JP2002252520A - Plane antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact plane antenna which can be preferably installed even at a place where the mounting position is limited, without deteriorating transmitting and receiving efficiency and directional characteristics. SOLUTION: The plane antenna 10 has a pane 12; an insular conductor 14b being formed on the surface side of the pane 12, having a patch-shaped radiation conductor 14a and a strip-shaped projecting section 14b projected from the radiation conductor 14a, and satisfying Lb <=k.λ/2 when the wavelength of a radio wave is represented by λ, the compaction ratio of the pane 12 by (k) and the projecting length of the projecting section 14b by Lb ; and a grounding conductor 16 formed on the same surface as the insular conductor 14, and separating and surrounding the periphery of the insular conductor 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar antenna, and more particularly to a high-frequency planar antenna suitable for microwave communication and millimeter wave communication. More specifically, a planar antenna for wireless communication between a vehicle and a transmitting device and / or a receiving device outside the vehicle, particularly at a frequency in the GHz band, for example, formed on a window glass of the vehicle. It relates to a planar antenna used.

[0002]

2. Description of the Related Art Today, demands for high-speed, large-capacity communication require
High-frequency communication for transmitting and receiving radio waves using microwaves and millimeter waves has been rapidly expanding. As an antenna for transmitting and receiving radio waves, for example, a microstrip antenna having a circular or square patch-shaped radiation conductor (hereinafter, the microstrip antenna is referred to as MSA) is suitably used. This MSA is also called a patch antenna. Since this MSA can be manufactured on a printed circuit board and has a planar structure, it is widely used as a small and thin antenna.

[0003] In this MSA, generally, a conductor plate such as a conductor thin film is formed on both surfaces of a dielectric substrate, one conductor plate is used as a ground conductor (also referred to as a ground plate or a ground plate), and the other conductor plate is used. Is subjected to an etching process to form a circular or square radiation conductor. This MS
In the power supply of A, for example, the center conductor of the coaxial cable is connected to a predetermined position of the radiation conductor, and the outer conductor of the coaxial cable is connected to MS.
This is done by connecting to the ground conductor on the side opposite the radiating conductor of A. As described above, since the MSA has conductor plates on both surfaces of the dielectric substrate, connection to the conductor plates on both surfaces of the MSA is required for power supply.

On the other hand, US Pat. No. 4,063,246 discloses “COPLANAR STRIPLINE AN”.
TENNA "is disclosed. That is, a ground conductor is provided on one surface of a dielectric substrate, and a patch-shaped radiating conductor is provided on the opposite surface and a predetermined distance (also referred to as a gap) around the radiating conductor. According to the disclosure, a radiation conductor and a ground conductor are formed on one surface of a dielectric substrate, for example, the center conductor of a coaxial cable is connected to a radiation conductor. At a predetermined position, and the outer conductor of the coaxial cable is connected to the ground conductor formed on the same surface as the radiation conductor, so that power can be supplied from one surface of the dielectric substrate.

[0005]

In recent years, on an expressway or toll road, an automatic toll collection system (ETC :) that automatically collects tolls by performing wireless communication using a 5.8 GHz frequency band. Electric Toll Collecti
on System) has been proposed. This system performs wireless data communication between a roadside device provided at a tollgate and a vehicle-mounted device provided in a vehicle. As the antenna used on the in-vehicle device side of this system, the above-mentioned MSA or a stacked type surface mount antenna is often used, and the antenna is mounted on the in-vehicle device or the antenna is housed in a separate housing and On the dashboard of the vehicle. However, the antenna such as the MSA installed on the dashboard is not preferable in design from the inside and outside of the vehicle, and hinders the driver's view. There is also a problem of directivity characteristics such that the characteristics of the antenna are not constant depending on the mounting position and the direction.

Further, since the above-mentioned MSA requires conductor plates on both sides of a dielectric substrate, when it is used for a window glass of a vehicle, the conductor is also exposed on the glass surface outside the vehicle.
There was a problem that the durability of SA decreased. Furthermore, forming conductors on both sides of the glass plate means that the manufacturing process is complicated, and the cost is also high. Further, in order to supply power to the radiator and the ground conductor of the MSA in which the glass plate is formed as a dielectric substrate, a complicated hole-piercing process for perforating the glass plate is required. Therefore, it was difficult to form MSA on the surface of the glass plate. Also, in the antenna disclosed in the above-mentioned US Pat. No. 4,063,246, the grounding conductor is provided on the glass surface on the vehicle interior side, and the radiation conductor is provided on the glass surface on the vehicle exterior side and is exposed to the outside. There was a problem that it became low. In this way, an antenna that satisfies both the antenna mounting position and the driver's field of view, and even in a place where the conventional mounting position is limited, does not lower the transmission / reception efficiency and further does not lower the directivity characteristics. At present, a compact antenna with good durability that can be suitably attached to the antenna has not been obtained today.

Accordingly, the present invention is directed to a planar antenna that transmits or receives radio waves, and is capable of improving transmission / reception efficiency even in places where the mounting position is restricted, for example, in front of a driver's seat of a vehicle. An object of the present invention is to provide a durable and compact antenna that can be suitably mounted without lowering the directivity characteristics.

[0008]

To achieve the above object, the present invention is a planar antenna having a dielectric substrate provided with an island conductor and a ground conductor, wherein the island conductor protrudes. It has a strip-shaped protrusion, a part or the whole of the island-shaped conductor is separated and surrounded by the ground conductor, the wavelength of a radio wave used for transmission or reception is λ, the radio wave in the dielectric substrate If the shortening coefficient k, and the protruding length of the protrusion was L _b, there is provided a planar antenna and satisfies the _{L b ≦ k · λ / 2} .

Here, the relative permittivity of the dielectric substrate is ε_r
, The shortening rate k is k = ε _r ^(-1/2)Is
preferable.

It is preferable that the projecting portion is formed in the island-shaped conductor in a circular or square shape. Here, it is preferable that the protruding portion of the island-shaped conductor and the grounding conductor form a co-brainer waveguide, and it is preferable that a power supply portion be provided at an end of the co-brainer waveguide. The island-shaped conductor may be provided with a notch at a portion connected to the protruding portion such that an edge of the protruding portion extends inside the island-shaped conductor.

Here, the island-shaped conductor and the ground conductor are thick films or conductor layers formed by firing silver paste, and a black ceramic film is formed on a surface layer of the dielectric substrate. Is also good.

Preferably, the dielectric substrate is a glass plate, and further, the glass plate is a glass plate for a vehicle. Further, the glass plate for a vehicle is preferably a windshield for a vehicle, and the planar antenna is preferably formed on the vehicle interior side of the windshield for a vehicle. Further, the glass plate for a vehicle may be a laminated glass plate, and the planar antenna may be formed on a glass substrate constituting the laminated glass. further,
The planar antenna is located 1 mm from the edge of the vehicle windshield.
It is preferably formed within a range of not more than 00 mm, and more preferably within a range of not more than 100 mm left and right about a center line in the left-right direction when the vehicle windshield is mounted on a vehicle.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a planar antenna according to the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIGS. 1A and 1B show a planar antenna 10 which is an embodiment of the planar antenna of the present invention. FIG. 1A is a plan view of the planar antenna 10, and FIG. 1B is a cross-sectional view of the planar antenna 10 taken along the line AA ′ shown in FIG.

As shown in FIGS. 1A and 1B, the planar antenna 10 is a planar antenna formed on at least one surface of a glass plate 12 as a dielectric substrate. An island-shaped conductor 14 formed on the surface of the glass plate 12 and having a square main body portion 14a and a strip-shaped protrusion 14b protruding from the main body portion 14a; and on the same surface as the island-shaped conductor 14. And a conductor 16 that surrounds the entire island-shaped conductor 14 at a predetermined distance.

A power feeding portion 18 is provided at an end of the protruding portion 14b, and is connected to the center conductor of the coaxial cable on the same surface side as the island-shaped conductor 14 via a surface mount type connector (not shown). The conductor 16 is connected to the outer conductor of the grounded coaxial cable and is always grounded. Therefore, in the planar antenna 10, the main body 1
4a is a radiation conductor for radiating radio waves, and the conductor 16 surrounding the radiation conductor functions as a ground conductor. Further, the protruding portion 14b forms, together with the conductor 16 which is a ground conductor, a cobrenner waveguide (CPW) which is a known transmission line in which a ground conductor is formed on both sides of a strip-shaped center conductor at a predetermined distance. In addition, the protruding portion 14b functions as a strip-shaped center conductor of the cobrener waveguide. Hereinafter, the main body 14a is referred to as a radiation conductor 14a, the protrusion 14b is referred to as a transmission line center conductor 14b, and the conductor 16 is referred to as a ground conductor 16.

[0017] Here, the width W and the length L _a of the radiating conductor 14a is wave by the wavelength of the radio wave to be transmitted and received planar antenna 10 is set to resonate. Planar antenna 1
0 of conductor length L _a, when the wavelength of the center frequency of a desired frequency band for transmitting and receiving and the lambda _M, in order to improve the reception efficiency of the _{antenna, k · (λ M / 4} ) ~k · λ
_M (k is a shortening rate of the glass plate 12) is preferably in the range. By setting the conductor length La in this range, the gain by several dB is improved as compared with the case where the conductor length _La is set outside this range. The width W of the radiation conductor 14a is k · (λ, where λ _H is the wavelength of the highest frequency in the desired frequency band for transmission and reception, and λ _L is the wavelength of the lowest frequency in the desired frequency band for transmission and reception. _H / 4) to k · λ _L.

On the other hand, the radiation conductor 1 of the transmission line center conductor 14b
Line length L of the protruding part protruding from 4a _bIs a planar antenna
The wavelength of the radio wave transmitted and received at 10, for example, the wavelength of the center frequency
To λ _MWhen the shortening rate in the glass plate 12 is k,
If k_M/ 2 or less. Thus, the transmission line center
Line length L of conductor 14b_bThe upper limit of k · λ_M/ 2
This ensures antenna transmission and reception efficiency, and
A compact planar antenna can be formed.

Here, the shortening rate k is related to the propagation speed of the radio wave propagating on the dielectric substrate, and is set so that the reactance component of the input impedance of the antenna becomes zero at a desired radio wave frequency. That is, the ratio of reducing the size of an antenna manufactured by using a dielectric substrate so as to resonate the antenna as compared to the antenna size considered without the dielectric substrate. here,
Shortening ratio k, when the relative dielectric constant of the dielectric substrate and epsilon _r, k
= It can be represented by ε _r ^(-1/2).

The ground conductor 16 is formed in a predetermined area on the glass plate 12 so as to have a predetermined area or more. That is, in the planar antenna 10, the area of the ground conductor 16 is adjusted so that the directivity characteristics are improved. The reason why the directivity characteristics can be improved in this way is considered to be because the influence of the reflection at the interface between the dielectric substrate and the air and the surface wave propagating through the glass plate on the directivity characteristics is reduced. .

The ground conductor 16 is formed around the island-shaped conductor 14.
Surround the enclosure at a certain distance. That is, the ground conductor 16
Is a fixed distance g from the edge of the radiation conductor 14a._appAway, biography
A fixed distance g from the edge of the transmission line center conductor 14b_apfSet apart
Be killed. Interval g_appIs the input in of the planar antenna 10
The impedance is set to be good, and almost
Preferably, the thickness is near the thickness of the metal plate 12. On the other hand, the interval g_apfIs
Set by the ratio with the line width of the transmission line center conductor 14b.
This interval g_apfAnd the line width ratio is the transmission line center conductor 1
4b and the ground conductor 16 in the CPW
Characteristic impedance is a predetermined value, usually a high-frequency transmission line
So that the characteristic impedance used in
The relative permittivity of the glass plate and the conductivity of the radiator and ground conductor and
It is set in consideration of the thickness. About this CPW
Is "Microstrip Lines and Slotines" (Artech House
Publishers and authors K.C.Gupta et al.) In addition,
In this embodiment, the ground conductor 16 is located between the edge of the radiation conductor 14a and
Constant interval g _appAway from the edge of the transmission line center conductor 14b
Constant interval g_apfAlthough they are apart, in the present invention, they will be described later.
When transmitting and receiving circularly polarized radio waves as in
The body 16 has a constant distance g different from the radiation conductor 14a on the left and right.
_app1, G_app2And may be separated from the ground conductor 16.
The distance between the radiating conductor 14a and the radiating conductor 14a
May change.

Such an island-shaped conductor 14 and a ground conductor 16
Is formed by printing a paste containing a conductive metal such as a silver paste on the glass plate 12 and baking the paste. The present invention is not limited to this forming method, and a linear or foil-like thin film made of a conductive substance such as copper may be formed on the surface of the glass plate 12. As described above, since the conductor obtained by firing the silver paste on the glass plate 12 is formed as a conductor, no gap is generated between the glass plate 12 and the radiation conductor 14a, the transmission line center conductor 14b, or the ground conductor 16, and the gap is caused by the gap. The transmission and reception characteristics of the planar antenna 10 do not deteriorate due to reflection at each interface and resonance.

Although the planar antenna 10 is formed on a single glass plate 12, in the present invention, it may be a laminated glass plate or a multilayer glass plate. It may be formed on any surface side of the glass plate constituting the laminated glass plate. For example, it may be formed on the mating surface side of a laminated glass plate, but in this case, a power supply means for supplying power to the antenna across the glass plate is required.
Further, in the present invention, the dielectric substrate is not limited to a glass plate, ceramic, polyimide resin, sapphire,
Further, any of a printed wiring board and the like may be used. At that time, taking into account the relative permittivity of the dielectric substrate and the conductivity and thickness of the conductor, the size of the radiating conductor 14a and the width of the CPW, for example, the width and interval g _apf of the transmission line center conductor 14b are determined according to the frequency of transmission and reception. It needs to be changed. It is preferable to use a dielectric substrate having a low dielectric loss in order to improve the transmission and reception efficiency of the antenna. Also, the dielectric substrate
A colored print film on the surface layer, for example, a black print film may be used.

Such a planar antenna 10 is, for example,
It is formed on the surface of a vehicle windshield and used as an antenna in ETC. That is, a vehicle windshield is used as the glass plate 12. Such a planar antenna 10 is used for short-range communication (DSRC: Dedicated Short Rang).
e Communication) It may be provided on the glass plate 12 integrally with the control circuit and the like. The planar antenna 10 has a radiation conductor 14a and a central transmission line central conductor 14b.
Are all surrounded by the ground conductor 16.
In the present invention, a planar antenna in which a part of the radiation conductor 14a and a part of the center transmission line center conductor 14b are surrounded by the ground conductor 16 may be used. As described above, the planar antenna 10
Is composed.

Next, the operation of the planar antenna 10 will be described.
explain. First, transmission of radio waves is performed by the transmission line center conductor 14b.
The power is supplied from a power supply unit 18 provided at the end of the radiating conductor 14a, propagates the CPW, and excites the radiation conductor 14a. At this time, if excited at the resonance frequency of the radiation conductor 14a, a radio wave is radiated from the radiation conductor 14a. The above-described MSA is an antenna that generates a magnetic current at an end of a radiation conductor from an electric field between the radiation conductor and the ground conductor and radiates radio waves using the magnetic current as a wave source. It is considered that a magnetic current is generated at the end of the radiation conductor 14a from an electric field between the ground conductor 16 and the ground conductor 16 arranged on the same surface with an interval around the magnetic field, and the magnetic current is used as a wave source to radiate radio waves. Planar antenna 10
Is located in the vicinity of the frequency of a radio wave having a half-wave length equal to the length of the planar antenna 10, but this resonance frequency depends on the influence of the end of the radiation conductor 14a and the distance g between the radiation conductor 14a and the ground conductor 16. It can be set finely using _app etc.

The operation of receiving a radio wave is the reverse of the above operation due to the reversibility of transmission and reception of the antenna. in this way,
The planar antenna 10 includes a dielectric substrate 12 on which a radiation conductor 14a, a ground conductor 16 and a transmission line center conductor 14b are formed.
No conductor is formed on the surface opposite to the surface, and the dielectric substrate 1
2 has a radiating conductor 14a, a ground conductor 16 and a transmission line center conductor 14b formed on only one surface, so that the antenna has the same plane or coplanar (coplanar) structure. 12, and the durability is improved as compared with the MSA which must be arranged on both sides of the dielectric substrate. Furthermore, since the power supply section 18 is also provided on the same surface side as the radiation conductor 14a and the like, power supply becomes easy and a compact configuration is realized.

The planar antenna 10 has a radiation conductor 14a having a square shape as shown in FIG. 1, but may have a rectangular shape such as a rectangular shape, and a circular shape as shown in FIG. Shape may be sufficient. Further, when transmitting and receiving circularly polarized radio waves as in ETC, FIG. 2 (b) to FIG. 2 (e)
As shown in (2), a notch 20 or a protrusion 21 may be provided in a part of the radiation conductor 14a to cope with circular polarization by using a degenerate element or a perturbation element. In addition, the radiation conductor 14a may be formed in a square shape, and a slot may be provided in the center of the square shape, and a method similar to the circular polarization technique in a normal MSA can be used. Further, FIG.
As shown in (f), the radiation conductor 14a is formed in a square shape, and the distance between the radiation conductor 14a and the ground conductor 16 is set to a distance g.
_app1 , g _app2 , etc.
As shown in (g), by changing the distance between the radiating conductor 14a and the ground conductor 16 in the longitudinal direction of the antenna, a change in capacitance due to the distance between the radiating conductor 14a and the ground conductor 16 occurs. An effect similar to that of the element or the perturbation element may be obtained to cope with circularly polarized waves.

As shown in FIG. 2 (h), in order to match the impedance of the transmission line center conductor 14b and the radiation conductor 14a, the radiation conductor 14a and the surrounding ground conductor 16
In consideration of the influence of the gap g _app with respect to the radiation conductor 14a
The cutout 22 may be provided in a portion connected to the transmission line center conductor 14b so that the edge of the transmission line center conductor 14b extends inside the radiation conductor 14a. In this case, the notch 20 and the protrusion 21 are formed in a part of the radiation conductor 14a.
And the like may be provided.

The size and shape of the ground conductor 16 are not limited to the embodiment, and various changes can be made as long as they do not affect the directivity characteristics. It is also possible to improve the design. Further, a metal or conductive plate may be provided on the indoor side to provide a reflector, thereby improving the transmission and reception efficiency of the antenna.

The flat antenna according to the present invention is an ETC that performs wireless communication using the above-mentioned 5.8 GHz frequency band.
However, the present invention is not limited to ETC and can be used for various data communications using the same frequency band. For example, 800 MHz band (810-
960 MHz), 1.5 GHz band (1.
429-1.501 GHz), UHF band (300 MHz)
３3 GHz), a GPS signal from a GPS satellite 1575.
It can also be used for transmitting and receiving radio waves such as 42 MHz. Of course, in addition to the above-mentioned band, radio waves (1G
Hz to 3 THz) or millimeter wave band radio waves (30 GHz to 30
0 GHz).

The following planar antenna was manufactured as such a planar antenna 10.

Example 1 A dielectric substrate having a thickness of 3.5
Fig. 1 is obtained by baking silver paste on a glass plate
The radiation conductor 14a and the transmission line center conductor 1 having the shape shown in FIG.
4b and the ground conductor 16 were formed. At this time, the shape of the radiation conductor 14a is large (width W × length L _a ) so as to be a planar antenna capable of transmitting and receiving at a center frequency of 5.8 GHz.
Has a square shape of 7.9 mm × 7.9 mm, and the gap g _app is 2 mm (or both the gap g _app1 and the gap g _app2 in FIG. _2F are 2 mm). Then, the width of the transmission line center conductor 14b constituting the CPW is set to 1
mm, and the gap g _apf was 0.3 mm. The CPW formed by the transmission line center conductor 14b is a dielectric substrate 1
Taking into account the relative dielectric constant, conductivity and thickness of the conductor, 5.8
The configuration was such that the characteristic impedance was approximately 50Ω at GHz. The size of the ground conductor 16 was set to 70 mm for xpl and 100 mm for ypl shown in FIG. Also,
The length of the transmission line center conductor 14b, i.e., the line length L _b of the transmission line center conductor 14b, corresponding to approximately k · λ _M / 4 and 6.45 mm, and a k · λ _M / 2 or less.

The input impedance characteristic at this time is shown in FIG.
The characteristics were as shown in FIG. That is, the frequency 5.8G
It is shown that at Hz, the reactance component takes a value near 0 and causes resonance. In addition, the frequency 5.8
The directivity characteristics in the case of vertical polarization at GHz were good characteristics as shown in FIG. 3 and 4 that the manufactured planar antenna resonates at a desired frequency, and that the ground conductor 16 has an area enough to obtain good directivity characteristics and functions as a good antenna. FIG.
0 degree on the horizontal axis indicates a direction perpendicular to the glass plate surface 12.

(Embodiment 2) Next, in addition to the structure of Embodiment 1, as shown in FIG.
2, a black ceramic film 24 was formed between the radiation conductor 14a and the ground conductor 16. As for the input impedance characteristic, the frequency resonating toward the lower frequency side is shifted by about 60 MHz as compared with the case of the first embodiment shown in FIG. 3, and the directivity characteristic in the vertical polarization is reduced by about 0.5 dB from the directivity characteristic shown in FIG. But functioned as a good antenna. If the size of the radiation conductor 14a is finely adjusted in consideration of the electric influence of the black ceramic film 24 (in this case, since the resonance frequency is shifted to a lower frequency side, the radiation conductor 14a is made smaller), It is thought that better characteristics can be obtained.

The second embodiment is an example in which the flat antenna 10 has a black print film between the glass plate 12 and the radiation conductor 14a and the ground conductor 16, but the present invention is not limited to the black print film, and the color of the print film is not limited to the black print film. May be any. When the planar antenna 10 is used for a vehicle window glass plate, for example, a vehicle windshield, the planar antenna 1
0 is preferably formed on the vehicle interior side of the vehicle windshield in terms of easiness of power supply through the power supply unit 18 and durability, and the radiation printed conductor of the planar antenna 10 from the outdoor side by the black printed film. 14a and transmission line center conductor 14b
And the ground conductor 16 can be optically (visually) shielded, and the appearance seen from the outside of the vehicle can be improved.
Further, by forming a black print film on the radiation conductor 14a and optically (visually) shielding it from the vehicle interior side, it is possible to improve the appearance as viewed from the vehicle interior side.

Further, since laminated glass is used as the windshield for a vehicle, a planar antenna is formed on the indoor side of the vehicle, and a colored interlayer film is sandwiched between the laminated surfaces of the laminated glass plates from the viewpoint of design. Planar antenna 1
0 may be optically (visually) shielded. The color of the interlayer is not limited to black. At that time, the planar antenna 10
In order not to obstruct the field of view, it is preferable that the front windshield is formed within a range of 100 mm or less from the edge of the vehicle windshield. Preferably, it is formed within a range of 100 mm left and right. For example, from the driver's point of view, the position on the back side of the rearview mirror is particularly preferable in terms of not obstructing the field of view and design.

Although the planar antenna of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course.

[0038]

As described in detail above, according to the planar antenna of the present invention, for example, the transmission and reception efficiency and the directivity characteristics are reduced on the glass of a moving body such as a vehicle such as a windshield of a vehicle. Without doing so, the high-frequency antenna can be suitably mounted. Moreover, it is durable and compact. For example, GPS (Global Positioning Sysyte
m), VICS (Vehicle information and communicat
It is an antenna suitable for dedicated short range communication (DSRC) systems such as ion systems and ETC. Furthermore, the planar antenna of the present invention can be formed not only on a communication system such as a telephone or a glass plate of a mobile body, but also on another dielectric substrate. Can be used as

[Brief description of the drawings]

FIG. 1A is a plan view showing an example of the shape of a planar antenna according to the present invention, and FIG.
It is sectional drawing of the planar antenna in the A 'line.

FIGS. 2A to 2H are plan views showing shapes of another example of the planar antenna of the present invention.

FIG. 3 is a diagram illustrating input impedance characteristics of the planar antenna of the present invention.

FIG. 4 is a diagram showing the directivity characteristics of the planar antenna of the present invention.

FIG. 5 is a sectional view showing a section of another example of the planar antenna of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Planar antenna 12 Glass plate 14 Island-shaped conductor 14a Body part (radiation conductor) 14b Projection part (transmission line center conductor) 16 Conductor (ground conductor) 18 Feeding part 20 Cutout part 21 Projection part 22 Cutout 24 Black ceramic film

Claims (2)

[Claims] 1. A planar antenna in which an island-shaped conductor and a ground conductor are provided on a dielectric substrate, wherein the island-shaped conductor has a projecting strip-shaped projection, and a part of the island-shaped conductor. Or the whole is separated and surrounded by the ground conductor, the wavelength of a radio wave used for transmission or reception is λ, the shortening rate of the radio wave on the dielectric substrate is k, and the protruding length of the protruding portion is L _b Wherein L _b ≤ k · λ / 2 is satisfied. Wherein when the relative dielectric constant of the dielectric substrate was epsilon _r, the shortening rate k is planar antenna of claim 1 wherein ^{_{k = ε r (-1 / 2}} ).