JPH09232813A - Band-pass filter for waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the electric characteristic and to facilitate manufacturing by forming an inductive coupling means with a couple of projections opposed to each other perpendicularly to the longitudinal direction of a waveguide and forming a curved part to the projection integrated with the waveguide toward the inductive coupling means. SOLUTION: An inductive coupling means is formed by a couple of projections opposed to each other perpendicularly to the longitudinal direction of a waveguide and a cured part is formed to a side face of the projection of the inductive coupling means. That is, for example, the inside of a waveguide main body 10 of a 3-stage waveguide band-pass filter has a size in which a resonator of a half wavelength with respect to a center frequency of the band- pass filter is formed, the entire length is three times the size of the half wavelength and one of side faces in the longitudinal direction is an open face. Then the inductive coupling means 11-18 are arranged in the waveguide main body 10 opposite to each other perpendicularly to the longitudinal direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency electric circuit, and more particularly to a waveguide band pass filter device having a pass band in a millimeter wave frequency band of 30 GHz to 300 GHz.

[0002]

2. Description of the Related Art A conventional method of designing a waveguide bandpass filter, which is the background of the present invention, has been established for a long time.
For example, Microwave Filters, Impedance-Matching Netw
8.06 from orks, and Coupling Structures (published 1964)
In the chapter SHUNT-INDUCTANCE-COUPLED, WAVEGUIDE FILTERS,
The design method is described. Furthermore, Figure 9.05-3 shows a concrete structure diagram. The basic operation of this waveguide bandpass filter is to provide an inductive coupling section for each half wavelength in the waveguide so that the section of the waveguide separated by these coupling sections is a half-wave resonator. To make it work. As a concrete structure of the inductive coupling portion, a very thin metal plate or a metal round bar has been conventionally used. However, in the millimeter wave whose pass band frequency of the waveguide band-pass filter is 30 GHz to 300 GHz, the conventional inductive coupling section is too difficult to manufacture in reality because its machining precision is too fine. For example, a waveguide bandpass filter with a pass band frequency of 77 GHz has a width of 2.5
An inductive coupling must be provided inside the EIAJ standard WRI-900 waveguide with a height of 4 mm and a height of 1.27 mm.

(Prior Art Using Thin Plate Inductive Coupling Section) FIG. 6 shows a structural diagram of a conventional three-stage waveguide bandpass filter using a thin plate inductive coupling section. Since the thickness of the thin metal plate 1 provided inside the waveguide must be sufficiently smaller than the dimensions of the waveguide, 1/100 of the width of the waveguide is 25.4 μm and 1/10. However, it is 254 μm, and it is difficult to accurately process such a metal foil. Further, in the assembly, as shown in FIG. 7, a slit 2 corresponding to the thickness of the metal plate 1 is processed on the wall surface of the waveguide, the metal plate 1 is inserted into the slit 2, and the electrical conduction is further conducted. It is necessary to fix it by brazing or some other method to secure its integrity. The width of the slit 2 is 25.4, which is the same as the thickness of the metal plate 1.
Since it is a minute slit of μm to 254 μm, its processing is very difficult.

(Prior Art Using Inductive Coupling Section of Round Bar) FIG. 8 is a structural diagram of a conventional three-stage waveguide bandpass filter using the inductive coupling section 3 of a round bar.
Shown in The diameter of the metal rod provided inside this waveguide is usually 1/10 to 1/5 of the width of the waveguide, so 2
It is about 54 μm to 512 μm, and it is difficult to accurately process such a metal rod. In the assembly, as shown in FIG. 9, a hole 4 corresponding to the diameter of the round bar is formed on the wall surface of the waveguide, and a metal bar is inserted into the hole to secure electrical conductivity. Therefore, it is necessary to fix it by a method such as brazing. The diameter of this hole is a minute hole of 254 μm to 512 μm, which is the same as the diameter of the round bar, and therefore its processing is very difficult.

[0005]

In view of the above-mentioned prior art, the present invention has good electrical characteristics in the millimeter wave band having a pass band frequency of 30 GHz to 300 GHz, and has a waveguide and an inductive coupling portion. It is an object of the present invention to provide a waveguide bandpass filter which can be manufactured integrally and easily, and is small in size and inexpensive.

[0006]

In order to solve the above problems, the present invention provides a waveguide having at least a pair of inductive coupling means provided so as to substantially correspond to a half wavelength of a center frequency of a bandpass filter. Add improvements to the bandpass filter. In this waveguide bandpass filter, the inductive coupling means is composed of a set of convex portions that are vertically opposed to the length direction of the waveguide, and the inductive portion of the convex portion integrated with the waveguide is formed. A curved portion is formed on the side surface of the coupling means.

A waveguide bandpass filter according to an aspect of the present invention is a waveguide bandpass filter including a waveguide body in which one side surface in the lengthwise direction of a rectangular parallelepiped is an open surface, and a side surface cover of the waveguide body. The present invention relates to a waveguide bandpass filter including a wave tube and at least a pair of inductive coupling means provided so as to substantially correspond to a half wavelength of a center frequency of the bandpass filter. In this waveguide bandpass filter, the inductive coupling means is composed of a set of convex portions that are vertically opposed to the length direction of the waveguide, and the inductive portion of the convex portion integrated with the waveguide is formed. A curved portion is formed on the side surface of the coupling means.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a waveguide bandpass filter provided with at least a pair of inductive coupling means so as to substantially correspond to a half wavelength of the center frequency of the bandpass filter in the length direction of the waveguide. The inductive coupling means is composed of a set of convex portions that are vertically opposed to the length direction of the waveguide, and a curved portion is formed on the side surface of the inductive coupling means of the convex portions. A waveguide bandpass filter according to an aspect of the present invention is a waveguide including a waveguide main body in which one side in the length direction of a rectangular parallelepiped is an open surface and a side cover of the waveguide main body. And at least a pair of inductive coupling means provided so as to substantially correspond to a half wavelength of the center frequency of the bandpass filter, the inductive coupling means being a set of convex portions that are vertically opposed to the length direction of the waveguide. And a curved portion is formed on a side surface of the inductive coupling means of the convex portion. In the waveguide bandpass filter device configured as described above, the inductive coupling means is composed of a set of convex portions that are vertically opposed to the length direction of the waveguide, and is integrated with the waveguide. Since the curved portion is provided on the side surface of the inductive coupling means of the convex portion, even in the millimeter wave band where the mechanical dimension of the waveguide becomes extremely small, the waveguide can be formed by using a general machine tool such as a milling machine. And inductive coupling means integrated,
And it can be easily manufactured.

FIG. 4 shows a perspective view of an embodiment of the inductive coupling means and its equivalent circuit. In this embodiment, the inductive coupling means is composed of a set of convex portions that are perpendicularly opposed to the length direction of the waveguide, and the convex portion integrated with the waveguide is curved on the side surface of the inductive coupling means. Parts are provided. The convex portion with the narrowed width of the waveguide acts as an equivalent parallel inductance EPL in the electrical equivalent circuit.
Further, the curved portion of the convex portion provided on the side surface of the inductive coupling means is a thin waveguide in an electrical equivalent circuit.
It works like EWRa and EWRb. The value of each element of these electrically equivalent circuits can be known using an electromagnetic field simulator. For example, FIG. 5 shows that in the EIAJ standard WRI-900 waveguide, the inductive coupling means is composed of a pair of convex portions that are perpendicularly opposed to the length direction of the waveguide and integrated with the waveguide. It is a value of each element of the electrical equivalent circuit of the inductive coupling means in which the curved portion is provided on the side surface between the inductive coupling means of the convex portion.

An embodiment of the present invention will be described below with reference to FIGS. 1 is a perspective view showing a three-stage waveguide bandpass filter which is one embodiment of the waveguide bandpass filter of the present invention, FIG. 2 is an equivalent circuit of the embodiment shown in FIG. 1, and FIG. 4 is a perspective view showing an embodiment of an inductive coupling portion provided in the waveguide bandpass filter of the present invention and its equivalent circuit, and FIG. 5 is an equivalent circuit diagram shown in FIG. It is an example of the element value of a circuit.

1 and 4, 10 and 40 are waveguide bodies, 11 to 18 and 41 to 42 are inductive coupling means constituting members, and 19 is a side cover of the waveguide body. The inside of the waveguide body 10 of the three-stage waveguide bandpass filter, which is one example of the waveguide bandpass filter of the present invention shown in FIG. 1, has a half width corresponding to a half wavelength of the center frequency of the bandpass filter. The size and shape of the wavelength resonator,
In addition, the total length is three times or more the size and shape corresponding to the half wavelength, and one of the side faces in the length direction is an open face. Inductive coupling means constituent members 11 and 12, 13
And 14, 15 and 16, and 17 and 18 are the waveguide body 1
0 are arranged so as to face each other perpendicularly to the length direction. Then, the inductive coupling means constituting members 11 and 12 have the first inductive coupling means J01.
The inductive coupling means constituting members 13 and 14, the second inductive coupling means J12, the inductive coupling means constituting members 15 and 16, the third inductive coupling means J23, the inductive coupling means constituting members 17 and 18, It constitutes a fourth inductive coupling means J34. The first, second, third, and fourth inductive coupling means are opposed to each other with a space therebetween so that a band required as a bandpass filter can be obtained. The side surface cover 19 of the waveguide body is in close contact with the open surface on the side surface of the waveguide 10 to form a waveguide bandpass filter including three waveguide resonators in the length direction of the waveguide 10. To be done.

FIG. 2 shows an equivalent circuit of a three-stage waveguide bandpass filter which is an embodiment of the waveguide bandpass filter of the present invention shown in FIG. The three-stage waveguide bandpass filter can be illustrated as an equivalent circuit of a configuration in which three waveguide portions WR1 to WR3 are connected by four inductive coupling portions J01 to J34. With these configurations, three resonators required for the three-stage bandpass filter, two coupling means between these resonators, and two external coupling means with an external circuit are realized.

The structure of a three-stage waveguide bandpass filter which is an embodiment of the waveguide bandpass filter of the present invention shown in FIG. 1 will be described using an equivalent circuit. The first resonator of this three-stage waveguide bandpass filter is the equivalent waveguide EWR01 on the second curved portion side of the first inductive coupling means J01.
b, the first waveguide portion WR1, and the equivalent waveguide EWR12a on the first curved portion side of the second inductive coupling means J12. The second resonator is an equivalent waveguide EWR12b on the side of the second curved portion of the second inductive coupling means J12.
And a second waveguide portion WR2 and an equivalent waveguide EWR23a on the first curved portion side of the third inductive coupling means J23. Further, the third resonator is an equivalent waveguide EWR23 on the second curved portion side of the third inductive coupling means J23.
b, the third waveguide portion WR3, and the equivalent waveguide EWR34a on the first curved portion side of the fourth inductive coupling means J34. Since the three resonators thus configured mainly determine the center frequency of the waveguide bandpass filter, the length thereof is set to about a half wavelength at the center frequency of the filter.

The coupling means between the first resonator and the second resonator of this waveguide bandpass filter is realized by the equivalent parallel inductor EPL12 of the second inductive coupling means J12. In addition, the coupling means of the second resonator and the third resonator is
The equivalent parallel inductor EPL23 of the third inductive coupling means J23 is realized. Since the coupling means between the resonators configured as described above mainly determines the bandwidth of the bandpass filter, widening the coupling width of the second and third inductive coupling means results in a wide band, and narrowing the coupling width of the second inductive coupling means. A bandpass bandpass filter can be realized.

This waveguide bandpass filter is provided with an external coupling means for connecting an external circuit at two places of input and output. The first external coupling means is the equivalent waveguide EWR01a of the first curved portion of the first inductive coupling means J01 and the equivalent parallel inductor E of the first inductive coupling means J01.
It is composed of PL01. The second external coupling means is the equivalent waveguide EWR34b of the second curved portion of the fourth inductive coupling means J34 and the fourth inductive coupling means J3.
It consists of four equivalent parallel inductors EPL34. Since the external coupling means thus configured mainly determines the matching condition between the waveguide bandpass filter and the external circuit, the coupling widths of the first and fourth inductive coupling means are matched with the external circuit. It can be set according to the conditions.

The characteristics of the waveguide band pass filter configured as described above can be clarified by giving the values of the respective elements of the equivalent circuit to the circuit simulator. The element values are adjusted according to the desired characteristics, and the corresponding mechanical dimensions are shown in Fig. 5.
Can be obtained from FIG. 1 is a perspective view of the three-stage waveguide bandpass filter designed as described above.
Shows its transmission characteristics. In this embodiment, the pass frequency band of the three-stage waveguide bandpass filter is 72 GHz to 78 G.
The desired characteristic was obtained by setting to Hz.

FIG. 10 is a perspective view of a two-stage waveguide bandpass filter according to another embodiment of the present invention. Unlike the above-mentioned three-stage waveguide bandpass filter, two half-wavelength resonators corresponding to the half-wavelength of the center frequency are provided.

The bandpass filter having the structure shown in the above embodiment has good electrical characteristics, and the metal block is integrated with the waveguide and the inductive coupling portion from one direction by using a general machine tool such as a milling machine. And easily manufactured.

[0019]

As is apparent from the above embodiments, the waveguide bandpass filter of the present invention has a pass band frequency of 30.
In the millimeter wave band from GHz to 300 GHz, the waveguide has excellent electrical characteristics such as variations in pass band width and transmission loss, and the waveguide and the inductive coupling part can be easily and integrally manufactured, which is suitable for mass production. A bandpass filter can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view of a three-stage waveguide bandpass filter that is an embodiment of the present invention.

FIG. 2 is an equivalent circuit of a three-stage waveguide bandpass filter that is an embodiment of the present invention.

FIG. 3 is an electrical characteristic of a three-stage waveguide bandpass filter that is an embodiment of the present invention.

FIG. 4 is a perspective view of the inductive coupling means provided in the waveguide bandpass filter of the present invention and its equivalent circuit.

FIG. 5 shows an example of element values of an equivalent circuit of inductive coupling means provided in the waveguide bandpass filter of the present invention.

FIG. 6 is a structural diagram of a conventional three-stage waveguide bandpass filter using a thin plate inductive coupling section.

FIG. 7 is an assembly diagram of a conventional three-stage waveguide bandpass filter using a thin plate inductive coupling section.

FIG. 8 is a structural diagram of a conventional three-stage waveguide bandpass filter using a round bar inductive coupling section.

FIG. 9 is an assembly diagram of a conventional three-stage waveguide bandpass filter using a round bar inductive coupling section.

FIG. 10 is an example of a two-stage waveguide bandpass filter using an inductive coupling section having a curved portion according to the present invention.

[Explanation of symbols]

10, 40 Waveguide main body 19 Side cover of waveguide main body 11, 12, 13, 14, 15, 16, 17, 18, 4
1,42 Inductive coupling means constituent member

Claims (2)

[Claims] 1. A waveguide bandpass filter comprising at least a pair of inductive coupling means provided so as to substantially correspond to a half wavelength of a center frequency of the bandpass filter, wherein the inductive coupling means is a waveguide A waveguide bandpass filter, comprising a pair of convex portions facing each other perpendicularly to the length direction, and a curved portion being formed on a side surface of the inductive coupling means of the convex portions. 2. A waveguide comprising a waveguide body whose one side in the lengthwise direction of a rectangular parallelepiped is an open surface, and a side cover of the waveguide body, and a half of the center frequency of a bandpass filter. In a waveguide bandpass filter including at least a pair of inductive coupling means provided so as to substantially correspond to a wavelength, the inductive coupling means is a set of pairs facing each other in a direction perpendicular to a length direction of the waveguide. A waveguide bandpass filter comprising a convex portion, and a curved portion is formed on a side surface of the inductive coupling means of the convex portion.