JP2007267088A - Multi-frequency shared antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-frequency shared antenna, wherein the isolation between antenna elements at a low frequency band can be improved or adjusted so as to obtain the desired electrical characteristics. <P>SOLUTION: The multi-frequency shared antenna includes a dielectric board 1 of almost a plate shape installed on a finite conductor plate; an antenna conductor pattern including at least two antenna elements 3, 5: the first antenna element 3 operating at a high frequency and the second antenna element 5 acting at a low frequency located on the front side of the dielectric board 1; and a ground conductor located on a rear side of the dielectric board 1, and a feeding point 12 of the first antenna element 3 operating at the high frequency is provided substantially in the middle of the dielectric board 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multi-frequency shared antenna, and more particularly to a multi-frequency shared antenna in which antenna conductor patterns having antenna elements that operate at a plurality of frequencies are arranged on the same dielectric substrate.

  In recent years, as information terminals mounted on automobiles and the like, ETC (Electronic Toll Collections “Electronic Toll Collection System”: about 5.8 GHz), GPS (Global Positioning System “Global Positioning System”: about 1.6 GHz), VICS (Vehicle Information and Communication System “Road Traffic Information Communication System”: about 2.5 GHz) and SDARS (Satellite Digital Audio Service “Satellite Digital Radio Service”: about 2.3 GHz) are widely used.

  Further, the combined use of the above-mentioned media is progressing. As antennas used for these communications, there is known a multi-frequency shared antenna in which a single-frequency antenna shown in FIG. 15 and a plurality of antennas as shown in, for example, Patent Document 1 and FIG. 16 are integrated. . In actual operation, a multi-frequency antenna is useful for reducing the size and simplification of the antenna installation space in terms of cost reduction (see, for example, Patent Document 1).

  Each aspect will be described below.

  A single frequency antenna 900 shown in FIG. 15 includes a dielectric substrate 1 made of ceramic, plastic, or the like, and a single radiating conductor 3 (hereinafter referred to as an antenna element) that is formed on the surface of the dielectric substrate 1 and transmits and receives radio waves. ) And a ground conductor formed on the back surface of the dielectric substrate 1. Usually, in actual use, the antenna is installed on a circuit board or a metal plate (hereinafter, both are collectively referred to as a finite conductor plate) due to electrical and mechanical requirements. The single-frequency antenna 900 having such a configuration can transmit and receive radio waves in one frequency band.

  On the other hand, a multi-frequency antenna 1000 shown in FIG. 16 includes a dielectric substrate 1 made of ceramic, plastic, or the like, a first antenna element 3 formed on the surface and the center of the dielectric substrate 1, and a dielectric. And a second antenna element 5 surrounding the first antenna element 3 formed on the front surface of the body substrate 1 and a ground conductor formed on the back surface of the dielectric substrate. That is, the multi-frequency shared antenna 1000 has a structure in which antenna elements that operate at different frequencies are arranged around the single-frequency antenna 900 described above. The first antenna element 3 operates for a high frequency band, and the second antenna element 5 disposed outside operates for a low frequency band. Each antenna element is provided with at least one feeding point corresponding thereto.

Similar to the single-frequency antenna 900, the multi-frequency shared antenna 1000 is installed on the finite conductor plate 7 in actual use. The multi-frequency shared antenna 1000 having such a configuration can transmit or receive radio waves in two frequency bands. Further, the configuration shown in FIG. 16 is an example in which multi-frequency sharing is attempted with an integrated antenna, and various aspects of multi-frequency sharing antennas have been proposed without being limited to the above configuration.
JP 2004-289332 A

  Although the multi-frequency shared antenna 1000 has merits in practical operation, there is a problem that desired electrical characteristics cannot be obtained as compared with the single-frequency antenna 900 described above. This is due to the occurrence of mutual interference between antenna elements corresponding to different frequencies due to the increase in the number of antennas. In particular, since antenna elements having different frequencies are arranged close to each other, there is a problem that it is difficult to secure isolation characteristics between the antennas.

  FIG. 17 is a graph showing the isolation characteristics at the feeding point for the multi-frequency antenna 1000, the horizontal axis is the normalized frequency (f / f0) of the multi-frequency antenna 1000, and the vertical axis is the isolation characteristic. is there. Here, the frequency band is a band of a low-frequency antenna among multiple frequencies, and f0 is an antenna resonance frequency. As can be seen from FIG. 17, the isolation characteristics of the low-frequency antenna in the vicinity of the antenna resonance frequency f0 are not necessarily sufficient.

  As described above, with the increase in the number of antennas, there has been a problem that the isolation between the feeding points of the high frequency band and the low frequency band is not sufficient and interference occurs. In order to promote the miniaturization of the antenna, for example, the periphery of one antenna element as described above appears conspicuously by arranging the antenna elements close to each other like a configuration surrounding the other antenna element.

  Accordingly, in order to solve the above-described problems, the present invention provides a multi-frequency shared antenna that can improve or adjust isolation between antenna elements in a low frequency band and obtain desired electrical characteristics. With the goal.

In order to solve the above problems, the multi-frequency antenna according to the present invention includes a substantially plate-like dielectric substrate installed on a finite conductor plate,
On the surface of the dielectric substrate, an antenna conductor pattern including at least two antenna elements of a first antenna element operating at a high frequency and a second antenna element operating at a low frequency;
The back surface of the dielectric substrate comprises a ground conductor,
The feeding point of the first antenna element is provided at a substantially central portion of the dielectric substrate.

  The multi-frequency antenna according to the present invention is preferably characterized in that at least one groove structure is provided on the surface of the dielectric substrate sandwiched between the first antenna element and the second antenna element. .

  In the multi-frequency antenna according to the present invention, preferably, the feeding point of the first antenna element is from the center of the multi-frequency antenna, which is the center of the dielectric substrate, and the resonance wavelength of the second antenna element is 0. It is arranged within a range of distance of 125 λgL.

  The multi-frequency shared antenna of the present invention is preferably characterized in that an air layer is provided in at least a part of the lower part of the second antenna element in the dielectric substrate.

  The multi-frequency shared antenna of the present invention is preferably characterized in that the first antenna element and the second antenna element are patch antennas.

  The multi-frequency shared antenna of the present invention is preferably characterized in that the multi-frequency shared antenna is used for at least one of GPS, VICS, ETC, SDARS, and Bluetooth.

  The multi-frequency shared antenna of the present invention is preferably used for in-vehicle use.

  According to the multi-frequency shared antenna of the present invention, the feeding point of the first antenna element is provided at a position that is substantially the center of the dielectric substrate and deviated from the center of the first antenna element. The isolation between the antenna elements in the band can be improved or adjusted, so that desired electrical characteristics can be obtained.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a perspective view showing a first preferred embodiment of a multi-frequency antenna according to the present invention, and FIG. 2 is a plan view of the multi-frequency antenna of FIG. 3 is a cross-sectional view taken along line BB in FIG. FIG. 4 is a graph showing an example of isolation characteristics between antenna elements of the multi-frequency antenna shown in FIG.

  As shown in FIGS. 1 and 2, the multi-frequency antenna 100 includes a dielectric substrate 1, a first antenna element 3, and a second antenna element 5, and a ground conductor on the back surface of the dielectric substrate 1. 8 and installed on the finite conductor plate 7. The finite conductor plate 7 is, for example, a circuit board or a metal plate, and substantially functions as an antenna ground.

  The dielectric substrate 1 is mounted on a finite conductor plate 7 and is made of ceramic or plastic. The first antenna element 3 is formed on the surface of the dielectric substrate 1 and substantially at the center. The second antenna element 5 is formed on the surface of the dielectric substrate 1 and surrounds the first antenna element 3.

  In the example shown in FIGS. 1 and 2, a second antenna element 5 that is a square ring-shaped patch antenna is disposed around a first antenna element 3 that is a square patch antenna. The first antenna element 3 installed on the inside operates for the high frequency band, and the second antenna element 5 installed on the outside operates for the low frequency band. The antenna conductor pattern 11 includes at least two antenna elements 3 and 5 on the surface of the dielectric substrate 1, that is, a first antenna element 3 that operates at a high frequency and a second antenna element 5 that operates at a low frequency.

  As shown in FIGS. 2 and 3, the first antenna element 3 has a feeding point 12, and the second antenna element 5 has a feeding point 10. The feeding point 12 is located on the center conductor (feeding pin) 15 shown in FIG. 3, and the feeding point 10 is located on the center conductor (feeding pin) 14 shown in FIG. The center conductor 15 performs direct power feeding or capacitive power feeding via a gap to the first antenna element 3. The center conductor 14 performs capacitive power feeding via a gap to the second antenna element 5. In FIG. 3, which is the first embodiment, the central conductor 15 represents direct power feeding, and the central conductor 14 represents capacitive power feeding via a gap. The second antenna element 5 operating at a low frequency is difficult to realize unless it is actually a capacitive power feed through a gap.

  The center C1 of the first antenna element 3 is shifted by a distance W from the center position C2 of the dielectric substrate 1 that is the center of the multi-frequency antenna 100 along the F direction. In the present embodiment, the center of the second antenna element 5 coincides with the center position C2 of the dielectric substrate 1 that is the center of the multi-frequency antenna 100, but it does not necessarily need to coincide. The feeding point 12 of the first antenna element 3 is in a substantially central portion including the center position C2 of the dielectric substrate 1, but is shifted from the center C1 of the first antenna element 3.

  The feeding point 12 of the first antenna element 3 operating at a high frequency is located at a substantially central portion (including the center position C2) of the dielectric substrate 1 and is shifted from the center C1 of the first antenna element 3. Placed in position. Thus, if the feeding point 12 is not deviated from the center of the first antenna element 3, the power fed from the feeding point 12 of the center conductor 14 to the first antenna element 3 is supplied to the first antenna element 3. And the radio wave does not radiate well from the first antenna element 3.

  The configuration in which the second antenna element 5 is surrounded around the first antenna element 3 is smaller than the configuration in which a plurality of antenna elements are integrated, compared to the configuration in which the antenna elements are arranged without surrounding. It has advantages such as ensuring structural or electrical symmetry.

  As shown in FIGS. 2 and 3, in the multi-frequency shared antenna 100, the central conductor (feeding pin) 15 of the first antenna 3 that operates at a high frequency is a substantially central portion including the center C <b> 2 of the multi-frequency shared antenna 100. Therefore, the isolation between the first antenna element 3 and the second antenna element 5 in the low frequency band can be improved. At this time, the position of the central conductor (feeding pin) 15 of the first antenna element 3 is preferably disposed within a radius of 0.125λgL from the center C2 of the multi-frequency antenna 100. Good characteristics are obtained when the radius is 0.125λgL from the center C2. The state of improvement of the isolation characteristic can be seen from the improvement from the curve G1 shown in FIG. 4 to the curve G2.

λL: resonance frequency on the low frequency side λH: resonance wavelength on the high frequency side λgL: effective wavelength in the dielectric on the low frequency side (λgL = λL / √εr, εr: relative dielectric constant)
λgH: effective wavelength in the dielectric on the high frequency side (λgH = λH / √εr, εr: relative permittivity)
FIG. 5 shows the position of the center conductor (feeding pin) 15 of the first antenna element 3 on the high frequency side, the first antenna element 3 and the second antenna element in the multi-frequency antenna 100 of FIGS. It is a graph which shows the relationship with the isolation between 5. FIG.

In FIG. 5, the horizontal axis represents the normalized distance of the high-frequency side central conductor (feeding pin) 15 with respect to the center of the multi-frequency antenna 100, and the vertical axis represents the worst value in the band of isolation between antenna elements. Is a threshold. By disposing the position of the center conductor (feeding pin) 15 within the range of plus or minus 0.125λgL of the resonance wavelength of the second antenna element 5 on the low frequency side from the center C2 of the multi-frequency shared antenna 100, It can be seen that the isolation between the first antenna element 3 and the second antenna element 5 can be suppressed to a desired characteristic. This is because the characteristics of the electromagnetic field distribution in the low frequency band of the dielectric substrate 1 or on the surface are used. A similar mechanism can be used for another embodiment of the present invention described below.
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 6 is a view showing a second preferred embodiment of the multi-frequency antenna according to the present invention, and FIG. 7 is a plan view of the multi-frequency antenna of FIG. FIG. 8 is a cross-sectional view taken along the line CC of FIG. 7. The components of the multi-frequency antenna 200 shown in FIGS. 6 to 8 are the same as the components of the multi-frequency antenna 100 shown in FIGS. In this case, the same reference numerals are used and the description thereof is omitted.

A characteristic of the multi-frequency antenna 200 is that a groove structure 9 is provided on the dielectric substrate 1 surrounded by the first antenna element 3 and the second antenna element 5. As shown in FIG. 8, the depth d of the groove structure 1 is about 75% of the thickness of the dielectric substrate 1. However, even in the experiment, good characteristics were shown even at 50%. Thus, the multi-frequency shared antenna 200 having the groove structure 9 maintains the isolation characteristics shown in FIG. 5, and the first antenna element 3 is adjusted by adjusting the position of the center conductor (feeding pin) 15. And the second antenna element 5 can be improved and adjusted.
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS.

FIG. 9 is a plan view showing a third preferred embodiment of the multi-frequency antenna according to the present invention, and FIG. 10 is a cross-sectional view taken along the line D-D in FIG. 9. When the components of the shared antenna 300 are the same as the components of the multi-frequency shared antenna 100 shown in FIGS. 1 to 3, the same reference numerals are given and the description thereof is omitted.

  As shown in FIGS. 9 and 10, the multi-frequency antenna 200 further includes a dielectric substrate 1 partially below the second antenna element 5 compared to the structure of the multi-frequency antenna 200 of the second embodiment. The air layer 16 is provided by cutting.

  The depth d of the groove structure 9 of the multi-frequency antenna 200 is the same as that of about 75% of the thickness of the dielectric substrate 1 of the multi-frequency antenna 200 of the second embodiment.

  FIG. 11 shows a comparison between the second embodiment and the third embodiment, showing the gain characteristics of an antenna that operates at a low frequency among the multi-frequency shared antennas, with the angle on the horizontal axis, The axis shows the gain. In the multi-frequency shared antenna 300 of the third embodiment, by providing the air layer 16 in a part of the lower part of the second antenna element 5, the area of the second antenna element 5 can be reduced without changing the resonance wavelength λL. You can make it bigger. In addition, the multi-frequency shared antenna 300 of the third embodiment can increase the gain of the second antenna element 5 on the low frequency side as compared with the multi-frequency shared antenna 200 of the second embodiment.

In the multi-frequency shared antenna 300 having such a structure, the isolation characteristics shown in FIG. 5 are maintained, and the position of the central conductor (feeding pin) 15 of the first antenna 3 operating at a high frequency is adjusted. As a result, the isolation between the first antenna element 3 and the second antenna element 5 can be improved and adjusted.
(Other embodiments)
Next, another embodiment of the present invention will be described.

12 is a plan view showing another preferred embodiment of the multi-frequency antenna according to the present invention. FIG. 13 is a cross-sectional view taken along the line FF in FIG. 12. The multi-frequency antenna 400 shown in FIG. A third antenna element 6 is further provided on the outer periphery of the first antenna element 3 and the second antenna element 5 on the surface of the dielectric substrate 1. That is, the multi-frequency shared antenna 400 is the same as the first antenna element 3 and the second antenna in the dielectric substrate 1 of the multi-frequency shared antenna 100 of the first embodiment and the multi-frequency shared antenna 200 of the second embodiment. A third antenna element 6 is additionally set on the outer periphery of the element 5. The multi-frequency shared antenna 400 having two or more frequencies as in the embodiment shown in FIGS. 12 and 13 can obtain the same effects as those in the first to third embodiments.

  In the multi-frequency antenna of the present invention, antenna elements that resonate at a plurality of frequencies are mounted on a single dielectric substrate, so that the isolation between the antenna elements can be improved and a design for obtaining desired electrical characteristics is achieved. Is possible. In the multi-frequency shared antenna of the present invention, by realizing multi-frequency sharing of the antenna, the convenience of users such as space saving, miniaturization, and cost reduction of the multi-frequency shared antenna is increased, The multi-frequency shared antenna can be applied particularly to in-vehicle use and portable terminal use.

  By the way, this invention is not limited to the said embodiment, It is possible to implement in various deformation | transformation in the range which does not deviate from the summary.

  For example, the inside of the groove structure 9 may be filled with a dielectric having a dielectric constant lower than that of the dielectric substrate 1.

In the second embodiment, the third embodiment, and the other embodiments, the dielectric substrate 1 should have a groove structure, an air layer, and a dielectric having a dielectric constant lower than that of the dielectric substrate 1, respectively. The relative dielectric constant needs to be considered as the effective dielectric constant. Here, since there is a relationship of εr> _εeff , the effective wavelengths of the second embodiment, the third embodiment, and other embodiments are longer than those of the first embodiment.

λe _L : Effective wavelength in the antenna on the low frequency side (λe _L = λ _L / √ε _eff ε _eff : Effective dielectric constant)
λe _H : Effective wavelength in the antenna on the high frequency side (λe _H = λ _H / √ε _eff ε _eff : Effective dielectric constant)
In the illustrated example, a square patch antenna is used as the first antenna element 3. However, in the present invention, the first antenna element 3 is not limited to the patch antenna, and can be implemented by adopting various types of antenna systems such as a slot antenna or a spiral antenna 3S as shown in FIG.

  In the embodiment of the present invention, a square or rectangular substrate is used as the dielectric substrate, and the shape can be any shape such as a cylinder, a polygon, a convex portion or a concave portion. Further, the present invention is applicable not only to linearly polarized waves but also to circularly polarized waves as an antenna operation. Of course, the power feeding method can be applied to methods other than the illustrated example.

  For example, the multi-frequency shared antenna of the present invention can be used for at least one of GPS, VICS, ETC, SDARS, and Bluetooth.

1 is a diagram showing a first preferred embodiment of a multi-frequency shared antenna of the present invention. It is a top view of the multi-frequency common antenna of FIG. It is sectional drawing in the BB line of FIG. It is a graph which shows the example of the isolation characteristic between the antenna elements of the multifrequency shared antenna of FIG. 4 is a graph showing a relationship between a position of a high frequency side feed pin and isolation between antenna elements in the multi-frequency shared antenna of FIGS. 1 to 3. It is a figure which shows preferable 2nd Embodiment of the multifrequency shared antenna of this invention. It is a top view of the multi-frequency common antenna of FIG. It is sectional drawing in the CC line of FIG. It is a top view which shows preferable 2nd Embodiment of the multifrequency shared antenna of this invention. It is sectional drawing in the DD line | wire of FIG. It is a figure which shows an angle on a horizontal axis and shows a gain on a vertical axis | shaft by the gain characteristic of the antenna which operate | moves at a low frequency among multi-frequency shared antennas. It is a top view which shows other preferable embodiment of the multifrequency shared antenna of this invention. It is sectional drawing in the FF line of FIG. It is a figure which shows the other implementation mobile phone of this invention. It is a figure which shows a prior art example. It is a figure which shows another prior art example. It is a figure which shows the isolation characteristic in a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric substrate 3 1st antenna element 5 2nd antenna element 8 Ground conductor 9 Groove structure 10 Feeding point 12 Feeding point 14 Center conductor (feeding pin)
15 Center conductor (feed pin)
16 Air layer 100 Multi-frequency antenna 200 Multi-frequency antenna 300 Multi-frequency antenna 400 Multi-frequency antenna 500 Multi-frequency antenna

Claims (7)

A substantially plate-like dielectric substrate installed on a finite conductor plate;
On the surface of the dielectric substrate, an antenna conductor pattern including at least two antenna elements of a first antenna element operating at a high frequency and a second antenna element operating at a low frequency;
The back surface of the dielectric substrate comprises a ground conductor,
A multi-frequency shared antenna comprising a feeding point of the first antenna element at a substantially central portion of the dielectric substrate. The multi-frequency shared antenna according to claim 1, wherein a surface of the dielectric substrate sandwiched between the first antenna element and the second antenna element is provided with at least one groove structure. The feeding point of the first antenna element is disposed within a distance of a resonance wavelength of 0.125λgL of the second antenna element from the center of the multi-frequency antenna that is the center of the dielectric substrate. 3. The multi-frequency shared antenna according to claim 1, wherein the multi-frequency antenna is used. 4. The multi-frequency antenna according to claim 3, wherein an air layer is provided in at least a part of a lower portion of the second antenna element in the dielectric substrate. 5. The multi-frequency shared antenna according to claim 3 or 4, wherein the first antenna element and the second antenna element are patch antennas. The multi-frequency shared antenna according to any one of claims 1 to 5, wherein the multi-frequency shared antenna is used in at least one of GPS, VICS, ETC, SDARS, and Bluetooth. The multi-frequency antenna according to claim 6, wherein the multi-frequency antenna is used for in-vehicle use.

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