JPS5986902A - Band pass filter - Google Patents

Abstract

PURPOSE:To make a cut-off characteristic steep and also to make a titled band pass filter thin by constituting it by combining a cavity resonator having a semi-circular section, which is brought into contact with a plate-like wall surface and forms a pair, with a cylindrical cavity resonator. CONSTITUTION:A plate-like wall surface 15 is provided on a face vertical to an electric field of a cylindrical cavity resonator, therefore, by providing this wall surface 15, a distribution of an electromagnetic field is not varied. A coupling hole 16 becomes a coupling hole of electric field coupling by being provided on a position where an electric field vertical to the wall surface becomes maximum, and realizes coupling whose polarity is different from that of a coupling hole 9 of magnetic field coupling.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bandpass filter that is used in the microwave band or millimeter wave band and utilizes TKOI+ mode resonance of a cylindrical cavity resonator with a high no-load Q.

In order to simplify the explanation, we will limit the explanation to three frequency bands, and let the frequencies of these three frequency bands be f, , f2
．． The following description assumes that i'3 and that there is a mutual relationship of f+<f2<fs.

Here, explanation will be given assuming that the f2 wave is filtered from among the waves consisting of the three frequency bands mentioned above.

There is a polarized filter as a bandpass filter having steep wave characteristics, but in this filter, the amount of attenuation is infinite.

In order to arrange the attenuation pole near the passband, it is necessary to realize positive and negative coupling with different polarities as coupling between the cavity resonators. There are two ways to achieve coupling with different polarities: a method that uses a combination of magnetic field coupling and electric field coupling, and a method that uses magnetic fields that have different polarities.9 T of the cylindrical cavity resonator
Since it is difficult to obtain electric field coupling in bandpass filters that utilize ECNI mode resonance, the latter method has been adopted in conventional bandpass filters.

First, the conventional bandpass filter shown in FIG. 1 will be briefly explained.

In FIG. 1, FIG. 1(a) is a plan view with some parts missing;
FIG. 1(b) is a side view with some parts missing, and shows (11°(
2) is an input/output waveguide, (3]-=(61 is a cylindrical cavity resonator, and (7)-(Iυ is a coupling hole for magnetic field coupling.

Input/output waveguide (1) 9 cylindrical cavity resonator (31, - (6
1 and the input/output waveguide (2) are sequentially connected to the coupling hole (71, -=
The cavity resonators (3) and (6) are further coupled through the coupling hole (12).

At this time, cavity resonators (4) and (5) are arranged so that their circular cross sections overlap, whereas cavity resonators (3) and (6) are arranged so that they are shifted by the radius of their circular cross sections. Therefore, as is clear from the electromagnetic field distribution in the cavity resonator (3) shown in Figure 2, the coupling magnetic field is different between the coupling hole (9) and the coupling hole (Iz). ] have different polarities,
Positive and negative couplings of different polarities are realized.

Now, fl, I2. A wave of I6 is introduced, and the axial length of resonator (3) H (6) is set to TE of frequency f2.
QIMo C1G, (I2 wave coupled by I3 resonates in cavity resonator (3i-(61).I2 wave is further taken out to input/output waveguide (2) through coupling hole I.Others Since the fl, +30 wave does not resonate in the resonator (31-(61), most of the power is reflected to the input/output waveguide (1).At this time, the negative coupling hole (I2) The cut-off characteristic becomes steep due to f, , + even if one frequency fl, I3 is close to frequency f2.
A large amount of attenuation can be given to 30 waves.

However, in such a band-pass filter, the cavity resonators are stacked in two stages, so there is a drawback that it cannot be accommodated in a low-height space.

In order to eliminate these drawbacks, the present invention is constructed by combining a pair of semicircular cross-section cavity resonators with flat wall surfaces in contact with each other and a cylindrical cavity resonator. explain.

FIG. 3 shows an embodiment of this invention, (11, +21
.

(41, (5), (71-'9. is the same as in Figure 1, (13, α) is a body resonator with a semicircular cross section, α4 is a flat wall surface, and αω is an electric field coupling. It is a hole. Same figure (a
) is a plan view, and (1)) is a side view with some parts missing.

Input/output waveguide (1), cavity resonator α3. (41, (5
1, (14 and the input/output waveguide (2) are sequentially coupled by a coupling hole (7) SαB for magnetic field coupling, and a cavity resonator (13 and I are coupled by a coupling hole (1E9) for electric field coupling). There is.

Since the flat wall surface α9 is provided in a plane perpendicular to the electric field E of the cylindrical cavity resonator shown in FIG. 2, the distribution of the electromagnetic field does not change by providing this wall surface (I9). The electromagnetic field inside the cavity resonator (I3.α) is the same as the electromagnetic field distribution in the semicircular part in Figure 2.The coupling hole σQ is provided at the position where the electric field E perpendicular to the wall surface is maximum. As a result, it becomes a coupling hole for electric field coupling, and a coupling hole for magnetic field coupling (9
) can realize a negative bond with a different polarity.

Now, fl, I2. Introducing the I3 wave and selecting the axial length of the resonator (41, +51, 03, (141) to be - the inner wavelength of the TEQI mode of frequency f2.

I2 bound by binding hole (71, -αω, (lI19)
The wave of the cavity resonator α31. (41, (51, ← 4) The wave of I2 is further taken out to the input/output waveguide (2) through the coupling hole α9. Others (7) fj, I5 (7
) waves are resonant, 1(4), (51, (Ll, (
14), most of the power is reflected to the input/output waveguide (1). At this time, the negative binding hole α
Due to the function of [, the cut-off characteristic becomes steep and 9 frequencies
, I3 are close to the frequency f2, it is possible to provide a large amount of attenuation to the waves il and I5.

Therefore, the bandpass filter of the present invention has the function of a bandpass filter with no steep cutoff characteristic similar to the conventional filter.

In the bandpass filter of the present invention, as is clear from FIG. 3, cavity resonators (41, (51) are arranged on one plane.

a3. FIG. 4 shows another embodiment of the present invention, which has the advantage that it can be accommodated in a low-height space because a< is arranged. (1) S(f
it is the same as in Figure 1, a3. The α ship has a cavity resonator with a semicircular cross section, (15 is a flat wall surface, (7), +8
1, H-(12, (Iη-9) is a coupling hole for magnetic field coupling, and αω is a coupling hole for electric field coupling.

Input/output waveguide (1), cavity resonator (31, (13, (4)
), (51.

(141, (61 and the input/output waveguide (2) are the coupling holes for magnetic field coupling (71, +31. (17), (IL (
19, (1 (1, (111), and the cavity resonators (3) and (6) are coupled by the coupling hole (Iz) for magnetic field coupling, and the cavity resonators t13 and a4 are coupled by the coupling hole ur for electric field coupling. They are connected together.

The function of the bandpass filter of this invention is basically the same as that of the bandpass filter of FIG. In addition to the effect of the coupling hole 03 of negative coupling, the number of cavity resonators is increased, so
The cutoff characteristic is even steeper than that of the bandpass filter shown in FIG.

In the filter of this invention, as is clear from FIG. 4, the cavity resonators (31S(6), α3.(14
1, it has the advantage that it can be accommodated in a low-height space.

In addition, for 9 or more, the number of cavity resonators having a semicircular cross section is 2.
1 Case where the number of cylindrical cavity resonators is 2 or 4 1 (Although this is described above, the present invention is not limited to this. It may be used when the number is 6 or more.

As described above, in the bandpass filter according to the present invention, *
``Constructed by combining a cylindrical cavity resonator that resonates in the ON mode and a cavity resonator with a semicircular cross section that is in contact with a flat wall surface to form a pair, and a coupling hole for electric field coupling is provided in the flat wall surface. By ■.

It is possible to create a thin filter with steep cutting characteristics.
It has the advantage of being able to be accommodated in spaces with low heights.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram showing a conventional bandpass filter.
Figure 2 shows the electromagnetic field distribution in the cavity resonator. FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention. FIG. 4 is a schematic diagram showing another embodiment of the present invention. In the figure, (1), (21 is the input/output waveguide, (3) H
(6) is a cylindrical cavity resonator, (7'l?Q2), (
1η-'α9 is a coupling hole for magnetic field coupling. (Lb, (14 is a cavity resonator with a semicircular cross section, (c) is a flat wall surface, and α is a coupling hole for electric field coupling. In Figure 9, the same or corresponding parts are denoted by the same reference numerals. It is shown as follows.Deputy Kuzuno Makoto - Hoj 6 ζα) 1 color' 7 Cow 3rhaU→ [1 ・(shi)

Claims (1)

[Claims] In a bandpass filter in which cavity resonators are coupled through a coupling hole, a cylindrical cavity resonator that resonates in the TEo++ mode is used as the cavity resonator, and a cavity with a semicircular cross section that is paired with a flat wall surface in contact with each other. Using a body resonator, the coupling between the pair of semicircular cross-section cavities is an electric field coupling through the coupling hole provided in the flat wall surface, and the coupling between the cylindrical cavity resonators and the cylindrical cavity A band-pass filter characterized in that the coupling between the body resonator and the cavity resonator having a semicircular cross section is magnetic field coupling.