JP3287987B2 - Adjustment method of resonance frequency of helical antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to frequency adjustment of a helical antenna which is effective mainly for satellite communication.

[0002]

2. Description of the Related Art In recent years, the concept of a portable telephone (portable radio) using a communication satellite has been proposed by various companies, and their frequency bands are 1.6 GHz / 2.4 GHz band (WARC-9).
2) and the 2.0 GHz band (WRC-95) are allocated, and antennas used for them are proposed.

In satellite communication, a circularly polarized antenna is generally used. Various systems have been devised for satellite communication systems based on differences in the number of satellites used, the inclination angle of the orbit, the altitude of the satellite, and the like. Therefore, the guaranteed minimum elevation angle differs depending on the satellite communication system.

[0004] Since the frequency band allocated to the terrestrial terminal (portable radio) for satellite communication is determined, the antenna determines the frequency, the radiation beam direction, and the physical size of the antenna in the system and the portable radio. Must meet the specifications. The minimum elevation angle of the Iridium system is 8.2 degrees, and the minimum elevation angle of the Inmarsat-P is 20 degrees.
P. 57).

As a circularly polarized antenna used for satellite communication, a conductor and a coaxial wire are wound in a spiral, a feed point is provided at the end, the conductor and the center conductor of the coaxial wire are connected, and the conductor is wound at the end of the winding. A helical antenna for circular polarization in which an outer conductor of a coaxial line is connected has been proposed (Japanese Patent Laid-Open No. 3-27490).
4).

[0006]

However, in such a helical antenna, it has been difficult to adjust the frequency while keeping the radiation beam in a desired direction.

[0007]

According to the present invention, a conductor and a coaxial wire are wound in a spiral form, a feeding point is provided at the tip, the conductor and the center conductor of the coaxial wire are connected, and the coaxial wire is coaxial with the conductor at the end of winding. In a helical antenna for circular polarization to which an external conductor of a line is connected, the resonance frequency is adjusted by increasing or decreasing the amount of an external dielectric around the external conductor of a coaxial line.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An object of the present invention is to provide a helical antenna in which the direction of a radiation beam and the operating frequency can be easily adjusted. The helical antenna includes a radiating portion composed of a coaxial line covered with a dielectric outer cover. When a part of the cover is removed, the resonance frequency shifts to a higher one. Also, if the periphery of the outer conductor of the coaxial line of the helical antenna including the radiating portion formed of the coaxial line having no outer cover is covered with a dielectric, the resonance frequency shifts to a lower one.

As described above, according to the present invention, in order to shift the resonance frequency, the amount of dielectric surrounding the central conductor of the coaxial line contributing to radiation is increased or decreased to thereby change the electrical antenna without changing the physical antenna length. The typical antenna length.

An embodiment of the present invention will be described below with reference to the drawings. An embodiment of the present invention is shown in FIGS.

FIG. 1 is a diagram showing the configuration of a helical antenna 11 for circularly polarized waves, in which 12 is a coaxial line, 13 is a conductor, 14 is a feed point,
Reference numeral 15 denotes a winding end of the helical antenna, and reference numeral 16 denotes a dielectric cylinder or a dielectric cylinder. 12a is a central conductor of the coaxial line, 12b is an inner dielectric of the coaxial line, 12c is an outer conductor of the coaxial line, and 12d is an outer cover of the coaxial line. FIG. 1 shows an example in which a coaxial wire 12 having an outer cover 12d is used.
The resonance frequency is adjusted by deleting d above the antenna. FIG. 2 shows the configuration of the coaxial cable 12. In FIG. 1, the resonance frequency is adjusted by removing the outer cover 12d.

FIG. 3 shows another embodiment in which a coaxial line 12 not covered with an outer cover is used. 1 are given the same reference numerals. in this way,
The resonance frequency of the antenna is adjusted by increasing or decreasing the outer sheath of the coaxial line.

Next, the helical antenna 11 will be described in more detail.

The helical antenna 11 can generate a circularly polarized wave by appropriately selecting shape parameters such as the radius R of the dielectric cylinder 16, the pitch angle θ of the coaxial wire 12, and the conducting wire 13, and the number of windings M. . Here, the frequency at which the antenna operates as a circularly polarized antenna and the radiation beam direction depend on the above parameters. Therefore, first, the radiation beam direction is set to a substantially desired elevation angle, and the frequency is adjusted relatively coarsely. Next, in order to adjust to the desired frequency, the resonance frequency is precisely adjusted by increasing or decreasing the dielectric (such as an outer cover) near the outer conductor of the coaxial line serving as the radiation element.

The helical antenna 11 has a conductor 13 and a coaxial line (center conductor of the coaxial line) 12 serving as a radiation element wound spirally on a dielectric cylindrical surface. The center conductor 12a of the coaxial cable 12 and the conductor 13 are electrically coupled at a feed point 14 at the tip. 2 below the feed point 14.
The conductor wire is wound down. Then, at the winding end end 15, the conductor 13 and the outer conductor 12c of the coaxial cable 12 are electrically connected.

The high-frequency current flows from the feeding point 14 through the conducting wire 13 and reaches the winding end 15, and the winding end 1
5 flows upward on the outer surface of the outer conductor 12 c of the coaxial cable 12. At this time, the outer conductor 12c of the coaxial line 12
Since high-frequency currents of the same size and opposite directions are flowing on the inner wall side of the
Does not flow high-frequency current. Therefore, the high-frequency current contributing to the radiation exists only in the conductor 13 and the central conductor 12 a of the coaxial cable 12. By changing the dielectric constant in the vicinity of the conductor line for these radiations, it is possible to change the electrical length of the antenna and adjust the frequency to a desired band. The two-wire helical antenna composed of one conductor and one coaxial line has been described above.
The same effect can be obtained with a line helical antenna. In addition, the holding of the conductor wire has been described by using the dielectric cylinder or the dielectric cylinder, but the dielectric cone may be used.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is an embodiment of frequency adjustment in the present invention.

The size of the helical antenna is 4 cm in diameter,
A paper cylinder having a height of 11.5 cm was used. The length of the coaxial cable was 27.6 cm, and the number of turns of the coaxial cable and the conductor was 2 turns. The multiple resonance frequencies at which the helical antenna operates as a circularly polarized antenna were compared depending on the presence or absence of the envelope.
The resonance frequency when the entire coaxial line is covered by the outer cover is 1.199 GHz, and when the entire outer cover is removed is 1.2.
Resonated at 13 GHz. The change in frequency per unit length of the envelope is 0.5 MHz / cm. Incidentally, the frequency band assigned to the satellite communication is about 10 MHz.

The main specifications of the wires used in the experiments are as follows. The coaxial cable is made by Fujikura 0.8
D-QEV, finished outer diameter 2.0 mm, envelope material is polyvinyl chloride. This example utilized the increase or decrease of the polyvinyl chloride.

The conductor wire is a reticulated copper wire made of HAKKO having a width of 2.3 mm and a thickness of 0.5 mm.

[0021]

According to the present invention, it is possible to easily adjust the frequency of a helical antenna including a radiating element composed of a coaxial line without affecting the radiation direction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a coaxial line.

FIG. 3 is a configuration diagram of another embodiment of the present invention.

[Explanation of symbols]

 11: Helical antenna 12: Coaxial line 12a: Central conductor of coaxial line 12b: Inner dielectric of coaxial line 12c: External conductor of coaxial line 12d: External dielectric of coaxial line (outer sheath) 13: Conductor 14: Feeding point 15 : End of winding 16: Dielectric cylinder (cylinder)

Claims (1)

(57) [Claims] 1. A circle in which a conducting wire and a coaxial wire are wound in a helical manner, a power feeding point is provided at a leading end portion, a conducting wire is connected to a central conductor of the coaxial wire, and a conducting wire is connected to an outer conductor of the coaxial wire at an end of winding. In a helical antenna for polarization, the outer coating of the coaxial line is simply
A resonance frequency adjusting method for a helical antenna, wherein the resonance frequency is adjusted by increasing or decreasing based on a frequency change amount per unit length .