JP2010081571A - Loop antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a loop antenna that radiates a circularly-polarized wave having a favorable axial ratio, suppresses generation of profile variations, and can simply adjust the profile even when variations occur in the profile. <P>SOLUTION: A first antenna element 11, a second antenna element 12, a third antenna element 13 and a fourth antenna element 14 in a loop element 10 form a rectangular shape in collaboration on a plane defined by a first direction and a second direction. There are provided a first perturbation element 20 that extends from the first antenna element 11 to the outside of the rectangular shape and has a portion coming close and opposing to the third antenna element 13, and a second perturbation element 30 that extends from the second antenna element 12 to the outside of the rectangular shape and has a portion coming close and opposing to the fourth antenna element 14. The loop element 10, the first perturbation element 20 and the second perturbation element 30 are arranged symmetrically about a center axis C intersecting at right angles with the plane defined by the first direction and the second direction. A non-feeding terminal 60 may be provided inside the loop element 10. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a loop antenna, and more particularly to a loop antenna that transmits and receives circularly polarized waves.

  In recent years, in mobile bodies such as vehicles, communication systems for transmitting and receiving vehicle traffic information such as ETC (highway toll billing system) to / from terminals outside the vehicle, GPS (global positioning system), satellite digital broadcasting for mobile bodies, etc. Various systems such as a one-way or two-way information providing system have been introduced. In such a system, since the radio wave environment of the moving body changes every moment, circularly polarized waves are used to suppress the influence of reflected waves and the influence of relative changes in the angle of the antenna. A loop antenna having a configuration corresponding to circular polarization has been proposed.

  In view of this situation, an antenna that can transmit and receive circularly polarized waves by providing a branch conductor or a perturbation element in a part of the loop antenna has been proposed. (See Patent Document 1 to Patent Document 3).

Japanese Examined Patent Publication No. 3-61363 JP 2005-236659 A JP 2006-186488 A

  However, in the configuration in which one branch conductor is extended inward from the loop conductor in the configuration proposed in Patent Document 1, there is a tendency for variation in shape due to processing distortion at the time of forming the loop antenna. When the shape variation occurs, it tends to be difficult to adjust the shape.

  Further, in the configuration in which one branch conductor spaced apart from the inside of the loop conductor in another configuration proposed in Patent Document 1 is provided, the relative position between the loop conductor and the branch conductor separated from the loop conductor tends to vary. In addition, when such variations in shape and relative position occur, it tends to be difficult to adjust them.

  Further, in the configuration proposed in Patent Documents 2 and 3, in the configuration in which one perturbation element that is bent apart from the loop antenna is disposed, the relative position variation between the loop antenna and the perturbation element that is separated from the loop antenna varies. In addition, when variations in the shape and relative position occur, it tends to be difficult to adjust them.

  The present invention has been made through the above studies, and radiates circularly polarized waves having a good axial ratio, suppresses the occurrence of shape variation, and easily adjusts the shape even when the shape variation occurs. An object of the present invention is to provide a loop antenna that can be used.

In order to achieve the above object, a loop antenna according to the first aspect of the present invention extends in a first antenna element extending in a first direction and facing the first antenna element in parallel. A second antenna element; a third antenna element extending in a second direction orthogonal to the first direction; and a fourth antenna element extending parallel to and opposite to the third antenna element. The third antenna element and the fourth antenna element communicate with each other between the first antenna element and the second antenna element, and the loop element comprises: A loop antenna that cooperates to form a rectangular shape in a plane defined by the first direction and the second direction, and extends outward from the first antenna element. , In close proximity to the third antenna element And a second perturbation element having a portion extending outwardly of the rectangular shape from the second antenna element and facing the fourth antenna element in close proximity. The loop element, the first perturbation element, and the second perturbation element are axisymmetric about a central axis that is orthogonal to the plane defined by the first direction and the second direction. It is arranged.

  In addition to the first aspect, the loop antenna of the present invention has a second aspect in which the rectangular shape is a square.

  In addition to the first or second aspect, the loop antenna of the present invention includes a fifth antenna element in which the first perturbation element extends outward from the first antenna element in the rectangular shape. And a sixth antenna element extending from the fifth antenna element and facing in parallel with the third antenna element, and the second perturbation element is the second antenna. A seventh antenna element extending outwardly from the rectangular shape from an element; and an eighth antenna element extending from the seventh antenna element and facing the fourth antenna element in close proximity to and parallel to the fourth antenna element; The third aspect is to have

  In addition to any one of the first to third aspects, the loop antenna of the present invention is further characterized in that a parasitic element is further provided in the vicinity of the power feeding portion provided in the loop element. And

  In addition to the fourth aspect, the loop antenna of the present invention includes the feeding unit provided in the second antenna element, and the parasitic element is parallel to the second antenna element, The fifth aspect includes a ninth antenna element provided inward of the loop element and in the vicinity of the feeding portion.

  In addition to the fifth aspect, the loop antenna of the present invention is further provided with a tenth antenna element parallel to the third antenna element, wherein the parasitic elements further communicate with the ninth antenna element, respectively. The sixth aspect includes an eleventh antenna element parallel to the fourth antenna element.

  In addition to any one of the first to sixth aspects, the loop antenna of the present invention includes the first antenna element, the second antenna element, the third antenna element, and the first element of the loop element. A seventh aspect is that the loop length formed by the four antenna elements is equal to one of the predetermined wavelengths of radio waves to be transmitted and received.

  In addition to any one of the first to seventh aspects, the loop antenna according to the present invention has a flat plate shape in which the loop element, the first perturbation element, and the second perturbation element are formed on a transparent substrate. Arrangement is the eighth aspect.

According to the configuration in the first aspect of the present invention, the first antenna element, the second antenna element, the third antenna element, and the fourth antenna element in the loop element are in the first direction and the second direction. The first antenna element has a rectangular shape that cooperates to form a rectangular shape, extends outwardly of the rectangular shape from the first antenna element, and has a portion facing and proximate to the third antenna element. A loop element, a first perturbation element, and a second perturbation element extending outwardly in a rectangular shape from the second antenna element and having a portion facing and close to the fourth antenna element. The perturbation element and the second perturbation element are arranged symmetrically with respect to a central axis orthogonal to the plane defined by the first direction and the second direction, so that a circularly polarized wave having a good axial ratio can be obtained. In addition to radiating, the shape variation is suppressed and Even when attached occurs, it is possible to easily adjust the shape.

  In addition, according to the configuration of the second aspect of the present invention, since the rectangular shape of the loop element is a square, it is possible to more reliably generate circularly polarized waves having a good axial ratio and to cause variation in shape. Can be suppressed.

  Further, according to the configuration of the third aspect of the present invention, the first perturbation element includes a fifth antenna element extending outward from the first antenna element in a rectangular shape, and a fifth antenna element. A sixth antenna element extending in parallel and facing the third antenna element in close proximity to and parallel to the third antenna element, the second perturbing element extending outwardly in a rectangular shape from the second antenna element. 7 and the eighth antenna element extending from the seventh antenna element and facing the fourth antenna element in parallel and facing in parallel, the shape can be changed even when the shape variation occurs. Adjustment can be made more reliably and easily.

  In addition, according to the configuration of the fourth aspect of the present invention, a parasitic element is further provided in the vicinity of the power supply unit provided in the loop element, so that the voltage standing wave ratio becomes a good value, and the loop Reflected waves returning from the antenna to the feeder line can be suppressed, and radio waves can be efficiently radiated from the loop antenna.

  Further, according to the configuration of the fifth aspect of the present invention, the parasitic element is parallel to the second antenna element provided with the feeding portion, and is located inward of the loop element and in the vicinity of the feeding portion. By including the ninth antenna element provided, the voltage standing wave ratio can be practically obtained as a good value.

  Further, according to the configuration of the sixth aspect of the present invention, the parasitic elements are connected to the ninth antenna element and the tenth antenna element parallel to the third antenna element and the fourth antenna element, respectively. By including the eleventh antenna element in parallel, the length of the parasitic element can be increased without interfering with the antenna element of the loop element, and the voltage standing wave ratio can be obtained as a better value. .

  Further, according to the configuration of the seventh aspect of the present invention, the loop length of the loop element including the first antenna element, the second antenna element, the third antenna element, and the fourth antenna element is the object to be transmitted / received. Therefore, it is possible to realize a more compact configuration while maintaining the characteristics of the circularly polarized wave to be radiated and the shape accuracy of the loop antenna.

  According to the configuration of the eighth aspect of the present invention, the loop element, the first perturbation element, and the second perturbation element have a flat plate shape and are disposed on the transparent substrate, so that the front of the vehicle It can be easily and reliably attached to glass or the like in a state where visibility is not hindered.

It is a top view of the loop antenna in the 1st Embodiment of this invention. It is sectional drawing by the AA line of FIG. It is a figure which shows the radiation pattern of the loop antenna in this embodiment. It is a figure which shows the input impedance characteristic of the loop antenna in this embodiment. It is a figure which shows the axial ratio at the time of changing the length of the perturbation element of the loop antenna in this embodiment. It is a figure which shows the axial ratio at the time of changing the gap of the perturbation element of the loop antenna in this embodiment. It is a top view of the loop antenna in the 2nd Embodiment of this invention. It is sectional drawing by the BB line of FIG. It is a figure which shows the voltage standing wave ratio at the time of changing the length of the parasitic element of the loop antenna in this embodiment. It is a figure which shows the axial ratio at the time of changing the length of the parasitic element of the loop antenna in this embodiment. It is a figure which shows the axial ratio at the time of changing the gap of the perturbation element of the loop antenna in this embodiment. It is a figure which shows the voltage standing wave ratio at the time of changing the gap of the perturbation element of the loop antenna in this embodiment.

  Hereinafter, a loop antenna in each embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the figure, the x-axis, y-axis, and z-axis form a three-axis orthogonal coordinate system.

(First embodiment)
First, the loop antenna according to the first embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a top view of a loop antenna according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

  As shown in FIG. 1 and FIG. 2, the loop antenna 1 includes a loop element 10 having a square loop shape on the xy plane, and a first perturbation element 20 and a second perturbation extending from the loop element 10. And an element 30. Furthermore, the loop element 10 is provided with a power feeding unit 40 connected to a communication circuit and a power supply circuit (not shown). The loop element 10 in a state where the first perturbation element 20 and the second perturbation element 30 are in communication with each other and the power feeding unit 40 is disposed is bonded to a single transparent substrate 50 having a predetermined plate thickness by an adhesive. It is pasted.

  The loop antenna 1 may be made of metal having practically sufficient conductivity and strength. For example, the loop antenna 1 is made of phosphor bronze. Moreover, the resin etc. which have the transmittance | permeability and intensity | strength with respect to visible light sufficient practically can be used for the transparent substrate 50, for example, the transparent substrate 50 is a product made from PET resin. Further, the transparent substrate 50 has a rectangular shape larger than the loop element 10 in a state where the first perturbation element 20 and the second perturbation element 30 are connected and the power feeding unit 40 is arranged on the xy plane. Have. Further, in principle, the loop shape of the loop element 10 may be a rectangular shape such as a rectangle.

More specifically, the loop element 10 includes a first antenna element 11 extending in a direction parallel to the x-axis, and extending in parallel to the first antenna element 11 so that the power feeding unit 40 is The provided second antenna element 12, the third antenna element 13 extending in the direction parallel to the y-axis, and the fourth antenna element 14 extending parallel to and opposed to the third antenna element 13. It consists of. Here, the third antenna element 13 and the fourth antenna element 14 communicate with each other between the first antenna element 11 and the second antenna element 12, and the loop element 10 is on the xy plane. A square loop shape will be formed. In addition, the loop length of the loop element 10 is a length that makes the first antenna element 11, the second antenna element 12, the third antenna element 13, and the fourth antenna element 14 make one round on the xy plane. 4L is set equal to the length of one wavelength of a predetermined wavelength corresponding to the frequency of the radio wave to be transmitted / received by the loop antenna 1. The power feeding unit 40 can be provided in any one of the antenna elements 11, 13, and 14 other than the second antenna element 12.

  Note that the corners of the first antenna element 11, the second antenna element 12, the third antenna element 13, and the fourth antenna element 14 in the loop element 10 are on the xy plane due to requests during molding and the like. And may have an R shape.

  In addition, the first perturbation element 20 includes a fifth antenna element 21 extending from the first antenna element 11 in the square outward direction of the loop element 10 along the positive direction of the x axis, and a fifth antenna. A sixth antenna element 22 that extends in the negative direction of the y-axis from the element and faces the third antenna element 13 of the loop element 10 in close proximity and in parallel. Further, the second perturbation element 30 includes a seventh antenna element 31 extending from the second antenna element 12 in a square outward direction of the loop element 10 along the negative x-axis direction, and a seventh antenna. And an eighth antenna element 32 extending in the positive direction of the y-axis from the element 31 and facing the fourth antenna element 14 of the loop element 10 in close proximity and in parallel.

  The sixth antenna element 22 of the first perturbation element 20 has a length Lp on the xy plane, and the sixth antenna element 22 and the third antenna element 13 of the loop element 10 The distance between adjacent ends is δ. The eighth antenna element 32 of the second perturbation element 30 has a length Lp on the xy plane. The eighth antenna element 32 and the fourth antenna element 14 of the loop element 10 The distance between adjacent ends is δ. Further, the fifth antenna element 21 of the first perturbation element 20 and the seventh antenna element 31 of the second perturbation element 30 are the sixth antenna elements on the xy plane because of a request at the time of molding or the like. Each of the second antenna element 32 and the eighth antenna element 32 may have a correspondingly curved shape.

  Here, the loop element 10, the first perturbation element 20, and the second perturbation element 30 are arranged symmetrically about a central axis C parallel to the z axis.

  The first antenna element 11, the second antenna element 12, the third antenna element 13 and the fourth antenna element 14 of the loop element 10, the fifth antenna element 21 and the sixth antenna element 20 of the first perturbation element 20. The antenna elements 22 and the seventh antenna element 31 and the eighth antenna element 32 of the second perturbation element 30 each have a rectangular shape of W having the same width on the xy plane. The plate thickness of each of these antenna elements is practically about 1 (mm) to 3 (mm).

  In the method of manufacturing the loop antenna 1 having the above-described configuration, first, a phosphor bronze thin plate having a predetermined plate thickness is punched, and the loop element 10 and the first perturbation element 20 connected thereto and The second perturbation element 30 is produced integrally. Next, a part of the second antenna element 12 of the loop element 10 is cut to form a power feeding unit 40 that is a pair of connection ends. Next, the loop element 10 in a state where the first perturbation element 20 and the second perturbation element 30 are in communication with each other and the power feeding unit 40 is disposed is attached to a single transparent substrate 50 via an adhesive. . Then, the power supply unit 40 arranged in the loop element 10 is connected to a power supply line S connected to a communication circuit and a power supply circuit (not shown) to obtain the loop antenna 1. At this time, since the loop element 10, the first perturbation element 20, and the second perturbation element 30 are arranged symmetrically about the central axis C parallel to the z axis, they are unnecessary even during punching. Generation of a distortion of a simple shape is effectively suppressed, and a practically sufficient processing accuracy can be obtained.

As another method for manufacturing the loop antenna 1, a phosphor bronze thin plate having a predetermined plate thickness is previously pasted on the transparent substrate 50 with an adhesive, and the thin plate in this state is transparent. The loop element 10 is punched to leave the substrate 50, and the first perturbation element 20 and the second perturbation element 30 connected to the loop element 10 and the loop element 10 are integrally manufactured to obtain a loop antenna. 1 may be obtained.

  Next, the radiation characteristics of the electromagnetic wave in the loop antenna 1 having the above configuration will be described in detail with reference to FIGS. The loop length 4L of the loop element 10 is set to 114 (mm) by setting L to 28.5 (mm), and the first antenna element 11, the second antenna element 12, and the third antenna element of the loop element 10 are set. Antenna element 13 and fourth antenna element 14, fifth antenna element 21 and sixth antenna element 22 of first perturbation element 20, and seventh antenna element 31 and eighth of second perturbation element 30 The width W of each antenna element 32 is 0.3 (mm), and the length of each of the sixth antenna element 22 of the first perturbation element 20 and the eighth antenna element 32 of the second perturbation element 30 is set. Lp is 15 (mm), the distance δ between adjacent ends of the sixth antenna element 22 of the first perturbation element 20 and the third antenna element 13 of the loop element 10 and the second perturbation element 30 eighth antenna elements 32 and Fourth distance between between the ends adjacent the antenna element 14 [delta] in-loop element 10, and with each 1 (mm).

  FIG. 3 is a diagram showing a radiation pattern for a radio wave having a frequency of 2.67 (GHz) in the loop antenna of the present embodiment. FIG. 3A shows a radiation pattern on the xz plane. 3 (b) shows a radiation pattern in the yz plane. 3 (a) and 3 (b), the circumferential direction indicates the angle (°) of the half-value width of the radiated wave, the radial direction indicates the axial ratio (db), and a solid curve. Indicates right-handed polarization, and a dotted curve indicates left-handed polarization. FIG. 4 is a diagram illustrating the input impedance characteristics of the loop antenna according to the present embodiment, where the horizontal axis represents the frequency f (GHz) of the radiated wave, and the vertical axis represents the input impedance Z (Ω). In FIG. 4, the solid curve indicates the real part of the input impedance, and the dotted curve indicates the imaginary part of the input impedance.

  As shown in FIGS. 3A and 3B, right-handed polarized light is emitted in the positive z-axis direction and left-handed polarized light is emitted in the negative z-axis direction. For both left-handed polarized waves, when the frequency is 2.67 (GHz), the half-width of the radiated wave with an axial ratio of 3 (db) is estimated to be about 102 (°), and exhibits a practically sufficient axial ratio. Circularly polarized light can be emitted.

  As shown in FIG. 4, when the frequency f (GHz) of the radiated wave is in the range of 2.59 (GHz) to 2.74 (GHz), the real part of the input impedance is about 250 (Ω). A constant value and an imaginary part of the input impedance can be practically estimated to be a constant value of about −50 (Ω), and good impedance characteristics can be obtained in such a frequency range.

  Now, the length Lp of each of the sixth antenna element 22 of the first perturbation element 20 and the eighth antenna element 32 of the second perturbation element 30 in the loop antenna 1 of the present embodiment is changed. The change characteristics of the axial ratio in this case will be described in detail with reference to FIG. In such a case, the loop length 4L of the loop element 10 is set to 114 (mm) by setting L to 28.5 (mm), and the first antenna element 11, the second antenna element 12 of the loop element 10, The third antenna element 13 and the fourth antenna element 14, the fifth antenna element 21 and the sixth antenna element 22 of the first perturbation element 20, and the seventh antenna element 31 of the second perturbation element 30 and The width W of each of the eighth antenna elements 32 is 0.3 (mm), and the sixth antenna element 22 of the first perturbation element 20 and the third antenna element 13 of the loop element 10 are adjacent to each other. The distance δ between the parts and the distance δ between the adjacent ends of the eighth antenna element 32 of the second perturbation element 30 and the fourth antenna element 14 of the loop element 10 are 1 (mm), respectively. did.

FIG. 5 shows the length of the perturbation element of the loop antenna 1 in the present embodiment, that is, the length of each of the sixth antenna element 22 of the first perturbation element 20 and the eighth antenna element 32 of the second perturbation element 30. It is a figure which shows the axial ratio at the time of changing length Lp. In FIG. 5, the horizontal axis represents the frequency f (GHz) of the radiated wave, the vertical axis represents the axial ratio AR (db), and the curves L1, L2, L3, and L4 are respectively the first The length Lp of each of the sixth antenna element 22 of the perturbation element 20 and the eighth antenna element 32 of the second perturbation element 30 is 5 (mm), 10 (mm), 15 (mm), and 20 (mm). ) Shows the characteristic of the axial ratio AR corresponding to the change in the frequency f.

  As shown in FIG. 5, the curve L3 indicates that the frequency band in which the axial ratio AR is 3 (db) or less is in the range of about 2.62 (GHz) to about 2.72 (GHz), and a favorable axial ratio is obtained. Referring to curves L1 and L2, which show the characteristics, the length Lp of each of the sixth antenna element 22 of the first perturbation element 20 and the eighth antenna element 32 of the second perturbation element 30 is smaller. It can be seen that the axial ratio best point moves to the high frequency side with a relatively large change width as the length Lp is reduced. On the other hand, referring to the curve L4 in which the length Lp is made larger, it can be seen that as the length Lp is increased, the axial ratio best point moves to the low frequency side with a relatively large change width.

  Next, the distance δ between adjacent ends of the sixth antenna element 22 of the first perturbation element 20 and the third antenna element 13 of the loop element 10 in the loop antenna 1 in the present embodiment and the second FIG. 6 further shows the change characteristics of the axial ratio when the distance δ between the adjacent ends of the eighth antenna element 32 of the perturbation element 30 and the fourth antenna element 14 of the loop element 10 is changed. The details will be described with reference to FIG. In such a case, the loop length 4L of the loop element 10 is set to 114 (mm) by setting L to 28.5 (mm), and the first antenna element 11, the second antenna element 12 of the loop element 10, The third antenna element 13 and the fourth antenna element 14, the fifth antenna element 21 and the sixth antenna element 22 of the first perturbation element 20, and the seventh antenna element 31 of the second perturbation element 30 and The width W of each of the eighth antenna elements 32 is 0.3 (mm), and each of the sixth antenna element 22 of the first perturbation element 20 and the eighth antenna element 32 of the second perturbation element 30 is set. The length Lp was set to 15 (mm).

  FIG. 6 shows the gap between the perturbation elements of the loop antenna 1 in this embodiment, that is, between the adjacent ends of the sixth antenna element 22 of the first perturbation element 20 and the third antenna element 13 of the loop element 10. And the axial ratio when the distance δ between the adjacent ends of the eighth antenna element 32 of the second perturbation element 30 and the fourth antenna element 14 of the loop element 10 is changed. It is. In FIG. 6, the horizontal axis represents the frequency f (GHz) of the radiated wave, the vertical axis represents the axial ratio AR (db), and the curves δ1, δ2, δ3, and δ4 represent the first The distance δ between adjacent ends of the sixth antenna element 22 of the perturbation element 20 and the third antenna element 13 of the loop element 10 and the eighth antenna element 32 and the loop element 10 of the second perturbation element 30 are the same. Of the frequency f when the distance δ between the adjacent ends of the fourth antenna element 14 is 0.5 (mm), 1 (mm), 2 (mm), and 3 (mm) The characteristic of the axial ratio AR corresponding to is shown.

  As shown in FIG. 6, the curve δ <b> 2 shows good axial ratio characteristics like the curve L <b> 3 in FIG. 5 for the frequency band in which the axial ratio AR is 3 (db) or less. The distance δ between adjacent ends of the sixth antenna element 22 and the third antenna element 13 of the loop element 10 and the fourth antenna element 32 of the second perturbation element 30 and the fourth of the loop element 10 Referring to the curve δ1 in which the distance δ between the adjacent ends of the antenna element 14 is reduced, as the distance δ is reduced, the axial ratio best point is relatively higher than that in FIG. It turns out that it moves with a small change width. On the other hand, referring to the curves δ3 and δ4 in which the distance δ is increased, as the distance δ is increased, the axial ratio best point moves to the lower frequency side with a relatively smaller change width than that in FIG. I understand.

  Here, considering the change characteristics of the axial ratio when the length Lp and the gap δ of the first perturbation element 20 and the second perturbation element 30 of the loop antenna 1 in the present embodiment obtained above are changed, It can be understood that the change in the axial ratio when the length Lp of the perturbation element is changed is relatively larger than the change in the axial ratio when the gap δ of the perturbation element is changed. That is, even if the gap δ between the first perturbation element 20 and the second perturbation element 30 varies during the formation of the loop element 10 in which the first perturbation element 20 and the second perturbation element 30 are arranged, It can be evaluated that the influence on the axial ratio characteristic is smaller than the case where the length Lp of the first perturbation element 20 and the second perturbation element 30 varies.

  Therefore, the length Lp of the first perturbation element 20 and the second perturbation element 30 tends to be relatively easily varied when forming the loop element 10 in which the first perturbation element 20 and the second perturbation element 30 are arranged. In consideration of this, the length Lp of the antenna element 22 and the antenna element 32 that are easy to cut in shape is set to be long in advance, and is appropriately cut corresponding to the length of L3. By doing so, it can be seen that a good axial ratio characteristic can be easily obtained. On the other hand, the gap δ between the first perturbation element 20 and the second perturbation element 30 has a relatively small variation when the loop element 10 is formed, and can easily fall within the tolerance range. The axial ratio characteristics can be obtained, and the adjustment of the gap δ tends to be difficult in terms of shape compared to the adjustment of the length Lp of the first perturbation element 20 and the second perturbation element 30. In view of this, in order to obtain an optimum axial ratio characteristic, the gap δ is within the tolerance range and the adjustment thereof is substantially omitted, and the lengths of the first perturbation element 20 and the second perturbation element 30 are obtained. It can be seen that Lp should be mainly adjusted.

  According to the configuration of the present embodiment described above, the first antenna element, the second antenna element, the third antenna element, and the fourth antenna element in the loop element are displayed in the first direction and the second direction. A first perturbation element having a rectangular shape in cooperation with each other, having a portion extending outwardly from the first antenna element and facing the third antenna element in close proximity to each other; And a second perturbation element extending outwardly in a rectangular shape from the second antenna element and having a portion facing and in close proximity to the fourth antenna element, the loop element, the first perturbation The element and the second perturbation element are arranged symmetrically with respect to a central axis perpendicular to the plane defined by the first direction and the second direction, thereby radiating circularly polarized waves with a good axial ratio. In addition, the shape variation is suppressed and the shape Even if the variability occurs, it is possible to easily adjust the shape.

  In addition, since the loop shape is square, it is possible to more reliably generate circularly polarized waves having a good axial ratio and to suppress occurrence of shape variations.

  In addition, the first perturbation element extends from the first antenna element to the outside of the rectangular shape of the loop element, and the first antenna element extends from the fifth antenna element and close to the third antenna element. A sixth antenna element facing in parallel, and a second perturbation element extending from the second antenna element to the outside of the rectangular shape of the loop element; By having the eighth antenna element extending from the antenna element 7 and facing the fourth antenna element in parallel and facing in parallel, the shape can be adjusted more reliably and easily even when the shape varies. be able to.

  In addition, since the loop length is equal to one of the predetermined wavelengths of radio waves to be transmitted and received, a more compact configuration can be realized while maintaining circularly polarized radiation characteristics and loop antenna shape accuracy.

In addition, the loop element, the first perturbation element, and the second perturbation element have a flat plate shape and are disposed on the transparent substrate, so that the vehicle windshield or the like can be reliably viewed without impeding visibility. Can be attached to.

  Now, it is preferable that the input impedance of the loop antenna 1 and the impedance of the feeder S connected to the feeder 40 are matched. Therefore, the configuration of the second embodiment for matching the impedance will be described in detail below.

(Second Embodiment)
The loop antenna according to the second embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 7 is a top view of the loop antenna in the present embodiment, and FIG. 8 is a cross-sectional view taken along the line BB in FIG.

  As shown in FIGS. 7 and 8, the loop antenna 100 of the present embodiment is mainly different from the loop antenna 1 of the first embodiment in that a parasitic element 60 is further provided. The configuration is the same. Therefore, in the present embodiment, the description will be made paying attention to such a difference, and the same components are denoted by the same reference numerals, and the description will be simplified or omitted as appropriate.

  Specifically, in the loop antenna 100, in addition to the loop element 10, the first perturbation element 20, the second perturbation element 30, and the power feeding unit 40, a parasitic element on the transparent substrate 50 in the vicinity of the power feeding unit 40. 60 is formed.

  The parasitic element 60 is made of phosphor bronze in the same manner as the loop element 10, the first perturbation element 20, and the second perturbation element 30, but the second antenna element in which the feeding unit 40 is provided in the loop element 10. 12, a ninth antenna element 61 provided in the vicinity of the rectangular loop element 10 and in the vicinity of the power feeding unit 40 is an essential component. The parasitic element 60 may be individually attached on the transparent substrate 50 via an adhesive, like the loop element 10, the first perturbation element 20, and the second perturbation element 30. A thin plate made of phosphor bronze previously pasted on 50 may be punched out so as to leave the transparent substrate 50.

  Here, when it is desired to increase the length of the parasitic element 60 to about the length of the second antenna element 12, the ninth antenna element 61 includes the third antenna element 13 and the fourth antenna element in the loop element 10. It is necessary to fold and extend the ninth antenna element 61 in the positive direction of the y-axis so as not to interfere with the antenna element 14. The tenth antenna element 62 is referred to as a component parallel to the third antenna element 13, and the eleventh antenna element 63 is referred to as a component parallel to the fourth antenna element 14.

That is, in such a case, the tenth antenna element 62 extending in the positive direction of the y-axis is connected to the positive end of the ninth axis of the ninth antenna element 61, and the ninth An eleventh antenna element 63 extending in the positive direction of the y-axis communicates with the end portion of the negative antenna element 61 in the x-axis direction. The tenth antenna element 62 and the eleventh antenna element 63 are respectively x with respect to the sixth antenna element 22 of the first perturbation element 20 and the eighth antenna element 32 of the second perturbation element 30. It is necessary to define and extend the length so as not to overlap when observed in the direction of the axis. The ninth antenna element 61, the tenth antenna element 62, and the eleventh antenna element 63 each have a rectangular shape of W having the same width on the xy plane. The plate thickness of each of these antenna elements is practically about 1 (mm) to 3 (mm). Further, the corner where the ninth antenna element 61 and the tenth antenna element 62 communicate with each other, and the corner where the ninth antenna element 61 and the eleventh antenna element 63 communicate with each other are requested from a request at the time of molding or the like. , Each may have an R shape on the xy plane.

  In the parasitic element 60, the distance between the end of the ninth antenna element 61 in the positive direction of the x axis and the end of the third antenna element 13 of the corresponding loop element 10 is the ninth antenna element. 61 is equal to the distance between the end of the negative direction of the x-axis in 61 and the end of the fourth antenna element 14 of the corresponding loop element 10. Further, when the tenth antenna element 62 and the eleventh antenna element 63 are provided, the distance between the adjacent ends of the tenth antenna element 62 and the third antenna element 13 of the loop element 10 is , Equal to the distance between adjacent ends of the eleventh antenna element 63 and the fourth antenna element 14 of the loop element 10. That is, the parasitic element 60 is symmetrical with respect to a plane including the central axis C and parallel to the yz plane, and positioning with respect to the loop element 10, the first perturbation element 20, and the second perturbation element 30 is simple and reliable. Can be done.

  Next, in the loop antenna 100 having the above configuration, the voltage standing wave ratio (VSWR) and the change ratio of the axial ratio when the length of the parasitic element 60 is changed are further referred to FIG. 9 and FIG. This will be described in detail. In such a case, the loop length 4L of the loop element 10 is set to 114 (mm) by setting L to 28.5 (mm), and the first antenna element 11, the second antenna element 12 of the loop element 10, The third antenna element 13 and the fourth antenna element 14, the fifth antenna element 21 and the sixth antenna element 22 of the first perturbation element 20, the seventh antenna element 31 of the second perturbation element 30 and the second antenna element 31. The width W of each of the eight antenna elements 32 and the ninth antenna element 61, the tenth antenna element 62, and the eleventh antenna element 63 of the parasitic element 60 is set to 0.3 (mm). The distance δ between adjacent ends of the sixth antenna element 22 of the perturbation element 20 and the third antenna element 13 of the loop element 10 and the eighth antenna element 32 and the loop element 10 of the second perturbation element 30 are the same. The first The distance between the between the end portions adjacent the antenna element 14 [delta], and with each 1 (mm). The distance δ ′ between adjacent end portions of the ninth antenna element 61 of the parasitic element 60 and the second antenna element 12 of the loop element 10 was 1.2 (mm).

  FIG. 9 is a diagram showing a voltage standing wave ratio when the length of the parasitic element 60 of the loop antenna 100 according to the present embodiment is changed, and FIG. 10 similarly shows the length of the parasitic element 60. It is a figure which shows the axial ratio at the time of changing. In FIG. 9, the horizontal axis represents the frequency f (GHz) of the radiated wave, the vertical axis represents the voltage standing wave ratio VSWR, and the curves L5, L6, and L7 represent the parasitic element 60, respectively. The characteristics of the voltage standing wave ratio VSWR corresponding to the change of the frequency f when the length is 0 (mm), 27 (mm), and 45 (mm) are shown. In FIG. 10, the horizontal axis represents the frequency f (GHz) of the radiated wave, the vertical axis represents the axial ratio AR (db), and the curves L8, L9, and L10 represent the parasitic element 60, respectively. The characteristic of the axial ratio AR corresponding to the change of the frequency f when the length is similarly set to 0 (mm), 27 (mm), and 45 (mm) is shown.

  Here, the length of the ninth antenna element 61 of the parasitic element 60 being 0 (mm) means that the parasitic element 60 itself is not provided. When the length of the parasitic element 60 is 27 (mm), the parasitic element 60 is provided with only the ninth antenna element 61 having a length Lx of 27 (mm). When the length of the parasitic element 60 exceeds 45 (mm) beyond the length, the ninth antenna element 61 is connected to the third antenna element 13 and the fourth antenna in the loop element 10. In order to prevent interference with the element 14, a tenth antenna element 62 and an eleventh antenna element 63 are provided in addition to the ninth antenna element 61, and the length Lx of the ninth antenna element 61 is The tenth antenna element 62 and the eleventh antenna element 63 both have a length Ly of 9 (mm).

As shown in FIG. 9, the curve L5 has a length of the ninth antenna element 61 of the parasitic element 60 of 0.
The frequency characteristic of the voltage standing wave ratio VSWR in the case of (mm) is shown. The relative value is 4 or more in the entire frequency band from 2.5 (GHz) to 3.0 (GHz). Therefore, there is room for improvement in the consistency between the input impedance of the loop antenna 1 and the impedance of the feeder line S. On the other hand, in the curve L6 in which the length of the ninth antenna element 61 of the parasitic element 60 is 27 (mm), the voltage standing wave ratio VSWR tends to decrease, and the length of the ninth antenna element 61 further increases. In the curve L7 with a thickness of 45 (mm), the voltage standing wave ratio VSWR is relatively small so that it is 2 or less in the frequency band of about 2.75 (GHz) to about 2.87 (GHz). It turns out that it is the characteristic which exhibits. That is, as the length of the parasitic element 60 is increased, it can be understood that the voltage standing wave ratio VSWR can be suppressed to a good value of 2 or less in a specific frequency band.

  At this time, with respect to the axial ratio AR, the length of the parasitic element 60 was similarly set to 0 (mm), 27 (mm), and 45 (mm) as shown by the curves L8, L9, and L10 in FIG. In particular, in the curve L10 in which the length of the parasitic element 60 is 45 (mm), the best axial ratio point tends to move to the high frequency side, and the axial ratio AR is about 2.72 (GHz). The axial ratio characteristic is 3 (db) or less in the frequency band of about 2.78 (GHz).

  However, when the length of the parasitic element 60 is set to 45 (mm) in this way, the frequency band exhibiting a good value such that the voltage standing wave ratio VSWR is 2 or less is about 2.75 ( From about 2.72 (GHz), the frequency band exhibiting a good value such that the axial ratio AR is 3 (db) or less, whereas the frequency band is from about 2.87 (GHz) to about 2.87 (GHz). The frequency band is about 2.78 (GHz), the frequency band with a good axial ratio AR is also narrow, and the frequency band with a good voltage standing wave ratio VSWR covers the entire frequency band with a good axial ratio AR. It is not possible.

  Therefore, next, while providing the parasitic element 60, the frequency band in which the axial ratio AR is 3 (db) or less is expanded, and the frequency band in which the voltage standing wave ratio VSWR is 2 or less is the axial ratio AR. A configuration that covers the entire frequency band of 3 (db) or less will be described in detail with reference to FIGS. In such a case, the loop length 4L of the loop element 10 is set to 114 (mm) by setting L to 28.5 (mm), and the first antenna element 11, the second antenna element 12 of the loop element 10, The third antenna element 13 and the fourth antenna element 14, the fifth antenna element 21 and the sixth antenna element 22 of the first perturbation element 20, the seventh antenna element 31 of the second perturbation element 30 and the second antenna element 31. The width W of each of the eighth antenna element 32 and the ninth antenna element 61, the tenth antenna element 62, and the eleventh antenna element 63 of the parasitic element 60 is 0.3 (mm). The distance δ ′ between the adjacent end portions of the 60th ninth antenna element 61 and the second antenna element 12 of the loop element 10 was 1.2 (mm). The parasitic element 60 has a length of 45 (mm), that is, the ninth antenna element 61 has a length Lx of 27 (mm), and the tenth antenna element 62 and the eleventh antenna. Regarding the element 63, the length Ly is 9 (mm).

FIG. 11 is a diagram showing an axial ratio when the gap of the perturbation element of the loop antenna in this embodiment is changed, and FIG. 12 is a voltage standing wave ratio when the gap of the perturbation element is similarly changed. FIG. Here, the gap of the perturbation element of the loop antenna is the distance δ between the adjacent ends of the sixth antenna element 22 of the first perturbation element 20 and the third antenna element 13 of the loop element 10 and the first This means a distance δ between adjacent end portions of the eighth antenna element 32 of the second perturbation element 30 and the fourth antenna element 14 of the loop element 10. In FIG. 11, the horizontal axis represents the frequency f (GHz) of the radiated wave, the vertical axis represents the axial ratio AR (db), and the curves δ5 and δ6 represent the first perturbation element 20 respectively. The distance δ between adjacent ends of the sixth antenna element 22 and the third antenna element 13 of the loop element 10 and the fourth antenna element 32 of the second perturbation element 30 and the fourth of the loop element 10 The characteristic of the axial ratio AR corresponding to the change of the frequency f when the distance δ between the adjacent ends with the antenna element 14 is 1 (mm) and 0.5 (mm) is shown. In FIG. 12, the horizontal axis represents the frequency f (GHz) of the radiated wave, the vertical axis represents the voltage standing wave ratio VSWR, and the curves δ7 and δ8 represent the first perturbation element 20 respectively. The distance δ between adjacent ends of the sixth antenna element 22 and the third antenna element 13 of the loop element 10 and the fourth antenna element 32 of the second perturbation element 30 and the fourth of the loop element 10 The characteristics of the voltage standing wave ratio VSWR corresponding to the change of the frequency f when the distance δ between the adjacent ends of the antenna element 14 is similarly 1 (mm) and 0.5 (mm). Show.

  As shown in FIG. 11, the distance δ between adjacent ends of the sixth antenna element 22 of the first perturbation element 20 and the third antenna element 13 of the loop element 10 and the second perturbation element 30 A curve δ5 in which the distance δ between adjacent end portions of the eighth antenna element 32 and the fourth antenna element 14 of the loop element 10 is 1 (mm) corresponds to the curve L10 in FIG. However, the axial ratio AR is such that the axial ratio AR is 3 (db) or less only in the frequency band of about 2.72 (GHz) to about 2.78 (GHz). On the other hand, in the curve δ6 where the distance δ is 0.5 (mm), the frequency band in which the axial ratio AR is 3 (db) or less while the axial ratio best point moves to the high frequency side is about 2.72. It can be seen that it has been expanded to a range from (GHz) to about 2.85 (GHz), and shows a good axial ratio characteristic with an axial ratio band of about 4.7%.

  12, the distance δ between adjacent ends of the sixth antenna element 22 of the first perturbation element 20 and the third antenna element 13 of the loop element 10 and the second perturbation element A curve δ7 in which the distance δ between adjacent end portions of the 30th eighth antenna element 32 and the fourth antenna element 14 of the loop element 10 is 1 (mm) corresponds to the curve L7 in FIG. However, the characteristic is such that the voltage standing wave ratio VSWR is 2 or less in the frequency band of about 2.75 (GHz) to about 2.87 (GHz). On the other hand, in the curve δ8 where the distance δ is 0.5 (mm), the voltage standing wave ratio VSWR is 2 or less in the frequency band of about 2.5 (GHz) to 2.86 (GHz). It can be seen that such a frequency band covers a frequency band of about 2.72 (GHz) to about 2.85 (GHz) where the axial ratio AR is 3 (db) or less.

  Therefore, in addition to the basic configuration in which the length of the parasitic element 60 can be increased and the voltage standing wave ratio VSWR can be suppressed to a good value of 2 or less, the gap between the perturbing elements 20 and 30 is reduced. The voltage standing wave ratio VSWR is 2 or less by further expanding while moving the frequency band in which the axial ratio AR is 3 (db) or less, and further expanding the frequency band that is the voltage standing wave ratio VSWR. It can be understood that a wide frequency band having a good value can be configured to cover a wide frequency band having a good value with an axial ratio AR of 3 (db) or less. Note that the value of the resonance frequency of the loop antenna 100 in the present embodiment is 2.78 (GHz), which is a high frequency from the value of 2.67 (GHz) that is the resonance frequency of the loop antenna 1 in the first embodiment. However, the value of the resonance frequency of the loop antenna 100 can be moved to the low frequency side by adjusting the loop length 4L of the loop element 10 as appropriate.

  According to the configuration of the present embodiment described above, the voltage standing wave ratio is good by providing the parasitic element in the vicinity of the power feeding unit provided in the loop element in addition to the configuration of the first embodiment. The reflected wave returning from the loop antenna to the feeder line can be suppressed, and radio waves can be efficiently radiated from the loop antenna.

  In addition, the parasitic element includes a ninth antenna element that is parallel to the second antenna element provided with the feeding unit and is provided inside the loop element and in the vicinity of the feeding unit. In practice, the voltage standing wave ratio can be obtained as a good value.

  The parasitic element also includes a tenth antenna element parallel to the third antenna element and an eleventh antenna element parallel to the fourth antenna element, each in communication with the ninth antenna element, so that the loop The length of the parasitic element can be increased without interfering with the antenna element of the element, and the voltage standing wave ratio can be obtained as a better value.

  In the present invention, the shape, arrangement, number, and the like of the members are not limited to the above-described embodiments, and the constituent elements thereof are appropriately replaced with those having the same operational effects, and the gist of the invention is not deviated. Of course, it can be appropriately changed within the range.

  As described above, according to the loop antenna of the present invention, circularly polarized waves having a good axial ratio are radiated and shape variation is suppressed, and even when shape variation occurs, the shape can be simplified. It can be adjusted and is expected to be widely applicable to mobile objects such as vehicles because of its universal universal character.

DESCRIPTION OF SYMBOLS 1 ......... Loop antenna 10 ... Loop element 11 ... 1st antenna element 12 ... 2nd antenna element 13 ... 3rd antenna element 14 ... 4th antenna element 20 ... 1st perturbation Element 21... Fifth antenna element 22... Sixth antenna element 30... Second perturbation element 31... Seventh antenna element 32. Substrate 60 ... Parasitic element 61 ... Ninth antenna element 62 ... Tenth antenna element 63 ... Eleventh antenna element

Claims (8)

A first antenna element extending in a first direction; a second antenna element extending in parallel opposite to the first antenna element; and a second direction orthogonal to the first direction. A loop element including a third antenna element that extends and a fourth antenna element that extends in parallel and opposite to the third antenna element, and the third antenna element and the fourth antenna element An antenna element communicates between the first antenna element and the second antenna element, respectively, and the loop element cooperates in a plane defined by the first direction and the second direction. A loop antenna that works to form a rectangular shape,
A first perturbation element having a portion extending outwardly of the rectangular shape from the first antenna element and having a portion facing and in close proximity to the third antenna element;
A second perturbation element having a portion extending outwardly of the rectangular shape from the second antenna element and having a portion facing and in close proximity to the fourth antenna element;
With
The loop element, the first perturbation element, and the second perturbation element are arranged symmetrically with respect to a central axis perpendicular to the plane defined by the first direction and the second direction. A loop antenna characterized by that.   The loop antenna according to claim 1, wherein the rectangular shape is a square.   The first perturbation element includes a fifth antenna element extending outward from the rectangular shape from one end of the first antenna element, and a third antenna element extending from the fifth antenna element. And a sixth antenna element facing and parallel to each other, wherein the second perturbation element extends from one end of the second antenna element to the outside of the rectangular shape. 3. The loop antenna according to claim 1, comprising: an element; and an eighth antenna element extending from the seventh antenna element and facing the fourth antenna element in close proximity to and parallel to the fourth antenna element. .  The loop antenna according to any one of claims 1 to 3, wherein a parasitic element is further provided in the vicinity of a power feeding portion provided in the loop element.   The power feeding unit is provided in the second antenna element, and the parasitic element is provided in parallel to the second antenna element and inward of the loop element and in the vicinity of the power feeding unit. The loop antenna according to claim 4, further comprising a ninth antenna element.   The parasitic element further includes a tenth antenna element parallel to the third antenna element and an eleventh antenna element parallel to the fourth antenna element, each communicating with the ninth antenna element. The loop antenna according to claim 5.   The loop length formed by the first antenna element, the second antenna element, the third antenna element, and the fourth antenna element of the loop element is one wavelength of a predetermined wavelength of radio waves to be transmitted and received The loop antenna according to claim 1, wherein the loop antenna is equal to:   The loop antenna according to claim 1, wherein the loop element, the first perturbation element, and the second perturbation element have a flat plate shape and are disposed on a transparent substrate. .

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