JP6602165B2 - Dual-frequency circularly polarized flat antenna and its axial ratio adjustment method - Google Patents

Description

  The present invention relates to a dual-frequency circularly polarized flat antenna that is a microstrip antenna capable of communicating circularly polarized radio waves of two frequencies, and more particularly to a dual-frequency circularly polarized flat antenna that facilitates adjustment of the axial ratio. And an axial ratio adjusting method thereof.

  For example, antennas mounted on satellite communication devices and mobile communication devices are small, thin, and lightweight, and are required to be able to transmit and receive simultaneously by operating with circular polarization. A dual-polarized circularly polarized flat antenna that can transmit and receive is used. In this dual-frequency circularly polarized flat antenna, for example, a lower dielectric substrate in which a lower layer patch (receiving patch) is arranged on the upper surface is laminated on a ground conductor, and further, on this lower dielectric substrate, An upper dielectric substrate having an upper layer patch (transmission patch) disposed on the upper surface is laminated. In addition, in order to solve the mode degeneracy orthogonal to the radiating conductor and excite circularly polarized waves, a degenerate separation segment (degeneration separation element) notched in the direction of 45 ° obliquely to the feeding point at the periphery of each patch Is provided.

  On the other hand, since the dual-frequency circularly polarized flat antenna performs transmission and reception at the same time, it is necessary to prevent the transmitted power from being mixed into the receiving circuit. That is, it is required to improve isolation characteristics (separation) between transmission and reception. One of the causes of deterioration of this isolation characteristic is the circular polarization axis ratio characteristic. When the cross polarization characteristic (circular polarization axis ratio) of the transmission patch is bad, the reception patch receives it, Isolation characteristics are inferior. For example, the electric field distribution on the ground conductor side of the transmission patch is disturbed by the degeneracy separation element of the reception patch, so that the circular polarization axial ratio and the circular polarization characteristic are deteriorated and deteriorated.

  For this reason, the reception patch is fed from two points, the transmission patch is fed from one point, and the reception patch is sufficiently larger than the transmission patch to suppress the influence of the degenerate separation element of the reception patch, A technique for improving the circular polarization axial ratio of the transmission patch and ensuring high isolation characteristics is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 06-140835

  By the way, by changing the size of the lower layer patch and the upper layer patch, the frequency of the communication target changes. However, since the lower layer patch and the upper layer patch are close to each other, it is difficult to adjust the frequency, that is, the axial ratio to a desired value. Met. That is, when the size of one patch is changed, not only the frequency for one patch but also the frequency for the other patch changes, making it difficult to adjust the two frequencies to desired values.

  For example, as shown in FIG. 6, in the dual-frequency circularly polarized wave planar antenna 100 in which the lower layer patch 101 and the upper layer patch 102 have a substantially square shape and the feed line 103 is provided only on the lower layer patch 101 side, As shown in FIG. 7, the axial ratio changes in each of the frequency bands f1 and f2. Here, the length of one side of the upper layer patch 102 is sequentially increased, the characteristic C11 indicates the minimum axial ratio characteristic, the characteristic C12 indicates the intermediate axial ratio characteristic, and the characteristic C13 indicates the maximum. The axial ratio characteristics in the case of The specification SP1 indicates an axial ratio in the specification in the frequency band f1 in the specification for the lower layer patch 101, and the specification SP2 indicates an axial ratio in the specification in the frequency band f2 in the specification for the upper layer patch 102. It is necessary that the characteristics C11 to C13 do not overlap SP1 and SP2. That is, the axial ratio in the two frequency bands f1 and f2 needs to be lower than the axial ratio of the specifications SP1 and SP2.

  As can be seen from this figure, changing the size of the upper layer patch 102 changes not only the axial ratio on the frequency band f2 side but also the axial ratio on the frequency band f1 side. Similarly, if the size of the lower layer patch 101 is changed, not only the axial ratio on the frequency band f1 side but also the axial ratio on the frequency band f2 side changes, and the axial ratios in the two frequency bands are adjusted to desired values. It was difficult to do.

  An object of the present invention is to provide a dual-frequency circularly polarized flat antenna that can easily and appropriately adjust axial ratios in two frequency bands and an axial ratio adjusting method thereof.

In order to achieve the above object, the invention according to claim 1 is characterized in that a planar dielectric is provided on a lower dielectric substrate provided with a lower layer patch having a substantially square shape, and the planar shape is located on the lower dielectric substrate. An upper dielectric substrate provided with an upper layer patch having a substantially square shape, and at least one of the lower layer patch and the upper layer patch has two feeder lines provided so as to have a relative phase angle of 90 °. A power supply unit, and a parasitic element provided in the vicinity of at least one of the lower layer patch and the upper layer patch so as to oppose any side of the substantially square shape of the patch and not to overlap the power supply line. By adjusting at least one of the size and position of the parasitic element, an axial ratio in a frequency band corresponding to the lower layer patch and the upper layer patch provided with the parasitic element is determined. Is set lower than the value, it is 2 frequency circularly polarized planar antenna according to claim.

According to a second aspect of the invention, a lower layer dielectric substrate planar shape substantially provided square-shaped lower patch, the located on the lower dielectric substrate, the upper layer patch planar shape substantially square shape And at least one of the lower layer patch and the upper layer patch, and a power supply unit having two power supply lines provided so as to have a relative phase angle of 90 °. An axial ratio adjusting method for adjusting an axial ratio in a dual-frequency circularly polarized wave planar antenna, wherein at least one of the lower layer patch and the upper layer patch is disposed near any side of the substantially square shape of the patch. A parasitic element is provided so as not to overlap the power supply line, and at least one of the size and position of the parasitic element is adjusted, so that the lower layer patch and the upper layer patch provided with the parasitic element are provided. Adjusting the axial ratio in the frequency band corresponding to the switch is a 2 frequency circularly polarized wave planar axial ratio adjusting method of the antenna, characterized in that.

  According to the first and second aspects of the present invention, the axial ratio in the frequency band corresponding to the patch provided with the parasitic element is adjusted by adjusting the size and position of the parasitic element. That is, since it is not necessary to adjust the size of the patch provided with the parasitic element, other patches are not affected (the axial ratio in the frequency band corresponding to the other patches is not affected). For this reason, for example, the size of one patch is adjusted to adjust the axial ratio in the frequency band corresponding to this patch, and the size and position are adjusted by providing a parasitic element in the other patch to correspond to this patch. The axial ratio in the frequency band may be adjusted. As described above, the axial ratios in the two frequency bands can be easily and appropriately adjusted.

1 is an exploded perspective view showing a dual-frequency circularly polarized flat antenna according to an embodiment of the present invention. FIG. 2 is a plan view showing an upper dielectric substrate of the dual-frequency circularly polarized planar antenna of FIG. 1. It is a figure which shows the axial ratio with respect to the frequency of the dual frequency shared circular polarization planar antenna of FIG. It is a figure which shows the linearly polarized wave amplitude with respect to the frequency of the dual-frequency circular polarization plane antenna of FIG. In an embodiment of this invention, it is a figure showing a linear polarization amplitude with respect to a frequency when a parasitic element is not provided. It is a disassembled perspective view which shows the conventional dual frequency shared circular polarization planar antenna. It is a figure which shows the axial ratio with respect to the frequency of the dual frequency shared circular polarization planar antenna of FIG.

  The present invention will be described below based on the illustrated embodiments.

1 to 5 show an embodiment of the present invention, and FIG. 1 is an exploded perspective view showing a dual-frequency circularly polarized flat antenna 1 according to this embodiment. This dual-frequency circularly polarized flat antenna 1 is a microstrip antenna that can communicate circularly polarized radio waves in two frequency bands f1 and f2 (can simultaneously transmit and receive circularly polarized radio waves), and is entirely flat. A lower dielectric substrate 3 provided with a lower layer patch 2 on a ground conductor (not shown), and an upper dielectric substrate provided on the lower dielectric substrate 3 and provided with an upper layer patch 4 5 and a feeding circuit (feeding unit) 6 and a parasitic element 7 are further provided. Here, in the implementation of the present invention, it is assumed that the first frequency band f1 and the second frequency band f2 have the following relationship.
f1 <f2

  The lower layer patch 2 is placed on the upper surface of the lower dielectric substrate 3 having a substantially square shape in plan and having a substantially square shape in plan view, and the length of one side is set based on the first frequency band f1. ing. That is, the frequency band corresponding to the lower layer patch 2 is the first frequency band f1.

  Similarly, the upper layer patch 4 is placed on the upper surface of the upper dielectric substrate 5 having a substantially square shape in plan view and a substantially square shape in plan view, and has a side length based on the second frequency band f2. Is set. That is, the frequency band corresponding to the upper layer patch 4 is the second frequency band f2.

  Here, the shape and size of the lower dielectric substrate 3 and the upper dielectric substrate 5 are the same, and the dielectric constant of the lower dielectric substrate 3 is set higher than the dielectric constant of the upper dielectric substrate 5, whereby the beam Becomes wider, the directivity is reduced, and it is easy to supplement radio waves. Further, since the dielectric constant of the lower dielectric substrate 3 is higher than that of the upper dielectric substrate 5, the first frequency band f1 corresponding to the lower patch 2 is the second frequency band f2 corresponding to the upper patch 4. Despite being lower, the lower layer patch 2 is smaller than the upper layer patch 4 (if the dielectric constant is the same, the lower layer patch 2 is larger than the upper layer patch 4).

  The power feeding circuit 6 is a circuit provided in the lower layer patch 2 and the upper layer patch 4 so as to have a relative phase angle of 90 °. In this embodiment, the lower layer patch 2 (lower dielectric substrate 3) Is provided. That is, a linear first power supply line 61 is disposed extending from the first side 21 of the lower layer patch 2 to the first side 31 of the lower layer dielectric substrate 3 facing the first side 21. ing. Similarly, it extends from the second side 22 orthogonal to the first side 21 of the lower layer patch 2 to the second side 32 of the lower layer dielectric substrate 3 facing the second side 22 to form a linear first Two feeder lines 62 are provided. Here, the phase angle is relatively shifted by 90 ° by providing a difference of ¼ wavelength in the line length of the first feeder 61 and the second feeder 62.

  The first power supply line 61 and the second power supply line 62 are connected to the input port 64 via the power distributor 63. Then, by supplying power / signal of the first frequency band f1 or the second frequency band f2 from the input port 64, communication of two circularly polarized radio waves can be performed.

  The parasitic element 7 is an element provided in the vicinity of the upper layer patch 4 so as to face the power feeding circuit 6. The parasitic element 7 corresponds to the upper layer patch 4 by adjusting at least one of the size and position of the parasitic element 7. The axial ratio in the second frequency band f2 is set lower than a predetermined value.

  That is, as shown in FIGS. 1 and 2, the upper layer patch that does not overlap the second power supply line 62 while facing the second power supply line 62 in a state where the lower dielectric substrate 3 and the upper dielectric substrate 5 are overlapped. The parasitic element 7 is disposed on the upper dielectric substrate 5 at a distance from the fourth fourth side 44. The parasitic element 7 has an elongated rectangular shape, extends in parallel with the fourth side 44, and is etched on the upper dielectric substrate 5. In addition, the width D1 of the parasitic element 7 and the position of the parasitic element 7, that is, the distance D2 from the fourth side 44 of the upper layer patch 4 are set and fixed in advance based on the second frequency band f2, In the embodiment, the axial ratio in the second frequency band f2 is set lower than the predetermined value by adjusting the length (size) D3 of the parasitic element 7.

  Specifically, the axial ratio depends on the amplitude of the linearly polarized wave, but when the parasitic element 7 is not provided, the amplitude of the linearly polarized wave in the horizontal direction (H) is shown by a curve L11 as shown in FIG. The amplitude of the linearly polarized wave in the vertical direction (V) is the characteristic indicated by the curve L12. At this time, in the second frequency band f2 (point P2 in FIG. 5), the difference between the curve L11 and the curve L12 is large, and an appropriate circularly polarized wave cannot be obtained and the axial ratio becomes large.

  On the other hand, when the parasitic element 7 is provided, as shown in FIG. 4, the amplitude of the linearly polarized wave in the horizontal direction (H) has the characteristic shown by the curve L1, and the amplitude of the linearly polarized wave in the vertical direction (V) is The characteristic is shown by the curve L2. At this time, in the second frequency band f2 (point P1 in FIG. 4), the difference between the curve L1 and the curve L2 is small, an appropriate circular polarization is obtained, and the axial ratio is small.

  This is because the parasitic element 7 functions as a reflector in the vicinity of the second frequency band f2, the propagation in the front direction is reduced, and the curve L1 drops sharply at the point P3 (becomes NULL). Then, by adjusting the length D3 of the parasitic element 7, the position (frequency) of the point P3 at which the curve L1 falls rapidly changes, so that the length of the parasitic element 7 is reduced so that the difference between the curves L1 and L2 becomes small. By adjusting D3, the axial ratio in the second frequency band f2 is set lower than a predetermined value. Here, the predetermined value is a specification SP2 to be described later, and is an axial ratio (maximum value) on the specification in the second frequency band f2.

  As described above, in this embodiment, the parasitic element 7 is provided so as to face the fourth side 44 (second feeding line 62) of the upper layer patch 4, and the amplitude curve L1 of the linearly polarized wave in the horizontal direction is adjusted. However, the parasitic element 7 may be provided at another position depending on the amplitude characteristics (curves L11 and L12) in a state where the parasitic element 7 is not provided.

  For example, the parasitic element 7 may be provided opposite to the third side 43 (first feeding line 61) of the upper layer patch 4, and in this case, the amplitude curve L2 of the linearly polarized wave in the vertical direction can be adjusted. . Similarly, when the parasitic element 7 is provided so as to face the second side 42 (second feeding line 62) of the upper layer patch 4, the amplitude curve L1 of the linearly polarized wave in the horizontal direction can be adjusted. When the parasitic element 7 is provided to face the first side 41 (first feeding line 61), the amplitude curve L2 of the linearly polarized wave in the vertical direction can be adjusted. However, if the parasitic element 7 is provided to face the sides 41 and 42 of the upper layer patch 4, the parasitic elements 7 are provided to face the sides 43 and 44 of the upper layer patch 4 because the feeding lines 61 and 62 are affected by overlap. Is desirable.

  Next, a method for adjusting the axial ratio of the dual-frequency circularly polarized flat antenna 1 having such a configuration will be described.

  First, the size of the lower layer patch 2 is adjusted to set the axial ratio in the first frequency band f1 lower than a predetermined value. Here, the predetermined value is the specification SP1 and is the axial ratio (maximum value) on the specification in the first frequency band f1. Next, the length D3 of the parasitic element 7 is adjusted to set the axial ratio in the second frequency band f2 lower than the specification SP2. Here, the parasitic element 7 is provided in advance and trimmed to shorten / adjust the length D3.

  By this adjustment, the axial ratio with respect to the frequency changes as shown in FIG. Here, the characteristic C1 indicates the axial ratio characteristic when the length D3 is the shortest, the characteristic C2 indicates the axial ratio characteristic when the length D3 is medium, and the characteristic C3 indicates that the length D3 is the longest. The axial ratio characteristics are shown. As can be seen from this figure, even when the length D3 of the parasitic element 7 is adjusted, the axial ratio in the first frequency band f1 hardly changes, and the axial ratio in the second frequency band f2 changes greatly. That is, even if the length D3 of the parasitic element 7 is adjusted to adjust the axial ratio in the second frequency band f2, the lower layer patch 2 is not affected.

  Then, the length D3 of the parasitic element 7 is shortened and adjusted until the axial ratio in the second frequency band f2 becomes lower than the axial ratio of the specification SP2, for example, until the characteristic C2 is obtained. Thereby, the axial ratios in the two frequency bands f1 and f2 are both lower than the axial ratios of the specifications SP1 and SP2.

  As described above, according to the dual-frequency circularly polarized wave planar antenna 1 and the axial ratio adjusting method thereof, the length D3 of the parasitic element 7 is adjusted, so that the second frequency band f2 corresponding to the upper layer patch 4 is adjusted. The axial ratio is adjusted. That is, since it is not necessary to adjust the size of the upper layer patch 4 provided with the parasitic element 7, the lower layer patch 2 is not affected (in the axial ratio in the first frequency band f1 corresponding to the lower layer patch 2). It has no effect.) Therefore, as described above, the size of the lower layer patch 2 is adjusted to adjust the axial ratio in the first frequency band f1, and the length D3 of the parasitic element 7 is adjusted to adjust the axis in the second frequency band f2. The ratio may be adjusted. Thus, the axial ratios in the two frequency bands f1 and f2 can be easily and appropriately adjusted. In addition, since the length (size) D3 of the parasitic element 7 only needs to be trimmed and shortened / adjusted, the parasitic element 7 can be adjusted more easily and appropriately.

  Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there is a design change or the like without departing from the gist of the present invention, Included in the invention. For example, in the above embodiment, the parasitic element 7 is provided in the vicinity of the upper layer patch 4, but the parasitic element 7 may be provided in the vicinity of the lower layer patch 2, and the vicinity of the upper layer patch 4 and the lower layer patch 2. Parasitic element 7 may be provided in this. At this time, for example, when the parasitic element 7 is provided in the vicinity of the lower layer patch 2, the size of the upper layer patch 4 is adjusted to adjust the axial ratio in the second frequency band f 2, The axial ratio in the first frequency band f1 may be adjusted by adjusting the position.

  Further, only the length (size) D3 of the parasitic element 7 is adjusted to adjust the axial ratio, but only the position of the parasitic element 7 is adjusted to adjust the axial ratio, or the size of the parasitic element 7 can be adjusted. The axial ratio may be adjusted by adjusting the position. Moreover, although the planar shape of the patches 2 and 4 is a substantially square shape, it may be circular. Furthermore, although the feeding circuit 6 is provided on the lower dielectric substrate 3 (lower patch 2), it may be provided on the upper dielectric substrate 5 (upper patch 4). You may provide in both. A plurality of parasitic elements 7 may be provided.

DESCRIPTION OF SYMBOLS 1 2 frequency shared circular polarization plane antenna 2 Lower layer patch 3 Lower layer dielectric substrate 4 Upper layer patch 5 Upper layer dielectric substrate 6 Feed circuit (feed part)
7 Parasitic element f1 1st frequency band f2 2nd frequency band

Claims (2)

A lower dielectric substrate provided with a lower layer patch having a substantially square shape in plan view ;
An upper dielectric substrate that is located on the lower dielectric substrate and provided with an upper layer patch having a substantially square shape in plan view ; and
A power feeding unit having two power feeding lines provided on at least one of the lower layer patch and the upper layer patch so as to have a relative phase angle of 90 °;
A parasitic element provided in the vicinity of at least one of the lower layer patch and the upper layer patch, facing either side of the substantially square shape of the patch and not overlapping the feeder line;
The axial ratio in the frequency band corresponding to the lower layer patch and the upper layer patch provided with the parasitic element is set to be lower than a predetermined value by adjusting at least one of the size and position of the parasitic element. Being
A dual-polarized circularly polarized planar antenna characterized by that. And lower dielectric substrate planar shape substantially provided square-shaped lower patch, positioned on the lower dielectric substrate, and the upper dielectric substrate planar shape substantially the square-shaped upper patch provided A dual-frequency circularly polarized wave planar antenna comprising: a feeding section having two feeding lines provided on at least one of the lower layer patch and the upper layer patch so as to have a relative phase angle of 90 °; An axial ratio adjustment method for adjusting the axial ratio,
A parasitic element is provided in the vicinity of at least one of the lower layer patch and the upper layer patch so as to be opposed to any side of the substantially square shape of the patch and not to overlap the feeder line. Adjusting the axial ratio in the frequency band corresponding to the lower layer patch and the upper layer patch provided with the parasitic element by adjusting at least one of the height and the position;
A method for adjusting the axial ratio of a dual-polarized circularly polarized wave planar antenna, characterized in that:

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