JPH06164232A - Antenna device - Google Patents

Abstract

PURPOSE:To obtain a conical beam in a desired direction by a small number of phase shifters and to improve the gains in a wide range of angles of elevation by providing a selecting circuit which selects the feeding terminals of plural helical antenna elements and a distributing means which distributes the electric power to the selected feeding terminals. CONSTITUTION:At least one of helical antenna elements 11, 12...1n which are arrayed in the lengthwise direction has the radiation directivity different from those of other elements. An element selecting circuit 3 selects one or more feeding terminals of the elements 11..., and an electric power distributor 5 distributes the electric power to the selected feeding terminals. Furthermore, the phase shifters 4 are individually set at the distributing side of the distributor 5. Then the circuit 3 selects optional (m) pieces of helical antenna elements out of (n) pieces of them (m<n). Then the distributor 5 are connected to the phase shifters 4 which can set the prescribed phase differences among those (m) pieces of terminals and then can set the prescribed phases to the selected helical antenna elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is suitable for use as a mobile station antenna for mobile satellite communications. The present invention relates to an antenna device that can satisfy a wide range of elevation angles and can obtain high gain with a simple configuration.

[0002]

2. Description of the Related Art Recently, focusing on the wide area of satellite communication,
Mobile communication using satellites called "mobile satellite communication system" is drawing attention. However, at present, the size of the antenna on the satellite side and the transmission power are limited, so it is necessary to increase the antenna gain on the mobile station side. Therefore, it is indispensable to use a mobile station antenna having directivity with respect to an omnidirectional antenna which has been used in mobile communication. For this reason, there is a demand for a simple antenna that can cover the required satellite elevation range and can realize high gain.

Conventionally, there is a cone beam antenna as an example of a mobile station antenna in which a beam is formed in an appropriate shape. The cone-beam antenna is an antenna that is omnidirectional in the circumferential direction and has directivity in the elevation direction as shown in FIG. The cone-beam antenna is a simple antenna that is suitable as a mobile station antenna because it can achieve high gain with respect to an omnidirectional antenna and does not require antenna tracking in the main direction.

As such a cone beam antenna,
“Shaped -conical radiation pat-tern performance o
f the backfire quadrifilar helix "(IEEE Trans.on
An-tennas & Prop.vol.23,5 1975) has a 4-wire helical antenna shown in FIG. 14 described by Kilgus. By appropriately selecting the pitch and the diameter, which are the shape parameters of the helical, the 4-wire helical antenna can realize directivity in an arbitrary elevation angle direction. However, in order to increase the antenna gain, it is necessary to increase the number of turns of the spiral, and the current travels on the spiral conductor of the helical antenna while radiating radio waves, so the current distribution on the antenna decreases exponentially. Therefore, even if the number of turns is increased, the current does not flow to the tip of the antenna, and the effect of increasing the gain by increasing the number of turns of the helix is limited.

Further, if the gain is increased, the beam width becomes narrower, and it is necessary to move the main radiation direction in the elevation direction in order to cover the required elevation range.
However, the main radiation direction in the helical antenna is determined by the shape of the spiral, and the beam direction cannot be oriented in any direction at the elevation angle.

As another antenna type for realizing a cone beam, "A conical beam ship array antenna w of Foster et al.
ith infinitely variable control of the elevation a
ngle "(1974 IEEE Antennas & Prop.Symposium, P.368)
There is a crossed dipole array antenna shown in FIG. This antenna has a plurality of crossed dipoles arranged as antenna elements on a straight line as shown in FIG. In order to realize a cone beam, a crossed dipole antenna which is an individual element can be given a proper phase by a phase shifter to form a cone beam in an arbitrary direction. However, a large number of phase shifters are required to give a phase to all antenna elements. Therefore, the antenna device becomes complicated and expensive, and since the directivity of the element has the axial directivity, the gain is high in the high elevation angle direction of the axis, and the gain is greatly deteriorated in the low elevation angle direction.

[0007]

In the four-wire helical antenna shown in FIG. 14 capable of realizing such a conventional cone beam, by selecting an appropriate helical shape parameter, directivity in an arbitrary elevation angle direction can be obtained. However, the main emission direction of the beam cannot be made variable because the main emission direction depends on the shape of the spiral. Further, in order to increase the antenna gain, it is necessary to increase the number of turns of the helical, but even if the number of turns is increased, there is a limit in increasing the gain of the antenna.

[0008] Further, there is an array antenna using cross dipole elements of the same shape shown in FIG. 15, but this antenna is designed to give an appropriate phase to each antenna element by a phase shifter, so that the antenna can be used mainly at an arbitrary angle. A cone beam with a radial direction can be created. However, there are disadvantages that a large number of phase shifters are required to give a phase to all the antenna elements, the antenna feeding system is complicated, and the apparatus becomes expensive.

The present invention solves such a problem, and provides an antenna device capable of realizing a cone beam in a desired direction by using a small number of phase shifters and increasing the gain over a wide elevation angle range. With the goal.

[0010]

According to the present invention, a plurality of helical antenna elements are arranged in a longitudinal direction, and at least one of the plurality of elements has a radiation directivity different from that of other elements, and the plurality of helical antenna elements are arranged. A selection circuit for selecting at least one of the power supply terminals and distribution means for distributing and connecting the power to the power supply terminals selected by the selection circuit.

The distribution means may include a power distributor and a phase shifter individually inserted on the distribution side thereof, and may be an in-phase power distributor, or may have a phase difference set individually. A power distributor for distributing power may be included.

[0012]

[Function] The required number is selected from the helical antenna elements having the radiation directivity in which the element selection circuits are arranged in a straight line and the radiation characteristics in the respective elevation angles differ from each other by at least one, and the selected helical antenna elements are selected. The phase is set individually for excitation.

As a result, a desired cone beam can be formed with a small number of phase shifters without lowering the gain in a wide elevation angle range.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing a basic configuration of an embodiment of the present invention.

In the embodiment of the present invention, the helical antenna element 1 is used.
1n are arranged in the longitudinal direction, and at least one of the helical antenna elements 11, 12, ..., 1n has a radiation directivity different from other elements, and a plurality of helical antenna elements 11, 12 ,. An element selection circuit 3 that selects one or more of the 1n power supply terminals, and a power distributor 5 that distributes and connects power to the power supply terminals selected by the element selection circuit 3.
The phase shifter 4 individually inserted on the distribution side of the power distributor 5.
With.

As described above, the embodiment of the present invention is basically
1n, n helical antenna elements are arranged in the axial direction, and the respective feeding cables are connected to the element selection circuit 3. The element selection circuit 3 selects any m (m <n) helical antenna elements from the n helical antenna elements. The power divider 5 is connected to the phase shifter 4 capable of setting a predetermined phase difference at m terminals, and is configured so that a predetermined phase can be set for the selected helical antenna element.

Next, a first embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a diagram showing the configuration of the first embodiment of the present invention. In this example, in order to simplify the description, the configuration is such that four antenna elements 11, 12, 13, and 14 are used, and two antenna elements are selected from the four antenna elements by the element selection circuit 3. The operation will be described. Figure 2
In the antenna device shown in FIG. 4, four antenna elements 11, 12, 13, 14 have cone beams 61, 62, 63, 64 having different main radiation directions as shown in FIG. By appropriately selecting the pitch P and the diameter D in such a helical antenna element, as shown in FIG. 4, a symmetric directivity in which the main radiation direction of the helical antenna arbitrarily changes from the antenna axial direction to the orthogonal direction is realized. can do.

In the element selection circuit 3, the conical beams formed by the two antennas Ant # 1 and Ant # 2 out of the four, for example, 62 and 63 shown in FIG. 3 are selected, and the phase shifter 4 has two. The phase difference between the antennas Ant # 1 and Ant # 2 is -π /
When given as 2, 0, and π / 2, the combined directivity is shown in FIG.
The one shown in is realized. As can be seen from the figure, the combined beam has a higher gain than a single conical beam created by the two antennas Ant # 1 and Ant # 2. Further, by appropriately setting the excitation phase difference between the antennas, the combined beam can be freely realized on the line of the realized gain shown in FIG. Therefore, a beam having a high gain can be obtained, and its main radiation direction can be arbitrarily set.

Therefore, in the configuration shown in FIG. 2, for example, as shown in Table 1, by selecting two antennas that are adjacent cone beams out of four antennas and giving a phase difference, As shown in FIG. 6, a high gain cone beam 9 (91 to 9) having different main radiation directions from a low elevation angle to a high elevation angle.
9) can be formed. Further, as compared with the conventional crossed dipole array antenna, the phase shifter 4 used in the present invention does not need to be attached to each antenna element, so that the number thereof can be reduced. In the above description, an example of selecting two antennas is described. However, even when the number of antennas selected by the element selection circuit 3 is three or more, a phase difference is similarly given to each antenna to obtain a high gain cone beam. Can be changed. It is not always necessary to select elements having adjacent beams as the elements to be selected, and the number of elements to be selected does not always have to be the same, and the number of elements to be selected may be changed according to the set elevation angle. . In the antenna configuration of the present invention, antennas having the same directivity may be selected as long as they are located at different positions.

Next, the fact that the present invention can downsize the antenna will be described. In a normal helical antenna, it is necessary to increase the number of turns in order to make the main radiation direction constant and increase the gain as shown in FIG. However, since the current on the antenna travels on the spiral conductor of the helical antenna while radiating radio waves, the current distribution on the antenna decreases exponentially. Therefore, even if the number of turns is increased, the current does not flow to the tip of the antenna, and there is a limit to the effect of increasing the gain by increasing the number of turns of the helix. FIG. 8 shows an example of directivity in the case where a cone beam having the same gain is realized in the present invention and the conventional four-wire winding helical antenna. In order to realize the directivity shown in FIG. 8, the present invention can be realized by using three antennas each having three turns, whereas the conventional helical antenna requires 15 turns. As is clear from the figure,
According to the present invention, an equivalent gain can be realized with a small number of turns, and a high gain can be obtained with a compact structure.

Next, a second embodiment of the present invention shown in FIG. 9 will be described. In the second embodiment, four helical antenna elements 11, 12 having different directivities are used as antenna elements.
13 and 14 are used, and three elements are selected from the four-element antenna and combined. The respective antenna elements have different directivities as shown in FIG. 10A, and in particular, the elements include antenna elements having directivity 64 close to non-directivity. At this time, the beam 64 close to omnidirectionality is always selected as an element to be selected, and two elements out of the three antenna elements are selected and phase combination is performed, so that the actual gain shown in FIG. Directivity can be realized.

FIG. 10 (c) shows the realized gain when a four-element helical antenna of a cone beam having different main radiation directions is used to achieve the same realized gain. Compared with the case shown in FIG. 10, in order to realize an equivalent gain, it is necessary to use a high gain as a single element in the configuration of FIG. On the other hand, one omnidirectional element is used in FIG.
In the configuration shown in (b), since there is an omnidirectional element having directivity over a wide elevation angle range, the gain can be increased over a wide elevation angle range even if an antenna with a low single gain is used. That is, in this embodiment,
The helical antenna elements 12 to 14 have a configuration in which a helical antenna having a small number of turns is sufficient, and the antenna length can be shortened as a whole.

Next, a third embodiment of the present invention shown in FIG. 11 will be described. This embodiment uses four helical antenna elements 11, 12, 13, and 14 having different numbers of turns as an antenna similarly to the configuration shown in FIG. 9, and each element has directivity in different radiation directions as shown in FIG. 61, 62,
It has 63 and 64. In this embodiment, one or two of the four antennas are selected and are in-phase excited. At this time, the directivities when one element is selected are directivities 61 and 6 as shown in FIG.
It becomes 2, 63, 64, but when two elements are selected,
By selecting an antenna with 61 and 62 beams, it is possible to realize a conical beam 91 with an elevation angle in between, so as shown in Table 2, a single 61 beam, 6
By selecting two beams 1 and 62, a single 62 beam, and the like, scanning can be performed in the elevation direction. At this time, since it is possible to realize an intermediate beam with respect to the minimum gain when the single antenna is switched, it is possible to achieve a high gain. Furthermore, only two beams are selected and in-phase excitation is performed. The phase shifter is not required because it is not necessary to change the phase of the selected antenna.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

As described above, according to the present invention, it is possible to realize a conical beam that satisfies a wide range of elevation angles without lowering the gain, and further, it is possible to reduce the number of movements compared with the conventional array antenna type. There is an effect that a high gain antenna having a small antenna size can be configured by the number of phase shifters.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 3 is a diagram showing the radiation directivity of the antenna element in the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a change in directivity of a helical antenna when a shape parameter is changed.

FIG. 5 is a diagram showing an example of beam scanning characteristics when two elements are selected in the embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between a beam to be selected and a beam to be realized.

FIG. 7 is a diagram for explaining the relationship between the number of turns and the gain in the helical antenna.

FIG. 8 is a diagram showing a comparison of radiation characteristics when the same gain is realized in the first embodiment of the present invention and the conventional example.

FIG. 9 is a diagram showing the configuration of a second embodiment of the present invention.

10A is a diagram showing the configuration of an antenna element beam in the second embodiment of the present invention, FIG. 10B is a diagram showing the realized gain in the second embodiment of the present invention, and FIG. 10C is a second embodiment of the present invention. The figure which shows the comparison of the realization gain in an example.

FIG. 11 is a diagram showing the configuration of a third embodiment of the present invention.

FIG. 12 is a view showing a beam selected to realize a required beam in the third embodiment of the present invention.

FIG. 13 is a diagram illustrating a cone beam.

FIG. 14 is a diagram showing a configuration of a conventional example.

FIG. 15 is a diagram showing another configuration example in the conventional example.

[Explanation of symbols]

 1, 11 12, 12, ... 1n Helical antenna element 2 Feeding circuit 3 Element selection circuit 4 Phase shifter 5 Power divider 6, 61, 62, ..., 6n Directivity 7 Satellite 8 Cross dipole 9, 91, 92 ,. , 9n cone beam

Claims (4)

[Claims] 1. A plurality of helical antenna elements are arranged in a longitudinal direction, at least one of the plurality of elements has a radiation directivity different from other elements, and one or more of the feeding ends of the plurality of helical antenna elements are arranged. An antenna device comprising: a selection circuit for selection; and a distribution means for distributing and connecting electric power to a power feeding end selected by the selection circuit. 2. The antenna device according to claim 1, wherein the distribution unit includes a power distributor and a phase shifter individually inserted on a distribution side thereof. 3. The antenna device according to claim 1, wherein the distribution unit is an in-phase power distributor. 4. The antenna device according to claim 1, wherein the distribution unit includes a power distributor that individually sets a phase difference and distributes power.