JP4238325B2 - Multi-frequency microstrip antenna - Google Patents

Description

  The present invention relates to a microstrip antenna (hereinafter abbreviated as “MSA”) having a multi-frequency shared characteristic that operates at a plurality of frequencies, and enables the element to be reduced in thickness and reduced in size. .

The MSA is an antenna that radiates radio waves using a magnetic current generated at the end of the radiation conductor due to an electric field between the radiation conductor and the ground conductor (GND) as a wave source.
The present inventors have previously developed a multi-frequency shared MSA in which one or a plurality of V-shaped slits are provided in a planar radiating element having a rhombus-shaped outer shape (the following Non-Patent Document 1).

As shown in FIG. 14, the multi-frequency shared MSA includes a radiating element 22 made of a rhombus metal conductor layer formed on a first insulating substrate 21 and a T-shape formed on a second insulating substrate 23. A power feeding unit 24 made of a metal conductor layer, a ground conductor 25 provided on the back surface of the second insulating substrate 23, and a coaxial connector 26 having a center conductor and an outer conductor are provided.
The tip of the central conductor of the coaxial connector 26 is connected to the T-shaped metal conductor layer of the power feeding unit 24 through the second insulating substrate 23. The structure of this power supply unit is called an “L probe”, and the L probe is known as a probe capable of supplying a broadband electromagnetic coupling type power supply. The outer conductor of the coaxial connector 26 insulated from the center conductor is connected to the ground conductor 25.
As described above, the second insulating substrate 23 plays a role as a power feeding substrate for holding the L probe 24 and is laminated so as to sandwich the L probe 24 and the first insulating substrate 21 which is the antenna portion substrate. The
On the first insulating substrate 21 of the antenna portion substrate, a diamond-shaped radiating element 22 formed by combining two equilateral triangles is formed. As shown in FIGS. The diamond is disposed at one acute angle position of the rhombus.
The radiating element 22 has three (31, 32, 33) V-shaped slits parallel to the two sides of the rhombus. The V-shape of each slit 31, 32, 33 is on the L probe side. (This V-shaped slit is hereinafter referred to as an “inverted V-shaped slit”).

When these three inverted V-shaped slits form four current paths shown in FIGS. 15A, 15B, 15C, and 15D in the radiating element 22, and are supplied with power from the L probe 24. In addition, a resonance phenomenon caused by each current path appears. Here, the phenomenon based on the current distribution of the longest current path (FIG. 15A) is “1st mode”, and the phenomenon based on the current distribution of the second longest current path (FIG. 15B) is “2nd mode”. The phenomenon based on the current distribution of the third longest current path (FIG. 15C) is called “3rd mode”, and the phenomenon based on the current distribution of the shortest current path (FIG. 15D) is called “4th mode”. I will decide.
FIG. 16 shows the return loss characteristics of this MSA. The vertical axis represents the return loss value, and the horizontal axis represents the frequency. (A), (b), (c), and (d) in the same figure correspond to resonance phenomena in the 1st mode, 2nd mode, 3rd mode, and 4th mode, respectively, and the resonance frequency increases as the mode order increases. Has shifted to the high frequency side.
As described above, the multi-frequency shared MSA has a plurality of modes having different resonance frequencies, and thus can be used as an antenna having multiband characteristics.
Yusuke Shinnohe, Osamu Haneishi, Yuichi Kimura "A Study on Slit-Loaded Diamond MSA with Multiband Characteristics" Proceedings of the 2005 IEICE General Conference, B-199, p199, February 2005

  However, this multi-frequency shared MSA needs to be assembled by accurately aligning and assembling the antenna portion substrate 21 on which the radiating element 22 is formed and the power supply substrate 23 on which the L probe 24 is formed. It becomes complicated. In addition, since the two substrates are stacked, it is difficult to reduce the size of the element by reducing the thickness.

  The present invention has been made in consideration of such circumstances, and an object thereof is to provide a multi-frequency shared MSA that is easy to manufacture and can be thinned.

The multi-frequency shared MSA of the present invention lies on an extension line of a diagonal line connecting a planar radiating element having a rhombus-shaped outer shape and a first acute angle and a second acute angle of the rhombus, and has the first acute angle. A feeding point located in the vicinity, and a stub that is on the same plane as the radiating element and extends in a V shape in parallel with two sides sandwiching the first acute angle of the rhombus with the position of the feeding point as a base point The radiating element has one or more V-shaped V-shaped slits having a base point on the diagonal line and opened on the first acute angle side. .
The multi-frequency shared MSA can be configured with a single substrate because the power supply stub is on the same plane as the diamond-shaped radiating element.

  The multi-frequency shared MSA of the present invention is easy to manufacture because it is not necessary to combine a plurality of substrates. Further, since no combination error occurs, it can be manufactured with high accuracy. Further, since it can be constituted by a single substrate, it can be thinned.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing the configuration of a multi-frequency shared MSA according to the first embodiment of the present invention, where FIG. 1 (a) is a perspective view, FIG. 1 (b) is a cross-sectional view, and FIG. It is an enlarged view of a radiation element and a feed stub. 2 is a current path formed in the multi-frequency shared MSA, FIG. 3 is a return loss characteristic of the multi-frequency shared MSA, FIG. 4 is a radiation pattern of the multi-frequency shared MSA, and FIG. The gain characteristics of the shared MSA are shown respectively.

The multi-frequency shared MSA includes a radiating element 42 made of a diamond-shaped metal conductor layer formed on the surface of the insulating substrate 41, and a feed stub 43 made of a V-shaped metal conductor layer formed on the surface of the insulating substrate 41. A ground conductor 45 provided on the back surface of the insulating substrate 41 and a coaxial connector 46 having a center conductor and an outer conductor are provided.
The central conductor of the coaxial connector 46 passes through the insulating substrate 41, and the tip thereof is connected to the V-shaped feeding stub 43. The outer conductor of the coaxial connector 46 insulated from the center conductor is connected to the ground conductor 45 on the back surface of the insulating substrate 41.
The radiating element 42 formed on the surface of the insulating substrate 41 has a rhombus shape, and the central conductor of the coaxial connector 46 is on the extended line of the diagonal line connecting the acute angles of the rhombus and is fed at a position close to one of the acute angles. It is connected to the stub 43 (this acute angle is referred to as “first acute angle”, and the other acute angle is referred to as “second acute angle”). The V-shaped feeding stub 43 is composed of stubs extending in two directions starting from the position of the central conductor of the coaxial connector 46, and each stub is parallel to each side sandwiching the first acute angle of the rhombus. .
The diamond-shaped radiating element 42 is formed with three inverted V-shaped slits (51, 52, 53) opened on the first acute angle side. The base point of each inverted V-shaped slit (51, 52, 53) is on a diagonal line connecting the first acute angle and the second acute angle of the rhombus, and each slit is on one of two sides sandwiching the second acute angle of the rhombus Parallel.

In this multi-frequency shared MSA, by feeding power from the coaxial connector 46, the V-shaped feeding stub 43 serves as a feeding line, and electromagnetic coupling type feeding to the diamond-shaped radiating element 42 is performed, and three inverted V-shaped. A diamond-shaped current path having four similar shapes shown in FIGS. 2A, 2B, 2C, and 2D appears in the radiating element 42 having a mold slit.
The arrows shown in FIGS. 2A, 2B, 2C, and 2D schematically represent the current distribution of each current path obtained by the electromagnetic field simulator (electromagnetic field simulator (IE3D) using the moment method). . Thus, in each current path, a current distribution that uniformly passes from the first acute angle to the other acute angle appears through each rhombus side. Therefore, the radiating element 42 has a 1st mode according to each current path, Resonance phenomena of 2nd mode, 3rd mode, and 4th mode appear.

FIG. 3 shows the return loss characteristic of the multi-frequency shared MSA. However, various dimensions of the multi-frequency shared MSA indicated by reference numerals in FIG. 1 were set as follows (unit: mm).
h1 = 23.8, w1 = 0.4, w2 = 3.2, w3 = 1.2, d1 = d2 = d3 = 0.4, g1 = g2 = g3 = 0.4, Pw = 1.5, Ph = 3.0, Pd = 0.4, Pf = 1.5, t = 2.4,
Further, a Teflon (registered trademark) glass fiber substrate (PTFE substrate, relative dielectric constant εr = 2.6) is used as the insulating substrate 41, and a printed circuit board having a copper thin film deposited on this substrate is etched. 1 and the feed stub 43 were formed.
In FIG. 3, the vertical axis represents the return loss value and the horizontal axis represents the frequency. In the figure, a solid line indicates an actual measurement value, and a dotted line indicates a simulation value.
In FIG. 3, the resonance phenomenon observed at 3.90 GHz (a) is due to the current distribution of the 1st mode, and the resonance phenomenon at 4.64 GHz (b), 7.00 GHz (c), and 9.88 GHz (d). Are due to the current distribution in the 2nd mode, 3rd mode, and 4th mode, respectively. Thus, as the order of the mode increases, the path length of the current path corresponding to each mode is shortened, and the resonance frequency of each mode is increased.

FIG. 4 shows the radiation patterns of the E plane and the H plane in the 1st mode, 2nd mode, 3rd mode and 4th mode of this multi-frequency shared MSA in (a), (b), (c) and (d). In the figure, the characteristic of the radiation pattern (actual measurement value and simulation value) is indicated by a solid line, and the cross polarization level (measurement value and simulation value) is indicated by a dotted line. As is clear from this figure, the radiation pattern of each mode shows a good unidirectional pattern on both the E and H planes. In the main polarization, the measured value of the radiation pattern characteristic and the simulation value are in good agreement.
FIG. 5 shows gains (actual values and simulation values) in each mode of the multi-frequency shared MSA. As is clear from this figure, a gain of 4.0 dBi or more is obtained in all of the 1st mode, 2nd mode, 3rd mode, and 4th mode.

Thus, this multi-frequency shared MSA has a multiband characteristic that resonates at a plurality of frequencies, and can cope with many types of communication using different frequencies.
Although the radiation characteristics of this multi-frequency shared MSA have been described here, it is obvious from the “reciprocity” of the antenna that exactly the same characteristics can be obtained when this MSA is used as a receiving antenna.
Also, here, a case where a Teflon (registered trademark) glass fiber substrate is used as the substrate and the copper thin film deposited on the substrate is etched to form the planar radiating element 42 and the V-shaped feeding stub 43 is used. As described above, the present invention is not limited to this. For example, a conductive pattern of a planar radiating element and a V-shaped feeding stub is printed with a metallized paste containing metal powder on a ceramic green sheet, and then fired. It may be formed by any method.

  In this multi-frequency shared MSA, the pattern of the radiating element and the feeding stub on the same plane can be formed simultaneously and with high accuracy using techniques such as etching and printing. Therefore, this multi-frequency shared MSA is easy to manufacture, and a highly accurate one can be obtained. Further, since it can be constituted by a single substrate, it can be thinned.

(Second Embodiment)
In the second embodiment of the present invention, characteristics when the radiating element has one inverted V-shaped slit will be described.
6A and 6B are diagrams showing the configuration of the multi-frequency shared MSA according to the second embodiment. FIG. 6A is a perspective view, FIG. 6B is a cross-sectional view, and FIG. It is an enlarged view of a feed stub. FIG. 7 shows a current path formed in the multi-frequency shared MSA, and FIG. 8 shows a change in resonance frequency when the position of the inverted V-shaped slit is changed.
This multi-frequency shared MSA has the same configuration as the multi-frequency shared MSA (FIG. 1) of the first embodiment, except that there is one inverted V-shaped slit 51 formed in the radiating element 42. In FIG. 6, this single inverted V-shaped slit 51 is provided at the same position as the inverted V-shaped slit 51 of the first embodiment. Various dimensions of the multi-frequency shared MSA are the same as those in the first embodiment, except that Ph = 4.0.

In this multi-frequency shared MSA, a rhombus-shaped current path having two similar shapes shown in FIGS. 7A and 7B is formed in the radiating element 42 by feeding from the coaxial connector 46, and the 1st mode by each current path is formed. And a 2nd mode resonance phenomenon appears.
The graph of FIG. 8 shows the relationship between W1 (horizontal axis) and the resonance frequency (vertical axis) when the position of the inverted V-shaped slit 51 is moved by changing the width of W1.
As is apparent from this figure, by moving the position of the inverted V-shaped slit, the resonance frequency of the 2nd mode (dotted line) is changed while maintaining the resonance frequency (solid line) of the 1st mode at a substantially constant value. Can do.

(Third embodiment)
In the third embodiment of the present invention, characteristics when the number of inverted V-shaped slits of the radiating element is increased will be described.
9A and 9B are diagrams showing a configuration of a multi-frequency shared MSA according to the third embodiment. FIG. 9A is a perspective view, FIG. 9B is a cross-sectional view, and FIG. It is an enlarged view of a feed stub. 10 shows a current path formed in the multi-frequency shared MSA, FIG. 11 shows a return loss characteristic of the multi-frequency shared MSA, and FIGS. 12 and 13 show a radiation pattern of the multi-frequency shared MSA, respectively. .

This multi-frequency shared MSA is the multi-frequency shared MSA of the first embodiment, except that there are six inverted V-shaped slits (51, 52, 53, 54, 55, 56) formed in the radiation element 42. It is the same structure as (FIG. 1). Various dimensions of the multi-frequency shared MSA indicated by reference numerals in FIG. 9 were set as follows (unit: mm).
h1 = 23.8, w1 = 0.4, w2 = 1.2, w3 = 0.8, w4 = w5 = w6 = 0.4, d1-d6 = 0.4, g1-g6 = 0.4, Pw = 1.5, Ph = 3.0, Pd = 0.4, Pf = 1.5, t = 2.4,
In this multi-frequency shared MSA, rhombus-shaped currents having seven similar shapes shown in FIGS. 10 (a), (b), (c), (d), (e), (f), and (g) are fed from the coaxial connector 46. A path is formed in the radiating element 42, and resonance phenomena of 1st mode, 2nd mode, 3rd mode, 4th mode, 5th mode, 6th mode, and 7th mode appear due to each current path.

FIG. 11 shows the return loss characteristics of this multi-frequency shared MSA. In FIG. 11, the resonance phenomenon of 3.63 GHz (a) is due to the current distribution of the 1st mode, and is 4.45 GHz (b), 5.25 GHz (c), 6.05 GHz (d), 6.78 GHz ( e) The resonance phenomenon at 7.73 GHz (f) and 9.87 GHz (g) is due to the current distribution of the 2nd mode, 3rd mode, 4th mode, 5th mode, 6th mode and 7th mode, respectively.
Also, the radiation patterns in the 1st mode, 2nd mode, 3rd mode, and 4th mode of this multi-frequency shared MSA are shown as FIGS. 12 (a), (b), (c), and (d), and the 5th mode of this multi-frequency shared MSA is shown. The radiation patterns in the 6th mode and the 7th mode are shown as FIGS. 13 (e), (f), and (g). In the figure, the thin solid line indicates the radiation pattern characteristic of the E plane, and the thick solid line indicates the radiation pattern characteristic of the H plane. The dotted line indicates the cross polarization level.

As is clear from these embodiments, in this multi-frequency shared MSA, the number of inverted V-shaped slits corresponds to the number of modes. Therefore, in this multi-frequency shared MSA, the number of modes can be set freely by selecting the number of inverted V-shaped slits.
In this multi-frequency shared MSA, the position of the inverted V-shaped slit corresponds to the resonance length of each mode. Therefore, in this multi-frequency shared MSA, the resonance frequency of each mode can be freely adjusted by selecting the position of the inverted V-shaped slit.
Such characteristics also include the multi-layer shared multi-frequency MSA described in Non-Patent Document 1. The multi-frequency shared MSA of the present invention can realize the same characteristics as the multi-frequency shared MSA having a two-layer structure with a single layer structure.
Therefore, the present invention can freely set the number of modes and the resonance frequency, can be reduced in thickness and size, can be easily manufactured, and can provide a highly accurate multi-frequency shared MSA.

  This multi-frequency shared MSA can be used, for example, as a 3-frequency shared multi-band antenna for cellular telephones that receives GSM, DCS, and PCS systems, and for wireless LAN (5.0 GHz band) and VICS (2. Application as a multiband antenna (4 GHz band) can be assumed. Moreover, it can also be used as an antenna that can handle any frequency band.

  The present invention can be widely used as a multi-frequency antenna in various fields including mobile communication, and can be widely used as an antenna that can handle any frequency band in existing fields where antennas are used. Can do.

The figure which shows the structure of multifrequency shared MSA which concerns on the 1st Embodiment of this invention. The figure which shows the electric current path | route formed in multifrequency shared MSA of FIG. The figure which shows the return loss characteristic of the multi-frequency common use MSA of FIG. The figure which shows the radiation pattern of multi-frequency common use MSA of FIG. The figure which shows the gain characteristic of multi-frequency common use MSA of FIG. The figure which shows the structure of multifrequency shared MSA which concerns on the 2nd Embodiment of this invention. The figure which shows the electric current path formed in multifrequency common use MSA of FIG. The figure which shows the change of the resonant frequency when the position of an inverted V-shaped slit is changed in the multi-frequency shared MSA of FIG. The figure which shows the structure of multifrequency shared MSA which concerns on the 3rd Embodiment of this invention. The figure which shows the electric current path formed in multifrequency shared MSA of FIG. The figure which shows the return loss characteristic of the multi-frequency common use MSA of FIG. The figure which shows the radiation pattern of 1st mode-4th mode in multi-frequency shared MSA of FIG. The figure which shows the radiation pattern of 5th mode-7th mode in the multi-frequency common use MSA of FIG. The figure which shows the structure of the conventional multi-frequency common use MSA The figure which shows the current pathway formed in the conventional multi-frequency common use MSA The figure which shows the return loss characteristic of the conventional multi-frequency common use MSA

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 1st insulated substrate 22 Radiating element 23 2nd insulated substrate 24 L probe 25 Ground conductor 26 Coaxial connector 31 Reverse V-shaped slit 32 Reverse V-shaped slit 33 Reverse V-shaped slit 41 Insulating substrate 42 Radiating element 43 Power feeding Stub 45 Ground conductor 46 Coaxial connector 51 Reverse V-shaped slit 52 Reverse V-shaped slit 53 Reverse V-shaped slit 54 Reverse V-shaped slit 55 Reverse V-shaped slit 56 Reverse V-shaped slit

Claims (2)

A planar radiating element having a diamond-shaped outer shape;
A feeding point located on an extension of a diagonal line connecting the first acute angle and the second acute angle of the rhombus and located in the vicinity of the first acute angle;
A stub that is on the same plane as the radiating element and extends in a V shape in parallel with two sides sandwiching the first acute angle of the rhombus with the position of the feeding point as a base point, the radiating element comprising: A multi-frequency shared microstrip antenna having one or a plurality of V-shaped V-shaped slits having a base point on the diagonal line and opened on the first acute angle side.   2. The multi-frequency microstrip antenna according to claim 1, wherein each side of the V-shaped slit is parallel to two sides sandwiching the second acute angle of the rhombus. antenna.