JP2000188511A - Microstrip antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relieve an effect of a feeding pattern onto a transmission reception characteristic. SOLUTION: Relating to the microstrip antenna where one side of a dielectric base 1 has plural antenna elements 2 and nearly the entire face of the other side has a ground pattern 3, a feeding pattern 4 connecting the antenna elements 2 and a feeder 5 is placed on the side opposite to the side on which the antenna elements 2 are placed. Since the feeding pattern 4 does not act like a component of the microstrip line acting like the microstrip antenna, the effect of the feeding pattern 4 on the transmission reception characteristic of the entire antenna can be prevented. Furthermore, power is transmitted through a coplanar line consisting of the feeding pattern 4 and the ground pattern 3 on the same plane as the feeding pattern 4 between the antenna elements 2 and the feeder 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microstrip antenna, and more particularly to a microstrip antenna provided with a plurality of antenna element plates (in a so-called array) for improving transmission / reception characteristics.

[0002]

2. Description of the Related Art As a microstrip antenna as described above, there is a conventional one as shown in FIG. As shown in the drawing, this antenna has a rectangular antenna element plate (patch) having a conductor plate structure on one surface of a dielectric substrate 1 (an upper surface in the drawing: this surface is hereinafter referred to as a surface). 2), for example, 4 in 2 rows and 2 columns.
And a ground plate 3 having a conductor plate structure is provided on substantially the entire surface of the other surface (that is, the back surface).

Each of the antenna element plates 2, 2,... Is provided on the surface of the dielectric substrate 1 via a power supply pattern 4 having a conductor pattern, for example, an internal conductor 5a of a feed line 5 having a coaxial cable configuration. Connected to. Although not shown in the figure, the outer conductor of the power supply line 5 is connected to the ground plate 3.

According to this configuration, the power supply pattern 4
As shown in FIG. 1B, the microstrip line 1 is formed by a ground plate 3 facing the dielectric substrate 1 therebetween.
0 is formed. (Strictly speaking, the dielectric substrate 1 is sandwiched between the antenna element plates 2, 2,... And the ground plate 3 via this microstrip line. Power transmission is performed between the (four microstrip antennas) configured and the feed line 4.

That is, when this antenna functions as a transmission antenna, when high-frequency power for transmission is input to this antenna from a transmitter (not shown) via a feed line 5, the high-frequency power is transmitted to the microstrip line 10. Are supplied to the respective antenna element plates 2, 2,..., Whereby radio waves are radiated from the surfaces of the respective antenna element plates 2, 2,. On the other hand, when this antenna functions as a receiving antenna, each antenna element plate 2, 2,.
Receives a radio wave transmitted from a transmitter (not shown), which is a communication partner, and converts this into high-frequency power. The high-frequency power is transmitted to the power supply line 5 via the microstrip line 10 and is input to a receiver (not shown) via the power supply line 5.

In the antenna shown in FIG. 1A, a stub (matching element) having the same conductor pattern as the power supply pattern 4 is provided at a connection point between the internal conductor 5a of the power supply line 5 and the power supply pattern 4. 11 are provided. The stub 11 realizes impedance matching between the input impedance of the entire antenna and the characteristic impedance of the feed line 5.

[0007]

However, according to the prior art, since the microstrip line 10 itself also functions as a microstrip antenna, each of the antenna element plates 2, 2,. Similarly, the microstrip line 10 emits or receives radio waves. Therefore, the action of radiating or receiving radio waves by the microstrip line 10 affects the action of radiating or receiving radio waves by each antenna element plate 2, 2,. There is a problem that is disturbed. In this,
The meaning of providing a plurality of antenna element plates 2, 2,... In order to improve transmission / reception characteristics is reduced by half.

In addition, in the above-mentioned prior art, since the stub 100 is provided on the dielectric substrate 1, there is a problem that the area of the dielectric substrate 1 is correspondingly increased and the antenna itself is enlarged. This is very disadvantageous when the antenna itself is required to be reduced in size, or when the size of a wireless device with a built-in antenna is reduced.

Therefore, the present invention can reduce the influence of the so-called power transmission line such as the microstrip 100 on the transmission / reception characteristics, and can realize the impedance matching with the power supply line 5 without adding the stub 11 or the like. It is an object to provide a microstrip antenna.

[0010]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 of the present invention provides a dielectric substrate and an antenna attached to one surface of the dielectric substrate. An element plate, a ground plate stuck on the other surface of the dielectric substrate, and the antenna stuck on the other surface of the dielectric substrate common to the surface on which the ground plate is stuck. A power supply pattern for connecting the element plate to an external power supply line.

The microstrip antenna according to the first aspect of the present invention can be constituted by, for example, a printed circuit board. In this case, for example, through holes can be used to connect the antenna element plate on one surface of the dielectric substrate and the power supply pattern on the other surface of the dielectric substrate.

According to the first aspect of the present invention, the power supply pattern for connecting the antenna element plate and the power supply line is connected to the other surface of the dielectric substrate, that is, the surface on which the antenna element plate is provided. It is provided on the opposite side. The power supply pattern and a ground plane provided on the same plane (that is, the other surface of the dielectric substrate) form a generally known coplanar line (hereinafter referred to as a coplanar line). This coplanar line causes the antenna element plate (strictly, a microstrip antenna having a configuration in which a dielectric substrate is sandwiched between the antenna element plate and the ground plate) and a feed line to transmit electric power. Perform transmission.

According to a second aspect of the present invention, in the microstrip antenna according to the first aspect of the present invention, a connection point between the power supply pattern and the power supply line is connected to the antenna element plate side via the power supply pattern. , That is, the input impedance of the entire antenna is substantially equivalent to the characteristic impedance of the feed line, and the impedance when the antenna element plate side is viewed from the connection point between the antenna element plate and the feed pattern, that is, The input impedance of the antenna element plate itself and the characteristic impedance of the coplanar line are set.

The input impedance of the antenna element plate can be varied depending on the external dimensions of the antenna element plate itself, the connection position between the antenna element plate and the power supply pattern, and the like. Further, the characteristic impedance of the coplanar line can be changed by the width of the power supply pattern itself constituting the coplanar line, the distance between the power supply pattern and the ground plate, and the like.

According to the second aspect of the present invention, the outer dimensions of the antenna element plate itself, the connection position between the antenna element plate and the power supply pattern, the width of the power supply pattern itself, and the width of the power supply pattern. By adjusting the distance from the ground plate and the like, the input impedance of the entire antenna and the characteristic impedance of the feed line can be made substantially equivalent, that is, impedance matching between the two can be realized.

According to a third aspect of the present invention, in the microstrip antenna according to the first aspect of the present invention, a plurality of the antenna element plates and the plurality of power supply patterns connected thereto are provided, and each of the power supply patterns is provided. Each is connected to the power supply line at one common point.

That is, according to the present invention, a plurality of antenna element plates are arrayed, and each power supply pattern connected to each of the antenna element plates is connected at one point, and a feeder line is connected to this connection point. Are connected.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a microstrip antenna according to the present invention will be described with reference to FIGS.

FIGS. 1A and 1B are diagrams showing a schematic configuration of an antenna according to the present embodiment. FIG. 1A is a perspective view of the antenna according to the present embodiment viewed obliquely from above (closer to the oblique surface), and FIG. , A perspective view as viewed from obliquely below (toward the oblique back surface), and (c) is an enlarged end view of a coplanar line 6 described later. As shown in the drawing, the antenna of the present embodiment also has four rectangular antenna element plates 2, 2 on the surface of a dielectric substrate 1, similarly to the conventional antenna shown in FIG.
Are arranged in two rows and two columns, and the grounding plate 3
Is provided.

However, in the present embodiment, the dielectric substrate 1
An X-shaped groove 3a is formed substantially at the center of the ground plate 3 provided on the back surface of the power supply pattern 3, and a power supply pattern 4 is formed inside the groove 3a. This is a point greatly different from the above-described conventional technology, and is the greatest feature of the present embodiment. Note that the antenna of the present embodiment is also formed by a printed circuit board. Specifically, as the dielectric substrate 1, for example, when the thickness t is t = 1.
By using a 6 mm glass epoxy resin substrate and processing a thin copper plate having a thickness of about 35 μm adhered to both surfaces thereof by photoetching or the like, the antenna element plate 2
.. And the groove 3a of the ground plate 3 and the power supply pattern 4
To form Details of each of these patterns are shown in FIG.

As shown in FIG. 1, a dielectric substrate 1 is a square substrate, and a square antenna element plate 2 having a side length a is provided slightly inward of each corner of the dielectric substrate 1. 2,
Are formed at intervals b in the direction along each side of the dielectric substrate 1. The side length a of each of the antenna element plates 2, 2,... Is determined by the radio frequency f used by the antenna of the present embodiment. Also, the distance b between the antenna element plates 2, 2,... Is determined by a balance with the electrical length c of the coplanar line 6, which will be described later.

Each of the antenna element plates 2, 2,... Is one side edge in the same direction (upper side edge in the figure).
Is connected to the ground plate 3 on the back surface side of the dielectric substrate 1 via three through holes 21, 21, 21, and is so-called grounded on one side. The through-holes 21, 21, 2 of the antenna element plates 2, 2,.
The through holes 2 are formed at right angles to one side edge provided with the first substrate 1 and at a predetermined distance d from the one side edge on the side edge located inside the dielectric substrate 1.
The through holes 22 different from 1, 21 and 21 are provided one by one. Each of these through holes 22, 22,.
Are connected to the tips of the branches of the X-shaped power supply pattern 4 on the back surface of the dielectric substrate 1, respectively.

The power supply pattern 4 is formed in parallel with the inside edge of the groove 3a of the ground plate 3 and at a predetermined interval e from the inside edge of the groove 3a. At the approximate center (intersection of each branch) of the X-shaped power supply pattern 4, FIG.
As shown in (b), for example, the inner conductor 5a of the power supply line 5 having a coaxial cable configuration is connected. Although not shown in the figure, the outer conductor of the feeder line 5 is connected to an arbitrary position on the ground plate 3.

According to this configuration, each antenna element plate 2,
, Are each one end (through hole 2)
A so-called inverted-F antenna having a configuration in which one side edge provided with 1, 21, and 21) is grounded and a feeding point is provided in the middle thereof (the position of the through hole 22). Here, the direction of each of the antenna element plates 2, 2,... (The direction of grounding on one side by the through holes 21, 21, 21) of the inverted F antenna configuration is unified, so that each of these antenna element plates is 2, 2, ... (strictly, each antenna element plate 2,
2,... And the ground plate 3 sandwich the dielectric substrate 1), each of which functions as an antenna for vertical or horizontal polarization. And
The power supply pattern 4 and the ground plate 3 provided on the same plane (that is, the back surface of the dielectric substrate 1) with the groove 3a interposed between the antenna element plates 2, 2,. 5 and the above-mentioned coplanar line 6 for transmitting power.

That is, when the antenna according to the present embodiment functions as a transmitting antenna, when high-frequency power for transmission is input from a transmitter (not shown) to the antenna via the feeder line 5, the high-frequency power is transmitted to the coplanar line. Are supplied to the respective antenna element plates 2, 2,. Thus, each of the antenna element plates 2, 2,... Radiates radio waves from their respective surfaces. On the other hand, when the antenna of the present embodiment functions as a receiving antenna, each antenna element plate 2, 2,... Receives a radio wave transmitted from a transmitter (not shown), which is a communication partner, and To high frequency power. The high-frequency power is transmitted to the power supply line 5 via the coplanar line 6 and is input to a receiver (not shown) via the power supply line 5.

As described above, according to the present embodiment, the feeding pattern 4 for connecting each antenna element plate 2,. , 2,... Are provided on the back side opposite to the front side. Therefore, since the power supply pattern 4 does not constitute the microstrip line 10 acting as a microstrip antenna as in the above-described related art, it is possible to prevent the transmission and reception characteristics of the entire antenna from being disturbed due to this.

The microstrip line 10
The coplanar line 6 as a power transmission line instead of
Each of the antenna element plates 2, 2,.
And formed on the opposite side. Therefore, this coplanar line 6
However, even if a small amount of radio waves are transmitted or received, the effect of this on the transmission / reception characteristics of the entire antenna can be reduced.
Therefore, the transmission and reception characteristics of the entire antenna are improved as compared with the above-described conventional technology, and the object of arraying a plurality of antenna element plates 2, 2,... In order to improve the transmission and reception characteristics can be achieved.

Further, the power supply pattern 4 has a configuration in which the periphery thereof is guarded by the ground plate 3. Therefore,
The effect of shielding the power supply pattern 4 by the ground plate 3 can also be expected.

In the present embodiment, impedance matching with the feeder line 5 can be realized without providing a matching circuit such as the stub 11 in the above-described conventional technology. This will be described below.

For example, each of the antenna element plates 2, 2,.
..Input impedance of each unit (ie, each antenna element plate 22 is connected to each through hole 22)
The impedance) Z _i that viewed from the position of, and substantially equivalent to the value and the characteristic impedance Z _X of the feed line 5. The input impedance Z _i of the antenna element plate 2 can be adjusted by, for example, the distance d from one side edge where the through holes 21, 21, 21 for ground are provided to the position of the through hole 22 for feeding. . Each of these impedances Z _i
And the relationship of Z _X, is represented by the Smith chart is generally known, the impedance Z _i and Z _X are both located at the origin O in FIG.

Here, each antenna element of the coplanar line 6
Connection points with sub-plates 2, 2,... (Each through hole for power supply
22, 22, ...) to the connection point with the feeder line 5
(Electric length c up to the center of the power supply pattern 4)
Let c = λ / 4 (each antenna element plate 2,
, And each power supply through hole 22, 2
From the positional relationship of 2,..., Each electric length c is the same.
Is obvious). In this case,
The characteristic impedance at each electrical length c of the ₀When
Then, the input impedance of each antenna element plate 2, 2,.
-Dance Z_iIs a power supply line 5 through a coplanar line 6.
At the connection point with
Impedance Z₁Is converted to

[0032]

## EQU1 ## Z ₁ = Z ₀ ² / Z _i

The converted impedance (that is, the input impedance of each antenna element plate 2, 2,... Viewed individually from the connection point between the coplanar line 6 and the feed line 5 via the coplanar line 6) Z ₁ Is represented by a point P on the real axis having a larger pure resistance value than the origin O in the Smith chart of FIG. Further, each antenna element plate 2, 2,.
Are connected at one point at the connection point with the feeder line 5 via the coplanar line 6, that is, are connected in parallel. Therefore, the combined input impedance Z _L of the entire antenna viewed from the connection point with the feeder line 5 is expressed by the following equation (2).

[0034]

[Number 2] _{Z L = Z 1 / n =} Z 0 2 / (Z i · n) , where, n is the antenna element plate 2,2 is the number of ....

## EQU2 ## Since the antenna element plates 2, 2,... Including the coplanar line 6 are connected in parallel at the connection point with the feeder line 5, the combined input impedance Z _{L of the} entire antenna becomes It is shown that it is close to the origin O in the Smith chart of FIG.

That is, if the characteristic impedance Z ₀ of the coplanar line 6 is set such that the combined input impedance Z _{L of the} entire antenna becomes equivalent to the characteristic impedance Z _X of the feed line 5 (Z _L = Z _X ), The impedance matching between the antenna of the present embodiment and the feeder line 5 can be realized without providing the stub 11 and the like. The characteristic impedance Z ₀ of the coplanar line 6 can be adjusted by the distance e between the power supply pattern 4 and the ground plate 3 constituting the coplanar line 6 and the pattern width g of the power supply pattern 4.

As an example, each antenna element plate 2, 2,.
··· The input impedance Z _i is set to Z _i = 50Ω (by setting the distance d), and the characteristic impedance Z
_Suppose that _X connects the feeder line 5 of Z _X = 50Ω. In this case, the characteristic impedance Z ₀ of the coplanar line 6 for realizing the impedance matching with the feeder line 5 is obtained by the following _equation 3 obtained by modifying the above _equation 2.

[0038]

## EQU3 ## Z ₀ = (Z _X · Z _i · n) ^1/2 = (50 · 50)
・ 4) ^1/2 = 100Ω

That is, from the equation (3), the power supply pattern 4 and
The distance e from the ground plate 3 and the pattern of the power supply pattern 4
Adjust the width g to adjust the characteristic impedance of the coplanar line 6.
Su Z ₀To Z₀= 100Ω, the characteristic impedance
Z_XIs Z_X= Impedance matching with 50Ω feeder line 5
Can be realized.

Up to this point, the above coplanar line 6
Is a case in which the electric length c of c is c = λ / 4 (including the case of an odd multiple thereof). However, in some cases, for example, when the antenna is required to be downsized, the electric length c may be forced to be shorter than λ / 4. In such a case, impedance adjustment with the feeder line 5 cannot be realized only by adjusting the characteristic impedance Z ₀ of the coplanar line 6.

To cope with this, the dimension a of each side of each antenna element plate 2, 2,.
In as indicated by the point P '(a), intentionally to each antenna element plate 2,2, reactance input impedance Z _i of ... (especially the induction (L) reactance) it is sufficient to have the ingredients. In this manner, the antenna element plates 2, 2,... From the connection point with the feeder line 5 via the coplanar line 6
Of the input impedance (i.e., the input impedance Z _{i of} one antenna element plate 2 and the characteristic impedance Z _{0 of the} coplanar line 6 whose electrical length c is less than λ / 4). Impedance) Z
_{As 1} , the impedance on the real axis (pure resistance) as shown by the point Q ′ in FIG. 4B can be obtained. The combined impedance obtained by impedance Z ₁ corresponding to the point Q 'are connected in parallel, i.e. synthetic input impedance Z _L of the antenna as a whole is, as shown in FIG. 4 (c), located at the origin O feed By making the characteristic impedance Z _X equivalent to the characteristic impedance Z _X of the electric wire 5 (Z _L ≒ Z _X ), impedance matching with the power supply line 5 can be realized.

As an example, a radio frequency f ≒ 800 MHz
, The electric length c of the coplanar line 6 is set to λ / 4
Set (approximately 95mm so) short c = 45.6 mm than, this characteristic impedance Z _X = 50 [Omega feeder lines 5
Tried an experiment to connect. In this experiment, the distance e between the power supply pattern 4 and the ground plate 3 constituting the coplanar line 6 was set to e = 0.3 mm, and the pattern width g of the power supply pattern 4 was set to g = 2.0 mm. The characteristic impedance Z of the coplanar line 6 at the electric length c.
₀ was set to Z ≒ 50Ω.

According to this experiment, each antenna element plate 2,
2,... Are set to e = 42 mm, and power is supplied from one side edge of each antenna element plate 2, 2,... Where the ground through holes 21, 21, 21 are provided. The distance d to the position of the through hole 22 is d = 31 mm
As a result, finally, the result that the input impedance Z _{L of the} entire antenna can be set to Z _L ≒ 50Ω substantially equivalent to the characteristic impedance Z _X of the feed line 5 is obtained.

Specifically, under the above conditions, each antenna element plate 2, 2,.
The input impedance Z _{i of a} single unit was measured at the position of the through hole 22. This measurement each antenna element plate 2,2, input impedance Z _i of ... simple substance, in FIG 4 (a), located in a point P of the phase theta of the real axis shifted by theta = 101 degrees I was able to confirm that. Then, at the connection point between Kopurenarain 6 the feed line 5, the antenna element plate 2, 2 including Kopurenarain 6 were measured respective impedances Z ₁ · · ·. Then, it was confirmed that the impedance Z ₁ became a pure resistance of Z ₁ ≒ 200Ω, that is, it was located at the point Q ′ on the real axis in FIG. 4B. Then, by measurement of the antenna overall impedance Z _L of the configurations of four parallel-connected impedance Z _L of the pure resistance of the 200 [Omega, Naturally it is a, located at the origin O impedance Z _L is shown in FIG. 4 (c) That is, it was confirmed that Z _L ≒ 50Ω.

As described above, according to the present embodiment, each antenna element plate 2 is determined by the external dimension a of each antenna element plate 2, 2,. , 2, as well as adjust the input impedance Z _i of ..., and spacing e between the power-supply pattern 4 and the ground plate 3,
By arbitrarily adjusting the characteristic impedance Z ₀ of the coplanar line 6 based on the pattern width g of the power supply pattern 4, impedance matching with the power supply line 5 can be realized. Therefore, since it is not necessary to provide the stub 11 and the like described above,
The antenna itself can be downsized accordingly. This is very advantageous when the antenna itself is required to be reduced in size, or when the size of a wireless device with a built-in antenna is reduced.

In this embodiment, the number n of the antenna element plates 2, 2,... Is n = 4, but the invention is not limited to this. Also, the shape and arrangement of each antenna element plate 2, 2,... Are not limited to the present embodiment. Further, each antenna element plate 2, 2,... Is connected to the ground plate 3 through through holes 22, 22,. This is one means for performing the above, and is not limited to this configuration. Further, in the present embodiment, the antenna according to the present invention is constituted by a printed board made of glass epoxy, but the present invention can be realized by other materials.

[0047]

As described above, according to the microstrip antenna of the first aspect of the present invention, the feed pattern for connecting the antenna element plate and the feed line is formed by the antenna element plate of the dielectric substrate. It is provided on the surface opposite to the surface on which it is provided. Therefore, unlike the above-described prior art, since the power supply pattern does not constitute a microstrip line acting as a microstrip antenna, this does not cause disturbance in transmission / reception characteristics of the entire antenna. Further, since the coplanar line constituted by the power supply pattern and the ground plate is arranged on the opposite side to the antenna element plate with the dielectric substrate interposed therebetween, the coplanar line hardly affects the transmission / reception characteristics.
Therefore, there is an effect that transmission / reception characteristics better than before can be obtained.

According to the microstrip antenna of the present invention, the external dimensions of the antenna element plate itself, the connection position between the antenna element plate and the power supply pattern, the width of the power supply pattern itself, the power supply By adjusting the distance between the antenna pattern and the ground plate, impedance matching between the antenna and the feeder can be realized. As described above, since the impedance matching between the antenna and the feeder line can be realized without using the stub 100 or the like in the above-described conventional technology, the antenna itself can be reduced in size accordingly. This is very advantageous when the antenna itself is required to be reduced in size, or when the size of a wireless device with a built-in antenna is reduced.

According to the microstrip antenna of the third aspect of the present invention, even when the antenna element plates are arrayed, similar to the first aspect of the invention, better transmission / reception characteristics can be obtained than in the prior art. . Therefore, there is an effect that the original purpose of arraying a plurality of antenna element plates in order to improve transmission / reception characteristics can be sufficiently achieved.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams illustrating an embodiment of a microstrip antenna according to the present invention, in which FIG. 1A is a perspective view of the microstrip antenna viewed from obliquely above, FIG.
(C) is an end view which expands and shows the part in which the power supply pattern was formed.

FIGS. 2A and 2B are external views of a printed circuit board constituting the embodiment, in which FIG. 2A is a pattern diagram of a front surface, FIG. 2B is a pattern diagram of a back surface, and FIG. It is an enlarged view.

FIG. 3 is a Smith chart showing a state of impedance matching in the embodiment.

FIG. 4 is a Smith chart showing a state of impedance matching under conditions different from those in FIG. 3;

5A and 5B are views showing an example of a conventional microstrip antenna, wherein FIG. 5A is a perspective view of the microstrip antenna viewed obliquely from above,
(B) is an end view which expands and shows the part in which the power supply pattern was formed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 dielectric substrate 2 antenna element plate 3 ground plate 4 power supply pattern 5 power supply line 10 coplanar line (coplanar line)

Claims (3)

[Claims] 1. A dielectric substrate, an antenna element plate attached to one surface of the dielectric substrate, a ground plate attached to the other surface of the dielectric substrate, and the ground plate A microstrip antenna, comprising: a power supply pattern attached to the other surface of the dielectric substrate common to the surface on which the antenna element plate is provided and connecting the antenna element plate to an external power supply line. 2. A state in which the impedance viewed from the connection point between the power supply pattern and the power supply line through the power supply pattern to the antenna element plate side is substantially equivalent to the characteristic impedance of the power supply line, 2. An impedance when the antenna element plate side is viewed from a connection point between the antenna element plate and the power supply pattern, and a characteristic impedance of a transmission line including the power supply pattern and the ground plate are set. A microstrip antenna according to claim 1. 3. The microstrip according to claim 1, wherein a plurality of the antenna element plates and the power supply patterns connected thereto are provided, and each of the power supply patterns is connected to the power supply line at one common point. antenna.