JP2001196841A - Planar antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a transmission loss in a high frequency band such as a submillimeter wave or a millimeter wave, to improve opening efficiency, to impart a small thickness and simple structure and to prevent breakage due to scattered matters, etc., and characteristics variation due to sediments. SOLUTION: In a planar antenna for leaking electromagnetic waves from the surfaces of a plurality of image lines 34 consisting of a dielectric material arranged in parallel to a base board conductor, a nearly flat cover member 40 having a dielectric constant smaller that that of the dielectric material forming the line 34 is fixed under the condition where its one surface side is abutted on the surface of the lines 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for simplifying the structure of a planar antenna used for a millimeter wave or the like, improving efficiency, and preventing deterioration of characteristics due to outdoor use.

[0002]

2. Description of the Related Art In systems such as wireless communication and radar, antennas have been reduced in size as electronic circuits have become smaller.
Although the antenna is required to be thin, the aperture area of the antenna is almost determined by the frequency and gain of the antenna required in the system. Therefore, it is important to reduce the overall volume of the antenna by reducing the thickness of the antenna. Become.

[0003] For this purpose, a microstrip array antenna and a waveguide slot array antenna have been put to practical use as typical thin planar antennas.

A microstrip array antenna uses a microstrip formed on a substrate as an antenna element. The antenna element can be manufactured by printing technology and is easy to manufacture. However, the frequency band is narrow and the millimeter wave band is used. However, there is a drawback that the transmission loss of the feed line is very large as compared with the microwave band.

On the other hand, a waveguide slot array antenna
A waveguide having a slot is used as an antenna element. For example, as described in Japanese Utility Model Publication No. 7-44091, a plurality of radiation waveguides 2
2. It is known that one end side of 2,... Is arranged so as to abut, and power is supplied from the power supply waveguide 1 to each radiation waveguide 2.

Such a waveguide slot array antenna has a small transmission loss in a high frequency band such as a quasi-millimeter wave or a millimeter wave, and is suitable for a system requiring a high gain antenna.

[0007]

However, a waveguide slot array antenna generally has a side wall for a feeding waveguide and a plurality of radiating waveguides which are fixed upright on a common base. Since a plurality of radiation waveguide slot plates are covered and fixed on the upper side to form a feeding waveguide and a plurality of radiation waveguides, the upper edge of a number of waveguide side walls is arranged. Manufacturing processes such as welding are required to complete the electrical contact of the slot plate, which results in low productivity and low cost.

In order to improve this, a method has been proposed in which adjacent waveguides are fed in opposite phase so that the side wall of the waveguide and the slot surface are not in contact with each other. There is a problem that coupling is likely to occur and antenna characteristics deteriorate.

In order to solve such a problem, the applicant of the present invention disclosed in Japanese Patent Application No. 10-359691 a rectangular cross-section in which an image line for electromagnetic waves is formed between the ground conductor and the ground conductor. A plurality of rod-shaped radiating dielectrics are arranged in parallel, and a plurality of loaded bodies are provided on the surface of each radiating dielectric at substantially constant intervals along the length direction to leak electromagnetic waves from the surface of each radiating dielectric. A planar antenna that is configured to cause such a phenomenon is proposed.

This planar antenna has an effect that the aperture efficiency is higher than that of the waveguide type antenna and the structure is simplified.

However, when the electromagnetic wave is leaked from an image line made of a dielectric material, such as a planar antenna, the line itself does not have the strength as a waveguide, and may be scattered when used outdoors. The image track is easily damaged.

[0012] Further, dust and dirt tend to accumulate on the surface of the image line and between the image lines, and the characteristics of the antenna are changed by these deposits.

The present invention solves this problem, has a small transmission loss in a high-frequency band such as a quasi-millimeter wave or a millimeter wave, has a high aperture efficiency, has a thin and simple structure, and is free from damage caused by flying objects. An object of the present invention is to provide a planar antenna in which a change in characteristics due to deposits is prevented.

[0014]

According to a first aspect of the present invention, there is provided a planar antenna for transmitting electromagnetic waves from a surface of a plurality of image lines made of a dielectric material arranged in parallel on a ground plane conductor. A planar antenna to be leaked, wherein a substantially plate-shaped cover member having a dielectric constant smaller than that of a dielectric material forming the image line is formed in a state where one surface thereof is in contact with the surfaces of the plurality of image lines. Installed.

In the planar antenna according to a second aspect of the present invention, in the planar antenna according to the first aspect, the cover member is provided with linearly polarized electromagnetic waves leaking from the plurality of image lines with respect to the linearly polarized waves. It is characterized in that it includes a polarization conversion plate that radiates by converting it into linearly polarized light having a tilt or circularly polarized light.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 4 schematically show a planar antenna 20 for millimeter waves according to an embodiment of the present invention. Note that these drawings are shown so that the structure of the antenna can be easily understood, and the dimensions of each part do not always correspond to actual ones.

In these figures, the planar antenna 20
Is formed on a rectangular flat base plate 21 made of metal.

The base plate 21 forms a part of the housing of the antenna, and has holes 22 at four corners for mounting the planar antenna 20 to other members. A plurality of holes 23 for screwing a holding frame 45 for holding a cover member 40 to be described later on the base plate 21 are formed along one edge of the base plate 21 at one end of the base plate 21. Is provided.

A power supply 25 is attached to one end of the base plate 21. The power supply section 25 is of an electromagnetic horn type including a waveguide section 26 and a horn section 27. Here, the waveguide section 26 and the horn section 27 have the same height and can be formed thin (H (magnetic field)). A surface sector horn is used.

This type of electromagnetic horn has a property that a plane wave input from the waveguide section 26 is converted into a cylindrical wave in the horn section 27.

One end of the radiation array section 30 enters the horn section 27 of the feeding section 25. Radiation array unit 30
Is a predetermined thickness (for example, 0.5 m
m) is constituted by a substantially flat dielectric substrate 31.

The outer shape of the dielectric substrate 31 is substantially rectangular, and is formed in a substantially arc shape that protrudes outward so that the length increases as it approaches the center from both ends on one end 31a side.

A metal film 32 of, for example, gold is printed on the entire lower surface of the dielectric substrate 31. The space between the metal film 32 and the upper surface of the base plate 21 is adhered by a conductive paste (not shown). ing. The metal film 32 is formed by printing a metal thin film, and is actually extremely thin compared to the thickness of the dielectric substrate 31.

On the upper surface of the dielectric substrate 31, grooves 33 having a predetermined width (for example, 2 mm) and a rectangular cross section having a predetermined depth (for example, 0.3 mm) are continuously formed from one end to the other end thereof. (E.g., the distance between the centers of the grooves is about 3.3 mm) and a plurality of parallel (in this example, 9 including the slightly narrow grooves at both ends).
And an image line 34 having a rectangular section with a predetermined width (for example, 1.3 mm) for transmitting an electromagnetic wave from one end to the other end using the metal film 32 and the base plate 21 as a ground plane conductor. Has formed.

A plurality (eight in this example) of image lines 34
The predetermined length range of the central part of the
4 is a radiating portion 35 leaking from the inside in the direction in which the surface of the dielectric substrate 31 faces, and the surface of the radiating portion 35 includes:
Metal strip 3 for leaking electromagnetic waves of a specific wavelength
6 are formed at predetermined intervals. The metal strip 36 is formed by etching a printed metal thin film.
Extremely thin compared to the thickness of.

The radiation pattern of this leaky wave is determined by the distance d (strip period) between the metal strips 36 and the length s (strip width) of the metal strip 36.

That is, the spatial harmonic β _n is represented by the following equation: β _n = β + 2nπ / d (-∞ ≦ n ≦ ∞) (where β is the phase constant of the dielectric line), and β _n
Is smaller than the free space wave number k ₀ , a leaky wave is emitted.

The direction of radiation of this leakage wave is
Of the image line 34 with respect to an axis x orthogonal to the surface of
The length direction z is defined as a positive angle direction, and the free space wavelength of the leaky wave
To λ ₀Then, it is expressed by the following equation.

Θ _n = sin ⁻¹ (β _n / k ₀ ) = sin ⁻¹ [(β / k ₀ ) + nλ ₀ / d]

Here, −1 ≦ sin θ _n ≦ 1, and in the case of a dielectric (β / k ₀ ), it is a constant larger than 1, so that θ _n usually has n = − Let it be 1.

From these equations, it can be seen that the direction of the radiation beam of the leaky wave is determined by the strip period d. Further, it is known that the radiation amount (leakage wave constant) per unit length of the leaky wave is substantially determined by the strip width s. The leaky wave is a linearly polarized electromagnetic wave having a plane of polarization along the length of the image line 34.

In this planar antenna 20, each radiating portion 35
Metal strips 3 so that the radiation characteristics of
The strip period and the strip width of No. 6 are set to be substantially equal and at the same position.

On one end side of each image line 34,
A wavefront adjuster 37 for adjusting the wavefront of the electromagnetic wave fed from the feeder 25 is provided. This wavefront adjusting unit 3
Numeral 7 is a diagram which utilizes the delay effect of the electromagnetic wave by the dielectric material. The inner image line has a higher wave front so that the cylindrical wave of the horn portion 27 of the feeder 25 can be supplied to the radiating portion 35 of each image line 34 in the same phase. The adjusting section 37 is longer.

Each wavefront adjusting unit 37 functions as a radio wave lens for converting a cylindrical wave into a plane wave, and a radio wave lens can be provided instead of the wavefront adjusting unit 37. In addition, the wavefront adjusting unit 37 of each image line 34 includes
In order to match with the power supply unit 25, a tapered portion 37a whose height decreases toward the tip is provided with the same length.

Around the radiation array section 30 formed in this way, the height from the base plate 21 is
And a spacer 39 continuous in a U-shape is fixed so as to surround both sides and the other end of the radiation array section 30.

On the radiation array section 30, a rectangular flat cover member 40 has an image line 34 on one surface 40a.
(Strictly speaking, the metal strip 3 of the image line 34)
6 surface) and the surface of the spacer 39,
The radiation array unit 30 is arranged so as to cover all the image lines 34 except for the tapered portion 37a.

The cover member 40 is connected to the radiation array section 30.
The hard material whose permittivity is smaller than the permittivity (about 10) of the dielectric (in this case, alumina) forming the image line 34 so as to reduce the loss to the electromagnetic wave leaked from the image line 34 of FIG. For example, the antenna is made of polytetrafluoroethylene (PTFE) (trade name: Teflon) having a dielectric constant of about 2, and its thickness is set to be λ / 2 with respect to the wavelength λ of the electromagnetic wave radiated by the antenna. I have.

The cover member 40 is held by the holding frame 45 so as not to move while being pushed to the image line 34 side.

The holding frame 45 is formed to be higher than the spacer 39 and is provided on the base plate 21 so as to surround the spacer 39. A holding plate 45 is provided with a predetermined width extending inward from the upper edge of the side plate 45a. A side plate 45b.
The inner wall a is brought into contact with the end face of the cover member 40 to restrict the movement of the cover member 40 in a direction parallel to the base plate 21, and the lower surface of the holding plate 45 b is brought into contact with the upper edge of the cover member 40 to cover The member 40 is pressed against the image line 34 side.

The lower surface of the side plate 45a of the holding frame 45 has grooves 4
6 are provided continuously over the entire length thereof, and rubber packing 47 is attached to the groove 46.

The base plate 2 is provided on the lower surface of the side plate 45a.
1 are provided with screw holes 48 respectively corresponding to the holes 23 provided therein, and flathead screws 49 are inserted into the screw holes 48 from the lower surface side of the base plate 21 and tightened. .

The tip of the holding frame 45 is
5 is in contact with the open end face of the horn portion 27 without any gap, and the one end 40a side of the cover member 40 enters so as to be in close contact with the inner upper wall of the horn portion 27 of the power supply portion 25.

For this reason, the radiation array unit 30 is
5 except for the opening surface of the waveguide portion 26 (the opening surface is connected to the transmission circuit and the reception circuit via another waveguide), the upper surface of the base plate 21 and the horn portion 27 of the feeding portion 25. Is located in a substantially closed space surrounded by the lower surface of the cover member 40 and the inner wall surface of the side plate 45a of the holding frame 45.

Therefore, even when the planar antenna 20 is used outdoors, the scattered matter does not directly hit the image line 34 of the radiation array unit 30, and dust and dirt accumulate on the image line 34 and the groove between them. Without
There is no fear that the characteristics of the antenna are degraded.

Further, since the planar antenna 20 has a structure in which a low-transmission-loss leaky-wave antenna element in which a metal strip 36 is provided on the image line 34 is provided in parallel, the aperture of the entire antenna is low with a low transmission loss. High surface efficiency.

Further, the entire antenna can be made extremely thin, and can be easily designed, manufactured and installed at low cost.

Further, since the metal strip 36 can be formed with high dimensional accuracy by a printing technique or an etching technique, the radiation characteristics of a plurality of radiating portions can be made uniform,
Alternatively, depending on the cycle and length of the metal strip 36,
The radiation characteristics of each radiation section 35 can be arbitrarily set,
Complex radiation characteristics can also be easily obtained.

Further, a groove 33 provided in parallel on one surface side
Accordingly, since the dielectric substrate 31 on which the image line 34 is formed is arranged on the base plate 21, it is suitable for mass production.

As described above, the image line 34
With one surface of the cover member 40 in contact with the surface of
Since the distance between the image line 34 and the cover member 40 is not changed by an external force, the antenna characteristics do not change due to a change in wind pressure even when used for a vehicle-mounted radar or the like.

When the cover member 40 having a small dielectric constant is used to cover the surface of the image line 34 as in the case of the flat antenna 20, the portion of the groove 33 is smaller than when the cover member 40 is not used. It has been confirmed that the leakage of unnecessary electromagnetic waves from the device slightly increases. For example, assuming that the level of the electromagnetic wave radiated from the center of the image line 34 is a reference (0 dB), the level of the electromagnetic wave radiated from the center of the groove 33 is 1 from approximately −30 dB to approximately −20 dB.
It increases by about 0 dB. However, since the absolute amount of the unnecessary leakage of the electromagnetic wave is low, the decrease in the efficiency of the entire antenna can be ignored unless the number of the image lines 34 is extremely increased.

In this planar antenna 20, the cover member 4
The case where the lower surface side of the substrate 0 is flat has been described. However, as in the cover member 40 'shown in FIG.
A rib 41 corresponding to the groove 33 is protruded, and the entire lower surface of the cover member 40 ′ is in contact with the entire surface of the dielectric substrate 31 except for the surface of the tapered portion 37 a receiving the electromagnetic wave from the power supply unit 25. You may. When a part of the cover member 40 'enters the groove 33 between the image lines 34 in this manner, unnecessary leakage of the electromagnetic wave from the groove 33 further increases slightly (about 5 dB) and slightly. However, as described above, since the absolute amount of the unnecessary leakage of the electromagnetic wave is low, the decrease in the efficiency of the entire antenna can be ignored unless the number of the image lines 34 is extremely increased.

Also, instead of using the cover member 40 'shown in FIG. 5, as shown in FIG. To fill the cover member 4
0 ″ may be configured.

In this case, since the surface of the dielectric substrate 31 is coated with another dielectric,
It is not necessary to use the spacer 39 and the holding frame 45.

In the above embodiment, the image line 3
From 4, the linearly polarized electromagnetic wave having a plane of polarization along its length direction was leaked, but by including a polarization conversion plate in the cover member, the plane of polarization of the electromagnetic wave radiated from the antenna can be arbitrarily changed. Can be set.

For example, as shown in FIG.
0 is formed into a three-layer structure by a polarization conversion plate 61 and protection plates 64 and 65 overlapping on both surfaces thereof.
By arranging the lower surface side of 0 so as to be in contact with the surface of the image line 34, the polarization plane of the electromagnetic wave radiated from the image line 34 can be changed.

Here, the polarization conversion plate 61 and the protection plate 6
4 and 65 are both made of the above-mentioned polytetrafluoroethylene (PTFE), and as shown in FIG.
One surface 61a side of the polarization conversion plate 61 (image line 34 side)
Has a predetermined width w1 in a direction orthogonal to the image line 34.
Are provided in parallel over the entire surface at a predetermined interval s1. As shown in FIG. 8B, a metal strip having a predetermined width w2 inclined 45 degrees with respect to the metal strip line 62 on the one surface 61a side is provided on the opposite surface 61b side (antenna surface side) of the polarization conversion plate 61. Lines 63 are provided in parallel over the entire surface at a predetermined interval s2.

The conversion characteristics of the polarization conversion plate 61 are determined mainly by the widths and intervals of the metal strip lines 62 and 63 on both sides.

That is, the thickness of the polarization conversion plate 61 is set to １ ／ wavelength, and the width and interval of the metal strip lines 62 and 63 are sufficiently smaller than the wavelength, for example, w1 = w2 = s1.
= S2 = 0.15 mm, the electromagnetic wave output from the image line 34 on the plane of polarization along its length is:
As shown in FIG. 9, the polarization conversion plate 61 converts the electromagnetic wave having a polarization plane orthogonal to the metal strip line 63 (that is, inclined at 45 degrees to the deflection plane of the electromagnetic wave output from the image line 34) with a small loss. Is output.

At 60 GHz, the dielectric constant is 2.
6, a glass cloth PTFE having a thickness of 0.8 mm was used.
5 mm, and the width w2 of the metal strip line 63 is set to 1.
When the distance is 4 mm and the interval s2 is 2.5 mm, the electromagnetic wave output from the image line 34 on the plane of polarization along the length thereof can be converted into a circularly polarized wave. Thus, 4
Five-degree or circularly polarized electromagnetic waves are more optimal for on-vehicle radars.

Further, in the above-described planar antenna 20, the metal strips 36 are provided on the surface of the image line 34 at predetermined intervals to leak electromagnetic waves. However, as shown in FIG. High step 36 '
May be provided at substantially constant intervals to form a corrugated (corrugated) shape so as to leak electromagnetic waves.

In this case, the interval (corrugated period) of the high step portion 36 'and the length (corrugated width) of the high step portion 36' correspond to the strip period and the strip width of the metal strip 36, respectively. The direction in which the electromagnetic wave leaks is determined by the corrugated period, and the amount of radiation is determined by the corrugated width and the height of the high step portion 36 '.

Further, in the planar antenna 20, an H-plane sector horn type electromagnetic horn is used as the feeding portion 25, but this is not intended to limit the present invention and is described in the above-mentioned Japanese Patent Application No. Hei 10-35969. Power supply unit can be used.

That is, electromagnetic waves are supplied to the plurality of image lines 34 from the electromagnetic horn whose horn part is open to the electric field surface,
Electromagnetic waves leaking to the side surface of the image line may be supplied to the plurality of image lines 34, or may be supplied from a strip line or coplanar line to the plurality of image lines 34. The adjusting unit 37a may form a bifocal radio wave lens, and provide a plurality of feed radiators having a radiation center on or near a line passing through the two focal points to form a multi-beam.

Further, in the planar antenna 20, the horn portion 27 of the electromagnetic horn as the feeding portion 25 has a trapezoidal shape and is opened in a C-shape toward the image line 34, but as shown in FIG. May be formed in a rectangular shape.

In the planar antenna 20, a plurality of parallel image lines 34 are integrally formed by forming the grooves 33 in the dielectric substrate 31 in parallel. However, the base plate 21 is used as a ground plate conductor. A plurality of image lines 34 each formed of a dielectric rod having a rectangular cross section are fixed in parallel, a metal strip 36 is provided on the surface of each image line 34, and a cover member 4 is provided so as to cover each image line 34 in the same manner as described above.
0, 40 ', 40 ", 60 may be attached.

Further, in the above-described embodiment, the tapered portion 37a is provided at the tip of the wavefront adjusting portion 37 in order to match with the power feeding portion. However, it is difficult to process the tapered portion 37a (the generation of cracks and cracks). For example, as shown in FIGS. 12A and 12B, a matching dielectric having a dielectric constant different from that of the image line 34 without providing a tapered portion. 70 may be connected to the tip of the wavefront adjusting unit 37 of the image line 34.

The dielectric constant of the matching dielectric 70 is
An object (in this case, air) between the dielectric 70 and the power supply unit 25
Ε0 and the dielectric constant of the image line 34 are ε1.
Then, the following equation: ε2 = (ε0 · ε1)^1/2  Is preferably equal to or close to the dielectric constant ε2 satisfying

Here, the image line 34 has a dielectric constant ε
If 1 = 10 alumina is used and ε0 = 1 (air), ε2 is 3.16. As a dielectric material having a dielectric constant close to 3.16, glass cloth Teflon or the like is used. By using this dielectric material as the matching dielectric material 70, electromagnetic waves radiated from the feeding unit 25 can be efficiently guided to the image line 34. Can be.

The length L of the matching dielectric 70 required for matching is set to １ ／ of the wavelength λ of the electromagnetic wave, and is set on the dielectric substrate 31 using an adhesive or the like, or as described above. Is a ground plate conductor, and a plurality of image lines 34 formed of dielectric rods having a rectangular cross section are fixed to the base plate 21 on the base plate conductor.

In the planar antenna 20, the cylindrical wave from the feeding section 25 is converted into a plane wave by the wavefront adjusting section 37 provided at the end of the image line 34. However, the feeding section 25 may be of a parabolic reflection type. Thus, a plane wave can be given to each image line at the same phase.

FIGS. 13 to 16 show the structure of a planar antenna 80 having this parabolic reflection type feeding section 81. FIG.

The feeder 81 of the planar antenna 80 is provided so as to face the H-plane spectral horn 82 disposed on the back side of the base plate 21 ′ (ground plane conductor), and the radiation surface of the H-plane sector horn 82. H-plane Sectoral Horn 8
A parabolic cylindrical reflecting mirror 83 that converts a cylindrical wave radiated from 2 into a plane wave and reflects the plane wave on the surface side of the base plate 21 ′;
It is constituted by a guide portion 84 for guiding a plane wave reflected by the parabolic cylindrical reflecting mirror 83 to the surface side of the base plate 21 ′ to the tip end side of the image line 34.

The focal point F of the parabolic cylindrical reflecting mirror 83 coincides with the phase center of the electromagnetic wave input to the H-plane spectral horn 82.

The edge of the base plate 21 'on the side of the parabolic cylindrical reflecting mirror 83 is formed in the same shape as the shape of the reflecting surface side of the parabolic cylindrical reflecting mirror 83.
3 is spaced from the reflecting surface by a predetermined distance G.

The upper flat plate 84a of the guide portion 84 is
A parallel plate waveguide is formed with the base plate 21 ', and the reflected wave from the parabolic cylindrical reflecting mirror 83 is efficiently guided to the tip end of the image line 34.

Since the feeder 81 for supplying such a plane wave is used, the leading ends of the image lines 34 are arranged in a straight line.

In the case of the planar antenna 80 using such a feeder 81, the electromagnetic wave input to the H-plane spectral horn 82 on the back side of the base plate 21 'is converted into a cylindrical wave in the H-plane spectral horn 82. However, each of the image lines 34 is converted into a plane wave by the parabolic cylindrical reflecting mirror 83.
, And the leakage wave from each image line 34 is radiated to the front side via the cover 40.

In the planar antenna 80, the base plate 2
Gap G between 1 '(ground conductor) and parabolic cylindrical reflecting mirror 83
By selecting, most of the electromagnetic waves radiated from the H-plane sectoral horn 82 can be guided to the parallel plate waveguide on the upper surface side of the base plate 21 ', and power can be supplied efficiently.

Further, by using the folded feeder as described above, the length of the planar antenna in the direction along the image line 34 can be greatly reduced, and the outer shape of the planar antenna can be made compact. Can be.

In this planar antenna 80,
Since the surface of each image line 34 is covered with the cover member 40 (which may be the cover 40 ', 40 ", or 60), even when this planar antenna is used outdoors, scattered matter is directly on the image line. There is no contact, no dust or dust accumulates on or between the image lines, and there is no fear that the characteristics of the antenna are degraded.

[0081]

As described above, the planar antenna according to the present invention is a planar antenna that leaks electromagnetic waves from the surface of a plurality of image lines made of a dielectric material arranged in parallel on a ground plane conductor. A substantially plate-shaped cover member having a dielectric constant smaller than the dielectric being formed,
The one side is attached in a state of contacting the surfaces of the plurality of image lines.

Therefore, even when this planar antenna is used outdoors, scattered objects do not directly hit the image line, and dust and dirt do not accumulate on the image line or between the image lines. There is no risk of deterioration.

In addition, since the planar antenna has a structure in which leaky wave type antenna elements of low transmission loss for leaking electromagnetic waves from the surface of the image line are provided in parallel, the entire antenna has low transmission loss and aperture surface efficiency. , The entire antenna can be made extremely thin, and it is easy to design, manufacture and install, and can be realized at low cost.

In addition, by including a polarization conversion plate in the cover member, a linearly polarized or circularly polarized electromagnetic wave at an arbitrary angle can be radiated, which is suitable for a vehicle-mounted radar or the like.

[Brief description of the drawings]

FIG. 1 is a plan view of an embodiment of the present invention.

FIG. 2 is a plan view of a main part of the embodiment.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a sectional view taken along line BB of FIG. 1;

FIG. 5 is a diagram showing a modification of the cover member.

FIG. 6 is a diagram showing a modification of the cover member.

FIG. 7 is a view showing another modification of the cover member.

FIG. 8 is a diagram showing the front and back surfaces of a polarization conversion plate constituting the cover member of FIG. 7;

9 is a diagram for explaining the operation of the polarization conversion plate in FIG.

FIG. 10 is a diagram showing another configuration example for leaking electromagnetic waves from an image line.

FIG. 11 is a diagram showing a modification of the power supply unit.

FIG. 12 is a diagram showing a modification of the wavefront adjusting unit.

FIG. 13 is a plan view of a planar antenna using a folded feed unit.

FIG. 14 is a plan view of a main part of a planar antenna using a folded feeding unit.

FIG. 15 is a sectional view taken along line CC of FIG. 13;

FIG. 16 is a rear view of a planar antenna using a folded feeding unit;

[Explanation of symbols]

 20, 80 Planar antenna 21, 21 'Base plate 25, 81 Feed unit 26 Waveguide unit 27, 27' Horn unit 30 Radiation array unit 31 Dielectric substrate 32 Metal film 33 Groove 34 Image line 35 Radiation unit 36 Metal strip 37 Wavefront adjusting portion 37a Tapered portion 39 Spacer 40, 40 ', 40 ", 60 Cover member 41 Rib 45 Holding frame 61 Polarization conversion plate 62, 63 Metal strip line 64, 65 Protection plate 70 Matching dielectric 82 H-plane sector horn 83 Parabolic cylindrical reflector 84 Guide

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J021 AA05 AA09 CA02 GA08 HA04 HA05 JA07 5J045 AA05 AB07 CA01 CA04 DA01 DA17 EA10 FA02 HA01 KA02 LA03 MA04 NA01

Claims (2)

[Claims] 1. A planar antenna for leaking electromagnetic waves from a surface of a plurality of image lines made of a dielectric material arranged in parallel on a ground plane conductor, wherein the planar antenna has a dielectric constant smaller than that of the dielectric material forming the image lines. A flat antenna, wherein a substantially plate-shaped cover member is attached with one surface thereof abutting against the surfaces of the plurality of image lines. 2. The cover member according to claim 1, wherein the cover member converts the linearly polarized electromagnetic wave leaking from the plurality of image lines into a linearly polarized wave having a slope with respect to the linearly polarized wave or a circularly polarized wave. A wave conversion plate is included.
The planar antenna as described.