JPH0376602B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to the structure of a helical conductor type leaky cable.

Prior Art and Problems A conventional leaky spiral conductor cable is made by twisting a pair of conductors 1 and 2 in a spiral shape at a constant pitch P, as shown in Fig. 1. As shown in the figure, a core type in which the conductors 1 and 2 are embedded in the center of the insulator 3, and a so-called spacer type in which the conductors 1 and 2 are inserted into grooves formed in the insulator 3 as shown in Fig. 3 are adopted. has been done.

By the way, a relationship as shown in the following equation is established between the radiation frequency and pitch P of such a spiral conductor type leaky cable.

(c/p)・{Kλ/(1+Kλ)}</n<
(c/p)·{Kλ/(1−Kλ)} (1) where c is the speed of light, Kλ is the wavelength shortening rate, and n is a natural number.

In equation (1), Kλ is determined by the insulator and is usually 0.5
~0.95. Therefore, if it is designed to be used at frequencies below 150 MHz, the pitch P must be set to 1 to 2 m or more. For this reason, the helical angle becomes extremely small, making it extremely difficult to manufacture with uniform pitch.

OBJECTS OF THE INVENTION The present invention improves on these conventional drawbacks, and aims to provide a helical conductor type leaky cable that can obtain a sufficiently low radiation frequency without increasing the pitch.

Structure of the Invention In the spiral conductor type leaky cable of the present invention, the cable has different periods P ₁ and P ₂ (double period).

If two pairs have different helical pitches P ₁ and P ₂ , and if the directions of the helices are the same, the relative pitch P between the pairs is P = P ₁ P ₂ / (P ₁ - _{P 2} )... (2) becomes. Therefore, by changing P ₂ (or P ₁ ), any pitch P in the range 0<P<∞ can be realized.

Since the strength of the electric field and/or magnetic field propagating through the cable, that is, the intensity distribution of the wave source, can be changed other than the helical pitch, the periods P ₁ and P ₂ can be changed depending on factors other than the helical pitch of the conductor, such as the conductor diameter and conductor spacing. Any parameters related to the structure of the cable, such as dimensions, thickness of insulator, degree of foaming, etc., can be set. At this time, it is preferable that the changes in each parameter be sinusoidal in order to widen the effective radiation bandwidth of the cable.

Embodiments of the Invention FIGS. 4 to 6 are structural explanatory diagrams of different embodiments of the present invention, and are oblique views of cross sections of helical conductor type leaky cables.

In the embodiment shown in FIG. 4, conductors 12 and 13 constituting one core wire are buried approximately in the center of insulators 16 and 17, respectively, and are twisted together with a helical pitch P ₂ and then covered with a tape or a low-loss insulating material. It is housed in a tube 18 made of thread, and around this tube 18,
Conductors 10 and 11 constituting another core wire embedded approximately in the center of insulators 14 and 15 are twisted together at a helical pitch P ₁ and housed in a tube 19.

Further, the embodiment shown in FIG. 5 has a conductor 10 covered with an insulator 14 and a conductor 11 covered with an insulator 15.
Twist them together with a spiral pitch of P ₁ to form the tube 21.
The conductor 12 covered with the insulator 16 and the conductor 13 covered with the insulator 17 are twisted together with a spiral pitch P ₂ and housed in the tube 20.
1 is housed in a tube 22. Conductor 10,1
1 constitutes one core wire, and conductors 12 and 13 constitute the other core wire.

In the embodiment shown in FIG. 6, a twisted spiral pitch of conductors 10 and 11 constituting one core wire covered with insulators 14 and 15 and a conductor 12 constituting the other core wire covered with insulators 16 and 17 are shown. _{. _} They are twisted together and stored in a tube 22.

When using the cables shown in Figures 4 to 6,
For example, as shown in FIG. 7, conductors 10 and 11 and conductors 12 and 13 are connected, and the output of the oscillator P is connected between the two pairs of conductors.

FIG. 8 is an external view of another embodiment of the present invention,
The outer diameters of the insulators 32, 33 that cover the conductor 30 constituting one core wire and the conductor 31 constituting the other core wire are varied at pitch _P2 , and such insulators 32, 33 are coated. conductors 30 and 31 to each other
It is made by twisting _P1 .

FIG. 9 is an external view of still another embodiment of the present invention, in which grooves of pitch P ₁ are formed in insulators 40 and 41, and a conductor 42 constituting one core wire and a conductor 42 constituting the other core wire are formed in the insulators 40 and 41. The conductor 43 constituting the structure is housed, and the insulators 40 and 41 are twisted together at a pitch of _P2 .

Effects of the Invention As explained above, according to the present invention, since the cable is configured to have different periods P ₁ and P ₂ , even if there is an upper limit to the helical pitch of the conductor due to manufacturing reasons, By using two different pitches P ₁ and P ₂ that are below the upper limit, it is possible to give the cable an arbitrary period. Therefore, manufacturing becomes extremely easy. In addition, by setting two different pitches independently to match the desired radiation frequency band, it is possible to obtain any two different radiation frequency bands, which also has the effect of allowing different users to share one cable. .

[Brief explanation of drawings]

Figures 1 to 3 are explanatory diagrams of conventional spiral conductor type leaky cables, Figures 4 to 6, Figures 8 and 9.
The figures are explanatory diagrams of different embodiments of the present invention, and FIG. 7 is a diagram showing how to use the helical conductor type leaky cable of the present invention. 10 to 13, 30, 31, 42, 43 are conductors,
14 to 17, 32, 33, 40, and 41 are insulating bands.

Claims (1)

[Claims] 1. In a helical conductor type leaky cable, it consists of two sets of core wires used as a pair, each core wire consists of one or two conductors, and the entire cable has two different periods. Features a spiral conductor type leaky cable.