JPS62186602A - Bandpass filter - Google Patents

Abstract

PURPOSE:To make a BPF broad by using a cavity resonator. CONSTITUTION:The cavity resonator 4 is provided between input/output waveguides 1a, 1b and a waveguide 2 at the cut-off region and the coupling quantity with an external part is adjusted by the size of an iris 5. An incident wave on a waveguie 1a at a frequency where the resonator 4 and a dielectric resonator 3 are resonated is coupled strongly with the resonators 3, 4 in the resonance state and propagated to a waveguide 1b. In this case, the broad band filter is obtained by increasing the interval of the iris 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a band 'Ifl filter using a dielectric resonator used in the microwave band and millimeter wave band.

[Conventional technology]

Figure 6 shows, for example, the engineering KFiE TRANSACT engineering ONS.
ONMIOROWAVE THEORY AND T
ECHNIQUES, Vol, MTT-29, Review II, PI'-754-7TO (AUGUST 1
981) is a perspective view showing the conventional bandpass filter shown in FIG. 9, (1a) and (1b).
is an input/output waveguide in the passband, (2) is a waveguide in the cutoff region, and (3) is a dielectric resonator. A waveguide (2) in the cut-off area with a reduced width and height of the waveguide is connected between the input and output waveguides (Ia) and (1b), and the waveguide (2) in the cut-off area is connected between the input and output waveguides (Ia) and (1b). A dielectric resonator (3) is placed at the top.

Next, the operation will be explained. At frequencies where the dielectric resonator (3) is non-resonant, the input/output waveguide (1a)
The incident wave is completely reflected by the waveguide (2) in the cutoff region and does not propagate to the input/output waveguide (1b). However, at the frequency at which the dielectric resonator (3) resonates, the incident wave to the input/output waveguide (1a) is strongly coupled to the resonant dielectric resonator (3), and the input/output waveguide (1b). In this way, this filter operates as a bandpass filter.

[Problem that the invention seeks to solve]

In conventional bandpass filters, as shown in Figure 7, the tips of the first and final stage dielectric resonators (3) provided in the waveguide (21) in the cutoff region are connected to the input/output waveguide (1). , (1
b) By placing it protruding inside.

As shown by broken lines and arrows in the figure, coupling with the outside (external Q) was obtained mainly by magnetic field energy.

The coupling with the outside is the protruding distance of the dielectric resonator (3)! As the total sky becomes louder, it becomes larger and the value of external Q becomes smaller.

However, even with this arrangement, the external Q is limited to about 60 as shown in Figure 8, so a broadband filter cannot be obtained, and the problem is that the maximum fractional bandwidth of a bandpass filter is about 2%. There was a point.

This invention was made to solve the above-mentioned problems, and its purpose is to obtain a wideband bandpass filter.

Means for Solving Problem C] In the band-pass filter according to the present invention, only the resonators at both ends are cavity resonators that do not use dielectric resonators.

[Effect]

Since the band-pass filter of the present invention uses cavity resonators that can obtain a large coupling with the outside as the first-stage and final-stage resonators that couple with the outside, a filter with a wide pass band width can be realized.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The entire drawings of an embodiment of the present invention will be described below. 1st
In the figure, (1a) and (1b) are input and output waveguides.

+21 is the waveguide in the cutoff region, (s) Fig electric resonator.

(4) is a cavity resonator, and (5) is an iris.

Figure 2 is a cross-sectional view of Figure 1. Cavity resonator 14) has input and output waveguides (one, (1b)
The amount of coupling with the outside is adjusted by the size of the iris (5).

In this case as well, at the frequency at which the dielectric resonator (3) is non-resonant, the incident wave to the input/output waveguide (1) is completely reflected by the waveguide (2) in the cutoff region, It does not propagate to the wave tube (1b).

However, at the frequency at which the cavity resonator 14) and the dielectric resonator (3) resonate, the incident wave to the input/output waveguide (1) is transmitted to the cavity resonator (4) and the Bit body in a resonant state. It is strongly coupled to the resonator (3) and propagated to the input/output waveguide (1b).In this way, the filter of the present invention also operates as a bandpass filter.

In a bandpass filter, the largest amount of coupling is required between the outside and the first stage resonator and between the outside and the last stage resonator, and a smaller amount of coupling is sufficient between the other resonators.

In a bandpass filter with a structure as shown in Fig. 1.

The coupling between the first stage cavity resonator "4" and the outside is the iris (5)
By increasing the interval of , the value of external Q is 10~2
Since a large coupling of 0 is obtained, a broadband filter with a fractional bandwidth of nearly 10% can be obtained. In addition, since the dielectric resonator (3) is used for the second and subsequent stages,
A very large amount of coupling is not required, and there is no need to protrude the dielectric resonator (3) into the adjacent cavity resonator [4].

FIG. 3 shows another embodiment of the present invention, (1
1 to 14) are the same as in FIG. 1, (6) is a metal post, and FIG. 4 is a sectional view of FIG. 3.

Since the metal posts (61) are provided perpendicularly to the wide surface of the waveguide, they exhibit rust conductivity, and by changing their number and thickness, the coupling with the outside can be adjusted. In this case as well, since a large coupling is obtained, a broadband filter can be obtained, and there is no need to protrude the dielectric resonator (3) into the cavity resonator +41.

FIG. 5 shows still another embodiment of the present invention, in which (1a) to (5) are the same as in FIG. 1.

A waveguide in which only the width of the waveguide is reduced is used as the cut-off waveguide (2). This case also has the same advantages as in FIG.

Note that although the above embodiment describes the case where the filter has four stages, the present invention is not limited to four stages.

Further, although the case where there are two metal posts has been described, the present invention is not limited to two metal posts.

〔Effect of the invention〕

As described above, according to the present invention, only the resonators at both ends of the band-pass filter are cavity resonators that do not use dielectric resonators, thereby making it possible to eliminate large coupling sounds with the outside and achieve a wide band. Bandpass filter gold can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a bandpass filter according to an embodiment of the present invention, and FIG. 2 is a sectional view of FIG. 1. FIG. 3 shows a bandpass filter according to another embodiment of the present invention? FIG. 4 is a sectional view of FIG. 3. FIG. 5 is a perspective view showing a band pass filter according to still another embodiment of the present invention, FIG. 6 is a perspective view showing a conventional band pass filter, FIG. 1 is a sectional view of FIG. 6, and FIG. is a diagram showing the relationship between the position of the dielectric resonator and the external Q. In the figure, (1a) and (1b) are input and output waveguides, (2)
Waveguide in cut-off region, (3) is dielectric resonance 2';i
, 14) is a cavity resonator, (5) is an iris, and (6) is a metal post. In addition, in FIG. 1, the same reference numerals indicate the same or equivalent parts.

Claims (3)

[Claims] (1) A waveguide in the shiya section, a dielectric resonator placed in the waveguide in the above shiya section, and a dielectric resonator connected to both ends of the waveguide in the above shiya section. A bandpass filter comprising a cavity resonator and a cavity resonator. (2) The bandpass filter according to claim (1), wherein the cavity resonator is connected to an input/output waveguide via an inductive iris. (3) The bandpass filter according to claim 1, wherein the cavity resonator is connected to an input/output waveguide via an inductive post.