JPS5977705A - Helical antenna device - Google Patents

Abstract

PURPOSE:To obtain an excellent circularly polarized wave characteristic by bending one end of a helical element conductor toward the helical center axis and prolonging the end so as to constitute a coaxial center conductor of a receptacle, inserting a dielectric, holding the center conductor with an outer conductor of the receptacle and providing a reflecting plate. CONSTITUTION:The antenna device consists of a helical element 30, the receptacle 50 and the reflecting plate 40. A terminal 31 at a feeding point of the element 30 is bent gently toward the helical center axis A-A', enters the outer conductor 51 of the receptacle 50 and becomes a center conductor 32. A hole 52 having a diameter less than the maximum diameter of the element 30 is drilled in the center of the outer conductor 51, and the hole 52 is linked to a hole 53 being a 50-ohm impedance via a section having a specific constant impedance. The holes 52, 53 are filled with ''Teflon,'' which supports the center conductor 32. The element 30 is supported in a free space, the axial symmetry of the directivity is improved, the cross polarized wave characteristic and the axis ratio are improved and stable and excellent circularly polarized wave characteristics are attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a helical antenna device, and particularly to an improvement of a helical antenna that can obtain good circular polarization characteristics.

[Technical background of the invention and its problems 1 Helical antennas, spiral antennas, cross dipole antennas, etc. are well known as linear antennas that can obtain circular wave characteristics. The above-described helical antenna is often used as a circularly polarized antenna with relatively high gain. However, at present, there are still problems that need to be improved in order for this helical antenna to have good circular polarization characteristics in the 12 GHz band. In particular, if we list the main problems, the following are:
From the standpoint of manufacturing high-quality antennas, it is strongly desired to solve these problems with the simplest possible technical means.

(1) Improvement of distortion in axial symmetry of directivity (2) Improvement of deterioration of crossed polarization characteristics and axial ratio (3) Above fingers +
Improving the 1iJ axis symmetry, cross-polarization characteristics, and frequency characteristics of the axial ratio (4) Improving the performance of the helical element and plug structure (5)
Simplification of the structure of helical elements and plugs.

High reliability (6) Easy attachment/detachment) Realization of a plug structure Generally, the characteristic impedance of the coaxial feed line is 50Ω. Whether this feed line is used at 100 MHz, 1G11z band, or 10 GHz band, its outer diameter is approximately iom to 2 mm. , their ratio is only about a five-fold difference in diameter. However, the wavelength is 10
800 Cm at 0MHz 30 countries at IGHz, l QG
Since Ht is 3CrIK, the ratio of their wavelengths is 10
0 times different.

Therefore, for example, in a 12 GHz helical antenna, the diameter is about one wound, so the diameter of the coaxial feeder line is a size that cannot be ignored compared to the diameter of the helix.
Therefore, the connection structure with the coaxial line affects the radiation characteristics and requires various considerations.

The axially symmetrical directivity described in the items listed above refers to the first
With respect to the helical axis x-x' of the helical antenna shown in the figure, the directivity is as shown by a dashed line.

On the other hand, the directivity with distorted axial symmetry is the directivity as indicated by the dotted line in the figure, and is the directivity with distorted symmetry with respect to the x-x' axis.

Considering the case where a helical antenna is used as the primary radiator of a reflector antenna, it is necessary to suppress the sand rope level within a predetermined value, but the electric field irradiated to the edge of the reflector is This has the disadvantage that the pedestal value is not reached and the desired value is not achieved.

Regarding the items listed above, if there is a technical means that can solve them at the same time, a good circularly polarized wave radiator can be created. It becomes possible to adopt It is also effective as an excellent circularly polarized wave element antenna for array antennas.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cylindrical wave helical antenna device which is easy to manufacture and which eliminates winding that impairs circular polarization characteristics in order to achieve good circular polarization characteristics.

[Summary of the invention]

The present invention first forms a coaxial central conductor by bending one end of a conductor of a helical element whose main radiation direction is in the direction of the helical axis toward the center of the helical axis and further extending it along the helical central axis. . On the other hand, a hole smaller than the maximum diameter of the helical element is provided in the outer conductor of the plug directly connected to this, and a concentric cylindrical hole with an impedance equal to the characteristic impedance of the feeder line is provided in continuation with this hole. The coaxial center conductor is inserted axially symmetrically along the center line of the hole.

In this way, undesirable radiated electric fields from the vicinity of the feed point are suppressed, and the coaxial outer conductor is integrated with the plug,
A reflector is attached to this to achieve the intended purpose.

〔Effect of the invention〕

According to the present invention, by integrating the helical element and the coaxial center conductor and by using the plug conductor as the outer conductor, the structure is simplified and manufacturing is easy. This has the great effect of achieving stable performance with good reproducibility.

Furthermore, in microwaves such as 12OF (Z band), it has the excellent effect of improving the distortion of the axial symmetry of the directivity and improving the deterioration of the cross polarization characteristics and axial ratio.

[Embodiments of the invention]

An embodiment of the invention is shown in FIGS. 2 and 3. FIG. 2 is a side view of this antenna device, and FIG. 8 is a top view. This antenna device basically uses a helical element (1, connector 6
11 reflectors (consisting of 4G combinations).

In order to eliminate interference with the circumferential wave characteristics, a structure is used in the connector ttil portion and the terminal portion OD of the helical element (toward) to reduce unnecessary radiated electric fields from the vicinity of the feeding point.

The terminal portion 01) of the helical element (to) on the feeding point side is gently bent toward the helical central axis A-A' as shown in FIG. 2, and passes through the helical central axis to the outer conductor ( 51) and becomes the center conductor 02 of the plug 6I.

The structure of the outer conductor (51) of the plug is such that a hole (5
2) is open. This hole (52) is connected to a hole (58) K through a section length of several millimeters where the characteristic impedance is constant and the impedance is 50Ω. The holes (52) and ``holes'' (53) are filled with Teflon, and the Teflon supports the center conductor part of Oa, which is an extension of the terminal part 6υ of the helical element. The structure is such that the helical element (to) is supported by the support of the helical element.If the helical element itself is supported by being wrapped around a dielectric material, the directivity will be deformed at high frequencies such as 12 GHz, which will cause a decrease in the antenna gain. Therefore, the structure of this antenna is such that the helical element is maintained in free space.If the wire used for the helical element is, for example, piano wire, it will have sufficient strength, and the helical shape will be suitable for use due to the design dimensions. It does not deform.Also, by taking the skin effect into account and plating the surface of the piano wire with steel, loss at high frequencies can be ignored.

The structure of the helical element and plug is simple and robust, so it is highly reliable and has stable electrical performance.
High performance can be achieved.

(55) in FIG. 2 is a screw for connecting the outer conductor (51) of the connector 1) 1 to another connector (not shown here). This screw (55) has a ring (56) that allows it to rotate freely relative to the outer conductor (51), so even if the screw (55) is tightened to another connector, the screw (55) will It does not come off the outer conductor (51). Since the connector (57) is provided with a gasket (57), the other connectors and the outer conductor (51) of this connector are in close contact with each other through the gasket, so it is reliable from a waterproof point of view. is taken into consideration.

If we consider the minute electric field radiated from the B-)3' plane which is the helical element side of the hole (52), it will be as shown in Fig. 4. .

A part of the electric field indicated by the arrow line is radiated to the outside, but if it is radiated axially symmetrically, even if the undesirable minute radiated electric field from the vicinity of the B-w plane deviates, the directivity of the antenna will change. It can be assumed that the axial symmetry of is not destroyed by this. Therefore, if the electric field from the center conductor to the outer conductor (51) on the B-13' plane in Fig. 4 is radially axially symmetrical as shown by the arrow line in the figure, then The electric fields cancel each other out and unwanted radiation from the B-1' plane is greatly reduced. In addition, as a result of experimental investigation,
If the diameter of the hole (52) is set to be less than or equal to the diameter of the helical element, the electric field protruding outward from the B BZ plane will be relatively small, and the emitted electric field itself will also be reduced. Furthermore, if the hole (52) is filled with Teflon, the electric field will be concentrated therein, further reducing the leakage of the electric field to the outside.

In the present invention, the reason why the plug and the helical element are configured as described above is that, as explained above, the radiation directivity of the antenna can be sufficiently small without adversely affecting the radiation directivity, and therefore the directivity can be minimized. This is because the distortion of the gender axis symmetry is eliminated.

The above-mentioned undesirable radiation components also have an adverse effect on the circular polarization characteristics. Therefore, in the antenna of this structure, deterioration in cross polarization characteristics and comparison is also improved.

Furthermore, since the above-mentioned axial symmetry is based on the structure of the present invention that combines the plug, the linear element, and the reflector, even if the frequency, that is, the wavelength is changed, no imbalance will occur due to the structure. . In other words, the radiation electric field of an antenna whose directivity and cross-polarization characteristics are stable when the frequency is changed is a superposition of the radiation electric fields from all parts of the feeder line, so as mentioned above, To realize a helical antenna having good axially symmetrical circularly polarized radiation directivity even in the 12 GHz band by creating an integral structure of the plug and helical that suppresses and further cancels the direct rise of unnecessary radiation. was completed. As already mentioned, axial symmetry is important when used as a primary radiator to illuminate a reflector.
This is a particularly important characteristic.

Next, the point to be noted here is that it must be taken into consideration that radiation from the end of the feed point cannot be completely reduced to zero. That is, in order to further enhance the effect of suppressing the anxiety radiation described above, one is to insert Teflon (60) as shown in Figure 2 to concentrate the electric field within the Teflon and prevent it from radiating outward from the end face of the hole (52). I have to.

Second, considering that unnecessary radiation from near the feed point increases as VSWR increases, the length of the hole (52) in Figure 2 is adjusted to reduce VSWR to 1.8 or less. It uses a structure that can be inserted.

One of the methods of impedance matching that has been conventionally used is to attach a strip conductor (l side) as shown in Fig. 5 to the feeding part I of the helical element. This method causes a large amount of unnecessary radiation due to radiation, and the axial ratio of the circularly polarized wave deteriorates.Also, this method has the disadvantage that the radiation from the strip conductor destroys the axial symmetry of the directivity.Furthermore, it is not suitable for mass production. In addition, the manufacturing sheath is also not good.

In contrast, it is relatively easy to reduce the VSWR to 1.8 or less for a characteristic impedance of 50Ω using the hole (52) in Figure 2. In other words, if the antenna feeding point impedance is Zant, then the hole (52) It is sufficient to set the characteristic impedance Zo=V'50·ant. According to our experiments, it was found that the length of the hole (52) should be selected from 0.20 to 0.88 of the wavelength used.

In circuit theory, 1/4 wavelength is used, but when combined with a helical antenna, the impedance of the helical element also has frequency characteristics, and it has been experimentally determined to be 0.20-0.8.
It was confirmed that good VSWR could be obtained in a relatively wide band of 8 wavelengths. As a specific example, the frequency is 11.8 GH
Z of a helical element with a pitch angle of 12' and a circumference of 1 wavelength.
ant is 144.50, and the characteristic impedance of the hole (52) at that time is 85Ω. Since the dielectric constant of Teflon (60) is 2.4, a helical element using a conducting wire with a diameter of 0.92 m was used, so the inner diameter of the hole (52) was 8.8 fl. The length of the hole (62) is 4.5
It was set as fl. VSWR for 50Ω is 1.8 or less,
It was possible to obtain a band of 700M1-1z or higher.

As described above, the helical antenna device having the configuration of the present invention has a configuration in which the axial symmetry of the directivity is improved, the crossed polarization characteristics and the axial ratio are improved, and the helical element and the plug mechanism are Simplification and high reliability are being achieved. Therefore, stable and good circular polarization performance can be obtained.

The simplification of the structure results in less variation in performance - and is suitable for mass production.

Therefore, the device of the present invention provides an industrially extremely useful helical antenna device used for circularly polarized wave radiation.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining the axial symmetry of directivity, Fig. 2 is a sectional view of an embodiment of the present invention, Fig. 8 is a top view of the embodiment of Fig. 2, and Fig. 4 is a diagram for explaining the axial symmetry of the directivity. FIG. 5 is a diagram for explaining unnecessary radiation from the vicinity of the feeding point, and is an explanatory diagram of a technique for improving the pvsw by using a strip conductor. 80...Helical element 31...Terminal part 32 on the feeding point side...Center conductor 10...Reflector plate 41...Circular hole 50 in the reflector plate...Coaxial feeder line 51...Outside Conductor 52... Hole 53 in the outer conductor filled with Teflon... Hole 54 in the outer conductor filled with Teflon... Rotating line portion 55... Junction 60... Teflon agent Patent attorney Nori Chika Yu (ti or 1 person) 1st
Figure X X' Figure 5 (α) (Muno Figure 3 - Figure 4! A'

Claims (2)

[Claims] (1) A helical element having a main radiation direction in the main axis direction,
One end of this helical element conductor is bent toward the helical center axis and extended along the helical center axis to form the coaxial center conductor of the connector, and a hole is provided in the outer conductor of the connector directly connected to this. A hole with a feed line characteristic impedance is connected in series in a concentric cylindrical shape with the hole, and the center conductor is inserted along the center axis with a dielectric interposed so that the helical element is supported, and a reflector is inserted outside the plug. A helical antenna device characterized in that it is configured by being attached to a conductor. (2) Claim 1, characterized in that the outer conductor having a concentric cylindrical hole into which the central conductor, which is an extension of the helical element, is inserted is integrally formed with the plug. The helical antenna device described in .