JP2606574B2 - Helical antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical antenna having a helical conductor, a coaxial cable for feeding the helical conductor, and a dielectric tube for maintaining the dimensions of the helical conductor.

[0002]

2. Description of the Related Art FIG. 5 is a perspective view showing an example of a conventional helical antenna. In FIG. 5, the helical antenna is formed of two spiral helical conductors 1 and 2, a coaxial cable 3 passing through the center thereof, and a support 4 made of a dielectric for holding the helical conductors 1 and 2. ing.

The helical antenna configured as described above radiates circularly polarized waves by inputting high-frequency power to the coaxial cable 3 and exciting the helical conductors 1 and 2 via the balun 5. This conventional helical antenna is also described in the IEICE Transactions on Antenna Propagation Research Report AP91-65,
Its applied form is used.

[0004]

However, the conventional helical antenna has a problem that the directivity pattern of the electric field radiated from the antenna is fixed, and the angle range that can be used with a desired gain is limited. There was a point.

An object of the present invention is to provide a helical antenna having a wide coverage area which can be used with a desired gain.

[0006]

SUMMARY OF THE INVENTION A helical antenna according to the present invention is covered with an elongated dielectric cylinder and a soft dielectric disposed within the dielectric cylinder so that the direction of the radiation pattern of the antenna can be adjusted. A spiral helical conductor pair formed by twisting a pair of parallel two-wire conductors a desired number of times; Structure.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a helical antenna according to one embodiment of the present invention. In FIG. 1, the helical antenna has a dielectric cylinder 6 and a linear coaxial cable 3 adhered to the outside of the dielectric cylinder 6 in parallel with the cylinder 6 with, for example, an adhesive.
A connector 10 is provided at the lower end of the coaxial cable 3, and a balun 5 is formed at the upper end thereof by bending a coaxial cable having a length of about half a wavelength into a U-shape. The extension of the central conductor at the upper end of the coaxial cable 3 is connected to one central conductor of the balun 5. On the other hand, helical conductors 1, 2
Is coated with a soft dielectric coating 7 like a TV feeder wire while keeping the distance between the two wires constant, and forms a spiral by twisting the pair of helical conductors 1 and 2 a desired number of times. The extension of the center conductor of the balun 5 and the extension of the upper ends of the helical conductors 1 and 2 are connected by feeder lines 8 and 9.

FIG. 2 is a cross-sectional view of the upper end of this embodiment. Helical conductors 1 and 2 use cap 1
2 fixed.

FIG. 3 is a perspective view of the lower end portion in this embodiment. Helical conductors 1 and 2 have holes 13 in cap 11
The number of twists for obtaining a desired pattern can be adjusted by rotating the cap 11 having a large number of irregularities on the inner wall of the dielectric cylinder 6 and the irregularities to be fitted with it, one step at a time. The twist is held by the cap 11. That is, the number of twists for obtaining a desired pattern is freely adjustable.

FIG. 4 shows another embodiment of the mechanism for adjusting the number of twists. Helical conductors 1 and 2 are holes 1 in cap 15
3, 14 and also a number of holes 17 in the dielectric cylinder 6
The cap 15 can be fixed by allowing the pins 16 to penetrate through the holes 16 and the many holes 18 of the cap 15.

Next, the electrical operation of this embodiment will be described.
When high-frequency power is supplied from the connector 10, the power passing through the coaxial cable 3 and the power further passing through the balun 5 having a length of about half a wavelength are electrically connected to the helical conductors 1 and 2, respectively.
2 is fed. That is, currents having phases opposite to each other flow through the upper ends of the helical conductors 1 and 2. The current supplied from the upper end attenuates while radiating circularly polarized waves in a desired direction in the process of flowing to the lower end.

The calculated values of the directivity pattern of this embodiment are shown below.

In FIG. 1, the length of the helical antenna is 700 [mm], and the interval between the helical conductors 1 and 2 is 8.5.
[Mm], and cap 11 at the lower end is turned 10 times (solid line).
FIG. 5 shows the results obtained by calculating the directivity pattern when twisting is performed 11 times (dotted line). In FIG. 5, 10
The direction of the radiation pattern is different between the winding and the eleventh winding, indicating that the radiation pattern can be controlled by rotating the cap.

[0014]

The helical antenna of the present invention can arbitrarily direct the radiation pattern by twisting the lower end cap a desired number of times. As a result, the coverage area can be widened.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a helical antenna according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an upper end of the helical antenna shown in FIG.

FIG. 3 is a perspective view showing a lower end of the helical antenna shown in FIG. 1;

FIG. 4 is a perspective view showing a lower end portion of the helical antenna shown in FIG. 1;

FIG. 5 is a diagram showing a directivity pattern of the helical antenna shown in FIG.

FIG. 6 is a perspective view showing a helical antenna according to a conventional example.

[Explanation of symbols]

 1, 2 Helical conductor 3 Coaxial cable 4 Support 5 Balun 6 Dielectric cylinder 7 Dielectric coating 8 Feed line 10 Connector 11, 12, 15 Cap 13, 14 Conductor hole 16 pin 17, 18 pin hole

Claims (3)

(57) [Claims] 1. An elongated dielectric cylinder, means for twisting a pair of parallel two-wire conductors coated with a soft dielectric in said dielectric cylinder a predetermined number of times, and along an outside of said dielectric cylinder. A helical antenna comprising: an arranged coaxial cable; and a feeding unit for feeding high-frequency power to the conductor pair from an upper end of the coaxial cable. 2. The means for twisting a conductor pair according to claim 1,
A helical antenna comprising: a first cap for fixing the conductor pair at an upper end of the dielectric cylinder; and a second cap which is fixed at a lower end of the dielectric cylinder and is rotatable. 3. The helical antenna according to claim 2, wherein the second cap can be fixed at a predetermined position.