JP4943298B2 - Helical antenna - Google Patents

Description

  The present invention relates to a helical antenna that exhibits a wide band characteristic and can be miniaturized in the length direction.

A conventional broadband plate antenna operating in a wide band (see Patent Document 1) includes an earth plate serving as a ground plane, a rectangular excitation plate, and a rectangular conductor plate arranged to face the excitation plate. I have. In addition, a power supply cable for supplying power to the broadband plate antenna is provided. The core of the power supply cable is connected to the edge of the excitation plate, and the braided wire that is the outer conductor of the power supply cable is connected to the edge of the conductor plate. ing. The power supply cable is provided so as to penetrate the ground plate, and the other end of the power supply cable is connected to a signal source. With this wideband plate antenna, a specific frequency band of about 15% can be obtained when the voltage standing wave ratio (VSWR) is 2 or less, and about 29% when the VSWR is 3 or less.
Japanese Patent Laid-Open No. 10-322124

The frequency band of terrestrial digital broadcasting is 470 MHz to 710 MHz, the center frequency is 590 MHz, and the bandwidth is 240 MHz. However, it has been difficult for a conventional antenna to secure a frequency band having a center frequency of 590 MHz and a bandwidth of 240 MHz, and thus cannot be made an antenna suitable as an antenna for receiving digital terrestrial broadcasting.
Therefore, an antenna of Japanese Patent Application No. 2006-338037 has been proposed as an antenna for receiving digital terrestrial broadcasting. The configuration of this antenna is shown in FIG. In the L-shaped antenna 200 shown in FIG. 32, the outer sheath of the end portion of the coaxial cable 202 is removed, and the braided wire that is the outer conductor is slightly exposed. Further, the braided wire is also removed at the tip portion, and the insulating portion is slightly exposed. Furthermore, the insulating portion is also removed at the tip portion, and the central conductor is exposed. The end of the L-shaped element 201 bent in an L shape is connected to the tip of the center conductor. The L-shaped element 201 is folded back with respect to the coaxial cable 202 and is stretched so as to be substantially parallel to the coaxial cable 202. The length of the L-type element 11 is a length that substantially resonates with the center frequency of the frequency band in which the L-type antenna 200 is operated. For example, when the wavelength of the center frequency is λ, the length is about λ / 4. The distance between the coaxial cable 202 and the L-shaped element 201 is about 0.009λ or more.

  With this L-type antenna 200, good electrical characteristics can be obtained in the frequency band of 470 MHz to 710 MHz. In this case, the antenna 200 has a height of about 10.2 mm and the length of the L-type element 201. Is about 127.1 mm corresponding to about 0.25λ of the wavelength λ of the center frequency 590 MHz. As described above, in the L-type antenna 200, the specific frequency band in which the maximum gain of 0 dBd or more can be obtained is 40% or more in spite of the low profile of the antenna height including the coaxial cable 202 of about 12 mm. A very broadband antenna can be realized. However, the L-type antenna 200 can be configured to have a low antenna height and can achieve a wide band characteristic. However, the length of the L-type element 201 in the length direction is λ / 4. Since it was necessary, there was a problem that it was not possible to further reduce the size in the length direction.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a low-profile helical antenna that exhibits a wide band gain characteristic and can be downsized in the length direction.

  In order to achieve the above object, the helical antenna of the present invention includes a helical element that is connected to the tip of the central conductor of the coaxial cable and is wound around the coaxial cable, and is eccentric from the winding center of the helical element. The main feature is that the coaxial cable is arranged at the position.

  The helical antenna of the present invention includes a helical element that is connected to the end of the central conductor of the coaxial cable and is wound around the coaxial cable, and the coaxial cable is disposed at a position that is eccentric from the winding center of the helical element. By being, it can be reduced in size in the length direction. In addition, the antenna can exhibit a wide band gain characteristic and can have a low attitude, and can be a helical antenna suitable as an antenna for receiving digital terrestrial broadcasting.

The configuration of the helical antenna according to the first embodiment of the present invention is shown in FIGS. FIG. 1 is a front view showing the configuration of the helical antenna of the first embodiment, and FIG. 2 is a side view showing the configuration of the helical antenna of the first embodiment.
In the helical antenna 1 according to the first embodiment shown in these drawings, the outer sheath of the end portion of the coaxial cable 11 is removed, and the braided wire 11c which is an outer conductor is slightly exposed. Further, the braided wire 11c is also removed at the tip portion, and the insulating portion 11b is slightly exposed. Furthermore, the insulating portion 11b is also removed at the tip portion, and the central conductor 11a is exposed. The helical portion 10 includes a connecting portion 10 a whose tip is bent substantially perpendicular to the coaxial cable 11 and a helical element 10 b that is helically wound around the coaxial cable 11. The central conductor 11a of the coaxial cable 11 and the helical element 10b are electrically connected via the connecting portion 10a.

  The helical element 10b wound around the coaxial cable 11 has a winding diameter D and an axial length L. And the coaxial cable 11 is arrange | positioned in the position eccentric from the winding center of the helical element 10b, and let the shortest space | interval of the radial direction of the outer peripheral surface of the coaxial cable 11 and the helical element 10b be GS, The longest interval is GL. The interval GL is substantially equal to the length of the connecting portion 10a. In this way, by arranging the coaxial cable 11 at a position eccentric from the winding center of the helical part 10, the VSWR characteristics of the helical antenna 1 of the first embodiment are described later in the frequency band of terrestrial digital broadcasting of 470 MHz to 710 MHz, for example. To be better.

Next, the configuration of the helical antenna 2 according to the second embodiment of the present invention is shown in FIGS. FIG. 3 is a front view showing the configuration of the helical antenna 2 of the second embodiment, and FIG. 4 is a side view showing the configuration of the helical antenna 2 of the second embodiment.
In the helical antenna 2 according to the second embodiment shown in these drawings, the outer sheath of the end portion of the coaxial cable 21 is removed, and the braided wire 21c which is an outer conductor is slightly exposed. Further, the braided wire 21c is also removed at the tip portion, and the insulating portion 21b is slightly exposed. Furthermore, the insulating portion 21b is also removed at the tip portion, and the central conductor 21a is exposed. The helical portion 20 includes a connection portion 20 a whose tip is bent substantially perpendicularly to the coaxial cable 21 and a helical element 20 b that is helically wound around the coaxial cable 21. The central conductor 21a of the coaxial cable 21 and the helical element 20b are electrically connected via the connecting portion 20a.

  The helical element 20b wound around the coaxial cable 21 has a winding diameter D and an axial length L. And the coaxial cable 21 is arrange | positioned in the position eccentric from the winding center of the helical element 20b, and the shortest space | interval of the radial direction of the outer peripheral surface of the coaxial cable 21 and the helical element 20b is set to GS, The longest interval is GL. The interval GS is substantially equal to the length of the connecting portion 20a. Thus, even if the length of the connecting portion 20a is shortened and the coaxial cable 21 is arranged at a position eccentric in the opposite direction to the helical antenna 1 of the first embodiment, for example, terrestrial digital broadcasting of 470 MHz to 710 MHz. The VSWR characteristics of the helical antenna 2 of the second preferred embodiment can be obtained in the frequency band.

Next, an example of specific dimensions when the helical antenna 1 of the first embodiment and the helical antenna 2 of the second embodiment are operated as antennas for receiving terrestrial digital broadcasting, for example, will be described below. The frequency of terrestrial digital broadcasting is 470 MHz to 710 MHz, and the wavelength λ of the free space with a center frequency of 590 MHz is about 508.5 mm.
The helical antenna 1 of the first embodiment and the helical antenna 2 of the second embodiment have the same dimensions, the diameter D of the helical elements 10b, 20b is about 8 mm, and the radial direction of the helical elements 10b, 20b and the coaxial cables 11, 21 Of the helical elements 10b and 20b and the coaxial cables 11 and 21 in the radial direction is about 2 mm, and the axial length L of the helical elements 10b and 20b is about 50.8 mm. The number of turns of the helical elements 10b and 20b is 3.5 turns.

  The helical elements 10b and 20b use a phosphor bronze wire having an elasticity of about 0.6 mm in diameter, and the coaxial cables 11 and 21 use 1.5C cables of about 3 mm in diameter. The helical elements 10b and 20b are not limited to phosphor bronze wires, but may be other wires, but an elastic wire is suitable, and may have a diameter other than about 0.6 mm. As the coaxial cables 11 and 21, not only a 1.5C cable having a characteristic impedance of 75Ω but also a 1.5D cable having a characteristic impedance of 50Ω or a coaxial cable having other characteristic impedance may be used. Further, not only a flexible coaxial cable but also a semi-rigid coaxial cable may be used.

  Next, the frequency characteristics of the voltage standing wave ratio (VSWR) of the helical antenna 1 according to the first embodiment of the present invention and the helical antenna 2 of the second embodiment are similar, and the frequency characteristics are shown in FIG. 7 and FIG. Here, the narrowest gap GS between the coaxial cables 11 and 21 and the helical portions 10 and 20 is fixed to about 2 mm, the diameter of the coaxial cables 11 and 21 is about 3 mm, and the coaxial cables 11 and 21 and the helical elements 10b and 20b. And the length L of the helical elements 10b and 20b as parameters. Further, the frequency band of 470 MHz to 710 MHz is assumed to operate in the frequency band of terrestrial digital broadcasting, and the wavelength λ of the free space with the center frequency of 590 MHz is set to about 508.5 mm. Further, the helical antennas 1 and 2 are installed at a position above the windshield of the vehicle as being installed in the vehicle, and are arranged at a position of about 50 mm from the left side of the windshield and about 15 mm from the upper side of the windshield. In this case, it is assumed that the coaxial cables 11 and 21 are wound along the metal frame at the left end of the windshield.

  The frequency characteristic of the VSWR shown in FIG. 6 is that when the widest gap GL between the coaxial cables 11 and 21 and the helical elements 10b and 20b is about 0.006λ (about 3.1 mm), the length of the helical elements 10b and 20b is long. Using length L as a parameter, changes to approximately 0.02λ (approximately 10.2 mm), approximately 0.04λ (approximately 20.3 mm), approximately 0.066λ (approximately 33.6 mm), and approximately 0.2λ (101.7 mm). The change of VSWR of the helical antennas 1 and 2 in 470 MHz-710 MHz at the time of making it show is shown. Referring to FIG. 6, when the length L of the helical elements 10b and 20b is about 0.02λ, the VSWR is 3.0 or more in a frequency band of about 525 MHz or less and a frequency band of about 625 MHz or more. Further, when the length L of the helical elements 10b and 20b is about 0.04λ, the VSWR becomes 3.0 or more in a frequency band of about 510 MHz or less and a frequency band of about 630 MHz or more. However, when the lengths L of the helical elements 10b and 20b are about 0.066λ and about 0.2λ, a VSWR characteristic of 3.0 or less can be obtained in the entire frequency band.

Here, consider a value Q obtained by multiplying the product of the interval GL represented by the wavelength λ and the length L of the helical elements 10b and 20b represented by the wavelength λ by 10,000. The value Q when the interval GL is about 0.02λ is about 1.2, and the value Q when the interval GL is about 0.04λ is about 2.4. The value Q when the interval GL is about 0.066λ is about 4.0, and the value Q when the interval GL is about 0.2λ is about 12. That is, when the value Q is 4 or more, a VSWR characteristic of 3.0 or less can be obtained in the entire frequency band. In general, if the VSWR is 3.0 or less, the antenna functions sufficiently. Therefore, the helical antenna according to the present invention is designed so that the VSWR satisfies 3.0 or less in the operating frequency band. The design formula in this case can be expressed as the following formula (1).
Q = GL [λ] × L [λ] × 10000 ≧ 4 (1)
However, in equation (1), GL [λ] and L [λ] are values represented by wavelengths, and the interval GS is a fixed value.

  The frequency characteristic of the VSWR shown in FIG. 7 is that when the widest gap GL between the coaxial cables 11 and 21 and the helical elements 10b and 20b is about 0.02λ (about 10.2 mm), the length of the helical elements 10b and 20b is long. Using length L as a parameter, changes to about 0.02λ (about 10.2 mm), about 0.04λ (about 20.3 mm), about 0.1λ (about 50.8 mm), about 0.2λ (101.7 mm) The change of VSWR of the helical antennas 1 and 2 in 470 MHz-710 MHz at the time of making it show is shown. Referring to FIG. 7, even if the length L of the helical elements 10b and 20b is changed to about 0.02λ, about 0.04λ, about 0.1λ, and about 0.2λ, it is 3.0 or less in the entire frequency band. VSWR characteristics are obtained. The value Q at this time is about 4.0 when the length L is about 0.02λ, about 8.0 when the length L is about 0.04λ, and when the length L is about 0.1λ. It is about 40 when the length L is about 0.2λ and about 20, and it can be seen that the value Q is 4 or more in any case.

  The frequency characteristic of the VSWR shown in FIG. 8 is that when the widest gap GL between the coaxial cables 11 and 21 and the helical elements 10b and 20b is about 0.03λ (about 15.3 mm), the length of the helical elements 10b and 20b is long. Using length L as a parameter, changes to about 0.02λ (about 10.2 mm), about 0.04λ (about 20.3 mm), about 0.1λ (about 50.8 mm), about 0.2λ (101.7 mm) The change of VSWR of the helical antennas 1 and 2 in 470 MHz-710 MHz at the time of making it show is shown. Referring to FIG. 8, even if the length L of the helical elements 10b and 20b is changed to about 0.02λ, about 0.04λ, about 0.1λ, and about 0.2λ, it is 3.0 or less in the entire frequency band. VSWR characteristics are obtained. The value Q at this time is about 6.0 when the length L is about 0.02λ, about 12 when the length L is about 0.04λ, and about 30 when the length L is about 0.1λ. When the length L is about 0.2λ, it is about 60, and it can be seen that the value Q is 4 or more in any case.

From the above, when the frequency band to be operated is set and the wavelength of the center frequency is set to λ, in order to obtain VSWR 3.0 or less in the entire frequency band, the interval GL [λ] and the length of the helical element It can be seen that the value Q obtained by multiplying the product of L [λ] by 10,000 should be 4 or more.
FIG. 9 shows the frequency characteristic of the average gain in the helical antenna 1 of the first embodiment of the present invention in comparison with the frequency characteristic of the average gain of the conventional L-type antenna 200 shown in FIG. In FIG. 9, the frequency characteristic of the average gain is indicated by a solid line in the helical antenna 1 of the first embodiment, and is indicated by a broken line in the conventional L-type antenna 200. The gain is the maximum value of the conventional L-type antenna 200. Is normalized and displayed as 0 dB. Referring to FIG. 9, it can be seen that although the gain is slightly reduced from the low frequency side and from the middle frequency to the high frequency in the frequency band, the frequency characteristics of substantially the same gain are obtained. Further, the frequency characteristic of the average gain in the helical antenna 2 of the second embodiment of the present invention is the same as the characteristic of the solid line shown in FIG.

Next, FIG. 5 is a perspective view showing the configuration of the helical antenna 3 according to the third embodiment of the present invention.
In the helical antenna 3 of the third embodiment shown in this figure, the helical antenna 1 of the first embodiment is housed in a protective case 12, and the coaxial cable 11 is led out from the protective case 12. The protective case 12 is provided in the helical antenna 3 for the purpose of protection from external pressure, stabilization of the antenna structure, and securing of an adhesive surface at the time of attachment. The protective case 12 has a rectangular parallelepiped shape. The protective case 12 accommodates a helical part 10 and a front part including the central conductor 11a, the insulating part 11b and the braided wire 11c of the coaxial cable 11 in one of the half-cased cases. Thus, the helical case 10 and the front portion of the coaxial cable 11 are accommodated in the protective case 12 by bonding the other case to the one case or fixing them with screws.

As an example of the dimensions of the protective case 12, the width W1 is about 12 mm, the height H1 is about 12 mm, and the length L2 is about 55 mm. As described above, the helical antenna 3 according to the third embodiment can have a simple structure and an antenna with a very low attitude. Moreover, since the electrical characteristics similar to those of the helical antenna 1 of the first embodiment are exhibited, a broadband frequency characteristic can be obtained, and a helical antenna suitable as an antenna for receiving terrestrial digital broadcasting can be obtained. Further, the helical antenna 3 can be attached by sticking one surface of the protective case 12 to the supported body.
In addition, since the protective case 12 is a dielectric, when the electrical length of the helical antenna 3 is shortened due to the influence, the diameter and length of the helical element so as to obtain a desired VSWR characteristic, Adjust the number of turns as appropriate. That is, when the wavelength is shortened, the above-described equation (1) may be calculated by replacing the wavelength λ described above with a wavelength considering the wavelength shortening rate. Further, the helical antenna 2 of the second embodiment may be housed in the protective case 12.

  As described above, in the helical antenna 1 according to the first embodiment of the present invention and the helical antenna 2 according to the second embodiment, the coaxial cables 11 and 21 are arranged at positions eccentric from the winding centers of the helical portions 10 and 20. At the same time, the longest gap GL in the radial direction between the outer peripheral surface of the coaxial cables 11 and 21 and the helical elements 10b and 20b and the length L of the helical elements 10b and 20b are set so as to satisfy the above expression (1). As a result, a VSWR characteristic of 3.0 or less in the frequency band of terrestrial digital broadcasting can be obtained. The same VSWR characteristic can also be obtained in the helical antenna 3 of the third embodiment. Thus, even if the axial length is shortened, the specific frequency band in which VSWR of 3.0 or less is obtained is 40.7%. Further, the helical antenna according to the present invention can have a simple structure with a low posture.

Next, the operation principle of the helical antenna according to the present invention shown as the helical antenna 1 of the first embodiment to the helical antenna 3 of the third embodiment will be described below with reference to FIGS.
FIG. 10A is a front view showing the configuration of the whip antenna 100 having a length of ¼ wavelength, and FIG. 10B is a side view showing the configuration of the whip antenna 100. A whip antenna 100 shown in FIGS. 10 (a) and 10 (b) is an antenna that is generally used in the past, and has a 1/4 wavelength (λ / 4) length at the tip of the central conductor of the coaxial cable 101. 100 a is connected to be perpendicular to the coaxial cable 101. In this case, the whip antenna 100 receives digital terrestrial broadcasting, and the length of the whip element 100a is about 130 mm.

FIG. 11A is a front view showing the configuration of the center-fed helical antenna 110, and FIG. 11B is a side view showing the configuration of the helical antenna 110.
In the helical antenna 110 shown in FIGS. 11 (a) and 11 (b), the outer conductor of the end portion of the coaxial cable 111, the braided wire as the outer conductor, and the insulating portion 11b are removed by a predetermined portion, and the central conductor is exposed. . The helical part 110 includes a connection part 110 a whose tip is bent substantially perpendicular to the coaxial cable 111 and a helical element 110 b wound around the coaxial cable 111. The central conductor of the coaxial cable 111 and the helical element 110b are electrically connected via the connection part 110a. The winding diameter of the helical part 110 is D, and the axial length is L. The coaxial cable 111 is disposed at the winding center of the helical part 110, and the radial distance GS and the distance GL between the outer peripheral surface of the coaxial cable 111 and the helical part 110 have the same length. The helical antenna 110 receives digital terrestrial broadcasting. The helical part 110 has a diameter D of about 20 mm, the helical part 110 has an axial length L of about 20 mm, and the helical part 110 has a number of turns of 2.25 turns. The GL and the interval GS are about 8.5 mm.

12A and 12B, the helical antenna 110-1 shown in FIGS. 11A and 11B is installed in a vehicle with the helical portion 110 having two turns, and the center-fed helical antenna 110-1 is about 50 mm from the left side of the vehicle window 150. It is a figure which shows the aspect attached to the position of about 15 mm from the upper side of the vehicle window 150. FIG. The coaxial cable is wound along the metal frame at the left end of the vehicle window 150.
FIG. 13 shows the present invention for offset feeding in the helical antenna 110 shown in FIGS. 11 (a) and 11 (b), in which the number of turns of the helical part 110 is two turns, the distance GS is about 2 mm, and the distance GL is about 15 mm. FIG. 6 is a view showing a state in which the helical antenna 120 is attached at a position of about 50 mm from the left side of the vehicle window 150 and about 15 mm from the upper side of the vehicle window 150. The coaxial cable is wound along the metal frame at the left end of the vehicle window 150.
The whip element 100a and the helical part 110 use, for example, a phosphor bronze wire with a diameter of about 0.6 mm, and the coaxial cables 101 and 111 use 1.5C cables with a diameter of about 3 mm.

14 is a graph showing the maximum value (Max) and minimum value (Min) of resistance of the whip antenna 100, the helical antenna 110, the helical antenna 110-1, and the helical antenna 120 at 470 MHz to 710 MHz, and FIG. It is a graph which shows the maximum value (Max) and minimum value (Min) of the reactance of the said antenna in 710 MHz.
14 and 15, (1) shown on the horizontal axis shows a case where the whip antenna 100 having the configuration shown in FIGS. 10 (a) and 10 (b) is installed in free space, and the resistance is about 140Ω in the above frequency band. The reactance changes to about -130Ω to about + 140Ω, and the VSWR increases because of the high resistance and the large reactance. In this case, the maximum value of VSWR is calculated to be about 5.
14 and 15, (2) shown on the horizontal axis shows the case where the helical antenna 110 having the configuration shown in FIGS. 11 (a) and 11 (b) is installed in free space and is center-fed, and the resistance in the above frequency band is shown. Changes from about 18 Ω to about 85 Ω, and reactance changes from about −120 Ω to about +110 Ω, resulting in low resistance and high VSWR. The maximum value of VSWR is calculated to be about 12.

14 and 15, (3) shown on the horizontal axis shows the case where the helical antenna 110-1 having the configuration shown in FIG. 12 is center-fed in the vehicle installation, and the resistance is about 55Ω to about 280Ω in the above frequency band. The reactance changes from about −125Ω to about + 92Ω. Since the reactance is large, the VSWR becomes high. The maximum value of VSWR is calculated to be about 4.8.
14 and 15, (4) shown on the horizontal axis shows a case where the helical antenna 120 according to the present invention having the configuration shown in FIG. 13 is offset-fed when installed in a vehicle, and the resistance is about 64Ω to the above frequency band. It changes to about 210Ω, and the reactance changes from about −80Ω to about + 60Ω, and both the resistance and the reactance become suitable values. At this time, the maximum value of VSWR is calculated to be about 2.5.

  From the above, when the element is helically wound around the coaxial cable as in the helical antenna 110 shown in FIGS. 11A and 11B, the resistance becomes the whip antenna shown in FIG. 10 as shown in FIG. Lower than 100. Further, by bringing the vehicle window 150 close to the metal frame like the helical antenna 110-1 shown in FIG. 12, it is possible to recover the resistance that has dropped too much as shown in FIG. Furthermore, the coaxial cable is eccentrically installed with respect to the helical element as in the helical antenna 120 shown in FIG. 13 and is brought close to the metal frame of the vehicle window 150, thereby providing an appropriate impedance as shown in FIGS. Since it shows over a wide band, a favorable impedance characteristic can be obtained in a wide band. This is the operating principle of the helical antenna according to the present invention which shows good electrical characteristics while being short in the axial direction and low in posture.

Next, FIG. 16 shows a configuration of a mounting example in which the helical antenna 3 according to the third embodiment of the present invention is mounted in a vehicle interior.
In the mounting example shown in FIG. 16, the helical antenna 3 is attached to the upper part of the vehicle window 150 that is a windshield. As shown in FIG. 5, the helical antenna 3 has a helical part 10 housed in a protective case 12. An adhesive means such as a double-sided tape or a suction cup is provided on one surface of the protective case 12 and is attached to the upper part of the vehicle window 150. is doing. Alternatively, the helical antenna 3 may be attached to the back surface of the rearview mirror 151, or may be fixed by screwing or the like. Further, any one of the helical antenna 1 of the first embodiment to the helical antenna 3 of the third embodiment may be built in the rearview mirror 151. Also when pasting on the rearview mirror 151, pasting means such as a double-sided tape is provided on one surface of the protective case 12, and pasted on the rear surface of the rearview mirror 151. In this case, the coaxial cable 11 led out from the helical antenna 3 is inserted into a roof lining (ceiling lining) or a pillar garnish (pillar interior cover) in the vicinity of the attached helical antenna 3 and is installed in the vehicle interior. Wire so that it can be connected to.

  Similarly, when the helical antenna 3 is attached to the upper surface or inside of the dashboard 152 of the vehicle, an adhesive means such as a double-sided tape or a suction cup is provided on one surface of the protective case 12 and is attached to the upper surface of the dashboard 152. . Alternatively, a fixing component is attached to the protective case 12 and fixed to an attachment portion prepared on the dashboard 152. Then, the coaxial cable 11 is wired so that it can be connected to a tuner installed in the passenger compartment.

Next, FIG. 17 shows a configuration of another mounting example in which the helical antenna 3 according to the third embodiment of the present invention is mounted in the vehicle interior. The installation example shown in FIG. 17 is an installation example of the helical antenna 3 in the case of diversity reception.
In diversity reception, a plurality of antennas are generally arranged at intervals of about λ / 2. λ is the wavelength of the center frequency of the operating frequency band. The two helical antennas 3 shown in FIG. 17 are respectively arranged on the left and right of the upper part of the vehicle window 150 with a predetermined distance therebetween. In this case, a sticking means such as a double-sided tape may be provided on one surface of the protective case 12 of each helical antenna 3 and stuck to a predetermined location on the top of the vehicle window 150. The coaxial cable 11 led out from the two helical antennas 3 is inserted into a roof lining (ceiling lining) or a pillar garnish (pillar interior cover) near the vehicle window 150 and connected to a tuner installed in the vehicle interior. Wire as much as possible. In this case, the interval between the two helical antennas 3 is preferably λ / 2, but this is not a limitation when there are restrictions on the dimensions of the vehicle. Further, the two helical antennas 3 may be arranged at a place other than the vehicle window 150, or may be installed not only in the horizontal installation but also in the vertical direction and other directions.

Next, the configuration of the helical antenna 4 according to the fourth embodiment of the present invention is shown in FIGS. FIG. 18A is a perspective view showing the configuration of the helical antenna of the fourth embodiment, and FIG. 18B is a side view showing the configuration of the helical antenna 4 of the fourth embodiment.
The helical antenna 4 of the fourth embodiment shown in FIGS. 18 (a) and 18 (b) is configured to include amplification means for amplifying the received signal. In the helical antenna 4 of the fourth embodiment, the outer sheath of the tip end portion of the coaxial cable 41 is removed, and the braided wire 41c which is an outer conductor is slightly exposed. Further, the braided wire 41c is also removed at the tip portion, and the insulating portion 41b is slightly exposed. Furthermore, the insulating portion 41b is also removed at the tip portion, and the central conductor 41a is exposed. An amplifier 43 is provided on one surface of the substrate 42, and a central conductor 41 a is connected to the output end of the amplifier 43. The helical portion 40 includes a connection portion 40 a whose tip is bent substantially perpendicular to the substrate 42, and a helical element 40 b that is helically wound around the substrate 42 and the coaxial cable 41. One end of the connection portion 40a is connected to the input end of the amplifier 43, and the end portion of the helical element 40b is connected to the other end of the connection portion 40a. The helical element 40b is installed eccentrically with respect to the coaxial cable 41 in the direction in which the length of the connecting portion 40a becomes longer or shorter. The substrate 42 may be provided with a circuit having other functions such as an impedance matching circuit of the helical unit 40 in addition to the amplifier 43. The amplifier 43 is supplied with electric power superimposed on the coaxial cable 41 from the tuner via the coaxial cable 41 as an operation power source.

  In the helical element 40b, the longest gap GL in the radial direction between the outer peripheral surface of the coaxial cable 41 and the helical element 40b and the length L of the helical element 40b are designed to satisfy the above-described equation (1). The Since the helical antenna 4 shown in FIG. 18 shows a good maximum gain frequency characteristic in which the characteristics of the amplifier 43 are added to the gain characteristics of the helical antennas 1 and 2, it is possible to realize a very wide band antenna. it can. The helical antenna 4 according to the fourth embodiment of the present invention can also have a simple structure, an extremely low profile antenna, and obtain a wideband gain characteristic. An antenna suitable as a receiving antenna can be obtained.

Next, FIG. 19 is a perspective view showing the configuration of the helical antenna 5 according to the fifth embodiment of the present invention.
In the helical antenna 5 of the fifth embodiment shown in this figure, the helical antenna 4 of the fourth embodiment is housed in a protective case 44, and the coaxial cable 41 is led out from the protective case 44. The protective case 44 is provided in the helical antenna 5 for the purpose of protection from external pressure, stabilization of the antenna structure, and securing of an adhesive surface at the time of attachment. The protective case 44 is composed of a lid portion 44a and a case portion 44b which are semi-rectangular in the shape of a rectangular parallelepiped. The front portion including 41c and the substrate 42 on which the amplifier 43 is provided are housed, and the lid portion 44a is bonded to the case portion 44b or fixed with screws so that the helical portion 40 and the coaxial cable 41 are placed in the protective case 44. The board 42 provided with the front part and the amplifier 43 is accommodated. In this case, a holding portion that holds the substrate 42 and the helical portion 40 may be formed inside the case portion 44b and the lid portion 44a, and the holding portion may hold the substrate 42 and the helical portion 40.

Next, the structure of the modification of the helical part 40 in the helical antenna 4 of 4th Example concerning this invention is shown in FIG. 20 thru | or FIG.
In the first modification shown in FIG. 20, the connecting portion 40a-1 connected to the input end of the amplifier 43 is pulled out substantially parallel to the substrate 42 and connected to the helical element in the helical portion 40-1. In this case, since the coaxial cable 41 is arranged eccentrically from the winding center of the helical part 40-1, the connecting part 40a-1 does not pass through the winding center of the helical part 40-1 as shown in FIG. Placed in. The substrate 42 is disposed vertically. In the illustrated example, the substrate 42 is eccentric so as to be close to the helical portion 40-1, but conversely, the coaxial cable 41 may be eccentric so that it is close to the helical portion 40-1. In the first modification, since the connection portion 40a-1 is installed substantially parallel to the substrate 42, it is possible to suppress variations in the mounting state of the connection portion 40a-1 during mass production.

  Further, in the second modified example shown in FIG. 21, the shape of the helical portion 40-2 is an elliptical shape crushed up and down. The connection portion 40a-2 connected to the input end of the amplifier 43 is substantially located on the short axis of the helical portion 40-2, and the coaxial cable 41 is installed with being shifted from the long axis of the helical portion 40-2. ing. In this case, the coaxial cable 41 may be positioned on the long axis of the helical part 40-2, and the connecting part 40a-2 may be installed so as not to pass through the short axis of the helical part 40-2. In the second modification, the height of the helical portion 40-2 can be suppressed, and a helical antenna having a lower posture can be obtained.

  Furthermore, in the 3rd modification shown in FIG. 22, the shape of the helical part 40-3 is made into the shape of a triangle. The connection part 40a-3 connected to the input end of the amplifier 43 is connected to the apex of the triangular helical part 40-3. The coaxial cable 41 is eccentrically arranged with respect to the helical portion 40-3 by arranging the substrate 42 so as to be close to the straight portion which is the bottom surface of the triangular helical portion 40-3. In the third modification, since the straight portion of the triangular helical portion 40-3 is the bottom surface, the shape of the helical portion 40-3 is difficult to deform, and non-standard products due to variations in mass production are reduced. Can do.

Furthermore, in the 4th modification shown in FIG. 23, the shape of the helical part 40-4 is made into the square shape. The connection portion 40a-4 connected to the input end of the amplifier 43 is connected to one side of the rectangular helical portion 40-4. In this case, you may make it connect the connection part 40a-4 to the square vertex of the square-shaped helical part 40-4. In addition, the coaxial cable 41 is arranged eccentrically with respect to the helical portion 40-4 by arranging the substrate 42 so as to be close to the straight portion which is the bottom surface of the rectangular helical portion 40-4. The coaxial cable 41 is arranged so as to be close to the straight line portion that is the upper surface of the rectangular helical portion 40-4 so that the coaxial cable 41 is arranged eccentrically with respect to the helical portion 40-4. Also good. In the fourth modification, the straight line portion of the helical portion 40-4 is the bottom surface, and the apex shape is more obtuse than the triangular shape. Therefore, the strength can be increased easily and non-standard products due to variations during mass production. Can be reduced.
In the above modification, the shape of the helical portion is an ellipse, a triangle, or a quadrangle. However, the shape is not limited to this, and the shape of the helical portion may be a polygon.
Moreover, since the modification of the above helical part is applied to 4th Example, it can be applied also to the helical antenna 5 of 5th Example. Furthermore, the present invention can be applied to the helical portion 10 in the helical antenna 1 to the helical antenna 3 of the first to third embodiments.

Next, a perspective view showing the configuration of the helical antenna of the sixth embodiment according to the present invention is shown in FIG. 24A, and the perspective view showing the configuration of the cylindrical portion of the helical antenna of the sixth embodiment is shown in FIG. ).
The helical antenna 6 of the sixth embodiment shown in FIG. 24A includes a cylindrical portion 45 made of a cylindrical dielectric having a circular cross section, and a helical portion 40 ′ on the outer peripheral surface of the cylindrical portion 45. Is provided. As shown in FIG. 24B, the cylindrical portion 45 has a helical groove 45a formed on the outer peripheral surface, and a helical element 40b ′ constituting the helical portion 40 ′ is inserted into the helical groove 45a. The elastic helical element 40b ′ made of a wire material such as phosphor bronze is inserted into the helical groove 45a on the outer peripheral surface of the cylindrical portion 45, which is a dielectric, so that it is held by the cylindrical portion 45. . Thereby, since the internal diameter of helical element 40b 'is controlled by the outer diameter of the helical groove 45a in the cylindrical part 45, the electrical dispersion | variation at the time of mass production can be suppressed.

  In the helical antenna 6 of the sixth embodiment, the front portion including the substrate 42 on which the amplifier 43 is provided on one side, the central conductor 41a of the coaxial cable 41, the insulating portion 41b, and the braided wire 41c is the through hole 45b of the cylindrical portion 45. The connecting portion 40 a that is disposed inside and is led out from the tip of the substrate 42 is connected to one end of a helical element 40 b ′ held on the outer peripheral surface of the cylindrical portion 45. The central conductor 41a of the coaxial cable 41 is connected to the output end of the amplifier 43, and one end of the connection portion 40a is connected to the input end of the amplifier 43. The helical element 40b 'is installed eccentrically with respect to the coaxial cable 41 in the direction in which the length of the connecting portion 40a becomes longer or shorter. Since the wavelength is shortened by the dielectric constant of the cylindrical portion 45 that is a dielectric, the helical antenna 6 can be further downsized. Further, since the wavelength is shortened, the above-described interval GL [λ] and the length L of the helical element 40b ′ are calculated by calculating the above equation (1) by replacing the wavelength λ with a wavelength considering the wavelength shortening rate. [Λ] is obtained.

Next, a perspective view showing the configuration of the helical antenna of the seventh embodiment according to the present invention is shown in FIG. 25A, and the perspective view showing the configuration of the cylindrical portion of the helical antenna of the seventh embodiment is shown in FIG. ).
The helical antenna 7 of the seventh embodiment shown in FIG. 25A includes a cylindrical portion 46 made of a cylindrical dielectric having a circular cross section, and the helical portion 40 ″ is provided on the outer peripheral surface of the cylindrical portion 46. A connecting fitting 47 is attached to the tip of the cylindrical portion 46. As shown in Fig. 25 (b), the cylindrical portion 46 has a helical groove 46a formed on the outer peripheral surface, and the helical portion 46 has a helical shape. A helical element 40b ″ is formed by depositing a conductive material in the groove 46a. A through hole 46c is formed over the entire cylindrical portion 46, and a protruding portion 46b whose outer diameter is slightly reduced by reducing the thickness of the tip portion is formed. A conductive material is deposited on the surface of the protrusion 46b so as to be connected to the helical element 40b ". The metal connection fitting 47 has a substantially circular cap shape and can be fitted into the protrusion 46b. A rectangular insertion hole 47b that has a fitting portion 47a and through which the substrate 42 can be inserted is formed on the front surface, and the periphery of the rectangular insertion hole 47b is formed to protrude forward.

In the helical antenna 7 of the seventh embodiment, the front portion including the substrate 42 on which the amplifier 43 is provided on one side, the central conductor 41a of the coaxial cable 41, the insulating portion 41b, and the braided wire 41c is the through hole 45b of the cylindrical portion 45. The tip end portion of the substrate 42 is inserted and held in the rectangular insertion hole 47 b of the connection fitting 47. Further, by fitting the fitting portion 47 a of the connection fitting 47 to the protruding portion 46 b of the cylindrical portion 46, the helical element 40 b ″ formed on the outer peripheral surface of the cylindrical portion 46 is connected to the connection fitting 47. The input end of the amplifier 43 is connected to a printed wiring formed on the substrate 42. By soldering the printed wiring of the substrate 42 inserted into the rectangular insertion hole 47b, the helical element 40b " The received signal received at is input. A central conductor 41a of the coaxial cable 41 is connected to the output end of the amplifier 43. The helical element 40b ″ is installed eccentrically with respect to the coaxial cable 41. Further, since the helical element 40b ″ is formed by vapor deposition on the outer peripheral surface of the cylindrical portion 46, its size is restricted. Electrical variations during mass production can be suppressed. Furthermore, since the wavelength is shortened by the dielectric constant of the cylindrical portion 46, the helical antenna 7 can be further downsized. Further, since the wavelength is shortened, the above-described interval GL [λ] and the length L of the helical element 40b ″ are calculated by replacing the wavelength λ with a wavelength considering the wavelength shortening rate and calculating the equation (1). [Λ] is obtained.
. Alternatively, the helical element 40b ″ may be formed by vapor deposition on the outer peripheral surface of the cylindrical portion 46 without providing the helical groove 46a.

FIG. 26 is a perspective view showing the configuration of the helical antenna according to the eighth embodiment of the present invention.
In the helical antenna 8 of the eighth embodiment shown in FIG. 26, the output end of the amplifier 43 is connected to the center conductor 41a of the coaxial cable 41 via the microstrip line 48 provided on the elongated substrate 42 ′. ing. The microstrip line 48 is formed on a substrate 42 ′ such as a glass epoxy substrate or a Teflon substrate having good high frequency characteristics so as to have substantially the same characteristic impedance as the coaxial cable 41 using a conductive vapor deposition material such as copper foil. Has been. The microstrip line 48 includes a line part and a ground part that sandwiches the line part from both sides. A center conductor 41a led out from the insulating portion 41b of the coaxial cable 41 is connected to the line portion, and a braided wire 41c, which is an outer conductor of the coaxial cable 41, is connected to the ground portions on both sides, and the through The hole is connected to the ground portion formed on the entire back surface of the substrate 42 '.

  The helical portion 40 includes a connection portion 40a whose tip is bent substantially perpendicularly to the substrate 42 'and a helical element 40b wound in a helical shape around the substrate 42'. One end of the connection portion 40a is connected to the input end of the amplifier 43, and the end portion of the helical element 40b is connected to the other end of the connection portion 40a. The helical element 40b is installed eccentrically with respect to the coaxial cable 41 in the direction in which the length of the connecting portion 40a becomes longer or shorter. By being connected to the coaxial cable 41 via the microstrip line 48, the coaxial cable 41 does not enter the helical portion 40, so that the structure is easy to assemble and the coaxial cable 41 does not wobble so that the electrical characteristics are stabilized. , Mass production becomes easy. Furthermore, the line width ratio of the microstrip line 48 may be changed to provide impedance matching or a balun function. Furthermore, if the microstrip line 48 is a coplanar line, the cost can be reduced.

Next, FIG. 27 is a perspective view showing the configuration of the helical antenna according to the ninth embodiment of the present invention.
The helical antenna 9 of the ninth embodiment shown in FIG. 27 is formed elongated in a cylindrical portion 45 made of a cylindrical dielectric having a circular cross section in the configuration shown in FIG. A substrate 42 'configured as shown in FIG. 26 is accommodated. That is, the helical groove 45a is formed in the outer peripheral surface of the cylindrical part 45, and helical element 40b 'which comprises helical part 40' is inserted in this helical groove 45a. Further, the output end of the amplifier 43 is connected to the central conductor 41a of the coaxial cable 41 via a microstrip line 48 provided on an elongated board 42 '. A central conductor 41a of the coaxial cable 41 is connected to the line portion of the microstrip line 48, and a braided wire 41c of the coaxial cable 41 is connected to the ground portions on both sides, and the entire back surface of the substrate 42 'is formed by through holes. Is connected to the ground portion formed on the substrate.

  In the helical antenna 9 of the ninth embodiment, an elongated substrate 42 ′ on which the amplifier 43 and the microstrip line 48 are provided is disposed in the through hole 45 b of the cylindrical portion 45, and the tip of the substrate 42 ′. Is connected to one end of a helical element 40 b ′ held on the outer peripheral surface of the cylindrical portion 45. Note that one end of the connection portion 40 a is connected to the input end of the amplifier 43. The helical element 40b 'is installed eccentrically with respect to the coaxial cable 41 in the direction in which the length of the connecting portion 40a becomes longer or shorter. Since the wavelength is shortened by the dielectric constant of the cylindrical portion 45 that is a dielectric, the helical antenna 9 can be further downsized. Further, since the wavelength is shortened, the above-described interval GL [λ] and the length L of the helical element 40b ′ are calculated by calculating the above equation (1) by replacing the wavelength λ with a wavelength considering the wavelength shortening rate. [Λ] is obtained.

Next, FIG. 28 is a perspective view showing a configuration of a modified example of the helical antenna 4 according to the fourth embodiment of the present invention.
In the modification of the helical antenna 4 of the fourth embodiment shown in FIG. 28, a conductive cable ring 49 is attached to a predetermined position of the coaxial cable 41. The inner diameter of the cable ring 49 is substantially equal to the outer diameter of the coaxial cable 41, and the shape of the cable ring 49 is circular. The cable ring 49 is fixed to the coaxial cable 41 by being deformed by a crimping die or the like. A mode in which the helical antenna 4 of this modification is attached to the vehicle window 150 is shown in FIG. As shown in this figure, the attachment position of the cable ring 49 on the coaxial cable 41 is a position in contact with the body frame 153 around the vehicle window 150 to which the helical antenna 4 is attached. The cable ring 49 is fixed to the body frame 153 with an adhesive tape or the like. For example, when the helical antenna 9 is fixed to the vehicle window 150 and there is an optimum value for the position where the coaxial cable 41 is passed over the body frame 153, the cable ring 49 plays a role of positioning, so that the installation work is simplified. , Electrical characteristics can be stabilized.

Next, FIG. 30 is a perspective view showing the configuration of another modification of the helical antenna 4 of the fourth embodiment according to the present invention.
In the modification of the helical antenna 4 of the fourth embodiment shown in FIG. 30, a conductive cable plate 50 is attached to a predetermined position of the coaxial cable 41. The cable plate 50 has a ring portion, and the cable plate 50 is fixed to the coaxial cable 41 by caulking the ring portion. A mode in which the helical antenna 4 of another modification is attached to the vehicle window 150 is shown in FIG. As shown in this figure, the attachment position of the cable plate 50 on the coaxial cable 41 is a position in contact with the body frame 153 around the vehicle window 150 to which the helical antenna 4 is attached. Since the installation area of the cable plate 50 is increased, the fixing strength to the body frame 153 can be increased. The cable plate 50 is fixed to the body frame 153 with an adhesive tape or a screw. The cable plate 50 has a positioning function, can simplify the mounting work and stabilize the electrical characteristics.
The cable ring 49 and the cable plate 50 are not limited to being applied to the helical antenna 4 of the fourth embodiment, but can be applied to the helical antennas of the other embodiments described above, and their coaxial cables. It can be attached at a predetermined position.

  In the embodiment of the helical antenna according to the present invention described above, the helical antenna for digital terrestrial broadcasting has been described. However, the present invention is not limited to this, and the present invention can be applied to a low-profile antenna having a wide use frequency band. it can.

It is a front view which shows the structure of the helical antenna of 1st Example concerning this invention. It is a side view which shows the structure of the helical antenna of 1st Example concerning this invention. It is a front view which shows the structure of the helical antenna of 2nd Example concerning this invention. It is a side view which shows the structure of the helical antenna of 2nd Example concerning this invention. It is a perspective view which shows the structure of the helical antenna concerning 3rd Example of this invention. It is a figure which shows the frequency characteristic of VSWR of the helical antenna of 1st Example of this invention, and 2nd Example. It is a figure which shows the frequency characteristic of VSWR which changed the parameter of the helical antenna of 1st Example of this invention, and 2nd Example. It is a figure which shows the frequency characteristic of VSWR which changed the parameter further of the helical antenna of 1st Example of this invention, and 2nd Example. It is a figure which shows the frequency characteristic of the average gain in the helical antenna of 1st Example of this invention contrasted with the frequency characteristic of the average gain of the conventional L-type antenna. It is the front view and side view which show the structure of the whip antenna made into 1/4 wavelength length. It is the front view and side view which show the structure of the helical antenna of center feeding. It is a figure which shows the aspect which installed the helical antenna of center feeding at the vehicle installation in the vehicle window. It is a figure which shows the aspect which installed the helical antenna of offset electric power feeding in the vehicle window by the vehicle installation concerning this invention. 14 is a graph showing a maximum value (Max) and a minimum value (Min) of resistance at 470 MHz to 710 MHz in the antenna shown in FIGS. 10 to 13. 14 is a graph showing a maximum value (Max) and a minimum value (Min) of reactance at 470 MHz to 710 MHz in the antenna shown in FIGS. 10 to 13. It is a figure which shows the structure of the mounting example which mounted | wore the interior of the vehicle with the helical antenna of 3rd Example concerning this invention. It is a figure which shows the structure of the other mounting example which mounted | wore the interior of the vehicle with the helical antenna of 3rd Example concerning this invention. It is the perspective view and side view which show the structure of the helical antenna of 4th Example concerning this invention. It is a perspective view which shows the structure of the helical antenna of 5th Example concerning this invention. It is a figure which shows the structure of the 1st modification of the helical part in the helical antenna of 4th Example concerning this invention. It is a figure which shows the structure of the 2nd modification of the helical part in the helical antenna of 4th Example concerning this invention. It is a figure which shows the structure of the 3rd modification of the helical part in the helical antenna of 4th Example concerning this invention. It is a figure which shows the structure of the 4th modification of the helical part in the helical antenna of 4th Example concerning this invention. It is a perspective view which shows the structure of the helical antenna of 6th Example concerning this invention, and the perspective view which shows the structure of the cylindrical part in the helical antenna of 6th Example. It is a perspective view which shows the structure of the helical antenna of 7th Example concerning this invention, and the perspective view which shows the structure of the cylindrical part and connection metal fitting in the helical antenna of 7th Example. It is a perspective view which shows the structure of the helical antenna of 8th Example concerning this invention. It is a perspective view which shows the structure of the helical antenna of 9th Example concerning this invention. It is a perspective view which shows the structure of the modification of the helical antenna of 4th Example concerning this invention. It is a figure which shows the aspect which attached the helical antenna of the modification of 4th Example concerning this invention to the vehicle window. It is a perspective view which shows the structure of the other modification of the helical antenna of 4th Example concerning this invention. It is a figure which shows the aspect which attached the helical antenna of the other modification of 4th Example concerning this invention to the vehicle window. It is a figure which shows the structure of the antenna for the conventional terrestrial digital broadcast reception.

Explanation of symbols

1 helical antenna, 2 helical antenna, 3 helical antenna, 4 helical antenna, 5 helical antenna, 6 helical antenna, 7 helical antenna, 8 helical antenna, 9 helical antenna, 10 helical part, 10a connection part, 10b helical element, 11 coaxial Cable, 11a Central conductor, 11b Insulating part, 11c Braided wire, 12 Protective case, 20 Helical part, 20a Connection part, 20b Helical element, 21 Coaxial cable, 21a Central conductor, 21b Insulating part, 21c Braided wire, 40 Helical part, 40a connection part, 40b helical element, 41 coaxial cable, 41a central conductor, 41b insulation part, 41c braided wire, 42 substrate, 43 amplifier, 44 protective case, 44a lid part, 44b case part, 45 cylindrical part, 45a Helical groove, 45b Through hole, 46 Cylindrical part, 46a Helical groove, 46b Protruding part, 46c Through hole, 47 Connection fitting, 47a Fitting part, 47b Rectangular insertion hole, 48 Microstrip line, 49 Cable ring, 50 Cable plate , 100 Whip antenna, 100a Whip element, 101 Coaxial cable, 110 Helical antenna, 110 Helical part, 110a Connection part, 110b Helical element, 111 Coaxial cable, 120 Helical antenna, 150 Vehicle window, 151 Rearview mirror, 152 Dashboard, 153 Body frame, 200 antenna, 200 L-type antenna, 201 L-type element, 202 coaxial cable

Claims (9)

Coaxial cable,
A helical element connected to the end of the central conductor of the coaxial cable and wound around the coaxial cable;
The helical antenna, wherein the coaxial cable is arranged at a position eccentric from a winding center of the helical element. Coaxial cable,
A helical element;
Amplifying means provided on a substrate, wherein a central conductor of the coaxial cable is connected to an output end, and the helical element is connected to an input end;
The helical element is wound around the coaxial cable and the substrate, and the coaxial cable and the substrate are arranged at a position eccentric from a winding center of the helical element. antenna.   The helical antenna according to claim 1 or 2, wherein a circumferential shape of the helical element is any one of a circle, an ellipse, a triangle, and a quadrangle.   The helical device according to claim 1, wherein the helical element is wound in a helical groove formed on a peripheral surface of an insulating cylindrical portion, and the coaxial cable is inserted into the cylindrical portion. antenna.   The helical element is wound in a helical groove formed on a peripheral surface of an insulating cylindrical portion, and the coaxial cable and the amplifying means are inserted into the cylindrical portion. The helical antenna according to 2 or 3.   2. The helical element is formed by depositing a conductive vapor deposition material on a peripheral surface of an insulating cylindrical portion, and the coaxial cable is inserted into the cylindrical portion. Helical antenna.   The helical element is formed by depositing a conductive vapor deposition material on a peripheral surface of an insulating cylindrical portion, and the coaxial cable and the amplification means are inserted into the cylindrical portion. The helical antenna according to claim 2 or 3.   The helical antenna according to any one of claims 1 to 7, wherein marking means for indicating an attachment position is provided at a predetermined position of the coaxial cable.   In the coaxial cable arranged eccentrically with respect to the helical element, when the distance between the outer peripheral surface of the coaxial cable and the helical element that is shortest in the radial direction is fixed, the coaxial cable A value GL representing the longest radial distance between the outer peripheral surface and the helical element in terms of the wavelength of the center frequency of the operating frequency band, and the axial length of the helical element in terms of the wavelength of the center frequency of the operating frequency band. The helical antenna according to any one of claims 1 to 7, wherein a value Q obtained by multiplying a product of the expressed value L by 10,000 is about 4 or more.

Images