Multi-band coil antenna

Abstract

To provide (A) a coil-shaped antenna which can perform reception and transmission with at least three amateur bands (amateur radio frequencies) in an MF-band and in an HF-band and a coil-shaped antenna which can perform reception and transmission with at least three amateur bands in a VHF band and a UHF band without a matching circuit.SOLUTION: The present invention realizes an antenna A and an antenna B by winding a coil backward a little in the same rotary direction or by optimizing pitches and the number of turns of the coil.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a coil antenna capable of multi-band transmission and reception.

Background Art

[0002] Some coil antennas that can be used in multi-bands have been proposed. For example, Patent Document 1 proposes a receiving antenna composed of a plurality of band-specific elements, but this antenna is not suitable for transmission. Patent Document 2 proposes a non-uniform helical antenna capable of transmission and reception in two bands, but does not show a specific method for enabling transmission and reception in three or more specific bands.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Existing antennas include (A) a coil-shaped antenna that can transmit and receive in three or more amateur bands (frequency bands for amateur radio) in the MF band or HF band and does not require a trap, and (B) there is no coil-shaped antenna that can transmit and receive in three or more amateur bands in the VHF band or UHF band and does not require a trap and a matching circuit.

Means for Solving the Problems

[0006] The present invention realizes antenna (A) and antenna (B) by slightly folding and winding the coil or devising the coil pitch and the number of turns.

Advantages of the Invention

[0007] According to the present invention, it is possible to achieve both miniaturization of the antenna and multi-band operation of three or more bands with a simple structure without a trap. In addition to these advantages, antenna (B) also has the advantages of weight reduction, extended service life, and reduced transmission power loss due to the non-use of a matching circuit.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0009] To reduce losses, a coil is wound around a cylinder made of a low-dielectric-constant material such as polyethylene. When the coil pitch is small or there are folded-back parts in the coil, to prevent short circuits, the coil is wound with a coated wire such as enameled wire. To prevent the wire from shifting, grooves are engraved at equal intervals horizontally on the cylinder, and at the places where the wire moves to another groove, the convex parts of the grooves may be removed.

[0010] In a coil antenna, the resonance frequency can be changed by varying the outer diameter of the cylinder, the thickness of the cylinder, the material of the cylinder, the length of the conductor, the diameter of the conductor, the coil pitch, etc. If the conductor is made longer or the coil pitch is made smaller, the first resonance frequency will be lower. If the coil pitch is made smaller, the interval between the resonance frequencies will also narrow, but there is a limit to this.

[0011] Table 1 is a graph of the frequency and VSWR of an antenna in which a polyurethane copper wire with a conductor diameter of 0.5 mm is wound 69 times at a pitch of 3 mm around a 10L (cylindrical) PE wide-mouth light-shielding bottle manufactured by Sampratech with an outer diameter of 217 mm. The light gray vertical bars in the table are, from left to right, the 1.8 MHz band (1.8 MHz to 1.9125 MHz), 3.5 MHz band (3.5 MHz to 3.805 MHz), 7 MHz band (7 MHz to 7.2 MHz), 10 MHz band (10.1 MHz to 10.15 MHz), 14 MHz band (14 MHz to 14.35 MHz), 18 MHz band (18.068 MHz to 18.168 MHz), 21 MHz band (21 MHz to 21.45 MHz), 24 MHz band (24.89 MHz to 24.99 MHz), 28 MHz band (28 MHz to 29.7 MHz) of amateur radio (the same applies to Tables 2, 4, and 6 below). In this case, the VSWR of each resonance frequency is relatively high, and impedance matching is required.

[0012]

Table 1

[0013] Table 2 is a graph of frequency and VSWR when a 9:1 unbalanced / unbalanced transformer (Figure 1) for impedance matching is connected to the antenna. In this transformer, a covered wire is wound around a Fair-Rite toroidal core FT-140-43 in a trifilar winding, with each wire wound 5 times at equal intervals. To prevent degradation of the transformer's performance, the distance between the transformer and the center conductor of the coaxial connector is made as short as possible. The VSWR of this transformer is less than 1.3 in the range of 1.8 MHz to 54 MHz (Table 3).

[0014]

Table 2

[0015]

Table 3

[0016] As can be seen from Table 1 and Table 2, when the first resonance frequency is adjusted to the 1.8 MHz band of amateur radio, the second resonance frequency becomes higher than the 3.5 MHz band. Even if the coil is wound tightly, the second resonance frequency becomes higher than the 3.5 MHz band.

[0017] In such a case, as shown in 6 of Figure 2 and Figure 3, by winding the coil back a little, the second resonance frequency approaches the first resonance frequency. The longer the folded-back part (the folded-back coil), the closer the second resonance frequency gets to the first resonance frequency. As a result, even if the coil is wound with space, it can be resonated in the 1.8 MHz band and the 3.5 MHz band. Antennas consisting of coils where the main coil and the folded-back part are about the same length have been published as in Non-Patent Document 1 and Non-Patent Document 2, but if the folded-back part is long, the gain of the antenna decreases. Therefore, the folded-back part should be made the minimum length necessary to obtain the target second resonance frequency.

[0018] To adjust the resonance frequencies after the third resonance frequency to the target frequencies, it is necessary to devise the pitch and number of turns of the main coil.

Example

[0019] Figure 2 is a front view of an antenna capable of transmitting and receiving in the 1.8 MHz band, 3.5 MHz band, 7 MHz band, 10 MHz band, 14 MHz band, 18 MHz band, 21 MHz band, 24 MHz band, 28 MHz band, and 50 MHz band of amateur radio. The main coil (5) is wound 47.625 times and the folded coil (6) is wound 4.437 times with a polyurethane copper wire having a conductor diameter of 0.5 mm on a 10 L (cylindrical) PE wide-mouth light-shielding bottle manufactured by Sampratech with an outer diameter of 217 mm. The maximum length of the coil is 66.5 mm. A coil and a 9:1 unbalanced / unbalanced transformer (Figure 1) are connected with the same wire having a length of 330 mm. In order to prevent the wire from shifting, 134 grooves are engraved horizontally on the cylinder at a pitch of 0.5 mm. Where the wire moves to another groove, the convex part of the groove may be removed.

[0020] The pitch on the left side of the coil is, from bottom to top, 2 mm, 2 mm, 1.5 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 3.5 mm, 1 mm, 1.5 mm, 1.5 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 1.5 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 1.5 mm, 1 mm, 5 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 1.5 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 2.5 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm. The pitch on the right side of the coil is, from bottom to top, 2 mm, 1.5 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 3.5 mm, 1 mm, 1.5 mm, 1.5 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 1.5 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 1.5 mm, 1 mm, 5 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 1.5 mm, 1 mm, 1 mm, 1 mm, 1.5 mm, 1.5 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm, 1 mm. Figure 3 is a rear view of the antenna.

[0021] Tables 4 and 5 are graphs of the frequency and VSWR of the antenna. The light gray vertical bars in Table 5 represent the 50 MHz band (50 MHz to 54 MHz) of amateur radio (the same applies to Table 7 below). The lowest VSWR points in the amateur band are 2.256 (1.87 MHz), 1.296 (3.50 MHz), 1.254 (7.15 MHz), 1.446 (10.11 MHz), 1.977 (14.07 MHz), 7.042 (18.16 MHz), 3.060 (21.05 MHz), 4.365 (24.89 MHz), 1.512 (29.65 MHz), and 2.335 (50.00 MHz). When transmitting at frequencies with a relatively high VSWR, an antenna tuner or the like is used.

[0022]

Table 4

[0023]

Table 5

[0024] The above pitch and number of turns are values under the above conditions, and need to be changed according to the outer diameter of the cylinder, the thickness of the cylinder, the material of the cylinder, the diameter of the wire, the material of the wire, the presence or absence of wire coating, the thickness of the wire coating, the material of the wire coating, the presence or absence of an antenna cover, the outer diameter of the antenna cover, the thickness of the antenna cover, the material of the antenna cover, etc.

[0025] When a part of the coil is slightly distorted as shown by 7 in Fig. 4, the VSWR may decrease overall as shown in Table 6 and Table 7. The lowest points of the VSWR in the amateur band in this case are 2.598 (1.87 MHz), 1.187 (3.52 MHz), 1.236 (7.16 MHz), 1.406 (10.10 MHz), 1.970 (14.09 MHz), 7.262 (18.16 MHz), 2.523 (21.22 MHz), 3.620 (24.99 MHz), 2.288 (29.70 MHz), 1.119 (50.98 MHz, 51.01 MHz). When transmitting at frequencies with a relatively high VSWR, an antenna tuner or the like is used. It is necessary to try and error to determine which part of the coil should be distorted, in which direction, and to what extent.

[0026]

Table 6

[0027]

Table 7

Example

[0028] Fig. 5 is a front view of an uncovered antenna capable of transmitting and receiving in the 144 MHz band, 430 MHz band, and 1200 MHz band of amateur radio. A main coil (5) is wound 20.4 times with a polyurethane copper wire having a conductor diameter of 0.5 mm and a length of 808 mm including the connection part around a polypropylene straw (cylinder) with an outer diameter of 12 mm and an inner diameter of 11 mm. The maximum length of the coil is 121.3 mm. The coaxial cable enters the straw from the lower left of the coil and is connected to the center conductor of the SMA connector at the shortest distance of 6 mm. No matching circuit is required.

[0029] The pitches on the left side of this coil are 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 4 mm, 4 mm, 4.5 mm, 4.5 mm, 5 mm, 5.5 mm, 9.5 mm, 12 mm, 12 mm, 12 mm, 12 mm from bottom to top.

[0030] Table 8 is a graph of the frequency and VSWR of this antenna. The light gray vertical bars in the table are, from left to right, the amateur radio 144 MHz band (144 MHz to 146 MHz), 430 MHz band (430 MHz to 440 MHz), and 1200 MHz band (1260 MHz to 1300 MHz) (the same applies to Table 9 below). The lowest points of VSWR in the amateur bands are 1.662 (145.6 MHz), 1.286 (434.5 MHz), and 1.161 (1295.8 MHz).

[0031]

Table 8

[0032] The above pitch and number of turns are values under the above conditions, and need to be changed depending on the outer diameter of the cylinder, the thickness of the cylinder, the material of the cylinder, the diameter of the conductor, the material of the conductor, the presence or absence of conductor coating, the thickness of the conductor coating, the material of the conductor coating, etc.

Example

[0033] Figure 6 is a front view of the antenna with cover removed, which can transmit and receive in the 144 MHz band, 430 MHz band, and 1200 MHz band of amateur radio. A main coil (5) is wound 19.7 times with a polyurethane copper wire having a conductor diameter of 0.5 mm and a length of 785 mm including the connection part on a polypropylene straw (cylinder) with an outer diameter of 12 mm and an inner diameter of 11 mm. The maximum length of the coil is 109 mm. The coaxial wire enters the straw from the lower left of the coil and is connected to the center conductor of the SMA connector at the shortest distance of 6 mm. No matching circuit is required. The cover is a vinyl chloride resin water pipe with an outer diameter of 18 mm and an inner diameter of 14 mm, and a polyethylene cap is attached to the upper end.

[0034] The pitch on the left side of this coil is, from bottom to top, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 3.5 mm, 4.5 mm, 5.5 mm, 6 mm, 6 mm, 6 mm, 8.5 mm, 11.5 mm, 13 mm, 9 mm, 6 mm, 3 mm.

[0035] Table 9 is a graph of the frequency and VSWR of this antenna. The lowest points of VSWR in the amateur band are 1.601 (146.0 MHz), 1.538 (434.9 MHz), and 1.144 (1291.7 MHz).

[0036]

Table 9

[0037] The above pitch and number of turns are values under the above conditions, and need to be changed depending on the outer diameter of the cylinder, the thickness of the cylinder, the material of the cylinder, the diameter of the wire, the material of the wire, the presence or absence of wire coating, the thickness of the wire coating, the material of the wire coating, the outer diameter of the antenna cover, the thickness of the antenna cover, the material of the antenna cover, etc.

Industrial Applicability

[0038] The antenna of the present invention can be installed even in a narrow space. Also, instead of installing a monoband antenna for each band and connecting them with coaxial cables respectively, by simply connecting the antenna of the present invention with one coaxial cable, transmission and reception can be performed in three or more amateur bands.

Explanation of Signs

[0039] 1 Toroidal core FT-140-43 manufactured by Fair-Rite Corporation 2 Covered wire 3 Contact point 4 Cylinder 5 Main coil (solid line) 6 Folded coil (dotted line) 7 Distortion of the coil

Claims

1. A coil-shaped antenna in which the coil is slightly folded back and wound, bringing the second resonance frequency closer to the first resonance frequency without significantly reducing the gain.

2. By slightly folding back and winding the coil as in Claim 1, or by devising the coil pitch and the number of turns, a coil-shaped antenna capable of transmitting and receiving in three or more bands out of the amateur radio 1.8 MHz band (1.8 MHz to 1.9125 MHz), 3.5 MHz band (3.5 MHz to 3.805 MHz), 7 MHz band (7 MHz to 7.2 MHz), 10 MHz band (10.1 MHz to 10.15 MHz), 14 MHz band (14 MHz to 14.35 MHz), 18 MHz band (18.068 MHz to 18.168 MHz), 21 MHz band (21 MHz to 21.45 MHz), 24 MHz band (24.89 MHz to 24.99 MHz), 28 MHz band (28 MHz to 29.7 MHz), 50 MHz band (50 MHz to 54 MHz) without using a trap.

3. By devising the coil pitch and the number of turns, a coil-shaped antenna capable of transmitting and receiving in the three bands of the amateur radio 144 MHz band (144 MHz to 146 MHz), 430 MHz band (430 MHz to 440 MHz), 1200 MHz band (1260 MHz to 1300 MHz) without using a trap and a matching circuit.

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