JPH10126150A - Cross dipole antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide two sets of cross dipole antennas, whose impedance is matched with each other through a comparatively simple configuration. SOLUTION: Branch conductors 16, 17 are arranged in parallel with coaxial feeders 12, 13, connecting to dipole antennas 10, 11 orthogonal to each other. When impedance of the two sets of the dipole antennas is matched by electrically connecting the branch conductors 16, 17 to outer conductors 12a, 13a of the coaxial feeders 12, 13 with a short-circuit plate 1, a spot facing 2 is formed on the short-circuit plate 1 so that a sum between a length of a center conductor 12b and a length from an end 17a of the branch conductor 17 to the branch conductor 17 in contact with the short-circuit plate 1 can be fine- adjusted to make the sum equal to 1/4 wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cross dipole antenna, and more particularly to a cross dipole antenna having a function of equalizing impedance characteristics of two sets of dipole antennas.

[0002]

2. Description of the Related Art FIG. 5 is a perspective view of an example of a conventional cross dipole antenna. A cross dipole antenna uses two sets of dipole antennas, which are mechanically arranged orthogonally, and electrically radiates circularly polarized waves by exciting each other with a phase difference of 90 degrees. Antenna.

Referring to FIG. 5, a conventional cross dipole antenna comprises two sets of dipole antennas 10 (elements 10a and 10b) and 11 (elements 11a and 11b) arranged orthogonally to each other, and these antennas 10 , 11 connected to the power supply coaxial feeder 1
2 and 13; coaxial connectors 14 and 15 connected to the ends of these coaxial feed lines 12 and 13;
And the outer conductors 1 of the branch conductors 16 and 17 and the coaxial feeder lines 12 and 13.
A short-circuit plate 18 for electrically short-circuiting 2a and 13a.

Further, the center conductor 12b of the coaxial feed line 12
Is connected to the element 11b, and the outer conductor 12a is connected to the element 11a. Similarly, the center conductor 13b of the coaxial feeder 13 is connected to the element 10b, and the outer conductor 13a is connected to the element 10a.

The sum L1 of the length of the center conductor 12b and the length from the end 17a of the branch conductor 17 to the point where the branch conductor 17 comes into contact with the short-circuiting plate 18, the length of the center conductor 13b and the end of the branch conductor 16 The sum L2 of the length from the portion 16a to the point where the branch conductor 16 contacts the short-circuit plate 18 is 4
The position of the short-circuit plate 18 is determined so as to be one-half wavelength.

For example, when the frequency of the dipole antennas 10 and 11 is 2 GHz, the wavelength is 150 mm, so that the quarter wavelength is 37.5 mm.
And the length of L2 must be 37.5 mm.

[0007] These coaxial feed lines 12, 13 and the center conductor 1
2b, 3b, the branch conductors 16, 17 and the short-circuiting plate 18 constitute a balanced-unbalanced conversion circuit, and the impedance of the two sets of dipole antennas 10, 11 viewed from the ends of the coaxial connectors 13, 14 is equal by this balanced-unbalanced conversion circuit. Is done.

By the way, the lengths of the center conductors 12b and 13b are actually set to different lengths in order to prevent the center conductors 12b and 13b from being short-circuited at the intersection.

Therefore, since the lengths L1 and L2 do not match, the impedance matching between the dipole antennas 10 and 11 cannot be sufficiently achieved.

On the other hand, as a measure for solving this drawback, Japanese Patent Application Laid-Open No. 57-65010 discloses two sets of dipoles printed on one or both sides of a dielectric substrate so as to be orthogonal to each other. A coaxial line for power supply provided correspondingly, and two connection lines connecting the two sets of dipoles and the inner conductor of the coaxial line are provided, and these two connection lines are provided on different surfaces of the dielectric substrate. A cross dipole antenna configured to intersect is disclosed.

In this cross dipole antenna, connection lines are respectively arranged on different surfaces of a dielectric substrate so that both are not short-circuited.

[0012]

However, in this prior art, a dielectric substrate printed on both sides must be used in order to prevent the connection lines from being short-circuited. Hole processing is also required. Accordingly, there is a disadvantage that the configuration is complicated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cross dipole antenna capable of achieving impedance matching between two sets of dipole antennas with a relatively simple configuration.

[0014]

In order to solve the above-mentioned problems, the present invention provides two sets of dipole antennas which are orthogonal to each other, a coaxial line for power supply connected to each of the dipole antennas, And a branch conductor, the center conductor of the coaxial line being connected to the end thereof, and the branch conductor and the outer conductor of the coaxial line at a point spaced a predetermined distance from the end of the branch conductor. And a short-circuit plate for electrically short-circuiting the branch conductor, wherein the short-circuit plate has means for changing a thickness in a longitudinal direction of the branch conductor at a portion in contact with the branch conductor.

According to the present invention, the length from the end of the branch conductor to the contact point of the short-circuit plate can be changed by changing the thickness of the contact portion between the short-circuit plate and the branch conductor. Thereby, the sum of the length of the center conductor of both antennas and the length from the end of the branch conductor to the contact point of the short-circuit plate can be made equal.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a perspective view of a preferred embodiment of a cross dipole antenna according to the present invention, FIG. 2 is a plan view of the antenna, FIG. 3 is a right side view of the antenna, and FIG. 4 is a front view of the antenna. The same components as those in the conventional example (FIG. 5) are denoted by the same reference numerals, and description thereof will be omitted.

The cross dipole antenna according to the present invention differs from the conventional cross dipole antenna (FIG. 5) only in the configuration of the short-circuit plate 1 corresponding to the short-circuit plate 18 of the conventional example. Therefore, the following description focuses on the configuration of the short-circuit plate 1.

In this cross dipole antenna, the lengths of the center conductors 12b and 13b are different from each other so as not to short-circuit the center conductors 12b and 13b. Now, it is assumed that the length of the center conductor 13b is set longer than the length of the center conductor 12b.

That is, the length of the center conductor 13b and the branch conductor 1
6, the sum L2 of the length from the end 16a to the contact point with the short-circuit plate 1 is the sum of the length of the center conductor 12b and the length from the end of the branch conductor 17 to the contact point with the short-circuit plate 1. This is the case where it is longer than L1. Then, the difference between the lengths L1 and L2 is L
3 is assumed.

A counterbore 2 is formed on the short-circuit plate 1 at a contact portion with the branch conductor 17. The thickness E in the longitudinal direction (the direction of arrow D) of the branch conductor 17 of the counterbore 2
(Notch length) is set equal to L3.

That is, since the counterbore 2 is formed on the short-circuit plate 1, the short-circuit plate 1 extends from the end 17 a of the branch conductor 17.
Therefore, the length from the end 16a of the branch conductor 16 to the point of contact with the short-circuit plate 1 is L2.
And the length of the center conductor 12b and the end 17a of the branch conductor 17
(L1 + L)
3) is equal.

Therefore, dipole antennas 10 and 11
Can be matched.

It is to be noted that, instead of forming a spot facing the contact portion of the short-circuit plate 1 with the branch conductor 17, the thickness of the contact portion of the short-circuit plate 1 with the branch conductor 16 in the longitudinal direction D may be increased. The effect of is obtained. In this case, the length L2 is shortened, but it goes without saying that the shortened length is set to be a quarter wavelength.

[0024]

According to the present invention, two sets of dipole antennas which are orthogonal to each other, a coaxial line for power supply connected to each of the dipole antennas, and the coaxial line arranged in parallel with the coaxial line A branch conductor whose center conductor is connected to its end, and a short-circuiting plate that electrically short-circuits the branch conductor and the outer conductor of the coaxial line at a point at a predetermined distance from the end of the branch conductor. A cross-dipole antenna comprising: a means for changing the longitudinal thickness of the branch conductor at a portion in contact with the branch conductor, so that the short-circuit plate has a relatively simple configuration without requiring a double-sided printed circuit board. Impedance matching of two sets of dipole antennas can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a cross dipole antenna according to a preferred embodiment of the present invention.

FIG. 2 is a plan view of the antenna.

FIG. 3 is a right side view of the antenna.

FIG. 4 is a front view of the antenna.

FIG. 5 is a perspective view of an example of a conventional cross dipole antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Short-circuit board 2 Counterbore 11 and 12 Dipole antenna 12b and 13b Central conductor 12, 13 Coaxial feed line 16, 17 Branch conductor

Claims (3)

[Claims] 1. A pair of mutually orthogonal dipole antennas, a feeding coaxial line connected to each of the dipole antennas, and a center conductor disposed parallel to the coaxial line and having a center conductor connected to the end of the coaxial line. A cross-dipole antenna comprising a branch conductor connected to the portion and a short-circuit plate for electrically short-circuiting the branch conductor and the outer conductor of the coaxial line at a point at a predetermined distance from the end of the branch conductor. A cross dipole antenna, wherein the short-circuit plate has means for changing a longitudinal thickness of a portion of the branch conductor in contact with the branch conductor. 2. The cross-dipole antenna according to claim 1, wherein said means for changing the thickness is formed by pitting a contact portion of the short-circuit plate with the branch conductor. 3. The means for changing the thickness is such that the sum of the length of the center conductor of the coaxial line connected to the branch conductor and the length from the end of the branch conductor to the contact point with the short-circuit plate is 4 3. The cross dipole antenna according to claim 1, wherein the cross dipole antenna is set to have one-half wavelength.