JP4224864B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device, and more particularly to a dipole antenna having a wide frequency band in which the antenna length requiring a basic length can be shortened or wirelessly operated.

  The dipole antenna is the first antenna used by Hertz to generate radio waves, and since then its shape has not changed and is still used as the basic antenna in wireless communications. In the structure, a radiator having a length of 1 / 2λ is divided at the center, and power is supplied from that position. It is a simple antenna. This dipole antenna is generally used as an antenna for transmission and reception from a short wave band to an ultra short wave band.

  The operation of amateur radio in wireless communication is also operated in a wavelength region having a relatively long wavelength. The lower limit of the practical frequency is 1.9 MHz for amateur radio, which is about 160 m in wavelength, about 80 m for a conventional 1 / 2λ dipole antenna, and about 40 m for a 1 / 4λ vertical antenna. Was physically difficult. In order to solve this problem, a shortened coil and a crown capacity have been used in the past, but the frequency band that can be operated has been narrowed because of shortening.

  The idea that a shortened antenna that omits the shortening coil and crown cap capacity can be realized if an antenna that uses the speed coefficient (shortening rate) of a material insulator using a coaxial cable can be invented. Many people involved in radio challenged the experiment and possibility, but could not be achieved. Although it has recently been theoretically tested in detail about the possibility, it has not been completed. (See Non-Patent Document 1)

  Although a similar power feeding method has been found in the conventional antenna technology, it has been used as a stub for securing a frequency bandwidth, and the antenna itself has not been shortened to operate. It was impossible to realize a shortened antenna by feeding only such standardized and commercially available materials. (See Non-Patent Document 1, Non-Patent Document 2, and Patent Document 1)

CQ Publishing Co., Ltd. HAM Journal No. 113 April 1, 2005 p114 "Understanding the characteristics of coaxial cables and experimenting with shortening rates"

(Patent Reference 1)
CQ Publishing Co., Ltd. Separate volume CQ ham radio March issue issued on March 1, 1993 Dynamic Ham Series 16 “Wire Antenna” p205 “6.17 7MHz Double Bazooka”

U.S. Pat. No. 4,479,130 Original text of [0007]

  When the antenna device is downsized, the feeding impedance is lowered, the efficiency is lowered, and the frequency band that can be operated is narrowed. Therefore, the shortened small antenna is difficult to use.

  An object of the present invention is to produce a wide-band dipole antenna device capable of shortening the length of an antenna and sufficiently securing an operating frequency bandwidth.

  By being able to grasp the power supply impedance of this antenna, an optimal power supply method was devised and the problems could be solved.

FIG. 1 shows a dipole antenna composed of coaxial cables. Although power can be supplied as it is, it can only be installed under conditions limited in strength, so it is arranged in a metal pipe (pipe) as shown in Fig. 2 to increase the strength as an antenna To do.

The shortened dipole antenna device according to the present invention shortens the wavelength by utilizing the speed coefficient (shortening rate) inherent to the insulator of the radiator (radiator) material, so that the shortened coil and the crown capacity are reduced. Unnecessary, simple structure, excellent cost performance and high applicability. It operates in a state where a sufficient frequency bandwidth can be secured. In the 50 MHz antenna installed in the experiment, a frequency bandwidth of 2 to 3 MHz can be secured by an internal coaxial cable.

  The principle according to the present invention is applicable to all conventional basic dipole antennas and conventional multi-element type dipole antennas with reflectors or directors of more complex antenna configurations.

Basically, a coaxial cable with a constant impedance is used, and each is used as a pair of radiators (radiators) with an electrical length of 1 / 4λ, the tips are short-circuited, and the center is crossed and connected. The central connection point is used as a power feeding part, each is placed in a metal pipe (pipe), and the tip part and the central part are joined to the metal pipe (pipe) and fed through an impedance conversion balun. It is possible to operate as a wideband dipole antenna device with a shortened wavelength utilizing the speed coefficient (shortening rate) inherent to the insulator.

  This antenna has a slightly higher feed impedance than usual and cannot be fed as it is, so the impedance must be converted. The temporary side depends on the output form of the transmitter, but currently 50Ω unbalanced output is almost all. Therefore, it must be converted to unbalanced 50Ω: balanced nnΩ. This value varies depending on the type of coaxial cable used for the radiator. As a result, a shortened dipole antenna device utilizing the speed coefficient (shortening rate) inherent to the insulating material can be realized.

  The feed impedance value obtained in the experiment is 250Ω when a 50Ω coaxial cable is placed in the metal pipe. 270Ω when a 75Ω coaxial cable is placed in a metal pipe. Impedance and unbalance / balance conversion can be realized with a balun using a general toroidal core and ferrite beads.

  In the VHF band, the feeding impedance tends to be low, and in a lower frequency band, the feeding can be performed with a slightly higher impedance.

  The dipole antenna in which the coaxial cable shown in FIG. 7 is arranged in a metal tube (pipe) is structurally strong and easy to realize multiple elements.

The perspective view which showed the implementation method with a 50-ohm type coaxial cable or a 75-ohm type coaxial cable. The perspective view of the dipole-type antenna which has arrange | positioned the coaxial cable in the metal pipe (pipe). Claim 1 and FIG. 2 A coaxial cable is arranged in a metal pipe (pipes), and a radiator on one side (radiator) is 910 mm, and the 75Ω system uses a 50Ω unbalanced 270Ω balanced balun specialized for VHF in FIG. 50Ω system is 50Ω unbalance specialized for VHF in Fig. 5: Actual measurement in 50MHz band (feed point height = 7m) using 250Ω balanced balun, 75Ω system coaxial cable is mounted on the left side of the figure, right side is Measurement results of mounting 50Ω coaxial cable 50Ω unbalanced 270Ω balanced balun specialized for VHF in which the 75Ω coaxial cable of claim 1 is placed in a metal pipe (pipe) and fed as a radiator. 50Ω unbalanced: 250Ω balanced balun specialized for VHF in which the 50Ω coaxial cable of claim 1 is placed in a metal pipe (pipe) and fed as a radiator (radiator)

Explanation of symbols

1 Coaxial cable with an electrical length of 1 / 4λ 2 Metal pipe (pipe) with a length corresponding to a coaxial cable with an electrical length of 1 / 4λ
3 Feed point, impedance and unbalance / balance conversion by balun to transmitter

Claims (1)

Two 1 / 4λ coaxial cables multiplied by the speed factor (shortening rate) are arranged on a straight line as the radiator of the antenna (radiator), and the inner conductor (core wire) and outer conductor (jacket) at both ends are arranged. Short-circuit, the central part is connected by crossing the inner conductor (core wire) and the outer conductor (coating wire) facing each other, and the connection point of the central part is used as a feeding part, and each is placed in a metal pipe (pipe) The tip and the center are joined to a metal pipe (pipe) and fed through an impedance converter balun. The length of the radiator (radiator) that is normally required is multiplied by the speed system (reduction rate) of the coaxial cable. This is a shortened dipole antenna device realized with the radiator length.

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