JPS5985B2 - Transmission line connection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission line having a dielectric line, a surface wave line (including an image line and an insular line), a dielectric filled and/or internal metal waveguide, and a combination thereof. It concerns the connection part.

Millimeter waves, submillimeter waves, and waves in the optical domain are transmitted by transmission lines as any one of an in-dielectric mode, a surface wave mode, and a waveguide mode, or any combination thereof.

A dielectric material is used in some (or all) of these transmission lines as a transmission medium for the waves. That is, conventionally, as a dielectric material through which wave energy propagates in a transmission line, a material without pores (generally referred to as a solid material in technical terms) such as polyethylene, polypropylene, or polytetrafluoroethylene has been used, and the cladding portion As the material having a low dielectric constant, polyethylene, polypropylene, etc., which have closed cells foamed with a foaming agent, are used.

However, the above-mentioned plastics that are foamed with a foaming agent have a large dielectric loss due to the foaming agent contained therein, it is difficult to control the dielectric constant, and the foaming rate changes at the boundary of the dielectric. It is difficult to make the diameter of the foamed pores less than a fraction of the wavelength, and it is difficult to mold the material. It was almost impossible to use this as a wave energy propagation part.

As a result of various studies in order to obtain a dielectric material for connection parts of transmission lines that does not have the drawbacks of conventional materials as described above, the present inventor discovered that a large number of micronodules are three-dimensionally connected to each other by microfibers. A dielectric material made of a crystalline polymer with a porous microstructure with high porosity has a small dielectric constant and tan δ, and the dielectric constant can be easily and uniformly controlled. It was discovered that the shape and dielectric constant of the dielectric material can be freely adjusted, and it has great flexibility, making it extremely suitable as a dielectric material for connection parts of transmission lines.Based on this knowledge, the present invention was completed.

That is, the present invention is characterized in that it is formed of a dielectric material made of a crystalline polymer having a porous microstructure with high porosity in which a large number of micronodules are three-dimensionally connected to each other by microfibers. This is the connection part of the transmission line.

The dielectric used as at least a part of the wave energy transmission part in the present invention is made of a crystalline polymer material, and its internal structure is composed of a large number of micronodules interconnected by a large number of fine fibers. These micronodules and microfibers are connected three-dimensionally, and a large number of intricate voids are formed between them, resulting in a porous microstructure with continuous pores as a whole.

A dielectric material having such a porous microstructure can be obtained by preparing a PTFE molded body in an unsintered state in accordance with the method described in Japanese Patent Publication No. 51-18991 and Japanese Unexamined Patent Publication No. 50-22881. It can be obtained by stretching to about twice as much.

By changing the stretching ratio, the specific gravity, porosity, dielectric constant, etc. of the PTFF molded product can be changed over a very wide range. Therefore, by this change, it is possible to easily obtain a dielectric material for a transmission line in which the propagation state of wave energy is adjusted as desired. Next, this stretched product is sintered and heat-set for about 1 to 15 minutes at a temperature above the melting point of PTFE (327°C), preferably 340 to 380°C, especially 360 to 375°C, or at least 250°C below the melting point. Fixing may be carried out at a temperature of about 100 mL. It is also possible to adjust the dielectric constant of the porous PTFE by appropriately changing the degree of sintering and/or heat setting of this drawn product, and this, together with the step of changing the drawing ratio, can be achieved according to the present invention. This is an important process used to adjust the characteristics and performance of transmission line connections. The porous PTFE material made of PTFE thus obtained usually has a high porosity of 60 to 90% and an average pore diameter of 0.01 to 90%.
50μ, airflow rate 100-5000CC/min (length 2.5
The water leakage pressure is 0.1 to 1.5 k9/Crii (approximate number under 1 psi pressure of a 4 cm tube), and the relationship between the stretching ratio, density, relative dielectric constant (εr), and Tan δ is as follows.

Next, a connection portion of a transmission line according to the present invention will be described with reference to the drawings. FIG. 1 shows a longitudinal cross-sectional view of a joint 4 between a transmission line 1 made of a dielectric 3 and a metal waveguide 2. As shown in FIG.

This transmission line 1 has a high-crystalline structure having a porous microstructure with high porosity in which a large number of micronodules are interconnected by fine fibers in at least a part of a central dielectric material 3 which is a wave energy transmission part. A dielectric material made of molecules is used, and the connecting portion 4 is also formed of the same dielectric material.

In addition, 5 is a clad part made of a dielectric material similar to the center dielectric material 3, and 6 is an outer cover. In this embodiment, the connection part 4 of the transmission line 1 is provided in a conical shape protruding into the metal waveguide 2, and electromagnetic waves enter the transmission line 1 made of a dielectric material from the metal waveguide 2. Or conversely, electromagnetic waves are transmitted from the transmission line 1 made of a dielectric material to the metal waveguide 2.

The conical shape of the connecting portion 4 may be formed by exposing the end of the center dielectric 3 and removing the excess portion, or may be formed by applying external pressure. According to this embodiment, since the connecting portion 4 is formed of a dielectric material made of a crystalline polymer having a porous microstructure with high porosity, the above-mentioned external pressure forming is easy; The dielectric constant is thus increased and signal focusing favors the capture or emission of electromagnetic waves.

That is, according to this embodiment, it is possible to achieve the effect that matching connection can be made well and relatively easily. In the embodiment shown in FIG. 1, the connecting portion 4 is shown as a protruding portion from the transmission line 1, but on the contrary, it may be a portion having a conical recess facing toward the transmission line 1. .

In this case, the dielectric material forming the connecting portion 4 is one in which the dielectric constant continuously decreases radially outward from the central axis, and the dielectric materials have different dielectric constants. It is formed of a plurality of coaxial dielectric layers, and the dielectric constants of the plurality of dielectric layers are selected to decrease radially outward from the central axis. In some cases, it decreases stepwise as it goes outward.

FIG. 2 shows a connection 7 of a transmission line 1 similar to FIG. 1, but the end 8 of the dielectric is cut at right angles to the longitudinal direction.

The density (permittivity) of the dielectric material in the connecting portion 7 is processed so as to gradually increase from the end portion 8 toward the right as shown by arrows A, b, and c. In order to adjust the density of the dielectric material in this way, it is possible to perform the stretching process in multiple stages as described above, to stretch a molded body heated to create a temperature gradient, or to concentrate infrared and far-infrared rays. This can be done by means such as changing the Furthermore, a connection having a structure that combines the examples of FIGS. 4 and 2 is also possible. In the connection portion of the transmission line according to the present invention as described above, the following various effects are achieved.

(1) Low transmission loss (T
an δ is small, and in expanded PTFE with a density of 0.2y/~, it is less than 1/10 of that in solid PTFE. Another reason for the low loss is that the dielectric does not contain a foaming agent unlike other foamed plastics (eg, polyethylene, polypropylene). ) (2) The dielectric constant of the dielectric material can be freely controlled over a wide range and is uniform.

(3) Fast propagation speed.

(4) Can transmit electromagnetic waves with high energy density.

(5) The shape and structure of the dielectric can be freely adjusted. (6)
Matching with the transmission line is easy. These effects were confirmed by the following example. Example The end of the material formed for the center dielectric of the transmission line was reheated and further stretched.
After performing this operation three times, the specific gravity becomes c- as shown in Figure 2.
0.3, b-0.2, and a-0.1, the center dielectric and its connecting portion 7 were made.

In addition to the 27mm connecting portion of this dielectric, similar to the transmission line,
Wrapping of expanded porous PTFE (outer diameter 15 mm) and vinyl chloride coating (wall thickness 1 mm) were applied. The connecting portion 27 mm was left as a joint portion with the metal waveguide. The transmission line (length 1m) whose end was processed into a connection part as described above was connected to another metal waveguide, and the transmission characteristics were measured at the other end, and the effect of the above connection part was confirmed. .

The dielectric material used for the connection part of the transmission line according to the present invention shown in the above specific example has fine pores, high porosity, and continuous pores, and furthermore, when an appropriate pressure is applied, it deforms plastically. Therefore, the volume change due to temperature change is smaller than that of general dielectric materials such as solid tetrafluoroethylene, and the volume is a characteristic of the material used to regulate the external shape (
Since the dielectric constant changes depending on expansion and contraction), the temperature characteristic of the dielectric constant can be almost zero, and a connection part of a transmission line that requires good temperature characteristics can be provided.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the idea of the present invention, such as manufacturing the transmission line and the connecting portion as separate bodies.

[Brief explanation of the drawing]

1 and 2 are longitudinal cross-sectional views of a connection portion of a transmission line, respectively, showing an embodiment of the present invention.

Claims (1)

[Claims] 1. A transmission line formed of a dielectric material made of a crystalline polymer having a porous microstructure with high porosity in which a large number of micronodules are interconnected by microfibers. connection part. 2. In the transmission line connection section according to claim 1, the dielectric has a dielectric constant that continuously decreases radially outward from the central axis. connection portion of the transmission line. 3. In the transmission line connection section according to claim 1, the dielectric is composed of a plurality of coaxial dielectric layers having different dielectric constants, and the plurality of dielectric layers are The connection portion of the transmission line, wherein the connection portion of the transmission line is arranged such that the dielectric constant decreases radially outward from the central axis. 4. In the connection portion of the transmission line according to claim 1, the dielectric material has a dielectric constant that is continuously changed in a direction along the axis of the central axis. Line connections. 5. In the connection portion of the transmission line according to any one of claims 1 to 4, the dielectric material is formed of stretched continuous porosity tetrafluoroethylene resin molding.