JPS6172402A - Variable length whip antenna - Google Patents

Abstract

PURPOSE:To prevent the change in the characteristic of a coaxial transmission line due to rainfall by connecting the solid coaxial transmission line to a basic element whose extension element is contained in a telescopic way freely. CONSTITUTION:The solid coaxial cable 10 is used as the coaxial transmission line. An inner pipe 21 and an outer pipe 22 are arranged around said cable 10. The tip of a center conductor 12 is fixed to the basic element 31 at a feeding point A. The extension elements 32-36 are contained in the basic element 31 via a phase correction coil 32d in a telescopic way freely. The hollow structure is adopted up to the basic element 31 and solid structure is used for the downward cable 10 from the feeding point A. Since the possibility of rainfall or the like sinking into the cable 10 is precluded. Thus, the change in the characteristic impedance of the coaxial transmission line due to rainfall is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a variable length whip antenna using a coaxial transmission line.

Conventional technology and problems Wireless communication antennas used in moving objects such as automobiles are
In order to obtain non-directional radiation characteristics in the horizontal plane, many use a so-called whip type in which the radiation element is vertical. In particular, for mobile objects that travel on the ground, there are many demands for improving the vertical radiation characteristics of the antenna and improving the gain of the antenna in order to expand the communication area. As a means to narrow down the radiation characteristics in the vertical plane,
In order to make the phases of the currents flowing through the vertical radiating elements as in-phase as possible, it is necessary to increase the physical length of the radiating elements while making appropriate phase corrections.

By the way, an actual vehicle-mounted antenna does not always need to use a large radiating element. For example, in amateur radio, when traveling relatively short distances such as driving around town, the total length λ/
One stage of short antenna with a relatively low gain of about 4 or 5λ/8 is used, and when a relatively long distance communication is desired, such as when driving in the suburbs, two or three stages of 5λ/8 radiating elements are connected. Use antenna.

However, such selective use requires time and effort to replace the entire radiating element at the antenna base, so while it may be fine for enthusiasts, it is not preferable to apply it to, for example, a personal radio antenna that is also used by the general public.

Therefore, the present invention etc. makes the central conductor hollow and stores the radiating element for expansion inside it in a freely insertable and removable manner.
We proposed a whip antenna whose total length can be easily varied. FIG. 1 shows an example of this, in which 1 is a coaxial transmission line, 2 is its center conductor, and 3 is an outer conductor. The center conductor 2 is hollow, and inside it is a radiating element for increasing λ/2 (multiplying element).
4 is stored in a removable manner. The tip of the outer conductor 3 is λ/
It is folded back by the length of 4 to form a skirt portion 5.

This λ/4 skirt portion 5 is the ground plane of this antenna, and the skirt portion 5 and the λ/4-long center conductor exposed from here to the tip constitute a λ/2 vertical dipole antenna (basic antenna), I 6 is configured. 7 is a λ/2 phase correction coil connected between the lower end of the multiplication element 4 and the sliding member 8, and its periphery is reinforced with a highly rigid dielectric resin 9 or the like. The sliding member 8 is made of the same metal as the center conductor 2 and ensures conductivity between it and the center conductor 2.

The coil 7 is connected to the dipole antenna 6 as shown in FIG.
An electric field E2 having a phase opposite to that of the electric field E1 is generated in the increasing element 4, so this is absorbed and turned into an electric field E2' having the same phase as El. Without this coil 7, the electric field E1 of the antenna 6
is canceled by the electric field E2 of opposite phase, so the increase element 4
It is better not to use it. If the coil 7 is interposed, the electric field generated in the entire antenna becomes the sum of E I (!: E 2').

With the above-described configuration, the antenna gain can be doubled simply by pulling out the multiplication element 4 as shown in FIG. By pushing the multiplication element 4 into the center conductor 2 when it is not needed, the antenna 6 can function as its own, and its handling is extremely simple. However, if the center conductor 2 is hollow, rainwater or the like may seep in through the opening at its tip, which may change the characteristic impedance of the coaxial transmission line 1 over a long period of time.

purpose of invention The present invention aims to further improve this point.

Structure of the Invention The present invention comprises a solid coaxial cable extending to a feed point, a hollow basic element connected to the center conductor of the coaxial cable and extending further upward from the feed point, and an external element of the coaxial cable. a conductor that is connected to a conductor and extends downward from the feed point and forms a basic dipole antenna together with the basic element; a multi-stage extension element that is telescopically housed within the basic element; It is characterized in that it has a phase correction element incorporated in a part thereof, and the overall gain can be switched by using or not using the amplifying element. Explain in detail.

Embodiment of the Invention FIG. 3 is a configuration diagram showing an embodiment of the present invention, (al is a cross-sectional view when expanded, (b) is a cross-sectional view when contracted, and fc is a perspective view of a single element of the phase correction stage. It is a diagram. In this example, a normal coaxial cable, for example, a coaxial cable 10 with a characteristic impedance of 50Ω, is used as the coaxial transmission line.

This coaxial cable 10 has its outer sheath removed to expose the outer conductor 11. 12 is a center conductor, and a dielectric material 13 is filled between it and the outer conductor 11. In other words, this coaxial cable 10 is solid.

A metal inner pipe 21 is attached tightly around the coaxial cable 10, and a large diameter outer pipe (conductor) 22 is further disposed around the outer circumference of the metal inner pipe 21. The total length of this outer vibe 22 is λ/
4, which corresponds to the skirt portion 5 in FIG. Both pipes 21
．． 22 are connected by a conductive plate 23 on the feeding point A side. A basic element 31 is fixed to the tip of the center conductor 12 of the coaxial cable 10 with a screw or the like. This element 31 is a conductive cylindrical body with a bottom plate 31a.
The total length is λ/4. This corresponds to the portion of the center conductor 2 in FIG. 1 that protrudes upward from the skirt portion 5. 3
2 is an element of a phase correction stage that is inserted into and removed from this element 31. This element 32 has a dielectric tubular part 32c interposed between a lower conductive tubular part 32a and an upper conductive tubular part 32b, and a coil 32d for position correction is embedded therein and wound. Both ends of the coil are connected to tubular portions 32a, 32b. Numerals 33 to 36 are elements whose diameters gradually become smaller, and each can be inserted into and removed from the lower element.

Figure 3 (all the increasing elements 32-3 as shown in al.
6 is pulled out, the length from the top of the uppermost element 36 to a part of the element 33 is λ/2, and the length including the remainder of the element 33 to the upper end of the element 31 is λ/2. .

However, in the element 32, the length of the extended coil 32d is λ/4, so the length of the dielectric 32c is shorter than that. Incidentally, since the length of the lower tubular portion 32a is λ/8, the remaining λ/8 is the aforementioned remaining portion of the element 33.

The operating principle as an antenna is the same as in Fig. 1, ′・T
a) There is a gain of about 4 dB (7) in the (7) state・This 9
On the other hand, if all of the elements 32 to 36 are housed within the basic element 31 as shown in FIG. 011), the antenna becomes the same as the basic antenna 6 in FIG. 1, and the gain decreases to about 2 dB. In this way, the gain can be varied by expanding and contracting the element, which is the same as in FIG. It has a solid structure. Therefore, there is no fear that rainwater or the like will seep in from the upper end of the coaxial cable 10 and change the characteristic impedance of the transmission path up to the transmitter/receiver. Incidentally, water that has entered the hollow element 31 can be naturally drained to the outside by making a hole in the bottom plate 31a.

Effects of the Invention As described above, according to the present invention, the advantage of the coaxial transmission line is that it is easy to change the gain of the whip antenna used, and the characteristic impedance of the coaxial transmission line does not need to be changed by rainwater or the like.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of a variable length whip antenna,
FIG. 2 is an explanatory diagram of the electric field distribution, and FIG. 3 is a configuration diagram showing an embodiment of the present invention. In the figure, 10 is a coaxial cable, 11 is an external conductor, ゛ 1
2 is a center conductor, 22 is an outer pipe (conductor), 31 is a basic element, 32 to 36 are expansion elements, and 32d is a phase correction coil. Applicant Fujitsu Ten Ltd. Applicant Toyota Motor Corporation Representative Patent Attorney Minoru Aoyagi Figure 1

Claims (1)

[Claims] A solid coaxial cable extended to a feed point, a hollow basic element connected to the center conductor of the coaxial cable and extending further upward from the feed point, and connected to an outer conductor of the coaxial cable to feed the feed. a conductor extending downward from the point and forming a basic dipole antenna together with the basic element;
It is equipped with a plurality of stages of extension elements that are telescopically housed within the basic element, and a phase correction element that is incorporated into a part of the extension element, and the overall gain can be adjusted by using or not using the extension elements. A variable length whip antenna characterized by being configured to switch between.