JPS6081902A - High frequency branching filter device - Google Patents

Abstract

PURPOSE:To prevent deterioration in branching filter characteristics and an increase in polarized wave dependency by varying the pattern size of a frequency selective surface plate continuously in two directions on the surface plate. CONSTITUTION:Three high-pass type frequency selective surface plates 10 are used, rectangular windows are formed in a metallic thin plate, and formed gratings differ in mutual distance. Further, the surface plates 10 are so slanted that distances between the surface plates 10 are different at points 31-33 where the surface plates 10 are viewed laterally. Namely, the interplate distances at the points 31-33 are made different so that interplate distance Xcostheta= constant, making the electric length between surface plates equal at the points 31-33. Therefore, the detrioration in branching filter characteristics and increase in polarized wave dependency are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency demultiplexing device for spherical wave incidence, which is applied to an antenna and is equipped with a frequency selective surface plate.

Recently, with the diversification of applications including satellite communications and the like, there has been a growing demand for antennas that can share multiple frequency bands. To meet this requirement, a frequency-selective surface plate that selectively transmits, reflects, or reflects electromagnetic waves depending on the difference in frequency has been put into practical use. One type of face plate uses a rectangular lattice 1 in which a plurality of windows 2 are formed in a thin metal plate, as shown in the top view of FIG. 1(a) and the side view of FIG. 1(b). has a complete transmission point 21 due to the resonance of the grating at one frequency f, as seen in the characteristics of Fig. 2.There are two ways to use such a rectangular grating, as described below.

The first method is the American magazine “IKEE Transac
tionon Antenna, s and Prop
”, VOl, AP-24.

No. 6 (7801' of 1976, t to 7th
85i'j. This is the 6th
As shown in Figure (a), at a relatively low frequency where the two gratings 1 are regarded as an inductance element 6 in terms of an equivalent circuit as shown in Figure (b), resonance due to the interaction of the two gratings occurs. Set the completely transparent point 22, and the same figure (c)
As seen in the characteristics of this method, the passband is set near this resonance point. The second method is disclosed by the inventors of the present application in Japanese Patent Application No. 55-40848 and Japanese Patent Application No. 5/>-178.
This was proposed in 31. This is shown in Figure 4 (
a) Side view.

As shown in the equivalent circuit of (b), the rectangular lattice 1 is
This is a method of using multiple pieces of this as a resonant circuit to construct a duplexer. This method uses the area from near the resonance point 21 of the grating to below the resonance point, as shown in FIG. 2(c), and has the advantage that the passband can be wider than the former method. Further, by appropriately setting the dimensions of the rectangle with respect to the incident angle, a demultiplexing device with less difference in characteristics due to differences in the plane of polarization of the incident wave can be obtained.

Now, when applying the demultiplexing device described in Section 2 to an actual antenna device, two cases are considered: a plane wave is incident as shown in Figure 5, and a spherical wave is incident as shown in Figure 6. . In the former case, the angle of incidence of the incident wave B is constant at all points on the surface of the frequency-selective surface plate 7 in the splitter, but in the latter case, the angle of incidence from the horns 8a and 8b is It varies depending on the position on the board. For this reason.

In the latter case, even if the polarization-independent grating size and plate distance are determined by optimal design at the beam center point 62, the demultiplexing loss will increase at the beam end points 31 and 33; The polarization dependence of reflected and transmitted waves increases.

There is a problem in that the cross-polarized wave characteristics deteriorate.

This is due to the fact that the characteristics of the single frequency selective surface plate change as the incident angle changes, and the isolateral length between the plates changes.

As a solution to this problem, for the demultiplexing device according to the first method mentioned above, the US lTi8EE Antenna Propagation Department Conference Proceedings+'AP-8', nterna
l;j, onal, sympos], um Djge
st, (1977), pages 560 to 566. That is, as shown in the top view of FIG. 7(a) and the side view of FIG. 7(b), the horizontal The dimension of the grid in the direction t3. In this method, x and a are continuously changed from a portion where the incident angle is small to a portion where the incident angle is large, and the inter-plate side 141 is sloped in order to compensate for the change in the electrical length between the plates. In such conventional methods.

When selecting d, x, and a, first consider the case where the incident polarization plane is perpendicular to the incident plane (TE incidence).

At this time, since the first method uses only the low frequency region, the influence of the horizontal strip can be ignored. And, as is well known, the equivalent reactance XTE due to longitudinal slip I/slip.

λ)) dx, dxria.

It can be expressed as -4 The XTE of the two equations changes in the incident angle θ”;
In order for the value to be constant, a, /d−x=constant, dx
cos θ - being constant, ie.

dx= d, x6/cosθ ・−−(2+a = a
It is sufficient if o/cos θ =−−+3+. here,
dx and a. is θ=o.

These are the optimally designed values of d, x, and a.

That is, as θ increases, dx and a may be increased according to 1/cos θ.

If the above method is applied to the second method described above, the following problem will arise. first.

While the first method selects the passband in the inductance region (λ)) d, x) of the grating, the second method selects the passband in the region close to the resonance point of the grating (λG<d
λ) dx ) is chosen. Therefore, in the first method, it was only necessary to consider compensation for the equivalent susceptance in the low frequency region.

In the second method, it is also necessary to consider correction for the movement of the resonance point of the grating due to a change in the angle of incidence. In order to explain this more clearly, an example of the continuous characteristics of a single frequency-selective surface plate 9, which was trained by the conventional method, was calculated by the mode matching method, and the results are shown in FIG. Shown in a graph. (a,) in the graph is 6 in Figure 7.
1, and the dimensions of the lattice are d, x=
dy=16.44mm, a==b=1315m?
It is 7+. Graph (b) corresponds to part 32 in Fig. 7, where the incident angle is θ-20°), dx=16.4
4/cos20°=17.49mrn,, a,=1
3.15/cos20°=14;00?71m,d,
y=16A4m, m, b=13,15m? It is 7+.

Graph (c) is.

(incident angle θ-40°) corresponding to part 36 in FIG.

dx-16,44/cos 40° = 21.457n
, m,, a = 13.15/co840°=iZi
7mm, d, y=L6.4'4?71.7+I1.
, b=13.15m? It is l+.

As can be seen from the explanation in section 2 below, the region where the first frequency is low (approximately 7
For GH2 and higher), there is little change in transmittance due to a change in the incident angle, and there is also little difference in transmittance due to a difference in incident polarization. Therefore, in order to adapt to the first method θmo,
The above conventional solutions are effective. However, resonance point 2
1 varies greatly depending on the incident angle, the resonance sharpness Q also differs greatly, and the characteristics for TE incident waves and TM incident waves also differ greatly. therefore.

When this conventional method is applied to the second method, there is a disadvantage that the characteristics deteriorate significantly as the incident angle increases.

An object of the present invention is to provide a high frequency demultiplexing device that can reduce the deterioration of the demultiplexing performance and the increase in polarization dependence due to the difference in the angle of incidence on the plate surface of the single frequency selective surface plate when a spherical wave is incident. The purpose is to submit the following.

According to the present invention, in a high frequency demultiplexing device equipped with a frequency selective face plate in which a periodic pattern is formed by metal or a combination of metal and a dielectric, the dimensions of the pattern of the frequency selective face plate are adjusted according to the frequency selective face plate. A high frequency demultiplexing device is obtained, which is characterized in that the surface plate -F is continuously varied along two directions.

Here, nine application conditions to the present invention will be explained in relation to the prior art. The second method mentioned above is.

In order for the resonance point plate of the grating and the vicinity of the resonance point to be selected as the passing region 41, this resonance point must remain unchanged depending on the incident angle. In general, the resonant frequency f of the TE incidence on a rectangular grating is approximately fl--! if the strip widths dx-a and ay-b are F smaller than d, x, and dy, respectively. -1zum- dx H-s: 1nlJ °(4) It is given by. Here, C indicates the speed of light. Therefore, θ
In order to keep f constant against changes in , ax (
1+sinθ)=constant, ie.

(], x.

++sinθ ・ ・ ...(5) There should be no difference. This means that as θ increases, 1
This means that dx must be decreased at a rate of /(1+sinθ). On the other hand, in the region where 9 frequencies are low, (1
) must be invariant to changes in θ.

becomes. According to the above equations (5) and (6), (IX-a
teeth.

becomes. That is, by increasing θ, the strip width dx
-a must also be reduced. By similar considerations, TM
In the case of incidence, b and strip width dy-b must also decrease as θ increases. From the above,
To use the demultiplexing device in the second method under spherical wave incidence.

It can be seen that as the angle of incidence changes, not only the lateral dimension but also the vertical dimension must be varied.

Next, an embodiment of a high frequency demultiplexing device according to the present invention will be described with reference to FIG. This example uses six high-pass frequency-selective surface plates 10, each of which has a rectangular window formed in a thin metal plate, as shown in the top view of Figure (a). The distance between them is different. When these six frequency-selective face plates 10 are viewed from the side, the distances between the six frequency-selective face plates are sequentially different at points 31, 32 and 33, as shown in Figure 1(b). The town has a slope. Here, the transmission characteristics at points 31, 32 and 66 of the three frequency selective surface plate 10 alone are as follows.

As can be seen in the graphs in Figures 10 (a), (b) and (C1), changes in the characteristics at incident angles θ of 0, 20 and 40 degrees compared to the conventional transmission characteristics in Figure 8. is decreasing, and the TE incident wave and TM
Differences in characteristics in the case of incident waves are also reduced.

In the high-frequency demultiplexing device configured with six frequency-selective surface plates as described above, now.

If the distance between each frequency-selective surface plate is a constant value, then the electrical length between each plate is:

Since it is determined by 27c ``7 cos θ, the electrical lengths at points 31, 32, and 63d with different incident angles θ are different.

As a result, the demultiplexing characteristics deteriorate. However, in this embodiment, the points 31.3 of the three frequency-selective surface plates 10
The inter-plate distances 1 at 2 and 33 are set to be different so that cos θ is constant. That is, as the incident angle θ becomes larger, the value of ] is selected to be larger.

Although the above example shows the case where three 9-frequency selective surface plates are used, the performance of each device can be improved by using multiple plates or only one plate. You can choose the demultiplexing characteristics that suit your needs.

In addition, in the embodiment described in Section 2, a high-pass type frequency-selective surface plate was used, but as a low-pass type, a frequency-selective surface plate with a structure in which the metal portion and the space portion are reversed is used. be able to.

Furthermore, in the present invention, the frequency selective surface plate is formed with a structure in which a metal thin film is sandwiched between dielectric thin plates,
Alternatively, a dielectric material can be inserted between a plurality of frequency selective faceplates. Also, a frequency selective surface plate having a single curved surface shape can be used.

As is clear from the following description, according to the present invention, the pattern dimensions of the frequency-selective surface plate are as follows.

By continuously changing the surface plate along the two directions, the angle of incidence on the plate surface is different for the incidence of the spherical wave, and the deterioration of the split wave characteristics and the polarization dependence can be reduced. It becomes possible to prevent the increase in the number of antennas, and the effect obtained when applied to antennas in particular to improve their performance is great.

[Brief explanation of drawings]

Figures 1 (a, 1 and (1)) are respectively a top view and a side view of a frequency selective face plate using a conventional rectangular grating, and Figure 2 is a transmission diagram of the frequency selective face plate of Figure 1. Graphs showing the characteristics, FIGS. 6(a), (b) and (C), respectively side view 1 equivalent circuit and characteristics of a frequency selective surface plate using a rectangular lattice according to the first method, FIG.
a), (b) and (c) are side views, respectively, of a frequency selective face plate using a rectangular grating according to the second method.
Equivalent circuit and characteristics. Figure 5 is a side view illustrating the case where a conventional frequency-selective surface plate is used under plane wave incidence, and Figure 6 is a side view illustrating the case where a conventional frequency-selective surface plate is used under spherical wave incidence. 7 (1,) and (1]) are a top view and a side view, respectively, for explaining the frequency selective surface plate according to the conventional method. FIG. Graph showing the transmission characteristics of the frequency selective surface plate, Figure 9 fa)
and (1) 1 is a top view and a side view showing the structure of an embodiment according to the present invention, respectively, and FIG. 10 is a graph showing the transmission characteristics obtained by the embodiment of FIG. 9. In the figure, 10 is a frequency selective surface plate. 11 is a spherical wave generation source. - Number of laps ((7H2) Number of turns per lap (GHz) Number of laps per lap (GHz') Figure 8

Claims (1)

[Claims] 1. In a high frequency demultiplexing device equipped with a frequency selective surface plate in which a periodic pattern is formed by metal or a combination of metal and a dielectric, the dimensions of the pattern of the frequency selective surface plate are A high frequency demultiplexing device characterized in that the surface plate is continuously varied along two directions. 2. The high frequency demultiplexing device according to claim 1, wherein a plurality of the frequency selective surface plates are provided, and the distance between the plurality of surface plates is defined as the surface of the surface plates. 2. A high frequency demultiplexing device characterized in that the angle of incidence of electromagnetic waves is varied at each point. Below is the rest