JPS5836842B2 - J type antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is primarily concerned with comprehensive improvements in problems with matching, strength, lightning protection, etc. of J-type antennas installed in small-scale fixed stations and mobile stations (vehicles, ships, aircraft), etc. It is related to.

Conventionally, the vertically polarized omnidirectional J-type antenna for very high frequency waves used in mobile stations such as small-scale land stations, vehicles, and ships is basically as shown in Figure 1, and the coaxial cable 1 A matching element 3 having a length of approximately 1/4 wavelength extended from the outer conductor 2 of
a radiating element 5 parallel to said element 3 and having a length of about 3/4 wavelength extending from the center conductor 4 of the coaxial cable 1;
The currents flowing between B and C are opposite to each other and have the same current value. Therefore, the radiation currents cancel each other out, so between A and B of the 1,/2 wavelength portion of the radiating element 5 is a vertical half-wave dipole antenna. It is well known that the directivity in the horizontal plane is omnidirectional.

In contrast, FIG. 2 shows a practical example in which a matching element 7 with a length of about 1/4 wavelength and a radiating element 8 with a length of about 3/4 wavelength are mounted parallel and perpendicular to each other on an insulating base 6. In this case, the diameter and length of the matching element 7 and the distance S between the matching element 7 and the radiating element 8 are adjusted via the fixed insulator piece 10 to connect the J-type antenna 9 and the coaxial cable 11. However, in reality, such a structure does not allow detailed matching, and the insulation of the insulating base 6 may deteriorate due to rain, snow, sea breeze, etc., and the antenna installation height and surrounding conditions may vary. Due to the change in antenna capacitance caused by the difference, the radiation current values flowing through both elements 7 and 8 of the l/4 wavelength matching section are not equal, and radiation in unnecessary directions increases, so the standing wave ratio (V
Furthermore, since the J-type antenna shown in Figures 1 and 2 does not have a lightning protection circuit, abnormally high voltage current flows through the antenna circuit, transmitter/receiver, etc. during a lightning strike, causing damage to the equipment. there were.

However, as shown in FIG. 3, the radiating element 13 and matching element 14 are directly installed on the grounded metal base 12,
The lightning protection type J-type antenna 16 of the two-wire parallel feeding method is adjusted by adjusting the connection position of the two-wire parallel feeding line 15, or as shown in FIG. 4, the radiating element 17 and matching element 18 are grounded. A J-type antenna 23 that is directly fixed to the metal base 19 that has been fixed, connects the external conductor 21 of the coaxial cable 20 to the lower part of the matching element 18, and adjusts the connection position between the center conductor 22 and the radiating element 17 for matching. As shown in FIG. 5, a radiating element 25 is directly fixed to a grounded metal base 24, a matching element 26 is fixed via an insulating base 27, and power is supplied from the lower end of the matching element 26, and the matching element 25 is fixed directly to a grounded metal base 24. The diameter and length of the element 26 and both elements 25, 2
There are J-type antennas 28, etc. that are matched by adjusting the spacing S of 6, but these conventional J-type antennas 9, 16, etc. , 23, and 28 cannot be precisely matched due to their structure.Moreover, if the structure is designed to be able to match even large changes in antenna capacity, it will not only be impossible to form a lightning arrester circuit, but also the strength will be reduced, especially for mobile stations. As for the aerial, sea breeze,
There was a problem with the strength against rain, snow, wind, vibration, etc., and in the end,
The J-type antenna had the disadvantage that it was hardly used at present.

SUMMARY OF THE INVENTION The object of the present invention is to provide a J-type antenna which is provided with a lightning protection circuit and has sufficient strength, and which can be easily matched to large changes in antenna capacity, thereby overcoming the above-mentioned drawbacks of the conventional antenna. It consists in removing.

Next, the structure of the first embodiment including the principle of the present invention is shown in FIGS.
This will be explained with reference to FIG.

A radiating element 29 having a length of approximately 3/4 wavelength and having a length of approximately 3/4 wavelength and having the shape of a metal pipe of an appropriate diameter is mounted vertically on a grounded metal base 30. A feeding matching element 31 is mounted parallel to the radiating element 29 at a constant distance through an insulating base 32, and a circle of an arbitrary radius centered on the radiating element 29 is formed on the metal base 30. A matching element 34 is attached to the arcuate long hole 33 via a nut 35 so that the distance between the matching element 34 and the feeding matching element 31 can be adjusted, and the radiating element 29 and the feeding matching element 31 are connected by a metal shorting piece 36 whose vertical position can be adjusted. , the center conducting wire 38 of the coaxial cable 37 is connected to a feeding point at the lower end of the feeding matching element 31, and its external conducting wire 39 is connected to the metal base 30.

Next, the operation of the J-type antenna 40 constructed as described above will be explained together with the principle of the present invention.

As shown in Fig. 8, if power is not fed from the center of a one-wavelength dipole antenna, but rather at a position exactly 1/4 wavelength from the end of the element 41, the current distribution will be as shown in the figure, and this will be When feeding power by changing the shape as shown in the figure, parallel l
The principle of the J-type antenna is that the radiation currents flowing through the pixel elements 42 and 43 in the /4 wavelength portion are in opposite directions and cancel each other out, thereby operating as a 1/2 wavelength dipole antenna.

On the other hand, as shown in FIG.
If the matching between the antenna 48 and the coaxial cable 47 is adjusted by sliding the shorting piece 46 while feeding power from points and points E through the coaxial cable 47, the current distribution will become approximately the same as that shown in FIG.

Therefore, as shown in FIG. 11, 1/
When the radiating element 44 is folded back at four wavelengths and the F point is grounded, a lightning-protected J-type antenna 49 is obtained.

However, with only this matching method, due to the structural relationship of the feeding matching element 45 and the shorting piece 46, the radiation current is approximately 3/4
The radiation current flows toward the radiating element 44 side having a wavelength length, and the radiation current flowing through the 1/4 wavelength matching portion of the radiating element 44 and the matching element 50 are not equal.

Therefore, by slightly loosening the nut 35 at the lower end of the matching element 34 that is fixed through the circular arc-shaped elongated hole 33, the matching element 34 is inserted into the seventh
When sliding along the elongated hole 33 between points a and b in FIG.
At the point, there is no change in the value of the radiation current flowing in the 1/4 wavelength matching portion of the matching element 34 and the radiating element 29, and the radiation current flows toward the radiating element 29 side. As it gradually slides from point b toward point a, the interval T between the feeding matching element 31 and the matching element 34 becomes narrower, and the coupling between the two elements 3L34 becomes tighter.

As a result, as can be understood from FIGS. 6, 10, and 11, the radiation currents flowing on the feeding matching element 31 and the matching element 34 are in opposite directions, and therefore, the back electromotive force between the two elements 31 and 34 is As a result, the value of the radiation current flowing through the matching element 34 gradually increases, and finally the radiation current flowing through the 1/4 wavelength matching portion of the radiation element 29 and the radiation current flowing through the matching element 34 become equal and cancel each other out. , stable vertically polarized omnidirectional radiation can be obtained from the 1/2 wavelength portion of the radiating element 29.

Next, the effects of the present invention will be explained.

In the present invention, a 3/4 wavelength radiating element formed of a metal pipe is mounted vertically on a grounded metal base, and a feeding matching element formed of a metal pipe is connected to the radiating element via an insulating base. and the radiating element and the feeding matching element are connected to each other by a shorting piece formed of a metal body such that the vertical position of the shorting piece can be adjusted. L/
A J-type antenna in which a four-wavelength matching element is attached to the feeding matching element so that the spacing between the radiating element and the feeding element can be arbitrarily set while maintaining the spacing between the radiating element and the radiating element at equal intervals, and the upper end of the feeding matching element is set as the feeding point. It is in.

As a result, the present invention facilitates matching between the coaxial cable and the antenna by moving the shorting piece up and down, and also slides the matching element through the elongated hole to change the distance between the feeding matching element and the radiating element. It is extremely easy to make the opposite direction radiation current values flowing in the 1/4 wavelength matching part of the radiating element and the matching element almost completely equal, and
Stable vertically polarized non-directional radiation can be obtained from the element in the wavelength region, and the adjustment can be made extremely finely even in response to changes in antenna capacity due to the height at which the antenna is installed and surrounding conditions. In addition, since the radiating element and matching element can be directly fixed to the metal base, the degree of lightning protection is increased, and sufficient strength can be obtained against upwind and vibration. Since power is supplied from the antenna, changes in antenna capacity can be minimized even when insulation deteriorates due to sea breeze, rain, snow, etc., and the structure is extremely simple and can be manufactured at low cost.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the principle of the J-type antenna, and Figure 2 is the conventional J-type antenna.
3 is an explanatory diagram of a lightning-protected type J-type antenna using the two-wire parallel power feeding method; Figures 4 and 5 are explanatory diagrams of a lightning-protected type J-type antenna using the coaxial cable feeding method; FIG. 6 is a front view of the first embodiment of the present invention, FIG. 7 is a plan view thereof, and FIGS. 8 to 11 are explanatory diagrams showing the principle of the present invention. Note that the arrow in the figure indicates the current direction. 29... Radiation element, 30... Metal base, 31... Feeding matching element, 32... Insulating base, 33... Elongated hole, 34... Matching element, 36... Short circuit piece.

Claims (1)

[Claims] 1. A 3/4 wavelength radiating element shaped like a metal pipe is mounted vertically on a grounded metal base, and a feeding matching element shaped like a metal pipe is attached to the radiating element via an insulating base. the radiating element and the feed matching element are connected to each other with a constant interval maintained therebetween, and the radiating element and the feeding matching element are connected to each other by a shorting piece formed of a metal body so that the vertical position of the shorting piece can be adjusted; A 1/4 wavelength matching element formed of a metal pipe is attached through an elongated hole to the radiating element so that the interval between the feeding element and the feeding matching element can be arbitrarily set while maintaining an equal interval between the radiating element and the radiating element. A J-type antenna characterized in that a lower end of a feeding matching element is used as a feeding point.