JPS62105503A - Spiral antenna - Google Patents

Abstract

PURPOSE:To obtain directivity which is excellent in a wide range and constant by constituting a reflecting plate spirally and placing the distance between the reflecting plate and a strip conductor in specific relation with the radius from an axis. CONSTITUTION:The reflecting plate 4 is formed spirally having the same common axis as the axis of the spiral of the strip conductor 2 and the distance (l) of the spiral reflecting plate 4 from the strip conductor 2 is placed almost in relation l=pir/2 with the radius (r) from the spiral axis. Further, the pitch of the spiral of the conductor 2 is equal to the pitch of the spiral of the reflecting late 4. This spiral antenna has large upward directivity because the distance of the conductor 2 with any radius from the reflecting plate 4 is a quarter as long as the wavelength of a radio wave whose wavelength corresponds to the peripheral length and an upward radiation wave and a reflected wave are superposed one over another in in-phase relation. This relation is born as to frequencies higher than the frequency of the wavelength determined by the outer periphery of the conductor 2, so excellent directivity is obtained over a wide frequency range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spiral antenna that radiates W waves over a wide band.

[Conventional technology]

Figure 3 is a sectional view showing a conventional spiral antenna. In Figure 1, (1) is a dielectric substrate 2 (2) is a strip conductor formed on this dielectric substrate, and (3) is a strip conductor formed on the dielectric substrate.
A feed line that supplies current to the IJ tube conductor (2), (4
) is a cavity-shaped reflecting plate that reflects radio waves emitted from the IJ tube conductor.

A conventional spiral antenna is constructed as described above. For example, the current supplied from the feed line (3) to the IJ conductor C2) flows in a spiral manner on the strip conductor (2). The circumference of the strip conductor (2) is approximately 1 of the radio wave.
Radio waves are efficiently radiated to both the upper and lower sides of the dielectric substrate (1) at a radius that corresponds to the wavelength. Here, the radio waves radiated downward from the substrate (1) are reflected by the reflector (4) with the phase rotated by 180 degrees, and the distance between the reflector (4) and the dielectric substrate (1) is the wavelength of the radio wave. If -, this reflected wave will be in phase with the upwardly radiated radio wave, so it can have stronger upward directivity.

[Problem that the invention seeks to solve]

In the conventional spiral antenna as described above, the distance between the dielectric substrate (1) and the reflector (4) is approximately 4 times the wavelength of the radio wave.
If not 2 For example, for radio waves with a frequency of approximately 1/2 wavelength, 9 reflector (4) after being radiated downward.
There was a problem in that the radio waves reflected by and the radio waves radiated upward were out of phase, resulting in a significant deterioration of the upward directivity. Furthermore, this has caused a problem in that the wideband performance of the spiral antenna is degraded.

This invention has been made to improve the above-mentioned problems, and its object is to obtain a spiral antenna having good directivity over a wide band.

[Means for solving problems]

The spiral antenna according to the present invention is formed into a spiral shape with the spiral axis of the IJ tube conductor (2) as a common axis, and the strip conductor (2) of the spiral reflector (4). ) is set so that the distance M/ from the helical axis has a relationship with the radius r from the helical axis approximately as 'R1=''f.

[For production]

In this invention, the downwardly emitted radio waves are reflected by the spiral reflector so that they are in phase with the upwardly emitted waves at any frequency, so good directivity can be obtained over a wide band.

〔Example〕

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a sectional perspective view, in which (1) to (3) are completely the same as the conventional antenna described above. (4) is a strip conductor (
Let the axis of the spiral in 2) be the common axis.

The reflector has a spiral structure, and the distance j between the reflector (4) and the strip conductor (2) is the radius r from the axis and approximately l=■
The relationship is as follows.

Nineteenth, the pitch of the spiral of the strip conductor (2) and the pitch of the spiral of the reflector (4) match.

In the spiral antenna configured as above, the strip conductor (2) of any radius has a circumference of 1
Regarding radio waves having a wavelength, the distance from the reflecting plate (4) is /4 wavelength, and the upwardly emitted wave and the reflected wave are superimposed in phase, so the upward directivity becomes strong. This relationship holds true for all frequencies above the wavelength determined by the outermost periphery of the IJ tube conductor (2), so good directivity can be obtained over a wide band.

〔Effect of the invention〕

As described above, according to the present invention, one reflecting plate (4) is configured in a spiral shape, and the distance l between one reflecting plate (4) and the strip conductor (2) is defined as the radius r from the axis and approximately t = W 1 Since this relationship is established, it is possible to obtain good and constant directivity over a wide band.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a spiral antenna according to an embodiment of the present invention, FIG. 2 is a sectional perspective view showing an embodiment of the invention, and FIG. 3 is a sectional view showing a conventional spiral antenna. In the figure, (1) is a dielectric substrate, (2) is a strip conductor, and (4) is a reflective plate. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (2)

[Claims] (1) In a spiral antenna having a structure in which a plurality of strip conductors are formed in a spiral shape on a thin dielectric substrate and power is supplied from the center of the spiral or the outermost edge of the strip conductor, the first strip conductor A spiral reflector is constructed with the central axis of the spiral as a common axis, and the distance l between the reflector and the strip conductor is the radius r from the axis.
A spiral antenna characterized by approximately having a relationship of l=πr/2. (2) The strip conductor is formed in a log spiral shape,
The spiral antenna according to claim 1, wherein the reflector has a log-spiral spiral shape.