JPH0227609Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a helical antenna used in various radio equipment.

Conventional configuration and its problems Conventional normal mode helical dipole antennas, where the inner diameter of the helix is sufficiently small compared to the wavelength, have the advantage of being significantly smaller in size than dipole antennas using straight conductors, but the feeding structure is It is not put into practical use much because it is complicated.

A conventional helical dipole antenna 1 having an inner diameter φ, a number of turns N, a radial length L, and a pitch P is shown. Since the above antenna is a balanced type, when feeding power using an unbalanced feed line such as a coaxial line, it is configured with a power top with a total length of λ/4 (λ: wavelength) as shown in Figure 2, as an example. A balanced/unbalanced converter is required. In FIG. 2, 1 is a helical dipole antenna, 2 is a coaxial line, and 3 is a short-circuited top with a length of λ/4 (λ: wavelength).

Therefore, even if the antenna itself can be shortened by using a helical dipole antenna, the antenna system including the feeding section cannot be made smaller by using a converter such as the Shupel top 3. FIG. 3 shows another conventional helical dipole antenna composed of a core wire of a coaxial line and a jacket conductor.

In Figure 3, 4 is the core wire of the coaxial line, 5 is the outer conductor of the coaxial line, and 6 is the connector.Since the balance/unbalance converter shown in Figure 2 is not used, the antenna configuration is very simple. It can be made smaller.

However, with the above configuration, it is not possible to prevent unbalanced current components flowing through the outer conductor 5 of the coaxial line, so the current distribution of the helical dipole antenna becomes asymmetrical, which deteriorates the antenna characteristics and causes unbalanced current to flow into the radio casing etc. flows, making the characteristics unstable.

Purpose of the invention The present invention eliminates the above-mentioned drawbacks of the conventional antenna, and provides a helical antenna with a simple configuration that can block unbalanced current components and provide stable characteristics.

Structure of the Invention In order to achieve the above object, the present invention is characterized in that a branch line is provided in parallel to the outer conductor of the coaxial line.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

This embodiment consists of a coaxial line core wire 4 a coaxial line jacket conductor 5 and a branch line 7 wound on a Teflon (registered trademark) rod 8, as shown in FIG. 4a. 6 is a connector.

The helical dipole antenna in Fig. 4a is extended to show the antenna structure in an easy-to-understand manner.
Shown in Figure b.

The core wire 4 and the branch wire 7 each have a length l approximately equal to λ/4, and the branch wire 7 is installed parallel to the jacket conductor 5 of the coaxial line, and one end thereof is connected to the center of the antenna. The transmission line is connected to the coaxial jacket conductor 5 at the feeding point, and the other end has an open-ended transmission line structure. As can be seen from the structure shown in Fig. 4b, a sinusoidal current distribution is applied to the core wire 4 and the branch wire 7, and the unbalanced current component that attempts to flow through the outer conductor 5 to the radio casing etc. is seen from the base of the antenna. This is blocked by a branch line 7 which operates as a λ/4 transmission line with short-circuited ends.

Effects of the invention The present invention has the above-mentioned configuration.According to the present invention, it has a relatively simple configuration, is short in length and has excellent operability, and since no unbalanced current flows, the coaxial outer conductor and There is an advantage that no high frequency current component flows on the radio casing and stable radiation characteristics are achieved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional helical antenna, Fig. 2 is a schematic diagram of a helical dipole antenna with a shovel top, Fig. 3 is a schematic diagram of another conventional helical antenna, and Fig. 4a is an implementation of the present invention. FIG. 4b, a front view of the helical antenna in the example, is a schematic diagram of the helical antenna. 4... Core wire, 5... Outer conductor, 6... Connector, 7... Branch wire.

Claims (1)

[Scope of utility model registration request] Consisting of a first element consisting of a core wire of a coaxial line, and a branch line having one end connected to the jacket conductor of the coaxial line at the feeding point, the other end being open-ended and parallel to the jacket conductor. A helical antenna consisting of a second element.