JPH0233379Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna, and more particularly to a coaxial antenna having a biconical antenna element and having a unique feeder structure.

As is well known, matching the input impedance of the feeder and the antenna impedance is a condition for supplying the output of the transmitter to the antenna without feeder loss and producing the maximum output from it. Therefore, in theory, it would be sufficient to simply set the input impedance of the feeder or the impedance of the antenna to match the other, but in practice, the impedance of the antenna depends on the purpose of use of the antenna. It is set to a specific value, for example 50Ω, so
In order to match the specific value, a matching circuit and means for impedance matching are separately provided. This impedance matching circuit consumes power in the circuit and does nothing, so something like a resistor cannot be used, so a combination of a coil and a capacitor is generally used. However, like the antenna to which this invention pertains, the coaxial feeder has a rod-shaped central conductor connected to the upper conical antenna element, and a pipe-shaped central conductor placed around it and connected to the lower conical antenna element. In the case of a structure consisting of an external conductor, it is difficult to apply an impedance matching circuit such as a general combination of a coil and a capacitor to the structure, and therefore, in practice, impedance matching requires some ingenuity.

The present invention was developed in view of these points, and its gist is that a coaxial cylindrical rod-shaped center conductor is connected to an upper conical antenna element made of a metal plate, and a pipe-shaped outer conductor is connected to a metal plate. In an antenna connected to a lower conical antenna element, the rod-shaped center conductor is formed into a tapered rod shape whose diameter gradually decreases from the lower end side where the connect pin connects to the upper end where it connects with the antenna. An antenna in which the input impedance of the feeder can be matched with the antenna impedance by forming a central conductor and an outer conductor such that the distance between the center conductor and the outer conductor gradually increases toward the upper end, and changing the inductance L and capacitance C, The purpose of this is to provide a biconical antenna that can match the feeder input impedance and antenna impedance as much as possible. To provide a biconical antenna that can be matched.
Therefore, it is easy to produce, and the center conductor and outer conductor can resist wind pressure and the antenna element of this antenna.
The object of the present invention is to provide a biconical antenna which has a firm supporting function and is capable of performing the impedance matching without impairing the supporting function.

Next, embodiments of the present invention will be described in detail based on the accompanying drawings.

Reference numeral 1 indicates an upper conical antenna element, 2 indicates a lower conical antenna element, 3 indicates a rod-shaped central conductor, and 4 indicates a pipe-shaped outer conductor. The means for attaching the upper conical antenna element 1 and the rod-shaped central conductor 3 and the means for attaching the lower conical antenna element 2 and the pipe-shaped outer conductor 4 are not particularly limited; A pipe-shaped outer conductor 4 is fixed to the base 5 of the conical antenna element 2 by brazing or the like, and an insulating collar 6 is screwed onto the upper end of the pipe-shaped outer conductor 4. And this insulation collar 6
an upper conical antenna element 1 is correspondingly installed with respect to a lower conical antenna element 2 via the
Next, the rod-shaped center conductor 3 is inserted into the pipe-shaped outer conductor 4 from the lower end 7 side, and passed through until the upper screw 8 passes through the insulating collar 6 and faces upward. The upper screw 8 of the center conductor 3 is screwed into the threaded portion 10 of the mounting body 9 attached to the holder 9, and tightened. When tightened, the rod-shaped center conductor 3 moves upward in the figure, and the stopper ring 11 provided on the center conductor 3 comes into contact with the lower end 7 of the pipe-shaped outer conductor 4. In this state, the lock screw 12 is tightened from the circumferential surface of the mounting body 9 to fix the center conductor 3. After assembling in this manner, an N-type connector 14 is attached with a contact collar 13 made of synthetic resin interposed therebetween. At this time,
A connect pin 15 at the lower end of the rod-shaped central conductor 3 is located at the center of the connector 14.

In the present invention, in a coaxial antenna having such a biconical antenna element, the rod-shaped central conductor 3 is arranged as shown in the enlarged view of FIG.
From the lower end 16 to which the connect pin 15 is connected,
It is formed into a tapered shape so that the diameter gradually decreases toward the upper part 17 where the mounting body 9 is screwed. That is, when the diameter of the upper end 17 is a and the diameter of the lower end is b, a<b and the diameter between them is continuously changed. By doing this, the thickness of the center conductor 3 and the distance between the center conductor 3 and the outer conductor 4 are made variable compared to a case where the diameter of the center conductor is uniform across the top and bottom and is the same diameter as a. To be more specific, the diameter of the center conductor 3 gradually increases as it approaches the lower end 16, and the distance between the center conductor 3 and the outer conductor 4 narrows as it approaches the lower end 17. The inductance L is smaller and the capacitance C is larger than that of the same diameter which remains a uniformly over the top and bottom. It can be set to be smaller than that. The present invention uses such a means to adjust the input impedance of the feeder so that it matches the impedance of the antenna, which is determined to be a specific value.

As an example, according to the applicant's experiments, the diameter of the center conductor 3 having a length (S) of 131 mm is made uniform from top to bottom.
2.5mm, and when the outer conductor 4 has an outer diameter of 8mm, an inner diameter of 7mm, and a wall thickness of 1mm, its input impedance is 75Ω, which is the impedance of a single coaxial type/2 antenna to which this invention is applied. Where there is no matching for 50Ω, the diameter of the center conductor 3 at the lower end 16 is 3 mm and the diameter at the upper end 17 is 2.5 mm.
By setting the input impedance to 50Ω, we were able to match the antenna impedance.

In this way, the present invention provides an antenna in which a coaxial cylindrical rod-shaped center conductor is connected to an upper conical antenna element made of a metal plate, and a pipe-shaped outer conductor is connected to a lower conical antenna element made of a metal plate. In this case, the rod-shaped center conductor is formed into a tapered rod shape whose diameter gradually decreases as it goes from the lower end where the connect pin connects to the upper end where it connects to the antenna, and the distance between the center conductor and the outer conductor is adjusted to the upper end. By changing the inductance and capacitance, it was possible to match the input impedance of the feeder with the antenna impedance, so the feeder could be adjusted by changing the shape of the feeder without using a circuit such as a combination of coils and capacitors. It is possible to provide a biconical antenna that can match the input impedance and antenna impedance, and therefore it can be easily produced during production. It has a firm and supportive function, but
It is possible to provide a biconical antenna capable of performing the above impedance matching without impairing these supporting functions.

[Brief explanation of the drawing]

The accompanying drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional side view, and FIG. 2 is an enlarged view schematically showing changes in the diameter of the center conductor.

Claims (1)

[Scope of utility model registration request] In an antenna, a coaxial cylindrical rod-shaped central conductor 3 is connected to an upper conical antenna element 1 made of a metal plate, and a pipe-shaped outer conductor 4 is connected to a lower conical antenna element 2 made of a metal plate. , connect the rod-shaped center conductor 3 to the connecting pin 15.
The rod is formed into a tapered rod shape that gradually becomes smaller in diameter as it goes from the lower end 16 side where it is connected to the upper part 17 that is the connection point with the antenna. An antenna in which the input impedance of the feeder is matched to the antenna impedance by changing the inductance L and capacitance C.