Patent Application
20180075945
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application Nos. 2016-181068, 2017-098502, and 2017-166221, filed on Sep. 15, 2016, May 17, 2017, and Aug. 30, 2017, respectively, the entire contents of which are hereby incorporated by reference.
The present invention is applied to a high frequency cable which may, for example, be used in a high bandwidth of 70 GHz or more.
Patent Document 1 discloses a coaxial cable which can be used in DC (direct current) to a high bandwidth up to 110 GHz and includes a central conductor, a dielectric layer, an outer conductor layer, and a sheath. Heat resistance is insufficient in the coaxial cable in which an outer side than the above sheath is exposed to air. Comparative Example 13 to be described later proves the above problem.
An object of the present invention is to provide a high frequency cable which may, for example, be used in a high bandwidth of 70 GHz or more and has high heat resistance.
A high frequency cable according to the present invention includes: one cable body which includes a central conductor and a dielectric layer provided at an outer side of the central conductor; and an outer tube which is provided at an outer side of the cable body, in which the outer tube includes a first structure body in a helical shape and a second structure body in a helical shape, an inner diameter of the first structure body is smaller than that of the second structure body, the first structure body and the second structure body are mutually fitted in helical pitches, and each of the first structure body and the second structure body includes a material having a thermal conductivity of 9 W·m−1·K−1 or more, and in which in a bend state of the cable, a helix at an outer ring side of the second structure body is configured to move to an inner ring side of the second structure body so that the helix is fitted in a state of being embedded in a gap formed at an outer ring side of the first structure body and is contacted with the cable body.
A high frequency cable according to the present invention includes: a plurality of cable bodies, each of which includes a central conductor and a dielectric layer provided at an outer side of the central conductor; and an outer tube which is provided at an outer side of the cable body, in which the outer tube includes a first structure body in a helical shape and a second structure body in a helical shape, an inner diameter of the first structure body is smaller than that of the second structure body, the first structure body and the second structure body are mutually fitted in helical pitches, and each of the first structure body and the second structure body includes a material having a thermal conductivity of 9 W·m−1·K−1 or more, an in which in a bent state of the cable, a helix at an outer ring side of the second structure body is configured to move to an inner ring side of the second structure body so that the helix is fitted in a state of being embedded in a gap formed at an outer ring side of the first structure body and is contacted with the cable body.
Preferably, the outer tube may have a void ratio of 75% or less, in which the void ratio is obtained by subtracting a sectional area S2 of the cable body from an area S1 of a circle whose diameter is an inner diameter of the first structure body in a linear state to provide a difference value, and dividing the difference value by the area S1 and multiplying the obtained quotient by 100.
More preferably, the void ratio may be 68% or less. Further, more preferably, the void ratio may be less than 50%.
More preferably, a dielectric constant of the dielectric layer may be 1.8 or less, and a sum of an effective outer diameter of the central conductor and an effective outer diameter of the dielectric layer may be 2.7 mm or less.
According to the present invention, a high frequency cable which may, for example, be used in a high bandwidth of 70 GHz or more and has high heat resistance may be obtained.
Hereinafter, a high frequency cable according to the present invention will be described with reference to the drawings. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to equivalents with the present invention described in the claims. In the examples and comparative examples to be shown below, one or two cable bodies are provided, but more than two cable bodies may be inserted through an outer tube.
(Configuration of High Frequency Cables According to Examples)
Next, a configuration of the outer tube 20 will be described by using
Herein, a relationship between the cable body 10 and the outer tube 20 will be explained by using
In contrast, according to the present example, since the outer tube having an excellent thermal conductivity is provided near the cable body, the heat of the cable body may be dissipated efficiently by contacting the cable body with the outer tube. Since the outer tube of the example is configured by the first and second structure bodies, in bending, the second structure body is engaged, in the radial direction, in a state of being embedded in the gap formed at the outer ring side of the first structure body. Therefore, a gap is not formed on the outer tube in bending, and since the outer tube having an excellent thermal conductivity is provided near the cable body in either the linear state or the bent state, frequency of contact between the cable body 10 and the outer tube 20 is increased, and the heat of the cable body may be dissipated efficiently by contacting the cable body with the outer tube.
As shown in
In contrast,
Hereinafter, results of heat resistance tests according to Examples and Comparative Examples are shown in Table 1. In Examples 1 to 16 and Comparative Examples 1 to 26, structures of the cable bodies are all the same, and structures and materials of the outer tubes and presence or absence of the outer tubes are different, respectively. Porosities of Examples 1 to 26 and Comparative Examples 1 to 26 are shown in Table 1 below. Herein, as shown in
Void Ratio (%)=(S1−S2)/S1×100
In order to obtain the excellent heat resistance (heat dissipation) of the cable, the cable body 10 may be contacted with the outer tube easily in the linear state and the bent state, and when a diameter of the cable body 10 is compared with an inner diameter of the outer tube 20, the void ratio is preferably 75% or less where the inner diameter of the outer tube 20 does not exceed two times the diameter of the cable body 10.
More preferably, the void ratio between the cable body 10 and the outer tube 20 is 68% or less, and thereby heat dissipation due to the contact between the cable body 10 and the outer tube 20 is further excellent.
More preferably, the void ratio between the cable body 10 and the outer tube 20 is less than 50%, and thereby heat dissipation due to the contact between the cable body 10 and the outer tube 20 is extremely excellent.
The heat resistance tests were conducted by respectively using ten cable bodies from Examples 1 to 16 and Comparative Examples 1 to 26. A test device was used in which a high power amplifier and a directional coupler were connected to a microwave transmitter, each of the cables according to Examples 1 to 8 and Comparative Examples 1 to 13 described above was connected to the directional coupler, and a terminator was connected to each of the cables. A test method is as follows: generating and amplifying a signal, dividing the signal into two signals by the directional coupler, using one signal as an object to be measured and using the other signal for observing electric energy, and then confirming, based on whether a dielectric is melted, whether the heat resistance is present, after a constant period of time has elapsed. This result is also shown in Table 1 described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-181068 | Sep 2016 | JP | national |
| 2017-098502 | May 2017 | JP | national |
| 2017-166221 | Aug 2017 | JP | national |
