JPH0334603A - Plane antenna - Google Patents

Abstract

PURPOSE:To realize a low loss by placing smooth surface sides of two earth conductors so as to confront a strip conductor side, respectively, and also, specifying the surface roughness of the smooth surface of the strip conductor and the earth conductor. CONSTITUTION:Both the upper and the lower smooth surfaces of earth conductors 2, 3 are placed so as to confront a strip conductor 1, respectively. Also, the surface roughness of the smooth surface of these strip conductor 1 and earth conductors 2, 3 is set to <=0.3mum, and preferably <=0.2mum as center line average roughness Ra prescribed by the JIS standard BO601. As a result, the distribution of a line of electric force going to the earth conductors 2, 3 from the strip conductor 1 becomes uniform, and resistance to a surface current of an earth side decreases. In such a way, a low loss of a feed line can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a feeding line for a suspended triplate planar antenna with low line loss.

[Conventional technology]

In recent years, communication technology that uses high frequencies in the microwave region, as seen in satellite communications and satellite broadcasting, has become popular, and along with this, there is a need for lines with as low loss as possible in such high frequency ranges. It has become to.

Conventionally, microstrip lines using rigid circuit boards or flexible circuit boards have often been used as such high-frequency lines from the viewpoints of ease of circuit patterning, mass production, cost, and light weight. Mainly for the purpose of suppressing radiation loss in the feed line, so-called suspended conductors are recently created in which these substrates are used to form strip conductors, and ground conductors are placed between the strip conductors above and below to form the feed line.・Tri-plate line systems are becoming mainstream.

Figure 2 shows the cross-sectional structure of a feed line system using this type of system, in which the strip conductor (1) is normally connected to the top and bottom, respectively, through a dielectric material (4) with a low permittivity and low dielectric loss. By arranging it near the center of the ground conductors (2) and (3), a suspended triplate type power supply line is constructed.

In addition, FIGS. 3(a) and (b) show the suspended
Examples of tri-plate strip conductor terminations and
This is an example of a radiation slot located just above this part, and the combination of these two determines the polarization characteristics such as right polarization, left polarization, etc. and the resonance frequency, and only radio signals that meet these conditions are stripped. It is excited at the end (8) of the conductor (1), propagates along the feed line and is collected at the converter.

Here, in order to maintain the flatness of the conductor or to pattern it by etching, the strip conductor (1) and at least the ground conductor (2) are normally attached to the rigid circuit substrate or the flexible circuit substrate (5) and ( 6)
It was common for it to be formed on top. In this case, the conductor is i (a), 2 (a) to ensure adhesion to the base material.
, 3 (a), one side of which is roughened. Therefore, conventionally, at least the ground conductor (2) or (2)
) and (3) were arranged so that the roughened surface of the conductor faced the strip conductor (1), but from the strip conductor (1) to the ground conductor (2) or the ground plate. 3) Electric lines of force toward the roughened surface 2(a) of the ground conductor
3(a) to 3(a) not only result in non-uniformity, but also the resistance to the current flowing to the ground increases significantly due to the roughening of the ground conductor surface, resulting in large line losses in the feeder line, and improvements have been desired.

[Problem to be solved by the invention]

The present invention was developed as a result of various studies in view of the above drawbacks of the prior art, and its purpose is to provide a low-loss feed line for a sustained triplate type planar antenna. .

[Means to solve the problem]

That is, the present invention provides a suspended triplate structure in which one of the basic elements is a feed line consisting of a strip conductor printed as a circuit on a dielectric substrate and two ground conductors arranged above and below the strip conductor. In the planar antenna of this method, the smooth surfaces of the two ground conductors are arranged so as to face the strip conductor side, and the surface roughness R of the smooth surfaces of the strip conductor and the ground conductor is
This is a planar antenna characterized in that both a are 0.3 μm or less.

Hereinafter, the feed line structure based on the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a feed line that is one of the basic elements of a suspended triplate planar antenna based on the present invention, and shows a strip conductor (1) and two ground conductors (2) and (3). are held at approximately equal distances through a dielectric material (4) having a low dielectric constant and low dielectric loss. (5), (6), and (7) are each conductor (1)
, (2), (3), and 1(a), 2
(a) and 3(a) are conductors (1), (2), and (3), respectively.
), and the roughened surface of 1 (b), 2 (b), 3 (b
) are respectively roughening the smooth surface.

As is clear from this figure, in the suspended triplate type power supply line according to the present invention, the ground conductor (2)
, (3) The first feature is that both the upper and lower smooth surfaces are arranged so as to face the strip conductor (1).

Next, the present inventors constructed the strip conductor (1) and the ground conductor (2) in the power supply line configured as shown in FIG.
), (3) The surface roughness of the smooth surface is JIS standard BO601.
Center line average roughness Ra defined by 0.3 μm or less,
It has been found that an even more important requirement is that the surface roughness is preferably 0.2 μm or less.If the surface roughness is more than this value, as will be seen in the examples later, the line loss becomes significant. It is not preferable because it does not reduce the effect and the effect is small.

The suspended triplate type power supply line obtained with this configuration is different from the suspended triple plate type in the conventional structure.
Compared to a triplate type feed line, the distribution of electric lines of force from the strip conductor (1) to the ground conductors (2) and (3) is uniform, and the resistance to surface current on the ground (ground conductor) side is increased. It is possible to reduce the loss of the power supply line due to the following reasons.

The conductor used in the present invention is not limited in any way as long as it is one that is normally used in printed circuit boards, such as aluminum or copper. In addition, although the dielectric substrates (5), (6), and (7) are not specified in any way, such as rigid circuit boards or flexible circuit boards whose base materials are sheets or films, In order to reduce the loss, it goes without saying that choosing a substrate that is as thin as possible and has the lowest possible dielectric constant and dielectric loss at high frequencies will give better results.

In addition, a low dielectric constant material interposed as a spacer between the strip conductor (1) and the ground conductors (2) and (3),
The dielectric (4) material with low dielectric loss may be air or a synthetic resin foam having an appropriate expansion ratio.

Further, in the present invention, base materials (5), (6) and (7)
) is not necessarily a necessary requirement, and may not be used as long as it does not affect the flatness or mechanical stability of the conductor.

As described above, in the suspended triplate type power supply vA path based on the present invention, the materials of the constituent members are completely unrelated to the effects claimed in the present invention, and the smooth surfaces of the strip conductor and the ground conductor meet the specified standards. By having the surface roughness and arranging the smooth side of the ground conductor facing the strip conductor side, both the top and bottom conductors have a similar remarkable power supply compared to the conventional suspended triplate type power supply line. It is characterized by its ability to reduce line loss.

Examples of the present invention and comparative examples will be described below.

(Example 1) Cu/PET as a flexible printed circuit board
(Cu thickness - 20 μm 5 PET = 60 μm),
Here, the center line average roughness Ra of the smooth surface side of the copper electrode is 0.3.
It was μm. A foamed polyethylene sheet (dielectric constant 1.1) with closed cells was used as a dielectric material for the spacer with a low dielectric constant and low dielectric loss, and as shown in Figure 1, the copper of the flexible printed circuit board for the two upper and lower ground conductors was used. Both smooth surfaces were placed facing the sl-IJ tube conductor side, and the feed line of the suspended triplate antenna was used. Further, the distance between the upper and lower ground conductors was 4 m, and the strip conductor was placed in the center.

When the characteristic impedance of this feed line system is 100Ω,
Line loss at 12GHz is 2.05 dB/m
Met.

(Example 2) A feeding line for a suspended triplate antenna was constructed in the same manner as in Example 1, except that Ra on the smooth surface side of the copper electrode was 0.2 μm.

When the characteristic impedance of this line system is 100Ω, 12
Line loss at GHz was 2.00 dB/m.

(Example 3) A feeder guide for a suspended triplate antenna was constructed in the same manner as in Example 1, except that Ra on the smooth surface side of the copper electrode was 0.1 μm.

When the characteristic impedance of this line system is 1.00Ω,
The line loss at 2 GHz was 1.95 dB/m.

(Comparative Example 1) The cross-sectional structure was exactly the same as in Example 1, except that the roughened surface of the ground conductor was oriented toward the strip conductor side on both the top and bottom, as shown in Figure 2 (a) 4. We constructed a suspended triplate antenna power supply system.

This line system has a characteristic impedance of 12
The line loss at GHz was 2.15 dB/m, which was larger than that in Example 1.

(Comparative Example 2) A feeding system for a suspended triplate antenna was constructed in exactly the same manner as in Example 1, except that Ra on the smooth surface side of the copper electrode was 0.4 μm. , when the characteristic impedance is 100Ω, 1
The line loss at 2GHz is 2. 10dB/m,
It was thicker than in Example 1.

(Comparative Example 3) A feeding system for a suspended triplate antenna was constructed in exactly the same manner as in Example 1, except that Ra on the smooth surface side of the copper electrode was 1.0 μm.

When the characteristic impedance of this line system is 100Ω, 12
The line loss at GHz was 2.09 dB/m, which was not much different from Comparative Example 2.

〔Effect of the invention〕

The feed line of the planar antenna according to the present invention has a lower loss than that of a conventional structure, and is suitable as a line structure for signal transmission in a high frequency region.

By making the feed line of a planar antenna have such a structure to reduce loss, the efficiency of the antenna can be improved and the antenna can be made smaller, which is extremely useful.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a feed line system which is one of the basic elements of the planar antenna according to the present invention, Fig. 2 is a sectional view of a conventional feed line system, and Fig. 3<a) shows the V! , an example of @ part, (b) is a diagram showing an example of four radiating slots.

Claims (1)

[Claims] (1) A strip conductor printed circuit on a dielectric substrate, and two circuits arranged above and below the strip conductor.
In a suspended triplate planar antenna in which one of the basic elements is a feed line consisting of two ground conductors, the smooth surface sides of the two ground conductors are arranged opposite to the strip conductor side, and the strip The surface roughness of the smooth surfaces of the conductor and ground conductor are both 0.3 μm.
A planar antenna characterized by: