to 12 mm, 10 mm, and 8 mm, respectively.

  As shown in FIG. 3, the resonance frequency is approximately 2250 MHz when the length of the main line 21B in the first antenna element 21 is 12 mm, approximately 2350 MHz when 10 mm, and approximately 2400 MHz when 8 mm. It was. From this, it can be seen that the shorter the length of the first antenna element 21 is, the more the resonance frequency is shifted to the higher frequency side. The VSWR was approximately 1.2 when the length of the main line portion 21B of the first antenna element 21 was 12 mm, approximately 1.4 when the length was 10 mm, and approximately 1.9 with 8 mm. From this, it can be seen that when the length of the first antenna element 21 is varied, the impedance changes with the resonance frequency.

  Thus, both the resonance frequency and the impedance can be adjusted when the length of the first antenna element 21 is varied, and only the resonance frequency can be adjusted mainly when the length of the second antenna element 22 is varied. Was confirmed.

(Second Embodiment)
FIG. 4 is a schematic view of the dipole antenna according to the second embodiment viewed from directly above. As shown in FIG. 4, the dipole antenna 2 of the second embodiment includes a second antenna element 32 having a shape different from that of the first embodiment.

  Specifically, in the second antenna element 22 (FIG. 1) in the first embodiment, the extension portion 22B extends as a pattern connected to one from the coupling portion 22A. On the other hand, in the 2nd antenna element 32 in this embodiment, the extension part 32B is extended as a pattern branched from the middle part of 22 A of coupling parts.

  In the case of this embodiment, the extension part 32B includes a first extension part 32Ba arranged in a direction orthogonal to the second binding part 22Ab in the connecting part 22A, and a second binding part 22Ab from the end of the first extension part 32Ba. And a second extension part 32Bb arranged along the line.

  As described above, in the dipole antenna 2 of the present embodiment, the extension part 32B of the second antenna element 32 branches off from the middle part of the coupling part 22A, and a part 32Bb thereof is arranged along the coupling part 22A.

  According to such a dipole antenna 2, even if the second antenna element 32 having a shape different from that of the second antenna element 22 of the first embodiment is provided, the same effect as that of the first embodiment can be obtained. That is, both the resonance frequency and the impedance can be adjusted by changing the length of the first antenna element 21, and the resonance frequency can be mainly adjusted by changing the length of the second antenna element 32.

  However, the dipole antenna 1 of the first embodiment is more suitable from the viewpoint of obtaining good radiation efficiency in the frequency band (2.4 GHz to 2.4835 GHz) used for the wireless LAN.

  Here, the measurement result regarding the radiation characteristic of the dipole antenna 1 of 1st Embodiment in the use frequency band of wireless LAN is shown in FIG. 5, and the measurement result regarding the radiation characteristic in the dipole antenna 2 of 2nd Embodiment is shown in FIG.

  As shown in FIG. 5, the radiation characteristic of the dipole antenna 1 of the first embodiment is about −3 dB, and as shown in FIG. 6, the radiation characteristic of the dipole antenna 2 of the second embodiment is about −6 dB. From the comparison between FIG. 5 and FIG. 6, it can be seen that the dipole antenna 1 of the first embodiment is better as the radiation characteristic in the use frequency band of the wireless LAN.

(Third embodiment)
FIG. 7 is a schematic view of the dipole antenna according to the third embodiment viewed from directly above. As shown in FIG. 7, the dipole antenna 3 of the third embodiment includes a second antenna element 42 having a shape different from that of the first embodiment.

  Specifically, in the second antenna element 22 (FIG. 1) in the first embodiment, the second coupling part is bent after being extended from one end of the second coupling part 22Ab in the coupling part 22A in a direction orthogonal to the second coupling part 22Ab. An extension 22B extending along 22Ab was employed. On the other hand, in the second antenna element 42 in the present embodiment, an extension portion 42B extending along the main line portion 21B of the first antenna element 21 straight from one end of the second coupling portion 22Ab in the coupling portion 22A is employed.

  According to the above-described dipole antenna 3 of the present embodiment, as with the dipole antenna 1 of the first embodiment, the impedance adjustment pattern is not provided separately from the antenna pattern, and the first antenna element 21 and the second antenna element 2 The impedance can be adjusted without forcing operations such as increasing the distance from the antenna element 42.

  In the case of the present embodiment, in the second antenna element 42, not only the second coupling part 22Ab in the coupling part 22A but also the extension part 42B extending from the second coupling part 22Ab is the main line of the first antenna element 21. It is in a state along the part 21B. Further, the main line portion 21 </ b> B of the first antenna element 21 is in a state along the coaxial cable 10.

  Therefore, according to the dipole antenna 3 of the present embodiment, the height can be reduced as compared with the dipole antenna 1 of the first embodiment and the dipole antenna 2 of the second embodiment.

(Fourth embodiment)
FIG. 8 is a schematic view of the dipole antenna of the fourth embodiment viewed from directly above. As shown in FIG. 8, the dipole antenna 4 of the fourth embodiment includes a first antenna element 51 and a second antenna element 52 having shapes different from those of the first embodiment.

  Specifically, in the first antenna element 21 (FIG. 1) in the first embodiment, the main line portion 21B extending from one end of the connection portion 21A in a direction orthogonal to the connection portion 21A is employed. On the other hand, in the first antenna element 51 in the present embodiment, a main body 51B that extends straight from one end of the connecting portion 51A is employed.

  On the other hand, in the second antenna element 22 (FIG. 1) in the first embodiment, the first coupling site 22Aa and the second coupling site 22Ab in the coupling unit 22A are orthogonal to each other. On the other hand, in the second antenna element 52 in the present embodiment, the first coupling part 52Aa and the second coupling part 52Ab in the coupling part 52A extend straight as one pattern.

  Further, in the second antenna element 22 (FIG. 1) in the first embodiment, the first extension portion 22Ba of the extension portion 22B is disposed orthogonal to the axis of the outer conductor 13, and the second extension portion 22Ba is along the axis. Arranged. On the other hand, in the second antenna element 52 in the present embodiment, the first extension part 52Bb of the extension part 52B is arranged along the axis of the outer conductor 13 connected to the connection part 51A, and the second extension part 52Ba is Arranged perpendicular to the axis.

  According to the dipole antenna 4 of the present embodiment as described above, similarly to the dipole antenna 1 of the first embodiment, the impedance adjustment pattern is not provided separately from the antenna pattern, and the first antenna element 51 and the second antenna element 2 The impedance can be adjusted without forcing an operation such as increasing the distance from the antenna element 52.

  Similarly to the dipole antenna 1 of the first embodiment, by adjusting the length of the first antenna element 51 to adjust both the resonance frequency and the impedance, and by changing the length of the second antenna element 52 ， Mainly can adjust the resonance frequency.

  However, from the viewpoint of reducing the height, the first to third embodiments in the state along the coaxial cable 10 are more preferable.

  The present invention is not limited to the above embodiment. For example, the first antenna element 21 or 51 is connected to the inner conductor 11 of the coaxial cable 10, and the second antenna element 22, 32, 42, or 52 is connected to the outer conductor 13 of the coaxial cable 10. However, the connection target of the first antenna element 21 or 51 can be a signal line other than the coaxial cable 10, and the connection target of the second antenna element 22, 32, 42, or 52 is a ground line other than the coaxial cable 10. be able to. Note that these signal lines and ground lines may not be essential components in the dipole antennas 1 to 4. The same applies to the coaxial cable 10.

  Further, the shape of the first antenna element may be other than the above embodiment. In short, the first antenna element connected to the ground line may be used.

  The shape of the second antenna element may be other than the above embodiment. In short, the second antenna element is connected to the signal line and is longer than the first antenna element, and the second antenna element is provided with a coupling portion that is capacitively coupled from one end to the other end of the first antenna element. It only has to be done.

  In addition, it is preferable that at least a part of the extended portion extended from the coupling portion is capacitively coupled to the coupling portion. As described above, the impedance can be reduced without providing an impedance adjustment pattern separately from the antenna pattern and without forcing an operation such as increasing the distance between the first antenna element and the second antenna element. This is because it can be adjusted.

  The present invention is applicable to communication terminals such as mobile phones, PDAs (Personal Digital Assistants), and game machines.

DESCRIPTION OF SYMBOLS 1 ... Dipole antenna 10 ... Coaxial cable 11 ... Inner conductor 12 ... Insulating member 13 ... Outer conductor 14 ... Jacket 21, 51 ... 1st antenna element 21A ... Connection Part 21B, 51B ... Main line part 22, 32, 42, 52 ... Second antenna element 22A ... Coupling part 22Aa, 52Aa ... First coupling part 22Ab, 52Ab ... Second coupling part 22B ... Extension part 22Ba, 32Ba ... First extension part 22Bb, 32Bb ... Second extension part

Claims (5)

A first antenna element connected to the ground wire;
A second antenna element connected to the signal line and longer than the first antenna element;
The dipole antenna according to claim 1, wherein the second antenna element is provided with a coupling portion that is close to the other end of the first antenna element so as to be capacitively coupled. The dipole antenna according to claim 1, wherein at least a part of the second antenna element other than the coupling portion is capacitively coupled to the coupling portion. The coupling portion is disposed along the first antenna element, and the part is disposed along the coupling portion on a side opposite to the side where the first antenna element is located with respect to the coupling portion. The dipole antenna according to claim 2. 4. The coaxial cable according to claim 1, further comprising a coaxial cable having an outer conductor electrically connected to the first antenna element and an inner conductor electrically connected to the second antenna element. The dipole antenna according to item 1. The said 1st antenna element consists of a connection part to which the said external conductor is electrically connected, and a main-body part extended along the axis | shaft of the said external conductor connected to the said connection part. The dipole antenna described in 1.

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