JP2007006246A - Microstrip antenna sharing many frequencies - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microstrip antenna (MSA) sharing many frequencies, which is capable of sharing a large number of frequencies and arbitrarily setting the frequencies. <P>SOLUTION: The MSA includes a planar radiating element 22 having a rhombic external shape, and an L probe 24 which is placed in the vicinity of one end part of a diagonal line connecting acute angles of this rhombus and supplies power by electromagnetic coupling with the radiating element 22. The radiating element 22 is provided with one or more V-shaped slits 31, 32, 33 opened toward the L probe. In the MSA, a plurality of current paths having different resonance frequencies are formed from the V-shaped slits 31, 32, and 33 to show multiple frequency sharing characteristics. The MSA sharing many frequencies is capable of sharing a large number of frequencies and arbitrarily setting the frequencies. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microstrip antenna (hereinafter abbreviated as “MSA”) having multi-frequency shared characteristics that operates at a plurality of frequencies, and in particular, allows a large number of operating frequencies to be freely set.

  The MSA is an antenna that generates a magnetic current at the end of the radiation conductor by an electric field between the radiation conductor and the ground conductor (GND), and radiates radio waves using the magnetic current as a wave source. Conventionally, MSA has been used in many fields including mobile communication because it is small, lightweight, and can be configured to be thin. In addition, MSA elements are stacked two times and have dual frequency shared characteristics, An antenna with three-frequency sharing characteristics is made by overlapping three layers.

Non-Patent Document 1 below describes a multi-frequency shared MSA having a single layer structure. As shown in FIG. 15A, this antenna is formed on the same plane as the MSA radiating element 12 formed on the insulating substrate 11, the ground conductor 13 provided on the back surface of the insulating substrate 11, and the ground conductor 13. The radiating element 12 is fed from the feed line 14 by an electromagnetic coupling type feed method.
The ground conductor 13 has a size of 60 × 60 mm. Further, as shown in FIG. 15B, the radiating element 12 has two slits 15 and 16 in which a part of the quadrangle is opened inside a 22 × 22 mm (area 480 mm ² ) square. The two ring-shaped element portions 17 and 18 partitioned by the slits 15 and 16 and the central MSA element portion 19 function as an antenna.

FIG. 16 shows the return loss characteristic of the multi-frequency shared MSA, and shows the three-frequency shared characteristic having resonance points at the frequencies f _L , f _M and f _H. In the figure, a solid line indicates an actual measurement value, and a dotted line indicates a simulation value.
FIG. 17 shows radiation patterns on the E plane and the H plane at the resonance frequencies of f _L , f _M, and f _H. In the figure, the solid line indicates the actual measurement value, the dotted line indicates the simulation value, and the alternate long and short dash line indicates the cross polarization level.
Cross polarization needs to be suppressed in order to avoid interference, but it is considered that there is no practical problem if it is −20 dB or less. In this three-frequency shared MSA, the cross polarization level in the boresight direction at each resonance frequency shows a value of −20 dB or less.
Suzuki, Haneishi "Folded slot loaded frequency sharing microstrip antenna" IEICE Transactions B, Vol. J85-B, no. 2, pp. 207-215, February 2002

  However, in this multi-frequency shared MSA, if the area of the radiating element is not changed, sharing of three frequencies is the limit, and if the number of sharing is further increased, the radiation pattern deteriorates such that the cross polarization level exceeds −20 dB. Accompanied by.

  The present invention was devised to improve such a situation, and it is intended to provide a multi-frequency shared MSA that can share a large number of frequencies and can arbitrarily set the frequencies. It is aimed.

The multi-frequency shared MSA according to the present invention includes a planar radiating element having a rhombus-shaped outer shape and an L probe that is located near one end of a diagonal line connecting the acute angles of the rhombus and that feeds power by electromagnetic coupling with the radiating element. The radiating element includes one or more V-shaped V-shaped slits opened on the L probe side.
In this MSA, a plurality of current paths having different resonance frequencies are formed by the V-shaped slit, and multi-frequency shared characteristics are exhibited.

In the multi-frequency shared MSA according to the present invention, each side of the V-shaped slit is parallel to two sides of the rhombus connected to the other end of the diagonal line.
Therefore, by providing a plurality of V-shaped slits, a plurality of similar rhombus-shaped current paths appear.

In the multi-frequency shared MSA of the present invention, the width of the V-shaped slit is the widest at the bottom of the V shape and the narrowest at both ends of the V shape.
The resonance frequency can be changed by changing the width at the bottom of the V-shape.

Further, in the multi-frequency shared MSA of the present invention, the interval between the V-shaped slit and the other V-shaped slit is not uniform, and the interval closer to the outer periphery of the rhombus is compared with the interval located inside the rhombus from the interval. It is set to be wide or equal.
By doing so, it is possible to provide excellent multi-frequency sharing characteristics.

In the multi-frequency shared MSA of the present invention, the distance between the V-shaped slit and the other V-shaped slit is set to be uniform.
By doing so, many V-shaped slits can be provided inside the rhombus, and the number of shared frequencies can be increased.

In the multi-frequency shared MSA of the present invention, the L probe is configured to have a T-shaped conductor.
By this L probe, a signal in a wide frequency range is fed to the radiating element, and multi-frequency sharing becomes possible.

  The multi-frequency shared MSA of the present invention can share a large number of frequencies and can arbitrarily set the frequencies.

FIG. 1 shows the configuration of a multi-frequency shared MSA in an embodiment of the present invention. 1A is a perspective view, and FIG. 1B is a cross-sectional view. FIG. 1 (c) is an enlarged view of the L probe, and magnetic field 1 (d) is an enlarged view of the radiating element.
This multi-frequency shared MSA includes a radiation element 22 formed of a rhombus metal conductor layer formed on a first insulating substrate 21 and a power feeding unit formed of a T-shaped metal conductor layer formed on a second insulating substrate 23. 24, 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.

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 supply substrate constituting the L probe 24 and is laminated with the first insulating substrate 21 serving as the antenna portion substrate and the L probe 24 interposed therebetween. ing.

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 rhombus is disposed at one acute angle position via the first insulating substrate 21.
The radiating element 22 has three V-shaped slits (31, 32, 33) formed of slits parallel to the two sides of the rhombus, and each V-shape opens to 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 the four current paths shown in FIGS. 2A, 2B, 2C, and 2D in the radiation element 22, and when power is supplied from the L probe 24 In addition, a resonance phenomenon due to each current path appears. In FIG. 2, the current distribution of each current path obtained by the electromagnetic field simulator (electromagnetic field simulator (IE3D) using the moment method) is schematically shown by arrows. As shown in FIGS. 2 (a), (b), (c), and (d), each current path passes through the side of the rhombus and is uniformly directed from the acute angle of the rhombus where the L probe 24 is located to the other acute angle. A distribution appears. Further, as shown in FIG. 2E, a current distribution in which the direction of the current is reversed also appears in a higher-order mode described later.

Here, the phenomenon based on the current distribution of FIG. 2A of the longest current path is “1st mode”, and the phenomenon based on the current distribution of FIG. 2B of the second longest current path is “2nd mode”. The phenomenon based on the current distribution of FIG. 2C of the second longest current path is referred to as “3rd mode”, and the phenomenon based on the current distribution of FIG. 2D of the shortest current path is referred to as “4th mode”.
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, h0 = 6.87, a = 13.74, w1 = w2 = 0.4, w3 = 3.2, w4 = 0.4, w5 = 1.2, w6 = 0.4, d = 0.4, Pl = 3.8, Pw = 1.5, P2 = 3.0, Ps = 0.0, Pd = 0.8, Pt = 0.8, Pf = 0.75, D = 0.50, t1 = t2 = 1.2, Wx = Wy = 60

The first and second insulating substrates 21 and 23 are Teflon (registered trademark) glass fiber substrates (PTFE substrates, relative dielectric constant εr = 2.6, tan δ = 1.8 × 10 ⁻³ ). The printed circuit board with the copper thin film deposited on this substrate was etched to form a radiation element 22 having an area of 163.5 mm ² and a T-shaped L probe 24.

3A shows the value of return loss on the vertical axis and the frequency on the horizontal axis, and FIG. 3B shows the frequency on the horizontal axis at the resonance frequency (3.89 GHz) of the first mode which will be described later. The normalized value is taken to show the return loss characteristic. In the figure, a solid line indicates an actual measurement value, and a dotted line indicates a simulation value.
In FIG. 3A, the resonance phenomenon observed at 3.89 GHz corresponds to the current distribution in the 1st mode. The resonance phenomena at 4.63 GHz, 6.99 GHz, and 9.75 GHz correspond to current distributions of the 2nd mode, the 3rd mode, and the 4th mode, respectively. As is apparent from FIG. 2, as the mode order increases, the path length of the current path corresponding to each mode is shortened, and as shown in FIG. 3, the resonance frequency of each mode increases. Yes.

In this multi-frequency shared MSA, as the mode order increases, the resonance frequency gradually shifts to the high frequency side, thereby realizing multiband characteristics. In addition, as can be seen from FIG. 3, the actual measurement value of the return loss characteristic agrees well with the simulation value within a design-significant range.
Note that the resonance phenomenon seen in (e-1) and (e-2) in FIG. 3 corresponds to the first and second higher order modes of the 1st mode. FIG. 2E shows the current distribution of the second higher-order mode that exhibits a particularly strong resonance phenomenon among these higher-order modes. The resonance frequencies of these higher-order modes may be excluded from the usage targets of the multi-frequency shared MSA.

FIG. 4 shows radiation patterns in the 1st mode, 2nd mode, 3rd mode and 4th mode of this multi-frequency shared MSA in (a), (b), (c) and (d). The radiation pattern corresponding to the higher order mode is shown in (e-2). In the figure, the solid line indicates the characteristics of the E plane (outer line) and the H plane (inner line), and the dotted line indicates the cross polarization level. As is clear from the figure, the radiation patterns in the 1st mode, 2nd mode, 3rd mode, and 4th mode show good unidirectional patterns on both the E plane and the H plane, and the cross polarization component is -22 dB or less at the worst value. It is suppressed until.
FIG. 5 shows gain simulation values in each mode. As in FIG. 3B, the horizontal axis of this figure represents a value obtained by normalizing the frequency at 3.89 GHz, and the vertical axis represents the gain. A gain of 4.0 dBi or more is obtained in all of the 1st mode, 2nd mode, 3rd mode, and 4th mode.

As described above, the multi-frequency shared MSA can hold more resonance frequencies even though the area of the radiating element 22 is the same as that of the radiating element 12 in FIG. The radiation pattern is superior to the MSA of FIG.
In this multi-frequency MSA, the radiating element 22 is formed in a diamond shape, and a plurality of modes of current paths are formed by the plurality of inverted V-shaped slits 31, 32, 33. Therefore, the current path in each mode has a similar shape with the position of the L probe 24 as one vertex. In the diamond-shaped radiating element 22, the diagonal line between the apexes forming an acute angle is long.
For this reason, the tip of the current path in each mode (position on the current path farthest from the L probe position) can be spaced at a position where no mutual interference occurs, which is the number of shared frequencies. In addition, it is considered that the superiority in the radiation pattern is hesitant.
Further, the L probe 24 formed in a T-shape of the multi-frequency shared MSA supplies a power supply signal that covers the entire range to the current path of each mode in which the resonance frequency extends over a wide range. Contributes to the realization of excellent multi-frequency characteristics.

Next, a basic method for controlling the resonance frequency of the multi-frequency shared MSA will be described.
There are two ways to do this. The first method is a method of changing the resonance frequency by moving the position of the inverted V-shaped slit. As shown in FIG. 6, the inverted V-shaped slit at the position of FIG. ) Position. At this time, the current path length of the 2nd mode formed along the inverted V-shaped slit changes, and accordingly, the resonance frequency of the 2nd mode changes.
FIG. 7 is a graph showing the change in resonance frequency accompanying the movement of the inverted V-shaped slit. The horizontal axis of this figure represents w1 / a where a is the length of one side of the diamond of the radiating element and w1 is the moving distance of the inverted V-shaped slit, and the vertical axis is the resonance frequency of the 1st mode. The resonance frequency normalized by 3.89 GHz is shown. The various dimensions of the MSA in this case are the same as those in FIG. 3 except for the position of the inverted V-shaped slit.
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 approximately tripled while maintaining the resonance frequency (solid line) of the 1st mode at a substantially constant value. Can vary up to.

The second method for controlling the resonance frequency is a method of changing the resonance frequency by expanding the shape of the inverted V-shaped slit of FIG. 6A as shown in FIG. 6C, and in this case also the 2nd mode. Therefore, the resonance frequency of the 2nd mode changes accordingly.
FIG. 8 is a graph showing changes in the resonance frequency in this case. The horizontal axis of this figure represents h2 / h1 where h1 is the diagonal line between acute angles in the rhombus of the radiating element, and h2 is the distance from the apex of the triangle formed by the inverted V-shaped slit to the center of the rhombus. The vertical axis represents the resonance frequency normalized at 3.89 GHz which is the resonance frequency of the 1st mode. The various dimensions of the MSA in this case are the same as in FIG. 3 except for the position and shape of the inverted V-shaped slit.
As is apparent from this figure, by changing the shape of the inverted V-shaped slit, the 2nd mode resonance frequency (dotted line) is approximately doubled while maintaining the 1st mode resonance frequency (solid line) at a substantially constant value. Can change up to.

FIG. 9 shows the radiation pattern when the shape of the inverted V-shaped slit is changed by the second method, where h2 is 11.45, 8.0, 5.0, 2.0 and 0.0 (units). ; Mm) in each case. Looking at this, even if the value of h2 is significantly changed (0 to 11.45 mm) and the resonance frequency of the 2nd mode is controlled from 5.35 GHz to 7.90 GHz, the radiation pattern has a cross polarization component. It is clear that the main polarization component shows a unidirectional pattern although it is slightly degraded.
6, 7, and 8 show a case where there is one inverted V-shaped slit, these methods are applied to each inverted V-shaped slit even when there are a plurality of inverted V-shaped slits. To control the resonance frequency of each mode.

Next, the arrangement of many inverted V-shaped slits on the radiating element will be described.
When a certain number of inverted V-shaped slits are arranged on the diamond-shaped radiating element, as shown in FIG. 10A, the interval between the outer inverted V-shaped slits is set between the inner inverted V-shaped slits. A better multiband characteristic can be obtained when the interval is larger than the interval. Here, such an arrangement of the inverted V-shaped slits at unequal intervals is referred to as “A type”.
FIG. 10A shows a shape when seven inverted V-shaped slits are arranged in the A type on a radiating element whose h1 is 23.8 mm. This slit interval (w1, w3, w5, w7, w9, w11, w13) and the distance between the end of each inverted V-shaped slit and the element end (w2, w4, w6, w8, w12, w14) Are determined by simulation so that good multiband characteristics (FIGS. 11 and 12) can be obtained, and their values are as follows.
w1 = w2 = 0.4, w3 = 1.2, w4 = 0.4, w5 = 0.8, w6-w14 = 0.4
The MSA in this case is the same as that in FIG. 3 except that Pl of the L probe is set to 5.0 and Pt is set to 2.0.

FIG. 11 shows the current distribution and the radiation pattern in each mode from the 1st mode to the 8th mode of this type A radiating element, and FIG. 12 shows the return loss characteristic of this antenna.
The current path length of each current corresponding to the 1st mode to the 8th mode becomes shorter as the order of the mode increases, and the resonance frequency corresponding to each current distribution shifts to the high frequency region. In addition, the actually measured value of the return loss characteristic shows a good agreement with the simulation value within a design-significant range.
Looking at the radiation pattern corresponding to each mode, a unidirectional pattern is obtained on both the E and H planes from the 1st mode to the 7th mode. Note that the asymmetry of the radiation pattern seen in the 8th mode is considered to be due to the influence of the higher order mode.
Thus, it is clear that this multi-frequency shared MSA has good multiband characteristics.

Further, when more inverted V-shaped slits are arranged on the diamond-shaped radiating element, the inverted V-shaped slits are arranged at equal intervals as shown in FIG. Here, such an arrangement of the inverted V-shaped slits at equal intervals is referred to as “B type”.
FIG. 10B shows a shape when nine inverted V-shaped slits are arranged in a B type on a radiating element having h1 of 23.8 mm. This slit interval (w1, w3, w5, w7, w9, w11, w13, w15, w17) and the distance (w2, w4, w6, w8, w12, w14, w16, and w18) are determined by simulation so that good multiband characteristics (FIG. 13) can be obtained, and their values are as follows.
w1-w18 = 0.4
Note that the MSA settings in this case are all the same as in FIG.

FIG. 13 shows the return loss characteristics of the multi-frequency shared MSA in which this B type inverted V-shaped slit is arranged. As is clear from this figure, good multiband characteristics are obtained, and the simulation values are in good agreement with the actual measurement values within a design-significant range.
FIG. 14 shows a radiation pattern of the multi-frequency shared MSA in which the B type inverted V-shaped slits are arranged. The radiation pattern of each mode from the 1st mode to the 10th mode shows a unidirectional pattern on both the E plane and the H plane.

From these, it is clear that the multi-frequency shared MSA of the present invention can be a useful form as a multiband antenna having a planar structure.
This multi-frequency shared MSA is used, for example, as a 3-frequency shared multi-band antenna for cellular phones that receive GSM, DCS and PCS systems, and for wireless LAN (5.0 GHz band) and VICS (2.4 GHz band). ) As a multiband antenna can be assumed. Moreover, it can also be used as an antenna that can handle any frequency band.

  Here, the case where a Teflon (registered trademark) glass fiber substrate is used as the substrate and the copper thin film formed on the substrate is etched to form the radiation element 22 and the L probe 24 has been described. However, it is not limited to this. For example, a conductive pattern such as a radiating element or a T-shaped probe may be printed on a ceramic green sheet with a metallized paste containing metal powder, and then stacked and fired. good.

  INDUSTRIAL APPLICABILITY 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 capable of dealing with any frequency band in existing fields where antennas are used. be able to.

The figure which shows the structure of multi-frequency shared MSA in embodiment of this invention. The figure which shows the current distribution of multi-frequency common use MSA in embodiment of this invention The figure which shows the return loss characteristic of the multi-frequency common use MSA in embodiment of this invention The figure which shows the radiation pattern of multifrequency shared MSA in embodiment of this invention The figure which shows the gain characteristic of multi-frequency shared MSA in embodiment of this invention The figure which shows the control method of the resonant frequency of multi-frequency shared MSA in embodiment of this invention The figure which shows the change of the resonant frequency when the position of the inverted V-shaped slit of multi-frequency shared MSA in the embodiment of the present invention is changed. The figure which shows the change of the resonant frequency when the shape of the inverted V-shaped slit of multi-frequency common use MSA in embodiment of this invention is changed. The figure which shows the radiation pattern when changing the shape of the reverse V-shaped slit of multi-frequency common use MSA in embodiment of this invention. The figure which shows the arrangement | positioning shape of the inverted V-shaped slit of multi-frequency shared MSA in embodiment of this invention. The figure which shows the electric current distribution and radiation pattern when the inverted V-shaped slit of multi-frequency common use MSA in embodiment of this invention is arrange | positioned by A type. The figure which shows the return loss characteristic when the inverted V-shaped slit of multi-frequency common use MSA in the embodiment of the present invention is arranged by A type. The figure which shows the return loss characteristic when the inverted V-shaped slit of multi-frequency common use MSA in the embodiment of the present invention is arranged by B type. The figure which shows a radiation pattern when the reverse V-shaped slit of multi-frequency common use MSA in embodiment of this invention is arrange | positioned by B type. The figure which shows the structure of the conventional multi-frequency common use MSA The figure which shows the return loss characteristic of the conventional multi-frequency common use MSA The figure which shows the radiation pattern of the conventional multi-frequency common use MSA

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Insulation board | substrate 12 Radiation element 13 Ground conductor 14 Feed line 15 Slit 16 Slit 17 Ring-shaped element part 18 Ring-shaped element part 19 MSA element part 21 1st insulation board 22 Radiation element 23 2nd insulation board 24 L probe 25 Ground Conductor 26 Coaxial connector 31 Inverted V-shaped slit 32 Inverted V-shaped slit 33 Inverted V-shaped slit

Claims (6)

A planar radiating element having a diamond-shaped outer shape;
A V-shaped V that is located near one end of a diagonal line connecting the acute angles of the rhombus, and that has an L probe that feeds power by electromagnetic coupling, and the radiating element opens to the L probe side. A multi-frequency shared microstrip antenna comprising one or more mold slits.   2. The multi-frequency microstrip antenna according to claim 1, wherein each side of the V-shaped slit is parallel to two sides of the rhombus connected to the other end of the diagonal line. Frequency shared microstrip antenna.   2. The multi-frequency shared microstrip antenna according to claim 1, wherein the width of the V-shaped slit is widest at the bottom of the V shape and narrowest at both ends of the V shape. .   4. The multi-frequency shared microstrip antenna according to claim 1, wherein a distance between the V-shaped slit and another V-shaped slit is non-uniform, and the distance close to the outer periphery of the rhombus is The multi-frequency shared microstrip antenna, which is wider than or equal to the interval located inside the rhombus than the interval.   4. The multi-frequency shared microstrip antenna according to claim 1, wherein a distance between the V-shaped slit and another V-shaped slit is uniform. 5. The multi-frequency shared microstrip antenna according to any one of claims 1 to 5, wherein the L probe includes a T-shaped conductor.