Circularly polarized antenna and communication device

Abstract

To provide a compact, wideband circularly polarized antenna and a communication device using the antenna.SOLUTION: A circularly polarized antenna 100 includes a metal layer 20, a plurality of radiating element layers 12 arranged to face the metal layer 20, and a plurality of non-contact excitation elements arranged between the metal layer 20 and the plurality of radiating element layers 12 or on the plurality of radiation element layers 12 via dielectric layers 31 and 32. The plurality of non-contact excitation elements has a phase difference of π / 2 from each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a small antenna having circular polarization characteristics. [Background technology]

[0002] Circular polarization appears when mutually orthogonal polarized waves have equal amplitude and a phase difference of ±π / 2. In recent years, circularly polarized antennas have been attracting attention with the development of mobile and satellite communications. However, a problem with circularly polarized antennas is that they generally require two linearly polarized antennas, which makes them large in size.

[0003] The present applicant has previously proposed an antenna (thin antenna) that is thin and compact and has linear polarization characteristics (Patent Documents 1 and 2). The present invention is an extension of the above technology to an antenna having circular polarization characteristics. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6452477 [Patent Document 2] Patent Publication No. 2021-10097 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a small-sized, wide-band circularly polarized antenna. [Means for solving the problem]

[0006] The circularly polarized antenna of the present invention comprises a metal layer, a plurality of radiating element layers arranged opposite the metal layer, and a plurality of non-contact excitation elements arranged between the metal layer and the plurality of radiating element layers or on top of the plurality of radiating element layers via a dielectric layer, and is characterized in that the plurality of non-contact excitation elements have a phase difference of π / 2 from each other.

[0007] The metal layer herein refers to a metal plate or a metal thin film formed on a substrate of various types, and has a predetermined area and outer shape. The radiating element layer is a conductive layer, and a plurality of radiating element layers are arranged in a plane with a predetermined interval (slits) therebetween, and are arranged opposite the metal layer via a dielectric layer. The dielectric layer may be a dielectric material such as a resin plate, or may be an air layer. Therefore, the structure for disposing the non-contact excitation element between the metal layer and the radiating element layer is a laminated structure in which a first dielectric layer is disposed on the metal layer, multiple non-contact excitation elements are disposed on this first dielectric layer, a second dielectric layer is disposed on the multiple non-contact excitation elements, and multiple radiating elements are further disposed on the second dielectric layer. The first and second dielectric layers may be air layers. The same effect can be obtained by arranging the non-contact excitation elements above the radiating element layer via a dielectric layer.

[0008] The non-contact excitation element has a power feed point electrically connected to the outside via a through hole or the like, and acts as an excitation antenna for generating excitation in the radiating element layer.

[0009] The following structural example is an example of a mode in which a plurality of radiating element layers are provided with circular polarization characteristics. The plurality of radiating element layers include a first radiating element layer, a second radiating element layer arranged in the X-axis direction relative to the first radiating element layer, and a third radiating element layer arranged in the Y-axis direction relative to the first radiating element layer, and the plurality of non-contact excitation elements include a first excitation element arranged in the X-axis direction and a second excitation element arranged in the Y-axis direction.

[0010] Alternatively, the plurality of radiating element layers are arranged in four radiating element layers, namely, first, second, third and fourth radiating element layers, in two rows in the X-axis direction and two rows in the Y-axis direction, and the plurality of non-contact excitation elements are composed of a first excitation element arranged in the X-axis direction and a second excitation element arranged in the Y-axis direction. In this case, the number of non-contact excitation elements is not limited to two, and the multiple non-contact excitation elements may be four, namely, first, second, third and fourth excitation elements, arranged in sequence with a phase difference of π / 2, with the first excitation element spanning the first and second radiating element layers, the second excitation element spanning the first and third radiating element layers, the third excitation element spanning the third and fourth radiating element layers, and the fourth excitation element spanning the fourth and second radiating element layers. Effect of the Invention

[0011] The circularly polarized antenna according to the present invention will be described in detail later, but since it is thin, small, and has a wide bandwidth, it can be applied to communication antennas for various mobile devices, etc. For example, the present invention can be applied to a wide range of fields, such as mobile communication devices, electronic devices, and in-vehicle devices. [Brief description of the drawings]

[0012] [Figure 1] 1 shows an external view of a circularly polarized antenna according to a first embodiment. [Diagram 2] 1 shows an exploded view of the antenna of Example 1, in which (a) shows the layout of the radiating element layer, (b) shows the layout of the excitation elements, and (c) shows the outline of the metal layer. [Diagram 3] 1 shows a cross-sectional view of the antenna of the first embodiment taken along the X-axis direction. [Figure 4] 4 shows analytical values ​​of antenna characteristics of the first embodiment. [Diagram 5] 3 shows the radiation pattern of the antenna of the first embodiment. [Figure 6] 2 shows an external view of a circularly polarized antenna according to a second embodiment. [Figure 7] 13A and 13B are exploded views of the antenna of Example 2, in which (a) shows the layout of the radiating element layer, (b) shows the layout of the excitation element layer, and (c) shows the outline of the metal layer. [Figure 8] 4 shows analytical values ​​of antenna characteristics of the second embodiment. [Figure 9] 4 shows the radiation pattern of the antenna of the second embodiment. [Figure 10] 3 shows an external view of a circularly polarized antenna according to a third embodiment. [Figure 11]13 shows an exploded view of the antenna of Example 3, in which (a) shows the layout of the radiating element layer, (b) shows the layout of the excitation elements, and (c) shows the outline of the metal layer. [Figure 12] 13 shows analytical values ​​of antenna characteristics of Example 3. [Figure 13] 13 shows a radiation pattern of the antenna of Example 3. [Figure 14] 13 shows an example of an antenna structure according to a fourth embodiment. [Figure 15] 13 shows an example of an antenna structure according to a fifth embodiment. [Figure 16] FIG. 2 shows an external view of an antenna of a comparative example. [Figure 17] 1 shows an exploded view of an antenna of a comparative example, where (a) shows a patch-type radiating element, and (b) shows the outline of the metal layer. [Figure 18] 1 shows a cross-sectional view of an antenna of a comparative example. [Figure 19] 4 shows analytical values ​​of antenna characteristics of the comparative example. [Figure 20] 3 shows the radiation pattern of an antenna of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An example of the configuration of a circularly polarized antenna according to the present invention will be described with reference to the drawings, but the present invention is not limited to this embodiment.

[0014] 1 to 3 show a configuration example of a circularly polarized antenna 100 of a two-point feed type having three radiating element layers and two excitation elements as a first embodiment. FIG. 1 shows an external view of a circularly polarized antenna 100. For the purpose of explaining the configuration of the antenna, the arrangement direction of the radiating element layer is expressed in an XY plane, and the X-axis direction and the direction perpendicular thereto are represented as the Y-axis direction. As shown in Figure 2(c), L X ,L Y A first dielectric layer 31 of the same external shape is placed on top of an L-shaped metal layer 20 made of an 81.2 mm copper plate, and on top of that is a first excitation element 41 arranged in the X-axis direction and a second excitation element 42 arranged in the Y-axis direction as shown in Figure 2(b), and on top of that is a second dielectric layer 32. Furthermore, as shown in Fig. 2(a), X ,W Y It has a layered structure consisting of three 36.6 mm square radiating element layers. The cross-sectional view along the X-axis is shown in FIG.

[0015] The first excitation element 41 and the second excitation element 42 are formed into a linear shape with a width d1 of 1.0 mm and a length L1 of 29.0 mm by patterning or the like, and the power supply points F1 and F2 are electrically connected to the outside by through holes or the like as shown in FIG. The radiating element layer is made of copper foil with a thickness of 0.018 mm, and each layer is made of W X ,W Y This is an example in which the first radiating element layer 11 is a square of 36.6 mm, the second radiating element layer 12 is arranged in the X-axis direction with a slit S1 of 8 mm in between, and the third radiating element layer 13 is arranged in the Y-axis direction with a slit S2 of 8 mm in between, in an L-shape. The first excitation element 41 is disposed across the first radiating element layer 11 and the second radiating element layer 12 and along the central portions of the first and second radiating element layers 11 and 12 in the X-axis direction. The second excitation element 42 is similarly disposed across the first radiating element layer 11 and the third radiating element layer 13 in the Y-axis direction. The first excitation element 41 and the second excitation element 42 act as a non-contact excitation antenna for the three radiating element layers 11, 12, and 13. As explained with reference to FIG. 2(b), the first excitation element 41 has a feeding point F1 at the left end thereof, while the second excitation element 42 has a feeding point F2 at the lower end thereof. In Example 1, the first dielectric layer 31 and the second dielectric layer 32 were made of NPC-F260A (Nippon Pillar Packing Co., Ltd.) multilayer boards having thicknesses t1 and t2 of 0.96 mm. Therefore, the total thickness T of the antenna is approximately 1.92 mm. Here, the first radiating element layer 11 is shared, and the first radiating element layer 11 and the second radiating element layer 12 are set to be approximately 1 / 2 wavelength in the X-axis direction, and the first radiating element layer 11 and the third radiating element layer 13 are set to be approximately 1 / 2 wavelength in the Y-axis direction, and the first excitation element 41 and the second excitation element 42 are arranged with a phase difference of 90°, making the antenna smaller than a conventional circularly polarized antenna using two linearly polarized waves.

[0016] FIG. 4 shows the analysis values ​​of the circularly polarized antenna characteristics of the first embodiment, and FIG. 5 shows the radiation pattern. In Figures 4 and 5, "free" (in free space) indicates analytical values ​​in free space, and "on" (on metal) indicates analytical values ​​on a conductor. 2.4GH Z In the band, the bandwidth is less than VSWR3, free: 2.40~2.52GHz Z , on metal: 2.41~2.52GH Z Bandwidth free of axial ratio 3 or less: 2.27~2.53GHz Z , on metal: 2.0~2.52GH Z ,2.57~3.0GH Z It was. The radiation pattern is shown in FIG. In FIG. 5, LHCP indicates left-handed circular polarization, and RHCP indicates right-handed polarization, and a wideband circular polarization with high gain is obtained.

[0017] For comparison, evaluation was performed using the patch antennas shown in Figs. L X ,L Y A dielectric layer 30 of the same shape was placed on a square metal layer 20 of 73 mm, and a patch-type radiating element layer 111 with L1: 36.5 mm and cut dimension V: 3.7 mm and opposite corners cut out was placed on top of that, and the feeding point F was located at a position a: 11.58 mm from the bottom side as shown in Figure 17(a) and was electrically connected to the outside via a through hole as shown in Figure 18. The thickness T of the antenna was set to 2 mm. The antenna characteristics of this comparative patch antenna are shown in FIG. 19, and the radiation pattern is shown in FIG. VSWR 3 or less, bandwidth 2.4~2.5GHzZ ,The bandwidth of the axial ratio characteristic is 2.44 to 2.45, which is very narrow and not practical. In contrast, the circularly polarized antenna of the first embodiment has a wide band and is a small antenna.

[0018] FIG. 6 shows, as a second embodiment, an example of a two-point feed structure consisting of four radiating element layers and two excitation elements. L X ,L Y 75.9 mm, the second radiating element layer 12, the third radiating element layer 13, and the fourth radiating element layer 14 were arranged in two rows in the X-axis direction and two rows in the Y-axis direction on the first radiating element layer 11. Slit section S1, S2: 2.5mm. The first excitation element 41 and the second excitation element 42 were set to d1: 1.0 mm, L1: 29.0 mm, and the antenna thickness T: 1.92 mm. The antenna characteristics of the second embodiment are shown in FIG. 8, and the radiation pattern is shown in FIG. Both the VSWR and axial ratio characteristics are wideband. Bandwidth free below VSWR3: 2.34~2.49GHz Z , on metal: 2.35~2.49GH Z In particular, the bandwidth of the axial ratio characteristic of 3 or less is 2.0 to 3.0 GHz for both free and on metal. Z It has become wider.

[0019] The antenna of the third embodiment is shown in FIG. 10 and FIG. The third embodiment is an example in which four excitation elements, ie, first to fourth excitation elements 43, 42, 43, and 44, are arranged in a circular manner. In addition, L X ,L Y :69.12mm, S1, S2:0.5mm. Also, in Figure 11(b), the dimension L X1 is W X is 1 / 2. In the second embodiment, as shown in FIG. 7(b), a two-point feeding structure is used, which is made up of a first excitation element 41 in the X-axis direction and a second excitation element 42 in the Y-axis direction. In contrast, in the third embodiment, as shown in FIG. 11(b), in addition to the first excitation element 41 in the X-axis direction having a feeding point F1 at its left end, the second excitation element 42 has a feeding point F2 at its lower end, the third excitation element 43 is arranged along the Y-axis direction center portion, straddling the third radiating element layer 13 and the fourth radiating element layer 14, and has a feeding point F3 at its right end, and the fourth excitation element 44 is arranged so as to rotate as a whole, straddling from the fourth radiating element layer 14 along the center portion of the second radiating element layer 12, and has a feeding point F4 at its upper end. In this way, a high-gain, wideband circularly polarized antenna can be obtained, as shown in FIG. 12 for the analytical values ​​of the antenna characteristics and in FIG. 13 for the radiation pattern.

[0020] An example of an antenna structure according to the fourth embodiment is shown in FIG. This embodiment is an example in which the non-contact excitation element in the first embodiment shown in FIGS. 1 and 2 is replaced with a dipole element type excitation element. In this case, the first excitation element 41 in the first embodiment is a dipole element consisting of a pair of a first element 41a and a second element 41b, and a pair of feeding points F1, F1 are electrically connected to the outside via through holes or the like. The second excitation element 42 is also a pair of dipole elements consisting of a first element 42a and a second element 42b, and has a pair of feeding points F2, F2.

[0021] An example of an antenna configuration according to the fifth embodiment is shown in FIG. While in Example 1 a non-contact excitation element is placed between the metal layer 20 and the radiating element layer, in this example a non-contact excitation element is placed on top of the radiating element layer via a dielectric layer, and thus the non-contact excitation element functions as a circularly polarized antenna even when placed above the radiating element layer. The example of the non-contact excitation element shown in FIG. 15 is an example in which a dipole element is used as in the fifth embodiment. [Explanation of symbols]

[0022] 11 First radiating element layer 12 Second radiating element layer 13 Third radiating element layer 20 metal layer 31 First dielectric layer 32 Second dielectric layer 41 First excitation element 42 Second excitation element 100 Circularly polarized antenna F1 feed point F2 feed point

Claims

1. a metal layer; a plurality of radiation element layers disposed opposite the metal layer; and a plurality of non-contact excitation elements disposed between the metal layer and the plurality of radiation element layers or on the plurality of radiation element layers via a dielectric layer; the plurality of radiating element layers include a first radiating element layer, a second radiating element layer disposed in the X-axis direction with respect to the first radiating element layer via a slit, and a third radiating element layer disposed in the Y-axis direction with respect to the first radiating element layer; A circularly polarized antenna characterized in that the multiple non-contact excitation elements comprise a first excitation element arranged across the first radiation element layer and the second radiation element layer and a second excitation element arranged across the first radiation element layer and the third radiation element layer, and the first excitation element and the second excitation element have a phase difference of π / 2 from each other.

2. The plurality of radiating element layers are arranged in two rows with slits in the X-axis direction and in two rows with slits in the Y-axis direction, the four radiating element layers being first, second, third and fourth radiating element layers; The circularly polarized antenna according to claim 1, characterized in that the plurality of non-contact excitation elements are a first excitation element arranged in the X-axis direction across the first radiation element layer and the second radiation element layer, and a second excitation element arranged in the Y-axis direction across the first radiation element layer and the third radiation element layer.

3. The non-contact excitation elements include a first excitation element, a second excitation element, a third excitation element, and a fourth excitation element, which are arranged in sequence with a phase difference of π / 2, and the first excitation element is arranged across the first and second radiation element layers, The second excitation element spans the first and third radiation element layers, The third excitation element spans the third and fourth radiation element layers, 3. The circularly polarized antenna according to claim 2, wherein a fourth excitation element is disposed across said fourth and second radiation element layers.

4. A communication device using the circularly polarized antenna according to any one of claims 1 to 3.

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