JP3966197B2 - Dual mode filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dual mode filter using a waveguide cavity resonator mainly used in the microwave and millimeter wave bands.
[0002]
[Prior art]
Currently, dual mode filters using cylindrical cavity resonators are widely used mainly for ground microwave equipment and satellite installation. There are various types of configurations.
As an example of the configuration of the dual mode filter, a dual mode cavity resonator that resonates in two orthogonal modes and two elongated orthogonal input / output coupling holes provided at the center of the partition walls are coupled to each other. A configuration in which cavity resonators that resonate in a mode are coupled via a cross-shaped central coupling hole is known (for example, see Non-Patent Document 1).
[0003]
[Non-Patent Document 1]
IEEE Trans.Microwave., Vol.MTT-18, no12, pp1109-1113, pp1110 Fig.2. Dec. 1970
[0004]
[Problems to be solved by the invention]
The dual mode filter includes at least one frequency correction screw 6a, 6b in the cavity resonator in addition to the coupling screw between the orthogonal modes in order to correct the difference in resonance frequency between the two orthogonal modes in the cavity resonator. Need to be inserted. The screw insertion into the cavity resonator has a problem of increasing the passage loss in the cavity resonator.
[0005]
In addition, in the central coupling hole, it is necessary to couple two orthogonal modes to the adjacent cavity resonator via the central coupling hole, but if coupling is obtained using a cross-shaped coupling hole or an elliptical coupling hole, The amount of coupling between the mode resonances is mixed and there is a problem that it is difficult to obtain the characteristics as a filter. It is necessary to adjust the frequency with an adjusting screw, and it is difficult to adjust the time.
[0006]
An object of the present invention is to solve the above-described problems and to obtain a dual mode filter in which the passage loss in the cavity resonator is low and the test adjustment time can be shortened.
[0007]
[Means for Solving the Problems]
The dual mode filter according to the present invention includes an input / output waveguide, a dual mode cavity resonator that resonates in two orthogonal modes, and an input / output coupling hole provided at substantially the center of the partition wall of the dual mode cavity resonator. In a dual mode filter in which dual mode resonators that resonate in two orthogonal modes are coupled via a cross-shaped central coupling hole, an input / output coupling hole of the dual mode cavity resonator includes: A circular or elliptical coupling hole is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 shows the configuration of the dual mode filter according to Embodiment 1, and FIG. 2 shows the shapes of the input / output coupling holes 3a and 3b.
In the dual mode filter according to the first embodiment, the input / output coupling hole of the rectangular waveguide and the dual mode cavity resonator is provided with a coupling hole having a concave portion, a convex portion, or both in a circular shape. .
[0009]
The square TE10 mode wave having the electric field E1 input from the wide surface of the input / output rectangular waveguide 1a is coupled to the cylindrical cavity resonator 2a by the cylindrical TE11 mode wave having the electric field n1 through the input / output coupling hole 3a. Resonates at the cylinder TE113. The cylindrical TE11 mode wave having the electric field E1 is coupled to the electric field n2 in the orthogonal mode by the effect of the coupling amount adjusting screw 5a provided at an angle of 45 degrees.
[0010]
Further, the cylindrical TE11 mode wave having the electric fields n1 and n2 orthogonal to each other through the cross coupling hole 4 is coupled to the cylindrical TE11 mode wave having the electric fields n3 and n4 which are orthogonal modes in the adjacent cylindrical cavity resonator 2b. . At the same time, the electric field n3 having the cylindrical TE11 mode wave is coupled to the orthogonal mode n4 by the effect of the coupling screw 5b provided at an angle of -45 degrees. The cylindrical TE11 mode wave having the electric field n1 is combined with the square TE10 mode wave having the electric field E2 of the input / output rectangular waveguide 1b through the input / output coupling hole 3b, and is taken out as an output.
[0011]
It is assumed that the resonance frequency f1 is due to the orthogonal resonance mode electric field n1, and the resonance frequency f2 is due to the resonance frequency f4 due to the electric field n3. At this time, the amount of coupling varies depending on the size of the coupling hole, and each of f1 to f4 passes through the input / output coupling hole and the central coupling hole. It is well known that there is a difference between f2 and f3 and f4.
[0012]
Now, the coupling amount from the electric field E1 to n1 in the input / output coupling hole is M1, the coupling amount from the electric field E1 to n2 is M2, the coupling amount from the electric field n2 to the electric field n3 is M3, and the coupling amount from the electric field n1 to n4 is Let it be M4. Here, in order for an input wave to the input / output rectangular waveguide 1a to be extracted to the input / output rectangular waveguide 1b, f1 is set so that all the orthogonal modes of the cylindrical cavity resonators 2a and 2b resonate at the same frequency. = F2 and f3 = f4 must be corrected. However, the resonance frequency f1 binding amount M1 and M 4, the resonance frequency f2 is determined by the amount of binding M2 and M 3.
[0013]
Conventionally, frequency correction screws 6a and 6b are inserted in parallel directions with respect to the orthogonal modes, and correction is performed so that all the orthogonal modes of the cylindrical cavity resonators 2a and 2b resonate at the same frequency. However, the insertion of screws into the cylindrical cavity resonator increases the loss in the filter characteristics, as is well known.
[0014]
The cylindrical TE11 mode wave having the electric field n1 propagates to the narrow surface of the rectangular waveguide through the circular convex coupling hole and the circular concave coupling hole so that the resonance frequencies of the two orthogonal modes match. It becomes the same as the resonance frequency of the cylindrical TE11 mode wave having the electric field n2. However, what propagates to the narrow surface of the rectangular waveguide is reflected to the cylindrical cavity resonator 2a with little propagation due to the cutoff frequency of the waveguide.
[0015]
Here, the operations that occur in the input / output rectangular waveguide 1b and the cylindrical cavity resonator 2b are also symmetric because they are symmetrical.
[0016]
If the resonance frequencies of the two orthogonal modes are f1 = f2 and f3 = f4 without using the frequency correction screws 6a and 6b, a dual mode filter with lower loss can be realized. In general, the relationship between the coupling amounts of the central coupling holes is M3> M4 or M4 = 0. When the conventional input / output coupling hole is elongated, the coupling amount of M2 is zero and is only M1, and in the case of a circle, M1 = M2. In the case of an ellipse, M1 >> M2 in the horizontal direction and M1 >> M2, in the vertical direction When the width is wide, M2 >> M1.
[0017]
Here, in order for the resonance frequency to coincide with f1 = f2 and f3 = f4, the coupling amount (M1 + M 4 ) = (M2 + M 3 ) may be set orthogonally. However, in satisfying the transfer characteristics of a desired filter, if M1, M3, and M4 are constants that determine the transfer characteristics, the coupling amounts are constant.
[0018]
With the conventional coupling holes listed above, the equation (M1 + M 4 ) = (M2 + M 3 ) cannot be realized. Therefore, if the amount of coupling M2 can be varied, the equation (M1 + M 4 ) = (M2 + M 3 ) can be satisfied. The coupling amount M2 is determined by the vertical width of the input / output coupling hole.
[0019]
FIG. 2 is a diagram for explaining the input / output coupling holes in the first embodiment. FIGS. 2 (a), 2 (b), and 2 (c) are conventional input / output coupling holes based on a circular shape. 2 (d), 2 (e) and 2 (f) are diagrams showing input / output coupling holes based on a conventional ellipse.
2 (a) and 2 (d) show a coupling hole 7 provided with a convex shape on a circular or elliptical reference shape, and FIGS. 2 (b) and 2 (e) show a circular or elliptical shape. FIG. 2 (c) and FIG. 2 (f) show a coupling hole 9 in which both a convex shape and a concave shape are provided in a circular or elliptical reference shape.
[0020]
Compared with the conventional input / output coupling hole, the coupling amount M2 is determined by the vertical width of the input / output coupling hole, so that a convex shape is provided to increase M2 with respect to a circular or elliptical reference shape. What is the coupling hole 7. Since the coupling amount M1 is determined by the horizontal width of the input / output coupling hole, the coupling hole 8 is provided with a concave shape to reduce M1 with respect to a circular or elliptical reference shape.
[0021]
The coupling hole 9 is provided with a convex shape in the vertical direction in order to increase M2 and a concave shape in the horizontal direction in order to decrease M1 with respect to the circular or elliptical reference shape.
[0022]
Thereby, the resonance frequencies of the two orthogonal modes can be set to f1 = f2 and f3 = f4, and a dual mode filter with lower loss can be realized without inserting the frequency correction screws 6a and 6b.
[0023]
Moreover, although this operation | movement demonstrated cylindrical TE113 mode resonance, it cannot be overemphasized that it can apply also to TE11N (N = 1,2,3 ...) which is another resonance mode.
[0024]
As is well known, the present embodiment can be applied to an elongated shape and an oval shape with respect to the shape of the central coupling hole.
[0025]
Embodiment 2. FIG.
FIG. 3 shows the configuration of the dual mode filter according to the second embodiment, and FIG. 4 shows the shape of the central coupling hole 4.
FIG. 3A shows an elliptical coupling hole, and FIG. 3B shows an elongated coupling hole.
[0026]
The dual mode filter according to the second embodiment has a central coupling hole 4 that couples the dual mode cavity resonators to the central portion of the conventional mode having the frequency correction screws 6a and 6b and the first embodiment. In this structure, an elongated coupling hole 10 having a wide surface in the vertical direction is provided, and two elongated coupling holes 11 having a wide surface in the horizontal direction are provided on both sides thereof.
[0027]
In the case where two orthogonal modes are coupled to the adjacent cavity resonator via the central coupling hole 4, it is necessary to design so as to obtain an optimum coupling. Conventionally, a cross-shaped or elliptical coupling hole is used for the central coupling hole 4 as is well known, but a cylinder having a cylinder TE11 mode wave having an electric field n1 and a cylinder having an electric field n2 present in the cylindrical cavity resonator 2a. The TE11 mode wave propagates to the cylindrical cavity resonator 2a through the same coupling hole.
[0028]
Accordingly, when the coupling between the cylindrical TE11 mode wave, the cylindrical TE11 mode wave having the electric field n2, the cylindrical TE11 mode wave, and the cylindrical TE11 mode wave having the electric field n3 is changed to an optimum size, the coupling holes are the same. Therefore, coupling of the cylindrical TE11 mode wave having the cylindrical TE11 mode wave, the cylindrical TE11 mode wave having the electric field n1, the cylindrical TE11 mode wave, and the cylindrical TE11 mode wave having the electric field n4 is affected, and there is a problem that it is difficult to obtain the filter characteristics.
[0029]
When elongated coupling holes such as the large coupling hole 10 and the small coupling hole 11 are used, the electric field vector exists only in the direction perpendicular to the wide surface. Therefore, only the electric field component in the direction perpendicular to the wide surface of the coupling hole is coupled.
[0030]
This is because the cylindrical TE11 mode wave having the electric field n2 existing in the cylindrical cavity resonator 2a passes through the large coupling hole 10 in the direction perpendicular to the central coupling hole, and the TE11 mode wave having the electric field n3 is the cylindrical cavity resonator. Combines with 2b.
[0031]
Further, the TE11 mode wave having the electric field n1 existing in the cylindrical cavity 2a is converted into the cylindrical cavity 2b by the TE11 mode wave having the electric field n4 through the small coupling holes 11 on both sides of the large coupling hole 10. Combine with. Therefore, both can be designed independently. Moreover, characteristic deterioration due to the coupling between the two can be suppressed.
[0032]
According to this embodiment, a cylindrical TE11 mode wave, a cylindrical TE11 mode wave having an electric field n2, a cylindrical TE11 mode wave, a cylindrical TE11 mode wave having an electric field n3, a cylindrical TE11 mode wave, and a cylindrical TE11 mode wave having an electric field n1. The coupling size can be designed without affecting the coupling between the cylindrical TE11 mode wave and the cylindrical TE11 mode wave having the electric field n4.
[0033]
Needless to say, the first embodiment can be applied to the present embodiment without using one of the frequency correction screws 6a and 6b having different resonance frequencies of the dual mode resonance.
[0034]
Moreover, although this operation | movement demonstrated cylindrical TE113 mode resonance, it cannot be overemphasized that it can apply also to TE11N (N = 1,2,3 ...) which is another resonance mode.
[0035]
Moreover, although this embodiment demonstrated the dual mode filter which has a center coupling hole which implement | achieves a polar transfer function, it cannot be overemphasized that another transfer function is realizable by arrangement | positioning of a center coupling hole.
[0036]
Embodiment 3 FIG.
FIG. 4 shows the configuration of the dual mode filter according to the third embodiment, and shows the shape of the central coupling hole 4.
[0037]
Regarding the central coupling hole 4 described in the second embodiment, the current is concentrated most in the central coupling hole 4, so that the current concentrates particularly near the edge of the central coupling hole 4. This concentration of current causes a loss. Therefore, by making the coupling hole large 12 and the coupling hole small 13 into an elongated elliptical shape, a dual mode filter that disperses the current component existing around the coupling hole without concentrating on the edge, and reduces the passage loss compared to the rectangular shape. realizable.
[0038]
Needless to say, the first embodiment can be applied to the first embodiment.
[0039]
In the dual mode filter according to the third embodiment, the shape of the three coupling holes with respect to the central coupling hole in the second embodiment is an elongated ellipse.
[0040]
With respect to the central coupling hole described in the second embodiment, the coupling hole large 12 and the coupling hole small 13 are formed into an elongated elliptical shape, thereby realizing a further low-loss dual mode filter.
[0041]
【The invention's effect】
As described above, the dual mode filter of the present invention can reduce the period by reducing the loss and eliminating the frequency adjustment work by the adjusting screw.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a dual mode filter according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining an input / output coupling hole according to Embodiment 1 of the present invention;
FIG. 3 is a diagram for explaining a dual mode filter according to a second embodiment of the present invention.
FIG. 4 is a view for explaining a central coupling hole in a third embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Input / output square waveguide, 2 Cylindrical cavity resonator, 3 Input / output coupling hole, 4 Center coupling hole, 5 Coupling amount adjustment screw, 6 Frequency correction screw, 7 Coupling hole, 8 Coupling hole, 9 Coupling hole, 10 Large coupling hole, 11 Small coupling hole, 12 Large coupling hole, 13 Small coupling hole.

Claims (5)

An input / output waveguide, a dual mode cavity resonator that resonates in two orthogonal modes, and an input / output coupling hole provided in a substantially central portion of the partition wall of the dual mode cavity resonator are coupled and orthogonalized. In a dual mode filter in which dual mode cavity resonators that resonate in two modes are coupled via a central coupling hole ,
The input / output coupling hole of the dual-mode cavity resonator has a circular cross section of the input / output coupling hole , and a part of the reference shape is concave, convex, or both concave and convex. A dual mode filter characterized in that a coupling hole formed by combining shapes is provided. An input / output waveguide, a dual mode cavity resonator that resonates in two orthogonal modes, and an input / output coupling hole provided in a substantially central portion of the partition wall of the dual mode cavity resonator are coupled and orthogonal In a dual mode filter in which dual mode cavity resonators that resonate in two modes are coupled via a central coupling hole,
In the input / output coupling hole of the dual mode cavity resonator, the input / output coupling hole has an elliptical cross section as a reference shape, and a part of the reference shape is concave, convex, or both concave and convex A dual mode filter, characterized in that a coupling hole formed by synthesizing the shape of is provided. The dual mode filter according to any one of claims 1 and 2, wherein a coupling hole formed by combining the convex shape in the vertical direction and the concave shape in the horizontal direction is provided.   About the shape of the central coupling hole between the dual-mode cavity resonators that resonate in two orthogonal modes, a long and narrow coupling hole having a wide surface in the vertical direction is provided in the central portion, and a wide surface in the horizontal direction is provided on both sides thereof. The dual mode filter according to any one of claims 1 to 3, wherein a central coupling hole having two elongated coupling holes is used. The dual mode filter according to claim 4, wherein the elongated coupling hole has an elliptical shape.

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