JPH0120802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna that has a simple and thin structure and emits a conical beam.

FIG. 1 is a diagram showing the use of a conical beam antenna.

1 is a ship, 2 is an antenna, 3 is a line connecting points of equal electric field strength of the conical beam of the antenna, 4 is a geostationary satellite, 5 is a vertical axis, and 6 is a line indicating the main beam direction.

When communicating between a ship and a satellite, in order to enable communication without being tracked regardless of the movement or direction of the ship, the antenna beam pattern must be such that its main beam is as shown in Figure 1. It is sufficient that the shape is close to a conical shape, with the generating line being a line in the direction from the antenna toward the satellite with respect to the vertical axis 5. This is called a conical beam.

Conventionally, a cross dipole array antenna as shown in FIG. 2 has been used as a circularly polarized antenna having a conical beam.

3 is a line connecting points of equal electric field strength of the conical beam of the antenna, 5 is a vertical axis, 6 is a line indicating the main beam direction, 7 is a cross dipole, and 8 is a feed line. However, since the structure is three-dimensional, the height of the antenna is large, and the length of the coaxial line for power feeding is different, the power feeding becomes complicated.

In order to eliminate these drawbacks, the present invention uses a microstrip antenna to construct a circular array antenna with a conical beam, thereby creating a planar antenna and using a microstrip line. It has improved compatibility with the previous power supply circuit, and the drawings will be explained in detail below.

FIG. 3 shows an embodiment of the present invention, in which one of six elements
The case using a point-fed circularly polarized microstrip is shown.

9 is a metal plate constituting a radiating element, 10 is a dielectric, 11 is a metal substrate, 12 is a center ground pin,
13 is a power supply pin, 14 is a microstrip power supply line, and 15 is a coaxial line. In the case of a radiating element like the one in this embodiment, it is not necessarily necessary to ground the center point, but even in that case, it effectively operates as a grounding point.

The 14 microstrip feed lines are divided in each direction from the center of the circular arrangement of the radiating element metal plates 9 to form a power distribution circuit. A microstrip line is usually used in the power distribution circuit because of its good matching with the radiating element. In order to simplify this power divider, in this embodiment, the center earth pin 12, the power supply pin 13, and the power supply microstrip line have exactly the same relative positional relationship with respect to the direction of the power supply microstrip line. are arranged at angular intervals of 60 degrees along the With this arrangement, the excitation to each radiating element can be of the same amplitude and phase, so the power distribution to each radiating element consists of microstrip lines of equal length extending in six directions from the center of the circular array. It is excellent in that it is easy to design and is easy to design.

With the arrangement of the radiating elements as described above, the coaxial line 15
When power is supplied from the two radiating elements facing each other, the directions of the vectors on the vertical axis passing through the center of the circular arrangement of the electromagnetic fields are exactly opposite to each other, so the electromagnetic field there is They cancel and a conical beam is obtained.

This means that elements facing each other across the vertical axis are arranged in opposite directions in space, and therefore the electromagnetic field vectors on the vertical axis are in opposite directions. If two radiating elements arranged in the same direction are excited with opposite phases to each other, the electromagnetic field vector at a point equidistant from both elements is
This is the same as going in the opposite direction and canceling out.

In FIG. 3, an example is shown in which a microstrip element (metal plate 9 is elliptical) that can obtain a circularly polarized beam with single-point feeding, but as metal plate 9,
When using circular, square, etc., in order to obtain circularly polarized waves, the vector directions must differ by 90°,
Since it is necessary to combine two electromagnetic fields whose excitation phases are shifted by 90°, two-point power feeding is required.

To explain based on the example in Fig. 3, look from the center ground pin 12 to the power supply pin 13, and from there
By setting another feed point at a position rotated by 90 degrees, a 90 degree difference in the electromagnetic field vector can be obtained, and then a 90 degree angle in the middle of the circuit that feeds power from the first feed point to the second feed point is obtained. If a phase difference circuit is provided, excitation with a 90° difference in excitation phase can be achieved, resulting in a circularly polarized beam similar to that obtained with single-point feeding.

In addition, as a metal plate constituting the radiating element, a fourth
If you use a double structure as shown in the figure, the metal plate 9
Since the resonant frequency of the metal plate 9' and the resonant frequency of the metal plate 9' can be selected to be different frequencies, by selecting two relatively close frequencies, the frequency band can be made wider than in the case of only a single frequency. In addition, by selecting two frequencies that are separated by a certain degree, it is possible to achieve dual frequency sharing in which either frequency can be used, and it is possible to satisfy the conditions regarding the actual usage band in satellite communication.

Figure 3 shows the case where power is supplied from the back side of the metal plate, but there are other methods such as directly feeding power from the same side as the metal plate using a microstrip line, or using a microstrip line on the same side as the metal plate. The same effect can be obtained by using a power feeding method such as providing a strip line and capacitively coupling it.

Note that the beam direction and gain of the conical beam are determined by the radius of the circle of the circular array, and the uniformity of the conical beam in the circumferential direction is determined by the number of elements in the circular array.

FIG. 5 shows actual measurement results of radiation characteristics obtained by making a prototype of the embodiment shown in FIG. The radiating element is
It is a 6-element elliptical microstrip antenna, the frequency is 2.64GHz, and the radius of the circular array is
0.4λ ₀ (λ ₀ : free space wavelength). In the figure it is clear that a conical beam is obtained.

FIG. 6 is an embodiment according to claim 2 of the present invention, in which a 12-element single-point feeding circularly polarized microstrip is used. 9 is a metal plate, 10 is a dielectric, 11 is a metal substrate, 12 is a center ground pin, 13 is a power supply pin, 14 is a microstrip power supply line, and 15 is a coaxial line.

In this antenna, as in the embodiment shown in Fig. 3, a pair of metal plates and a microstrip feed line, which face each other and are fed power, have the same relative positional relationship with respect to the center of the circular array. They are arranged at angular intervals of 60 degrees.

As a result, the power divider only needs to supply power with the same amplitude and phase, and the design is easy as in the case of FIG. 3. Further, the positional relationship between the metal plates that face each other and are supplied with power is such that they are symmetrical with respect to the midpoint between them.

As a whole, similar to the example shown in FIG. 3, the radiated electric field in the broadside direction is canceled out and a conical beam is obtained.

Although the feeding circuit of this antenna is somewhat more complicated than the example shown in FIG. 3, it has the advantage of having a higher degree of freedom in pattern formation because of the larger number of elements.

The above description has been made regarding the case of using circularly polarized waves, but if a shape that emits linearly polarized waves is used as the radiating element (for example, the metal plate 9 in FIG. 3 may be circular), the above explanation will be possible. With this configuration, a linearly polarized conical beam can be obtained.

As explained above, by using a microstrip antenna to construct a circular array in which opposing elements have opposite phases, it is possible to achieve good compatibility with a power supply circuit using a microstrip line. There is an advantage that a planar conical beam antenna can be constructed.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the application of a conical beam antenna.
FIG. 2 shows an example of the configuration of a conventional circularly polarized antenna having a conical beam, FIG. 3 shows an embodiment of the present invention, and FIG.
The figures show another example of the element used in the present invention, where figure a is a plan view thereof, and figure b shows a cross section taken along line A-A' in figure a.
FIG. 5 shows actually measured characteristics of a prototype example, and FIG. 6 shows another embodiment of the present invention. 1...Ship, 2...Antenna, 3...Line connecting points of equal electric field strength of the antenna's conical beam,
4...Geostationary satellite, 5...Vertical axis, 6...Line indicating the main beam direction, 7...Cross dipole, 8...
Feed line, 9, 9'...metal plate constituting the radiating element,
10, 10'...Dielectric material, 11...Metal substrate, 1
2... Center ground pin, 13... Power supply pin, 1
4...Microstrip feed line, 15...Coaxial line.

Claims (1)

[Claims] 1. A circularly arrayed microstructure comprising a dielectric plate, a metal substrate disposed on one side of the dielectric plate, and a plurality of metal plates arranged in a circular shape on the other side of the dielectric plate. In a lip array antenna, among the radiating elements composed of metal plates arranged in a circular shape, a center point and a feed point are set for each radiating element facing each other on a straight line passing through the center of the circular array. A conical beam array antenna characterized in that a feed distribution line of equal length is provided at a position symmetrical with respect to the center of the circular array and connected to a feed point of each radiating element.