JPS6232844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a fan-shaped beam antenna suitable for small to medium capacity microwave multidirectional multiplex communication.

b. Prior Art Conventionally, fan-shaped beam antennas have been widely used in radar devices and the like. The fan beam antenna used in this radar uses a rotating paraboloid reflector cut into a rectangular shape, so the rise of the main beam is slow and the excitation wave of the primary radiator is It has the disadvantage that it leaks from the short side direction of the reflector and the side/rear direction level becomes high, that is, it does not have a low side rope. Therefore, in order to make the directional beam more flat and increase the gain, a reflecting mirror with an extremely large long side is required.

By the way, in the small to medium capacity microwave multiplex communication system, it is preferable to configure a so-called multidirectional line in order to make the communication line economical. When implementing this, installing a large number of parabolic antennas corresponding to each line at the master station is extremely disadvantageous economically from a comprehensive perspective of wireless communication lines, such as increasing wind pressure on the antenna support tower. be. Therefore, it is advantageous to install one wide-angle fan-shaped beam antenna in the master station to evenly communicate with slave stations distributed in multiple directions. Furthermore, by combining multiple fan beam antennas, it is possible to combine slave stations in all directions, or one or a small number of fan beam antennas and a one-to-one opposing antenna (for example, a pencil beam antenna). Therefore, it is also possible to communicate with a necessary number of slave stations simultaneously. Of course, in order to prevent coupling and interference with other antennas, the fan beam antenna used in such cases must have a main beam with a sharp rise and a low backward directivity level on that side, that is, the so-called low side. It is important that it is a rope, and it is desired that it be compact and economically constructed. The radar type antenna described above cannot satisfy such conditions and is therefore unsuitable for the multidirectional multiplex communication described above.

A combination of a hyperbolic paraboloid and a paraboloid of revolution, or
A small wide-angle fan beam antenna that shapes a secondary directional beam using a compound curved reflector formed by a combination of a plurality of paraboloids of revolution has been reported in the literature. However, in these composite curved reflectors, the intersection lines of each curved surface have a complicated shape, so the original curved surface is cut to find this shape, and the desired composite shape is welded and connected without damaging the shape. It is not easy to manufacture and process a reflecting mirror with a curved surface shape. Furthermore, since the opening surface is flat, it is not easy to trim the opening shape into a circular, elliptical, square, polygonal, etc., or to reinforce the periphery, and the cost efficiency is low. moreover,
Compared to the original single curved reflector antenna, the composite curved reflector antenna has side and rear directivity characteristics that do not exceed those of the original single curved reflector antenna.

General microwave multiplex communication antennas use an axially symmetric rotating paraboloid reflector whose mirror surface is machined or pressed, and the gain is proportional to the aperture area of the reflector for the same frequency.
Further, the half-value width of the directional power is inversely proportional to the aperture diameter of the reflecting mirror for the same frequency used. In order to improve the backward directivity level of this antenna, a cylindrical metal shielding plate is attached along the periphery of the aperture of the reflecting mirror.

c Problems to be Solved by the Invention The present invention is suitable for application to the above-mentioned small and medium capacity microwave multi-directional multiplex communication system, is easy to manufacture and process, and has a main beam with a steep rise. It is an object of the present invention to provide a fan-shaped beam antenna that has excellent characteristics such as being able to improve (lower) the directivity level compared to the original paraboloid of revolution reflector antenna.

d. Means for Solving the Problems The above problems have been solved by the fan beam antenna described in the claims. To elaborate further, a compound curved reflector consists of two parabolic reflectors located at both ends and a parabolic cylindrical reflector interposed between both parabolic reflectors. and a primary radiator arranged so that the focal point of both parabolic reflecting mirrors is approximately the center of the radiation, and both parabolic reflecting mirrors are configured to direct the parabolic reflecting mirror of revolution to its light beam. If the optical axis is parallel to the optical axis and divided by two opposing planes sandwiching the optical axis, two partial parabolic reflectors with the same shape that would be formed at both ends of the mirror, each having approximately the same shape. The problem was solved by a fan-beam antenna with

The shape will be explained in more detail below with reference to the drawings.

As shown in FIGS. 1 and 2, a reflector 1 of a fan beam antenna according to the present invention has parabolic reflector sections 2 and 4 located at both ends thereof, and a parabolic reflector section located at the center thereof. It has a compound curved structure formed by joining the cylindrical reflecting mirror part 3.

The parabolic reflecting mirror sections 2 and 4 are configured such that, for example, the original axisymmetric rotating parabolic reflecting mirror 5 shown by the dashed line in FIG. It can be obtained by dividing it into three parts (indicated by two-dot chain lines 6 and 6' in the figure) at two opposing planes, and the dividing position is determined as follows. That is, the opening area of both the parabolic reflecting mirror parts 2 and 4 and the opening area of the parabolic cylindrical reflecting mirror part 3 are determined according to the illuminance distribution characteristics of the primary radiator 8 (see FIG. 3), which will be described later. A position that is divided into approximately equal areas (a position separated by l from the mirror axis X) is determined as the division position.

In a Cartesian coordinate system in which the direction of the main beam is the Z-axis, and the two orthogonal axes in a plane perpendicular to the Z-axis are the The object surface is expressed by the following equation when the focal length is f and the focal point is the origin.

4f(Z+f)=X ² +Y ² Also, a plane that is distance l from the Z axis is expressed by the following equation.

Y=±l The line of intersection between the axisymmetric paraboloid of rotation and the above plane is the common part of the curved surface (4f(Z+f)=X ² +Y ² ) and the plane (Y=±l), but this is a paraboloid. Surface (4f(Z+f)
=X ² +l It is equal to the intersection of ² and the plane (Y=±l).

As mentioned above, the parabolic reflecting mirror sections 2 and 4 are
Since it can be obtained by cutting the original parabolic reflecting mirror 5 in a straight line, its processing is extremely easy. In addition, since the curve of the cut plane is the same as the parabola that is the intersection of the plane containing the Z axis of the original paraboloid of revolution reflector 5 and the paraboloid of revolution reflector, correction of the cut plane, When manufacturing and processing the cut surface reinforcing member (rim), there is an advantage that the jigs, tools, and gauges for manufacturing and processing the original paraboloid of revolution reflector 5 can be used as they are. In addition, if you fix the area near the cut point with a rim etc. during the above cutting,
Deformation of the shape of the cut end can be prevented.

The two parabolic reflecting mirrors 2 and 4 obtained as described above are polarized about their respective focal points F, which are made to coincide with each other so that their aperture surfaces approximately form the angle β shown in the following formula. It has been placed.

β = 180° - 2α α = (Φ - Θ) / 2 ∴β = 180° = (Φ - Θ) where Φ = Directional power half width of desired fan beam Θ = Said original paraboloid of revolution reflector The half-power width of an antenna of the same type with half the gain of the antenna consisting of are rotated by an angle α clockwise and counterclockwise, respectively.

At this time, the plane of Y=±l moves to a position expressed by the following equation.

Ycosα±Zsinα=±l Further, the parabolic reflecting mirror 2 is expressed by the following equation.

4f (Ysinα+Zcosα+f) =X ² +(Ycosα−Zsinα) ^2where Ycosα−Zsinα>+l Similarly, the parabolic reflecting mirror 4 is expressed by the following equation.

4f ( ^-Ysinα +Zcosα+f ⁾ = It is arranged so as to close the mirror defect formed between the edges. Therefore, this parabolic cylindrical reflecting mirror section 3 has a configuration in which a flat plate is curved along the parabolic cut edges of the above-mentioned both reflecting mirror sections 2 and 4, and its curved surface is 4f (Z + fcos α + lsin α). =(X ² +l ² )cosα where Ycosα−Zsinα<+l and Ycosα+Zsinα>−l. Note that in this specification, the Cartesian coordinate system means an orthogonal coordinate system based on a linear coordinate system.

The size of the radiation surface reflector 5 in its original form is as follows:
It is determined by the required gain of the fan beam to be obtained. Reference numeral 7 denotes a seat for attaching the compound curved reflector 1 formed as described above to a steel tower, a pedestal, etc. using direction adjustment bolts.

e Function The fan beam antenna according to the present invention including the compound curved reflector 1 having the above configuration functions as follows. That is, as shown in the operation explanatory diagram of Fig. 3,
The compound curved reflector 1 is a primary radiator 8 whose radiation center is at the focal point F of the paraboloid of revolution reflector parts 2 and 4.
If excited, the main direction directivity of the reflecting mirror section 2 will be a sharp directivity (indicated by the broken line in the figure) that is shifted to the right by an angle α with respect to the optical axis Z of the original paraboloid of revolution reflector 5. Similarly, the main direction directivity of the reflecting mirror portion 4 is a directivity shifted to the left by α with respect to the axis Z. On the other hand, the directivity of the parabolic cylindrical reflecting mirror section 3 in the short axis direction is significantly broader than that of the paraboloid of revolution reflecting mirror sections 2 and 4.
Since the parabolic cylindrical reflecting mirror section 3 has a long axis in the vertical direction, its directivity in the horizontal plane is broad, and as a result, the directivity shown by the dotted line in the figure is obtained. Since this directivity fills the recess between the above-mentioned directivity, each of these directivity and the combined directivity have a fan shape with a steep rise as shown by the solid line.

The aperture areas of the paraboloid of revolution reflectors 2 and 4 and the aperture area of the parabolic cylindrical reflector 3 are divided proportionally according to the illuminance distribution characteristics of the primary radiator 8, so that both have approximately equal areas. The above-mentioned directivity was selected so that
This is to smooth the tip of the fan-shaped beam by aligning the peak value levels of the beams, thereby uniformly transmitting waves to slave stations within the service area.

As is clear from FIGS. 2 and 3, the fan beam antenna according to the present invention has a configuration in which the peripheral edges of the paraboloid of revolution reflectors 2 and 4 located at both ends thereof surround the primary radiator 8. Since it protrudes forward (towards the aperture side), it exhibits side and rear wide-angle directivity that is substantially equivalent to the case where a shielding plate is provided around the aperture of the paraboloid of revolution reflector 5 in the original shape. As a result, its wide-angle directivity level in the horizontal plane is improved over that of the original paraboloid of revolution reflector 5 without the shielding plate.

The gain is determined by moving the parabolic cylindrical reflector 3 back and forth as appropriate along the optical axis so that the phases of the radiation waves (reflected waves of the excitation wave of the primary radiator) from all parts of the mirror are aligned at the aperture surface. This can be improved by fixing the material with a holder, and the processing for this purpose is easy.

f Example The solid line curve 9 in Fig. 4 shows the gain in the 2GHz band.
The actual measured directivity in the horizontal plane of the fan-shaped beam antenna according to the present invention, which was designed with a target of 20 dB and a power half width of approximately 45° (=Φ), is also shown in the dashed-dotted curve 1 in the same figure.
0 indicates the directivity peak envelope value of the original paraboloid of revolution reflector 5 corresponding to the compound curved reflector 1 of this antenna. In addition, the above-mentioned original paraboloid of revolution reflector 5
The aperture diameter is 2.4 square meters, the gain is 31 dB, and the power width at half maximum is 5.5 degrees. In addition, the deviation angle α of the paraboloid of revolution reflectors 2 and 4 on both sides of the compound curved reflector 1 is as follows:
Since the power half width of the parabolic antenna is about 9° (=Θ), which is 6 dB lower than the gain of the antenna using the original parabolic reflector 5 of revolution, α=18°, that is,
It is designed so that β=144°.

As is clear from the figure, in the fan-shaped beam antenna according to the present invention, the power half width satisfies the target value, and the rise of the main beam is also steep. In addition, in comparing curves 9 and 10, considering the gain reduction of approximately 10 dB when the pencil beam antenna is replaced with a wide-angle fan beam antenna, curve 9 shows that the antenna of the present invention has a pronounced side and rearward direction even without a shielding plate. This indicates that it has the effect of reducing the level. Note that the main beam directivity in the vertical plane is the same as the characteristics of the original parabolic antenna.

It goes without saying that the present invention can also be applied to offset reflector antennas.

g. Effects of the Invention As described above, the fan-shaped beam antenna according to the present invention can be easily constructed by applying simple processing to a conventional paraboloid of revolution reflector, and therefore the manufacturing cost is extremely low. Moreover, not only can a fan-shaped beam with a steep rise and the desired half-width power be obtained, but also the side and rear directivity levels can be improved without a shielding plate, which has great practical effects.

[Brief explanation of the drawing]

1 is a front view of a reflector of a fan beam antenna according to the present invention, FIG. 2 is a partially cutaway side view of the reflector, and FIG. 3 is a diagram for explaining the operation of the antenna of the present invention. FIG. 4 is a graph showing actually measured values of the directivity in the horizontal plane of the antenna according to the present invention. 1... Composite curved reflector, 2, 4... Paraboloid of revolution reflector section, 3... Parabolic cylindrical reflector section, 5... Original paraboloid of revolution reflector, 7... Direction adjustment bolt Mounting seat, 8...Primary radiator.

Claims (1)

[Claims] 1. When the three orthogonal axes of a rectangular coordinate system with the direction of the main beam of the antenna as the X-axis are the X-axis, Y-axis, and Z-axis, and l is an arbitrary real number having a dimension of length. , a first paraboloid of revolution reflecting mirror portion that is a paraboloid of revolution with a focal length f expressed by equation (a), and a parabolic cylindrical reflecting mirror that is a parabolic cylinder surface expressed by equation (b). A fan-shaped beam antenna comprising: a second paraboloid of revolution reflecting mirror section that is a paraboloid of revolution expressed by equation (c); and a primary radiator located at the origin. . 4f(Ysinα+Zcosα+f) =X ² +(Ycosα−Zsinα) ² …(a) (However, Ycosα+Zsinα<+l) 4f(Z+fcosα+lsinα) =(X ² +l ² )cosα ……(b) (However, Ycosα+Zsinα<l and Ycosα− Zsinα<-l) 4f(-Ysinα+Zsinα+f) =X ² +(Ycosα+Zsinα) ² ...(c) (However, Ycosα+Zsinα<l) Here, α has the angular dimension and is the directional power half width of the desired fan beam. Φ, the power half width of the parabolic reflector with half the gain of the beam antenna consisting of the rotating parabolic reflector and the primary radiator located at the origin expressed by equation (d) is Θ
When , it is defined as α=(Φ−Θ)/2. 4f (Z + f) = X ² + Y ² ...(d) 2 The above l is the aperture area of the bi-rotating parabolic reflector and the aperture of the parabolic cylindrical reflector considering the illuminance distribution characteristics of the primary radiator. 2. Fan beam antenna according to claim 1, characterized in that the areas are chosen to be equal at α=0.