JP2004221965A - Circularly polarized wave patch antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circularly polarized wave patch antenna in which frequency-axial ratio characteristics are excellent and adjustment for impedance matching is easy to perform while utilizing the feature of the circularly polarized wave patch antenna suitable for small-sized and compact constitution. <P>SOLUTION: In the circularly polarized wave patch antenna 10 provided with a patch element 12 formed on the surface of an antenna base substrate 11 and two power supply conductors 13 and 14 capacitively coupled or resonance coupled to two adjacent edge sides of the patch element 12, the two power supply conductors 13 and 14 are arranged off the center lines Xc and Yc of the patch element respectively. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a circularly-polarized patch antenna for transmission and / or reception using a patch-shaped planar antenna element, a so-called patch element, and is particularly effective when applied to transmission and reception of ultrahigh-frequency radio signals such as microwaves or millimeter waves. There are mobile communication devices, wireless LAN (Local Area Network), ITS (Intelligent Transport Systems), ETC (Electronic Toll Collection System), GPS (Global Positioning), and the like.
[0002]
[Prior art]
FIG. 7 shows a configuration of a conventional circularly polarized patch antenna described in, for example, JP-A-2002-9536. The circularly polarized patch antenna 101 shown in FIG. 1 has an antenna base substrate 11, a patch element 12, a ground conductor 18, feed conductors 131 and 141, feed terminals 15 and 16, and the like. The antenna base substrate 11 is made of a dielectric or magnetic material made of at least one of ceramic, resin, and a composite material of ceramic and resin. A patch element 12 is formed on the front surface of the base substrate 11. An excitation ground conductor 18 of the patch element 12 is disposed on the back surface.
[0003]
The patch element 12 is formed of a substantially square rectangular conductor pattern. In order to excite the patch element 12 as a radiation conductor of a circularly polarized antenna, two feeding conductors 131 and 141 that are capacitively or resonantly coupled are arranged on edges of two adjacent sides of the patch element 12. The power supply conductors 131 and 141 are formed of an elongated rectangular conductor pattern, and are disposed so as to be parallel to and close to the edge of the patch element 12 and that the center in the longitudinal direction substantially coincides with the center lines Xc and Yc of the patch element. ing.
[0004]
The center lines (virtual lines) Xc and Yc are two straight lines passing through the center of the surface of the patch element 12 and orthogonal to the surface thereof, and the longitudinal centers of the two feed conductors 131 and 141 are the center lines. They are arranged so as to substantially match Xc and Yc. Signals having a phase difference of 90 degrees (λ / 4) from each other in the hybrid circuit 20 are supplied to the two power supply conductors 131 and 141 via the power supply terminals 15 and 16. As a result, the patch element 12 is excited with a phase difference of 90 degrees from two orthogonal directions, and emits a circularly polarized mode electromagnetic wave in the vertical direction of the element 12 surface. The hybrid circuit 20 is formed on the substrate different from the antenna base substrate 11 using the microstrip lines 21 and 22. The input terminal IN and the terminating resistor Re are connected to the hybrid circuit 20.
[0005]
[Problems to be solved by the invention]
In a circularly polarized antenna, it is desired that the circularity of polarization be high, that is, the axial ratio be small (good axial ratio). A characteristic of circularly polarized antennas is that they have gain for circularly polarized waves in the same phase with the same direction of rotation of the electric field, but do not have gain for circularly polarized waves in the opposite phase with the opposite direction of rotation. There are characteristics. This characteristic can be used to discriminate radio signals of the same frequency based on polarization differences. However, if the axis ratio is poor (large), the characteristics will be weakened. Therefore, a circularly polarized antenna is desired to have a good axial ratio in which the circularity of polarization is high. Further, it is also desired that the good axis ratio be obtained in the widest possible range, that is, that the frequency-axis ratio characteristics be good.
[0006]
In the conventional circularly polarized patch antenna 101 described above, the patch element 12 has a phase difference of 90 degrees from two orthogonal directions by two feeding conductors 131 and 141 arranged on the center lines Xc and Yc of the patch element 12. Are configured to excite circularly polarized waves. This configuration is said to be suitable for obtaining a good axis ratio in a wide frequency range. However, according to what the inventor has learned, it has been found that the configuration is not necessarily suitable for improving the frequency-axis ratio characteristic, but rather there are obstructive factors that hinder it.
[0007]
That is, an antenna current that changes in a planar manner flows through the patch element 12 that is excited with a phase difference of 90 degrees from two orthogonal directions. The current distribution state and vector state are as shown in FIG. 8 in the conventional circularly polarized antenna 101 described above. FIG. 8 shows the distribution state and the vector state of the antenna current on the surface of the patch element 12 for each phase (0 degrees, 90 degrees) of the feed current. In the state shown in FIG. The distribution is biased, and the bias state of the distribution changes for each phase (0 degree and 90 degrees) of the supply current. In addition, the magnitude of the current vector for exciting circularly polarized waves differs depending on the phase of the feed current, so that circularly polarized waves with high circularity cannot be excited. This is a hindrance to the improvement of the frequency-axis ratio characteristic.
[0008]
In the above-described circularly polarized patch antenna 101, the feed conductors 131 and 141 are coupled to the center of the edge of the patch element 12 and a wide range on both sides thereof. As can be seen from FIG. 2, the distribution density of the antenna current is about to increase. For this reason, it has been found that the power supply conductors 131 and 141 also affect the current vector and cause a deterioration (increase) in the axial ratio. The power supply conductors 131 and 141 coupled to the patch element 12 need to be set so that the position, the shape, and the like can be matched with the patch element 12 in impedance. However, since the positions and shapes of the power supply conductors 131 and 141 also affect the current vector, if the positions and shapes are changed for impedance matching, there is a contradiction that the axial ratio becomes worse. That is, there is a problem that impedance adjustment is difficult and cannot be easily performed.
[0009]
The present invention has been made in view of the above-described problems, and its object is to make use of the features of a circularly-polarized patch antenna suitable for a small and compact configuration, while having a good frequency-axis ratio characteristic, It is an object of the present invention to provide a circularly polarized patch antenna that can easily perform adjustment for impedance matching.
[0010]
[Means for Solving the Problems]
According to the present invention, there is provided a dielectric or magnetic antenna base substrate made of at least one of ceramic, resin, and a composite material of ceramic and resin, and a first surface which is one surface of the base substrate. A patch element arranged on the surface of the antenna and serving as a radiation conductor of the circularly polarized antenna, and a ground conductor for excitation of the patch element arranged on the second surface opposite to the first surface via the base substrate And two power supply conductors capacitively or resonantly coupled in two directions to the edge of the patch element on the first surface, and a power supply terminal for supplying power to the two power supply conductors. In the circularly polarized patch antenna, the two feeding conductors pass through the center of the patch element on the first surface and are orthogonal to each other on the surface, and It is formed within the width sandwiched by the extension from the edge of the element, and is arranged so as to be capacitively coupled or resonantly coupled to the edge of the patch element from two directions at a position avoiding the center line. It is characterized by.
[0011]
According to the above means, it is possible to stabilize the distribution state and the vector state of the antenna current that excites circularly polarized waves distributed to the patch element, and that the shape and position of the feed conductor and the distribution state of the antenna current Deterioration of the axial ratio due to the influence of the vector state can be reduced. This makes it possible to obtain a circularly polarized patch antenna that has good frequency-axis ratio characteristics and is easy to adjust for impedance matching, while taking advantage of the characteristics of a circularly polarized patch antenna suitable for compact and compact configuration. Can be.
[0012]
The circularly polarized patch antenna is easily integrated (high-density mounting) into a wireless device by integrating and integrating a hybrid circuit that feeds the antenna input signals to the two feed terminals with a phase difference of 90 degrees. can do. As a form of the collective integration, a configuration in which the circuit board on which the hybrid circuit is formed is laminated on the antenna base substrate and the two are collectively integrated is preferable.
[0013]
Further, in the above-mentioned collective integration, a ground conductor laminated and fixed on one surface of a dielectric substrate different from the antenna base substrate is arranged on the second surface of the antenna base substrate, and the dielectric substrate is provided on the ground conductor. The conductor pattern of the microstrip line that forms the hybrid circuit is arranged on the surface of the younger brother 3 that is opposed to the ground conductor, so that the ground conductor also serves as the ground conductor for excitation of the patch element and the ground conductor of the microstrip line. Therefore, the configuration can be simplified or rationalized.
[0014]
For this purpose, it is preferable to use a multilayer printed circuit board having two or more layers having a layer structure in which a conductor pattern and a ground conductor face each other with a dielectric layer interposed therebetween. If a microstrip line constituting the hybrid circuit is formed by the conductor pattern of the multilayer printed circuit board and the grounding conductor, the grounding conductor of the microstrip line can also serve as the grounding conductor for excitation of the patch element.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, representative embodiments of the present invention will be described. Although the antenna is used for transmission and / or reception, the description will be made on the assumption of the transmission antenna in accordance with the customary in the art.
[0016]
FIG. 1 shows a first embodiment of a circularly polarized patch antenna to which the technology of the present invention is applied. The circularly polarized patch antenna 10 shown in FIG. 1 includes an antenna base substrate 11, a patch element 12, a ground conductor 18, feed conductors 13 and 14, feed terminals 15 and 16, and the like. The antenna base substrate 11 is made of a dielectric or magnetic material made of at least one of ceramic, resin, and a composite material of ceramic and resin. A patch element 12 is formed on the front (front) surface of the base substrate 11, that is, on the first surface. An excitation ground conductor 18 of the patch element 12 is arranged on the back surface of the base substrate 11, that is, on the second surface.
[0017]
The patch element 12 is formed of a substantially square rectangular conductor pattern. In order to excite the patch element 12 as a radiation conductor of a circularly polarized antenna, two feed conductors 13 and 14 that are capacitively or resonantly coupled are arranged on edges of two adjacent sides of the patch element 12. Each of the power supply conductors 13 and 14 is formed of an elongated rectangular conductor pattern. The power supply conductors 13 and 14 are arranged on the same surface of the base substrate 11 as the patch element 12 in parallel with and near the edge of the patch element 12 so as to be capacitively or resonantly coupled to the edge of the patch element 12. Has become.
[0018]
The two power supply conductors 13 and 14 are supplied with signals that have a phase difference of 90 degrees from each other in the hybrid circuit 20 and are divided into two, via power supply terminals 15 and 16. As a result, the patch element 12 is excited with a phase difference of 90 degrees from two orthogonal directions, and emits a circularly polarized mode electromagnetic wave in the vertical direction of the element 12 surface. The hybrid circuit 20 is a combination of λ / 4 transmission lines formed by the microstrip lines 21 and 22 in a bridge shape, and outputs the signal of the input terminal IN by dividing the signal into two with a phase difference of 90 degrees. The hybrid circuit 20 has an isolation terminal, which is terminated by a resistor Re. If this hybrid circuit 20 and the above-mentioned circularly polarized antenna 10 are collectively integrated in a module form, it can be easily integrated into a wireless device (high-density mounting).
[0019]
Here, the two power supply conductors 13 and 14 pass through the center of the surface of the patch element 12 on the surface of the base substrate 11 on which the patch element 12 is formed and are orthogonal to each other on the surface. It is formed within a width sandwiched between Xc and Yc and an extension (not shown) extending from the edge of the patch element 12. That is, the longitudinal direction of the power supply conductors 13 and 14 is formed shorter than half of one side of the rectangular patch element 12. Further, the power supply conductors 13 and 14 are arranged so as to be capacitively coupled or resonantly coupled to the edge of the patch element 12 from two directions at positions avoiding the center lines Xc and Yc.
[0020]
FIG. 2 shows a distribution state and a vector state of the antenna current excited in the patch element 12 of the circularly polarized patch antenna 10 shown in FIG. The patch element 12 is excited by the two feeding conductors 13 and 14 with a phase difference of 90 degrees from two orthogonal directions, and the antenna current flows. The distribution state and vector state of the antenna current are the same as those of the conventional antenna described above. This is significantly different from the case of the circularly polarized antenna (FIG. 8). In other words, the antenna current flowing through the patch element 12 excited by the power supply is distributed almost uniformly over the entire element 12 without being locally unevenly distributed. This uniform distribution state does not change so much even if the current phase (0 degree and 90 degrees) changes. That is, even if the phase changes, the vector state of the antenna current that excites circularly polarized waves does not change so much. As a result, a state in which circularly polarized waves with high circularity are excited can be obtained stably, and excellent frequency-axis ratio characteristics are realized.
[0021]
Further, in the above-described circularly polarized patch antenna 10 of the present invention, the coupling between the feed conductors 13 and 14 and the patch element 12 is performed in a portion avoiding the center of the element edge where the distribution density of the antenna current is relatively high. As a result, the influence of the power supply conductors 13 and 14 on the current vector is small. Thus, it is possible to prevent or reduce the deterioration of the axial ratio due to the influence of the power supply conductors 13 and 14. Further, this allows the positions and shapes of the power supply conductors 13 and 14 to be changed for impedance matching between the power supply conductors 13 and 14 and the patch element 12 without deteriorating the axial ratio. Become. That is, impedance adjustment becomes easy.
[0022]
FIG. 3 shows the frequency-axis ratio characteristic of the above-described circularly polarized patch antenna according to the present invention and the frequency-axis ratio characteristic of the above-mentioned conventional circularly polarized patch antenna. In the figure, the horizontal axis represents frequency (MHz), and the vertical axis represents axial ratio (dB). As can be seen from the figure, the circularly polarized patch antenna according to the present invention surely has improved frequency-axis ratio characteristics as compared with the conventional one.
[0023]
As described above, the above-described circularly-polarized patch antenna 10 of the present invention has good frequency-axis ratio characteristics and impedance matching while utilizing the features of the circularly-polarized patch antenna suitable for being compact and compact. Can be easily adjusted.
[0024]
FIG. 4 shows a second embodiment of the circularly polarized antenna according to the present invention. In this embodiment, the above-described hybrid circuit 20 is formed on a dielectric substrate 31 prepared separately from the antenna base substrate 11, but the two substrates 11, 31 are assembled and integrated in a laminated state, so that the whole is small and compact. Can be formed.
[0025]
In the figure, the excitation ground conductor (18) of the patch element 12 is not a back surface (second surface) of the antenna base substrate 11 on which the patch element 12 is formed, but a dielectric prepared separately from the base substrate 11. It is formed by a ground conductor 32 laminated and fixed on the front (front) surface of the body substrate 31. That is, on the second surface of the antenna base substrate 11, the ground conductor 32 laminated and fixed on one surface of the dielectric substrate 31 different from the base substrate 11 is arranged. Then, the conductor patterns of the microstrip lines 21 and 22 forming the hybrid circuit 20 are arranged on the surface of the lower substrate 3 facing the ground conductor 32 via the dielectric substrate 31, that is, on the back surface of the dielectric substrate 31. This allows the ground conductor 32 to also serve as the ground conductor for excitation of the patch element 12 and the ground conductor of the microstrip lines 21 and 22, thereby simplifying or streamlining the configuration.
[0026]
The above configuration can be easily realized using a multilayer printed circuit board. Since a multilayer printed circuit board having two or more layers has a layer structure in which a conductor pattern and a ground conductor face each other with a dielectric layer interposed therebetween, the microstrip lines 21 and 22 of the hybrid circuit 20 can be formed by using this. The ground conductors of the microstrip lines 21 and 22 can also be used as excitation ground conductors of the patch element 12.
[0027]
Feeding terminal pads 33 and 34 for connecting the feeding terminals 15 and 16 formed on the antenna base substrate 11 side to the hybrid circuit 20 formed on the dielectric substrate 31 side are formed on the ground conductor 32 of the dielectric substrate 31. Is formed. The terminal pads 33 and 34 are formed by arranging patch-shaped conductor lands in an insulating enclosure formed by cutting out a conductor portion in a ring shape. The antenna base substrate 11 and the dielectric substrate 31 are collectively integrated so that the antenna base substrate 11 is surface-mounted on the ground conductor 32 of the dielectric substrate 31. The power supply terminals 15, 16 and the terminal pads 33, 34 are formed in advance so as to be connected to each other in a state where they are surface-mounted. The terminal pads 33 and 34 and the hybrid circuit 20 are connected through the dielectric substrate 31 by so-called through-hole wirings 35 and 36.
[0028]
The conductor patterns of the microstrip lines 21 and 22 may be formed on, for example, a film-like substrate. The microstrip lines 21 and 22 can be formed by attaching this film-shaped substrate to the back side (third surface) of the dielectric substrate 31. Alternatively, the dielectric substrate 31 may be surface-mounted together with the antenna base substrate 11 on another printed circuit board on which the conductor pattern is formed.
[0029]
As described above, the circularly polarized patch antenna 10 and the hybrid circuit 20 can be compactly and compactly integrated. The positional relationship between the hybrid circuit 20 and the power supply terminals 15 and 16 can be increased by slightly changing the line patterns of the power supply terminals 15 and 16 as shown in, for example, FIG. Can be designed with
[0030]
FIG. 6 shows a fourth embodiment of the circularly polarized antenna according to the present invention. As shown in FIG. 2, two feed conductors 13 and 14 connected to the patch element 12 are arranged on two adjacent sides at positions avoiding the center lines Xc and Yc of the patch element 12, respectively. Is also good. That is, the two power supply conductors 13 and 14 for exciting the patch element 12 with a phase difference of 90 degrees from two orthogonal directions may be divided into two.
[0031]
In the above embodiments, the conductors such as the patch element 12, the power supply conductors 13 and 14, the power supply terminals 15 and 16, the ground conductors 18 and 32, and the microstrip lines 21 and 22 are made of gold, silver, copper, palladium, platinum, or the like. A conductor such as silver palladium, silver platinum, or aluminum can be formed by printing, plating, vapor deposition, sputtering, etching, or the like.
[0032]
As described above, the present invention has been described based on the typical embodiments. However, the present invention can have various aspects and applications other than those described above. For example, the hybrid circuit 20 may use a transmission line other than the microstrip lines 21 and 22, for example, a configuration using a coaxial cable or the like. Further, the present invention can of course be used as a receiving antenna.
[0033]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, while utilizing the characteristic of the circularly-polarized patch antenna suitable for being comprised small and compact, the frequency-axis ratio characteristic is favorable, and the circularly-polarized patch is easy to adjust for impedance matching. Antenna can be obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a first embodiment of a circularly polarized patch antenna according to the present invention.
FIG. 2 is a plan view showing a distribution state and a vector state of an antenna current excited by a patch element in the circularly polarized patch antenna of the present invention.
FIG. 3 is a characteristic graph showing frequency-axis ratio characteristics of the present invention and a conventional circularly polarized patch antenna.
FIG. 4 is a perspective view illustrating a circularly polarized antenna according to a second embodiment of the present invention.
FIG. 5 is a perspective view illustrating a circularly polarized antenna according to a third embodiment of the present invention.
FIG. 6 is a perspective view illustrating a circularly polarized antenna according to a fourth embodiment of the present invention.
FIG. 7 is a perspective view showing a configuration of a conventional circularly polarized patch antenna.
FIG. 8 is a plan view showing a distribution state and a vector state of an antenna current excited by a patch element in a conventional circularly polarized patch antenna.
[Explanation of symbols]
10 Circularly polarized patch antenna (the present invention)
101 Circularly polarized patch antenna (conventional)
DESCRIPTION OF SYMBOLS 11 Antenna base substrate 12 Patch element Xc, Yc Center line 18 Grounding conductor 13, 14 Feeding conductor (this invention)
131,141 power supply conductor (conventional)
15, 16 power supply terminal 20 hybrid circuit 21, 22 microstrip line IN input terminal Re termination resistor 31 dielectric substrate 32 ground conductor 33, 34 power supply terminal pad 35, 36 through-hole wiring

Claims (5)

A dielectric or magnetic antenna base substrate made of at least one of ceramic, resin, and a composite material of ceramic and resin; and a first surface which is one surface of the base substrate. A patch element serving as a radiation conductor of the circularly polarized antenna, an excitation ground conductor for the patch element disposed on a second surface opposed to the first surface via the base substrate, A transmitting and / or receiving circularly polarized patch having two power supply conductors capacitively or resonantly coupled in two directions to the edge of the patch element in a plane and a power supply terminal for supplying power to the two power supply conductors In the antenna, the two feeding conductors pass through the center of the patch element on the first surface and are orthogonal to each other on the surface, and extend from an edge of the patch element. And is arranged so as to be capacitively coupled or resonantly coupled to the edge of the patch element from two directions at a position avoiding the center line. Patch antenna. 2. The circularly polarized patch antenna according to claim 1, wherein hybrid circuits for feeding an antenna input signal to the two feed terminals with a phase difference of 90 degrees are integrated. 3. The circularly polarized patch antenna according to claim 1, wherein a circuit board on which the hybrid circuit is formed is stacked on the antenna base board, and the two are assembled and integrated. 4. The grounding conductor according to claim 1, wherein a ground conductor laminated and fixed on one surface of a dielectric substrate different from the antenna base substrate is arranged on the second surface of the antenna base substrate, and the dielectric conductor is provided on the ground conductor. By arranging a conductor pattern of a microstrip line forming a hybrid circuit on the surface of the younger brother 3 facing through the body substrate, the ground conductor also serves as an excitation ground conductor of the patch element and a ground conductor of the microstrip line. A circularly polarized patch antenna characterized in that: 5. The hybrid circuit according to claim 4, wherein a multilayer printed circuit board having two or more layers having a layer structure in which a conductor pattern and a ground conductor face each other with a dielectric layer interposed therebetween is used, and the conductor pattern of the circuit board and the ground conductor constitute the hybrid circuit. And a ground conductor of the microstrip line also serves as a ground conductor for excitation of the patch element.

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