JPS6345122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an open coaxial cable used in mobile communications.

BACKGROUND OF THE INVENTION It has been a common practice to install open transmission lines that generate an electromagnetic field in an external space along a moving path, and to perform mobile communications via these lines.

As the open type transmission line used in this case, there is an open type coaxial cable, and the types shown in FIGS. 1 and 2 have been used conventionally.

In FIG. 1, 11 is an inner conductor, 12 is an insulator, 13 is an outer conductor, and 14 is a plastic sheath, and the outer conductor 13 is formed to have an opening 15 continuously in the longitudinal direction.

Further, in FIG. 2, 21 is an inner conductor, 22 is an insulator, 23 is an outer conductor, and 24 is a plastic sheath, and the outer conductor 23 is formed by winding a metal tape spirally at a predetermined pitch.

When the open-type coaxial cable shown in FIGS. 1 and 2 is laid in the ground space along the moving path, and a signal in the inductive radio frequency band is fed between the inner conductor and the outer conductor, the A current flows through the wire, and this current creates an electromagnetic field, the strength of which is proportional to the coupling impedance.

In this case, the coupling impedance can be increased by increasing the opening width of the opening 15 in the case of FIG. 1, and by increasing the winding pitch of the outer conductor 23 in the case of FIG. 2. However, if the coupling impedance is increased, the transmission characteristics of the line formed by the inner conductor and the outer conductor will be impaired, resulting in increased transmission loss.

Conversely, if the coupling impedance is made smaller, the electromagnetic field formed outside will be weaker.

The present invention has been made based on the above, and includes:
The object of the present invention is to provide an open coaxial cable that can strengthen the electromagnetic field formed outside while keeping transmission loss low.

That is, in the present invention, the outer conductor has a two-layer structure, an inner and outer layer insulated from each other, the inner layer outer conductor is formed by longitudinally attaching a metal tape so as to have a continuous opening in the longitudinal direction, and the outer layer outer conductor is formed by forming a spiral conductor. It is characterized by being formed by winding it into a shape.

FIG. 3 shows an embodiment of the present invention.

1 is an inner conductor, 2 is an insulator, 3 is an inner layer outer conductor, 6 is an outer layer outer conductor, and 7 is a plastic sheath. The inner layer outer conductor 3 is formed to have an opening 4 continuously in the longitudinal direction.

An insulator 5 is interposed between the inner layer external conductor 3 and the outer layer outer conductor 6 to insulate them from each other.
The insulator 5 is formed by winding plastic tape or extruding plastic.

The outer layer external conductor 6 is formed by spirally winding a metal tape.

Here, the opening width of the opening 4 and the outer layer external conductor 6
The winding pitch of the circuit is appropriately selected, the coupling impedance of the line formed between the inner conductor 1 and the inner layer outer conductor 3 is set low (approximately 10 to 100 Ω/Km), and the coupling impedance of the line formed between the outer layer outer conductor 6 and the ground is set to be low. By setting the coupling impedance of the line high (approximately 100 to 1000 Ω/Km), it becomes possible to have both the signal transmission function and the external electromagnetic field formation function, allowing low-loss transmission and strong electromagnetic field. Formation can be realized.

Note that the formation of the outer layer external conductor 6 is not limited to winding a metal tape, but may also be formed by winding a plurality of thin bare conductors arranged in parallel (single-stripe braiding), or by winding a plurality of thin bare conductors arranged in parallel. It is also possible to wind the wires arranged in parallel with an insulated conductor wire.

As explained above, according to the present invention, the transmission function of the line formed by the inner conductor and the inner layer outer conductor, the signal energy introduction function of the line formed by the inner layer outer conductor and the outer layer outer conductor, the outer layer The radiation function of the line formed between the conductor and the ground is continuously integrated, resulting in an open coaxial cable with excellent transmission and radiation characteristics.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of a conventional example, respectively, and FIG. 3 is an explanatory diagram of one embodiment of the present invention. 1: Inner conductor, 2: Insulator, 3: Inner layer outer conductor, 5: Insulator, 6: Outer layer outer conductor.

Claims (1)

[Claims] 1 An outer conductor is provided around the outer periphery of the inner conductor via an insulator, and this outer conductor has a two-layer structure, inside and outside insulated from each other, and the inner layer outer conductor is made of metal tape so as to have continuous openings in the longitudinal direction. An open type coaxial cable characterized in that the outer conductor is formed by winding the conductor in a spiral shape.