JPH02226802A - Plane antenna - Google Patents

Abstract

PURPOSE:To constitute a low-loss line and to improve the aperture efficiency by selecting the roughness of the conductor foil of a circuit board. CONSTITUTION:A feed circuit pattern 1 and a radiation circuit Pattern 2 are formed on one-surface sides of synthetic resin boards 4 and 5, a support 6 is arranged so as to hold a space between the two patterns 1 and 2, and an earth conductor 3 is arranged opposite the feed circuit pattern 1 across a support 7. Here, the conductor foil for forming the pattern circuits 1 and 2 is rolled pure copper foil which has <=0.2mum roughness Ra on both surfaces and >=99.99% purity. Thus, the surface roughness of the conductor foil of the circuit boards 4 and 5 is selected, so the line loss is reduced and the aperture efficiency is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention comprises a patterned circuit formed using a synthetic resin film or sheet (hereinafter referred to as a substrate) and a laminate on a conductive foil. The present invention relates to a highly efficient planar antenna.

[Prior art] As planar antennas in the microwave region used for satellite broadcasting, satellite communications, etc., dielectric substrates made from synthetic resin have recently been developed from the viewpoints of flexibility in processing fine patterns, light weight, and cost. On top of that, devices in which patterned circuits are formed for the feeding section and the radiation section are being actively developed.

FIG. 2 shows a typical configuration of this type of antenna, and the synthetic resin groups vi, (4) and (5) each have a structure shown as an example in FIG. A feeding circuit pattern (]) and a radiation circuit pattern (2) are formed, and a support (6) is arranged to maintain a space between the two patterns (1) and (2). ] A ground conductor (3) is arranged at a position facing the power supply circuit pattern (1) via the ground conductor (3).These supports (6) and (7) are usually made of synthetic resin and hold the circuit pattern. Ki! Ji (4),
(5) may be an insulating spacer inserted at an optimal location where spatial flatness can be maintained, or a sheet with a low induction rate such as a foam sheet may be used. Generally, the basic structure shown in FIG. 2 is called a suspended triplate system.

The synthetic resin substrates (4) and (5) may be plates, sheets, or films; if they are plate-shaped, the circuit board formed together with the circuit patterns (1) and (2) may be a normal rigid substrate. On the other hand, in the case of a sheet or film, it is a so-called flexible printed circuit board.

Figure 4 is a sectional view showing the structure of a conventional circuit board for a flat antenna, in which a feeder circuit pattern (1) is bonded to a synthetic resin board (4) with an adhesive (8), and Figure 5 The distribution of current (9) in the conductor of circuit pattern (1), and Figure 6 shows the pattern of electric lines of force 0ω in the power supply circuit board, but as can be seen from Figure 5, in the high frequency region Most of the current (9) in the conductor is concentrated on the front and back surfaces of the conductor, that is, the skin layer.

However, in the conventional planar antenna, the surface of the circuit conductor is not smooth but roughened, as shown in FIG. Generally, one side of the conductor foil used for circuit boards is JI
The center line surface roughness Ra specified in S B 0601 (1976) is 1°0 to 2.0 μm, or the roughness degree is such that the maximum height Rmax is about 6 to 15 μm,
The opposite surface, the so-called glossy surface, also has an Ra of 0.2 to Q and a 4μmSRmax of 1.0 to 2. Own
In conventional circuit boards for planar antennas, where the skin of the circuit conductor has been roughened to some degree, as mentioned above, the current in the high frequency region is almost entirely absorbed by the conductor. Since the electrical resistance is concentrated on the skin surface of the wire, the electrical resistance is large, resulting in an increase in line loss. For this reason, the aperture efficiency of the conventional planar antenna having the structure shown in FIG. 2 has remained at 60% or less.

[The invention tries to solve i! l! a) The present invention has been made in view of the situation with conventional planar antennas, and its purpose is to configure a low-loss line by selecting the degree of roughness of the conductor foil of the circuit board. The object of the present invention is to provide a planar antenna with improved aperture efficiency.

[Means to solve the problem]

That is, the present invention provides a method for forming a pattern circuit in a planar antenna that basically consists of a pattern circuit of a radiating part and a feeding part, which are formed by etching a conductive foil bonded to a synthetic resin substrate. The conductor foil has a surface roughness Ra of 0.2 μm or less on both sides and a purity of 99
．． This is a planar antenna characterized by being made of 99% or more rolled oxygen-free copper foil.

The present invention was made based on the knowledge that line loss in a planar antenna can be reduced by selecting the surface roughness and type of conductive foil used in the circuit board.

In the present invention, the first requirement is to use a conductor foil that has low surface roughness and is as smooth as possible, and as described later, it is necessary to use a synthetic resin that has high adhesion to the conductor foil. By selecting, it is possible to avoid the use of adhesives (it is preferable to directly bond the conductor foil and the synthetic resin substrate).
In addition, metal foils with as low electrical resistance as possible are selected,
Candidates include gold, copper, and aluminum, but
In addition to having a surface as smooth as possible, a rolled oxygen-free copper foil with a low oxygen content is suitable as a foil that can be used industrially, considering the viewpoints of ease of handling and cost. The copper purity in this rolled oxygen-free copper foil is preferably 99.99% or more. If the copper purity is lower than this, the electrical resistance will increase and the effects of the present invention will not be fully exhibited.The surface roughness of this rolled oxygen-free copper foil is in accordance with JIS standard B 060.
The center line average roughness Ra defined by 1 is 0.2 on both sides.
μm or less, and more preferably 0.1 μm or less on both sides by mechanical polishing or electrolytic polishing after rolling, although the method is not particularly limited. Here, the Ra evaluation method is as follows: Measurement length 0.24 m,
It is a stylus type, and its stylus shape is a square bell shape with an opening angle of 90°C and a tip shape of 2 x 3 μm. If the surface roughness of at least one side exceeds this value, the electrical resistance on the surface of the copper foil will increase and the loss will increase significantly, which is not preferable.

In addition, if the surface roughness of the conductor foil has such smoothness, even if an adhesive is used, it will not be possible to obtain adhesion between the conductor foil and a[. Since electric lines of force penetrate through the adhesive layer, the dielectric layer of the line cannot be ignored. Therefore, in the present invention, a synthetic resin with high adhesion to conductor foil is used as a conductor without using any adhesive. It is desirable to paste directly on the foil. It goes without saying that the greater the adhesion force between the conductor foil and the board, the better, but circuit boards used for planar antennas do not require very high adhesion force, unlike ordinary printed circuit boards for wiring. It is sufficient that the degree of adhesion is maintained during the etching process of circuit pattern processing and under normal use environments. From this point of view, if the degree of adhesion between the conductor foil and the board in a circuit board for a planar antenna is 0.3 kg/cm or more, it is sufficient adhesion, and there is no practical problem. In the invention, the centerline surface height Ra of the roughened surface is 0.01 to 0. A synthetic resin having a beer strength of 0.3 kg/cI* or more with copper foil, which is now am, is preferable, and suitable examples include, for example, linear polyimide resin via amic acid.

〔Example〕

The present invention will be explained below with seven examples.

Example 1 59.4 g (55% mole of amine component) of purified anhydrous phenylenediamine was added to a solid content of 15% by weight
Dissolve in a mixed solution of 90% anhydrous N-methyl-2-pyrrolidone and 10% toluene so that 158.5 g of anhydride (55 mol % of the acid component) was added while cooling the entire system, and then heated at 20"C for 5
The reaction was carried out for 00 hours. Then, 90.0 g of purified anhydrous 4,4'-diaminophenyl ether (45 mol% of the amine component) and 96.0 g of purified pyromellitic anhydride dianhydride were added.
g (45 mol % of the acid component) were added in this order with stirring, and the mixture was further reacted at 20° C. for 5 hours.

The obtained polyamic acid solution had a surface roughness Ra of 00/0 μm on both sides, a thickness of 35 μm, and a purity of 99.9.
On 9% rolled oxygen-free copper foil, the final solids thickness was 2.
Coat and cast to a thickness of 5 μm, and heat from 100°C to 350°C.
It was heated to ℃ over 2 hours.

Regarding the flexible printed circuit board obtained in this way, the beer strength with w4ffl was measured and was 0.
．． The weight was 5 kg/+c+e, and the degree of adhesion was such that it did not pose any problem during work.

Next, on this replica board, a straight line with a width of 1.5 mm was formed by etching, and the same copper foil as in the example was coated with a thickness of 2 g.
Prepare m foam polyethylene sheet and w4fF! −
Foamed polyethylene sheet - flexible printed circuit - foamed polyethylene sheet + - wAta were laminated on this till' (suspension type triplate type conductor of line with characteristic impedance of 100Ω... was measured. 0.90 dB / m, and the dielectric volume is 0.55
It was dB/m.

Furthermore, using the flexible printed circuit board of this example, a flexible printed circuit for radiation and a flexible printed circuit for power feeding were fabricated by etching, and a space of 2 squares was formed on the glossy side of the grounding copper foil. They were stacked and held in this order.

The aperture efficiency of the planar antenna obtained as in step 2 is 61
%Met.

Example 2 A flexible printed circuit was produced in exactly the same manner as in Example 1, except that the surface roughness Ra of the copper foil used was O, OS μm on both sides, and the rolled oxygen-free copper foil had a purity of 99°99%. A substrate for use was obtained.

The beer strength of the body foil of this board is 0.3 kg/cr
y, but there was no practical problem. As a result of measurement using the same method as in Example 1, the conductor loss of the line was 0.80d1
3/m, and the aperture efficiency of the antenna was 63%.

Comparative Example 1 The surface roughness na of the copper foil used was 0.15 pm on the glossy surface.
A flexible printed circuit board was obtained in the same manner as in Example 1, except that the roughened surface was 2.0 urn and the rolled oxygen-free copper foil had a purity of 99.99%.

The beer strength of the copper foil on this board is 0.8 kg/cm
Met. Next, the conductor loss of the line and the aperture efficiency of the antenna were measured using the same method as in Example 1 for the glossy surfaces of the upper and lower W4 foils and the Susbend I type triplate system for flexible printed circuits, and the result was 1.05 dB/
m and 57%.

Comparative Example 2 The surface roughness Ra of the copper foil used was 0.30 μm on the glossy surface.
, [A flexible printed circuit board was obtained in the same manner as in Example 1, except that the electrolytic steel foil was 1.6 Bm on the north side and had a purity of 99.9%.

The beer strength of the copper foil of this board is 0.8 kg/c■, and Example 1 of the suspended type triplate method for upper and lower II glossy surfaces and flexible printed circuits.
The results of measuring the line conductor m and antenna aperture efficiency using the same method as above are 1.25 dB/m and 5 dB/m, respectively.
It was 5%.

Comparative Example 3 After a flexible printed circuit board was obtained in the same manner as in Example 1, the copper foil was removed by etching. Next, apply 3. enol-based adhesive (modified nitrile rubber) on the same steel foil. The film with the copper foil removed was laminated and heated and pressed to obtain a new flexible printed circuit board.

The beer strength of the copper foil of this board was 0.6 kg/c. When measured using the same method as in Example 1, the line conductor loss was 0.95 dB/m, the dielectric loss was 0.75 dB/m, and the antenna aperture efficiency was 58%. .

Comparative Example 4 A flexible printed circuit board was obtained in the same manner as in Example 1, except that the purity of the copper foil used was 99.95%.

The beer strength of the copper foil of this board is 0.5 kg/cm, and the results of measuring the conductor loss of the line and the aperture efficiency of the antenna using the same method as in Example 1 are 1.15 dB.
/ m and 58%.

〔Effect of the invention〕

As described above, in the present invention, by selecting the surface roughness of the conductor foil of the circuit board, it is possible to reduce line loss and realize a planar antenna with excellent efficiency.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a circuit board for a planar antenna according to the present invention, and FIG. 2 is a diagram showing a typical configuration of a planar antenna.
FIG. 3 is a diagram showing an example of a pattern of a circuit board of a planar antenna, in which (a) is a radiation circuit pattern, and (b) is a feeding circuit pattern. Figure 4 is a cross-sectional view of a conventional circuit board for a planar antenna, Figure 5 is a current distribution in the conductor of the circuit board of a flat antenna, and Figure 6 is a distribution of electric lines of force in a conventional power supply circuit board. This is a diagram showing a hailstorm. Figure 1 Patent applicant Sumitomo Bakelite Co., Ltd. Figure 3 ζa) (b)

Claims (1)

[Claims] (1) A conductor for forming the pattern circuit in a planar antenna that basically consists of a pattern circuit of a radiation part and a power feeding part, which is formed by etching a conductor foil bonded to a synthetic resin substrate. A planar antenna characterized in that the foil is a rolled oxygen-free copper foil having a surface roughness Ra of 0.2 μm or less on both surfaces and a purity of 99.99% or more.