JPH01200801A - Helical antenna - Google Patents

Abstract

PURPOSE:To execute a miniaturization and to increase a profitability by arranging a conductor to be connected to a helical conductor and to form a coaxial line with a reflecting plate and a conductor bar to support one edge to be extended in the waveguide of the conductor and, simultaneously, to be penetrating-inserted along the E surface of the waveguide. CONSTITUTION:A helical conductor 15 connected to a coaxial central conductor 16 is operated as an axial mode helical antenna along with a reflecting plate 14. A receiving signal to be received by the helical antenna is propagated from the conductor 15 into a coaxial part composed of the reflecting plate 14, an insulator 19 and the central conductor 16 in a coaxial mode, and the signal is conducted to an L-shaped magnetic field coupling loop composed of a conductor 18 and a machine screw 20. A current induced to the magnetic field coupling loop by the receiving signal is made to flow through the magnetic field coupling loop to the waveguide. As a result, in the waveguide, an induction field H (circle mark) is generated so as to link the magnetic field coupling loop. According to it, a main component E (circle mark) of an electric field is induced. As a result, a signal, in which a waveguide 13 is excited in a waveguide propagating mode corresponding to an electromagnetic component, is propagated inside the waveguide 13.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a helical antenna used as a primary radiator, such as in a satellite antenna system.

2. Description of the Related Art With the development of satellite communication technology in recent years, direct satellite broadcast receiving antenna systems have been attracting attention. This type of antenna is mainly a parabolic antenna.

A flat antenna is used. A waveguide horn is used as the primary radiator of a parabolic antenna. Helical antennas and the like have been put into practical use. Under these circumstances, in order to popularize satellite broadcasting receiving antennas as consumer equipment, etc., it is necessary to make the antennas smaller and lower in price. In response to such demands, antenna systems using a helical antenna as a primary radiator have been put into practical use, and the output of this helical antenna is generally a coaxial output. By the way, since the input of the converter attached to the output of the -order radiator generally has a waveguide input, a coaxial waveguide converter is required on the output side of the helical antenna as a system. A conventional example using a helical antenna as a primary radiator is shown in FIG.

In FIG. 8, a part is shown in a cross-sectional view. In the figure, (1) is a waveguide on the antenna side, (2) is a reflector, and (3) is a helical conductor whose principal axis is perpendicular to the reflector (2). 3) The coaxial center conductor (4) coupled to one end passes through the reflector (2) and is surrounded by an insulator (5) that forms the coaxial line. (6)
(7) is an antenna probe for a coaxial waveguide converter on the antenna side attached to the other end side of the coaxial center conductor (4);
) is a coaxial outer conductor that covers the outer periphery of the insulator (5) and is coupled to the reflection plate (2). The second waveguide (8) coupled to the waveguide (1) has the antenna probe (
6) Coaxial waveguide converter antenna probe (
9) is arranged, and the antenna probe (
6) is equipped with an insulating support (1) to prevent short circuits.
0) is inserted. (11) is a converter on the second waveguide (8) side, and (12) is a helical conductor (
3) is a radome that surrounds and protects the reflective plate (2) provided with the reflective plate (2).

The helical conductor (3) 9 reflectors (2) constitute an axial mode helical antenna, and the signal received by the helical conductor (3) is transmitted to the outer conductor (7), insulator (5), and center conductor (4). The constructed coaxial line leads to the antenna probe (6). The above antenna probe (6) is a waveguide (1)
The signal guided by the coaxial line is effectively converted into the waveguide propagation mode by the antenna probe (6), and the signal propagation mode is inserted along the electric field direction of the waveguide (1) and It propagates within the second waveguide (8).

Moreover, since the antenna probe (9) is inserted along the electric field direction of the signal propagation mode of the second waveguide (8), the signal propagating inside the second waveguide (8) is transmitted to the antenna probe (8). 9), the signal is converted back to coaxial mode and guided to the microwave circuit inside the converter.

In the configuration of the primary radiator as in the conventional example, since the antenna probe (6) must be inserted along the direction of the electric field, a coaxial line section and a This method requires a waveguide, which results in a complicated structure, large shape and size, and has the drawback of increasing microwave loss.

To overcome these drawbacks, if it were possible to optimally convert the helical antenna output from a coaxial line to a waveguide output using a simple and compact structure, it would be possible to downsize the satellite broadcast receiving antenna system and improve its economic efficiency. can be increased. The present invention has been made in view of the above points.

In the present invention, a waveguide section is formed on the back side of a reflecting plate of a helical antenna, the reflecting plate is used as a coaxial outer conductor, and a coaxial center conductor is electrically connected to an insulator and a helical conductor. form a coaxial part, and connect one end of the conductor that is electrically connected to the coaxial center conductor and inserted into the waveguide from the H plane (magnetic field parallel plane) to the E plane (electric field parallel plane) of the waveguide wall. ) is connected and fixed by methods such as soldering, welding, and screws to form a magnetic field coupling loop.The conductor and conductor rod inserted into the waveguide are guided into the waveguide. The position, length, and other arrangement relationships are adjusted so that the generated electromagnetic field propagates through the waveguide in the waveguide propagation mode most efficiently.

A resonant frequency adjustment conductor can be provided on the waveguide wall by being inserted into the wall, and it is preferable to insert an elastic body such as an O-ring between the resonant frequency adjustment conductor and the waveguide wall. .

In the above configuration, the signal received by the helical antenna is transmitted to the conductor and conductor rod electrically connected to one end of the helical conductor via the coaxial center conductor inserted inside the waveguide. enters the magnetic field coupling loop created by and. Current induced by the received signal flows into the waveguide through the magnetic coupling loop.

As a result, an induced electromagnetic field is generated inside the waveguide that links the current flowing through the magnetic field coupling loop.

The generated induced electromagnetic field is in waveguide propagation mode,
Therefore, it is possible to propagate within the waveguide.

Furthermore, by varying the position of the tuning conductor inserted into the waveguide wall, the frequency can be adjusted for the best conversion.

Also, L spots This will be specifically explained below by giving examples.

FIG. 1 is a diagram showing an embodiment of the present invention, showing the antenna side coupled to the converter. In the figure, (13) is a waveguide with an open end, and a plate-shaped reflecting plate (
14) are directly connected.

(15) is a helical conductor for receiving signals, and the other end of this helical conductor (15) is a hole (17) formed in the reflecting plate (14) as a coaxial center conductor (16) forming the center conductor of the coaxial portion. ), and further extends inside the waveguide (13) as a conductor (18) so as to coincide with the main radiation direction of the helical conductor (15). Here, the conductor (18) and the coaxial center conductor (16) can be configured as separate bodies and connected, but it is also possible to have an integral structure with the helical conductor (15) using, for example, piano wire. can.

For the reflection t&(14), the coaxial center conductor (16) has a hole (
17) is supported by an insulator (19) filled in the insulator (17).

A conductor rod (20) is inserted into the H side of the waveguide (13) wall with its tip facing into the waveguide (parallel to the 8th plane), and the tip of the conductor rod (20) protruding into the waveguide is inserted. The other end of the conductor (18) is electrically and mechanically connected by soldering, welding, screwing, or the like. In this embodiment, the conductor rod is made of a screw (20), and the position is fixed by the screw (20) itself between the screw groove on the waveguide wall side without using any other fixing means. Electrically contacts the H surface of the waveguide wall. In the above structure, the helical conductor (15) connected to the coaxial center conductor (16) operates as an axial mode helical antenna together with the reflector (14).

The received signal received by the helical antenna is transmitted from the helical conductor (15) to the reflector (14), ! ! ! Rim body (19
) and a coaxial center conductor (16) in a coaxial mode, and is guided to an L-shaped magnetic field coupling loop composed of a conductor (18) and a screw (20). A current induced in the magnetic coupling loop by the received signal flows into the waveguide through the magnetic coupling loop. The resulting waveguide (13)
Inside, an induced magnetic field is generated to link the magnetic field coupling loops as shown in Figure 2 (■).

Accordingly, the main components of the electric field are induced as shown in FIG. 2 [F]. As a result, the waveguide (13) is excited in a waveguide propagation mode corresponding to the electromagnetic field component as shown in FIG. 2, and the signal propagates inside the waveguide (13).

The distance from the screw (20) inserted from the H-plane of the waveguide (13) wall to the reflection plate (14) and the distance from the H-plane of the waveguide (13) wall to the tip of the screw (20) are as described above. Determine the most efficient conversion of the electromagnetic field excitation.

According to the experimental results, the waveguide WRJ-120 has a bis(
20) (outside diameter 2.0mm) from the central axis of the reflector plate (14
), the frequency is 9.2 Gll when the distance to
The best transformation occurs near z.

FIG. 3 shows a second embodiment of the present invention, in which a coaxial center conductor (1
6), and is formed integrally with or separately from the waveguide (13).
The conductor (18a) inserted inside is the coaxial center conductor (16
) is bent in the direction of extension of the central axis of the
It is soldered to the tip of 20). Here the conductor (L8
By adjusting the bending angle in a), the input impedance seen from the waveguide opening can be adjusted, and the frequency at which the excitation of the electromagnetic field is most efficiently converted can be adjusted. For example, when the distance from the center of the coaxial center conductor (16) to the H-plane of the waveguide (13) wall is 7111 m, and the height of the screw (20) inserted inside the waveguide is 5.2 mm, the frequency At 11.50+Iz to 12°5 GHz, the human power return loss seen from the waveguide opening is 20 dB or more.

In each of the above embodiments, the conductor (18) is fixed and supported within the waveguide (13) using a screw (20) that has a fixing function as a conductor rod. Embodiment 3 shows a structure in which the conductor rod is further fixed using a fixture. FIG. A conductor (18) is fixed to the tip of the metal rod (21) inside the waveguide in the same way as in the previous embodiment, and the other end is electrically connected to the wall of the waveguide (13). It makes contact and penetrates the wall. In order to fix the metal rod (21) to the waveguide (13), a screw hole is provided at the other open end side of the waveguide (13), which is different from the open end connected to the reflecting plate (14). A screw (22) is inserted into the screw hole, and the metal rod (21) is fixed to the waveguide (13) with the tip of the screw. The position of the screw hole into which the screw (22) is inserted is not limited to the opening surface of the waveguide, but may be provided on the side surface of the waveguide and the screw may be inserted (inserted perpendicularly to the plane of the paper in the figure).

In this embodiment as well, the metal rod (21) is connected to the reflector plate (14).
) and the distance from the H-plane of the waveguide (13) wall to the metal rod (
The distance to the tip of 21) is determined so that the excitation of the electromagnetic field is converted most efficiently. According to the experimental results,
For the waveguide RJ-120, a metal rod with an outer diameter of 1.3 mm (
21), when the distance from the central axis to the reflector was set to 5.7 hazy, the best conversion was performed at a frequency around 10.8 GHz.

FIG. 5 shows a fourth embodiment of the present invention, in which a metal rod (21) is fixed to the waveguide wall with screws (22).
The conductor (18b) having one end fixed to the coaxial center conductor (16) is bent with respect to the extending direction of the central axis of the coaxial center conductor (16), as in the second embodiment. By adjusting this bending angle, the input impedance seen from the waveguide opening is adjusted, and the frequency at which the electromagnetic field excitation is most efficiently converted is adjusted. For example, when the distance between the center of the coaxial center conductor (16) and the H plane of the waveguide (13) wall is 7 m+a, the height of the metal rod (21) inserted inside the waveguide is 5.9 m.
When m, the best conversion was performed around a frequency of 12.0 GHz.

Next, a structure in which the resonant frequency can be adjusted independently of the conductor and the conductor bar made of a screw, metal rod, etc. that fixes the conductor will be explained.

That is, in each of the above embodiments, an adjustment screw is provided that penetrates the earthen wall of the waveguide (13) and whose tip faces the inside of the waveguide (13), and the insertion length of this adjustment screw into the pipe is adjusted. This adjusts the frequency at which the electromagnetic field excitation is most efficiently converted. In the case of this embodiment, since the insertion length of the adjusting screw is variable, a problem may arise in that the connection between the adjusting screw and the waveguide cannot be airtight.

Therefore, we developed a helical antenna structure that can adjust the resonant frequency while maintaining airtightness inside the waveguide.
This will be explained using figures. The same parts as in each of the above embodiments are designated by the same reference numerals. In Figure 6, the waveguide (13)
The conductor (18) extending inward is fixed to the tip of a screw (20) inserted from the H-plane of the waveguide wall. Screw (20
) has a fixed length in this embodiment, so it is inserted into the waveguide wall and fixed with an adhesive or the like in a fixed position to maintain airtightness within the waveguide. The screw (2) whose position is fixed
0), a resonant frequency adjustment screw (23) penetrating the wall is inserted into the upper part of the waveguide (13). A rubber-like elastic body (24) such as an O-ring is inserted between the adjusting screw (23) and the waveguide wall, and when the adjusting screw (23) is screwed in, the elastic body ( 24), the hole for screw insertion in the waveguide wall is sealed, and the airtightness inside the waveguide is maintained, and at the same time, the adjustment screw (23) is also securely fixed in position by the waveguide wall. Ru. In the figure (25) is a radome that protects the helical conductor (15).

In this embodiment as well, the received signal is propagated in the same way as in each of the embodiments described above. Here, the frequency at which the excitation of the electromagnetic field is most efficiently converted varies depending on the length of the adjusting screw (23) that protrudes into the waveguide, and FIG.
3) is a graph of input return loss characteristics as seen from the waveguide opening surface due to differences in the length inserted inside the waveguide.

When the length of the adjusting screw (23) inserted into the waveguide is 1 m (broken line in the figure), when the length is 0 mm (solid line in the figure)
Frequency band 11.7-12 used in satellite broadcasting compared to
．． Input return loss at OGMz shows good characteristics,
It can be seen that the frequency at which the excitation of the electromagnetic field is most efficiently converted can be adjusted by adjusting the insertion length of the adjusting screw (23).

The range in which the length of the adjusting screw (23) inserted into the waveguide can be changed is approximately 1!1111, and the deformation required of the rubber-like elastic body (24) is also within this range. This is within the elastic limit, and within this range, the rubber-like elastic body can effectively maintain internal airtightness as an O-ring that causes plastic deformation.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, according to the present invention, the structure can be extremely simple and compact, and the received signal of the helical antenna can be efficiently guided to the waveguide.

Furthermore, since the conductor connected to the helical conductor is fixed to a conductor rod that passes through the waveguide wall, the structure is simple, easy to assemble, and suitable for mass production.

Further, the angle of the conductor in the waveguide with respect to the main radiation direction of the helical conductor can be adjusted, and the frequency characteristics in signal propagation can be easily adjusted, allowing efficient propagation.

Furthermore, adjustment screws are provided on the waveguide wall to adjust the frequency characteristics of signal propagation, and since the adjustment screws are attached to the waveguide wall with an elastic body inserted, it is possible to obtain the optimum signal propagation. It is possible to obtain a primary radiator for a parabolic antenna that is not only easy to perform adjustment operations, but also has excellent environmental resistance without impairing the airtightness within the waveguide even when the characteristics are adjusted.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view of a helical antenna in which the present invention is implemented, and FIG. 3 are side sectional views showing other embodiments of the present invention, FIGS. 4, 5 and 6 are side sectional views showing still other embodiments of the present invention,
FIG. 7 is a characteristic diagram showing the relationship between frequency and input return loss in the embodiment shown in FIG. 6. FIG. 8 is a partial sectional view showing a conventional example. (13) - a waveguide, (14) - a reflection plate. (15) - Helical conductor, (16) - Coaxial center conductor. (18), (18a) - conductor, (20)
-・Bis (conductor rod). (21)--metal rod (conductor rod), (22)--screw. (23)-Adjustment screw, (24)-Elastic body.

Claims (3)

[Claims] (1) In a helical antenna equipped with a helical conductor having a central axis in a plane perpendicular to one surface of the reflector and a waveguide coupled to the other surface of the reflector, the waveguide is connected to the helical conductor. a conductor forming a coaxial line with the reflector;
A helical antenna comprising: a conductor rod that supports one end of the conductor extending into the waveguide and is inserted along the E plane of the waveguide. (2) The helical antenna according to claim 1, wherein the conductor is supported by a conductor bar at a position inclined from the central axis extension of the helical conductor. (3) In a helical antenna equipped with a helical conductor having a central axis in a plane perpendicular to one surface of the reflector and a waveguide coupled to the other surface of the reflector, the waveguide is connected to the helical conductor. a conductor forming a coaxial line with the reflector;
A conductor rod that supports one end of the conductor extending into the waveguide and is inserted along the E plane of the waveguide, and a tip that is inserted through the wall of the waveguide with an elastic body interposed therebetween and faces the inside of the waveguide. A helical antenna characterized by comprising a resonant frequency adjuster whose length is freely adjustable.