JP2008098727A - Band-pass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a simple high-performance band-pass filter which has attenuation poles formed without using any negative coupling coefficient between resonators and performs even delay equalization. <P>SOLUTION: In the band-pass filter composed of a plurality of resonators which are coupled to one another, all of the plurality of resonators have the same shape, where a resonator group of six resonators 115 to 120 in total which are arrayed in two rows by three columns is included as the component of the plurality of resonators, the respective resonators included in the resonator group being coupled to the resonators in all adjacent rows and columns with coupling coefficients of the same polarity, and the resonators other than the resonator group are also coupled to the resonator group with coupling coefficients of the same polarity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a bandpass filter having a delay equalization function and having a steep attenuation characteristic.

  In a conventional bandpass filter, a so-called attenuation pole whose pass amount is theoretically 0 in the attenuation region is formed, so that the attenuation characteristics are steepened. Of these, non-adjacent resonators are coupled with a negative coupling coefficient.

  FIG. 9 is a configuration diagram of a conventional bandpass filter. 9 includes an outer conductor 501, a partition wall 502, a capacitive element 503 constituting a sub-coupling circuit, loop-like elements 504 and 505 constituting a sub-coupling circuit, coaxial resonators 511 to 518, and inner conductors 531 to 511. 538 and input / output terminals 551a and 551b.

  This conventional band pass filter has a circuit configuration in which a group of eight resonators in total is folded in a U-shape, and resonators 513 and 516, 512 and 517, 511 and 518 are arranged. Each is a sub-joint, or “jump-join” in another name. In these sub-couplings, by appropriately providing a so-called “negative coupling” having a polarity opposite to the coupling coefficient between the resonators along the U-shaped path, an attenuation pole can be formed in the characteristics of the entire filter. It is well known that group delay equalization can be performed (see, for example, Patent Document 1).

JP 2000-22403 A

However, the prior art has the following problems.
A band-pass filter is generally configured by using a plurality of resonators having the same shape and electromagnetically coupling them by arranging them close to each other. However, generally only a positive coupling coefficient can be obtained by simply bringing resonators of the same shape close to each other.

  In the conventional band-pass filter, the above-described resonators are appropriately coupled with a negative coupling coefficient, thereby providing a higher filter function such as formation of an attenuation pole and delay equalization. However, in order to realize a negative coupling coefficient, the phase of the electromagnetic field contributing to coupling must be reversed by using components such as the capacitive element 503 and loop elements 504 and 505 shown in FIG. Don't be. Therefore, in manufacturing the filter, such separate parts are required, and there is a problem that the number of parts in the filter manufacturing increases.

  The present invention has been made to solve the above-described problems, and is a simple and high-performance band that forms an attenuation pole without using any negative coupling coefficient between resonators and performs delay equalization. The purpose is to obtain a pass filter.

  The bandpass filter according to the present invention is a bandpass filter composed of a plurality of resonators coupled to each other, and the plurality of resonators all have the same shape, and are arranged in 2 rows × 3 columns. A resonator group consisting of a plurality of resonators is included as a component of a plurality of resonators, and each resonator included in the resonator group is coupled to resonators in adjacent rows and columns by a coupling coefficient having the same polarity. The remaining resonators other than the resonator group are also coupled by the coupling coefficient having the same polarity as that of the resonator group.

  According to the present invention, the bandpass filter is configured to include a plurality of resonators having the same shape and to include a group of resonators arranged in a specific layout as a component of the plurality of resonators. A simple and high-performance band that forms an attenuation pole without using any negative coupling coefficient between the resonators, and even performs delay equalization by coupling the resonators with the same polarity coupling coefficient. A pass filter can be obtained.

Hereinafter, preferred embodiments of the band-pass filter of the present invention will be described with reference to the drawings.
The band-pass filter of the present invention is composed of a plurality of resonators having the same shape, and a group of resonators composed of a total of six resonators arranged in 2 rows × 3 columns is formed of a plurality of resonators. Each resonator included in the resonator group included as a component and arranged in such a specific layout is coupled to the resonators in the adjacent rows and columns by the coupling coefficient having the same polarity, and the resonator group The remaining resonators except for are also coupled with a coupling coefficient having the same polarity.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a band-pass filter according to Embodiment 1 of the present invention. The band-pass filter of FIG. 1 includes a metal casing 101, a metal screw 102, a support base 103, a plurality of dielectric resonators 111 to 120, coupling windows 131 to 141, and coaxial line probes 151a and 151b.

  Here, the plurality of dielectric resonators 111 to 120 all have the same shape. Among these, the six dielectric resonators 115 to 120 are a total of six resonators arranged in 2 rows × 3 columns constituting the resonator group, and are arranged in a specific layout. Corresponds to the instrument group.

  The metal screw 102 is a screw for adjusting the resonance frequency of the dielectric resonators 111 to 120. The support base 103 is a low dielectric constant material for fixing the dielectric resonators 111 to 120. The coaxial line probes 151a and 151b are probes that excite the two dielectric resonators 111 and 120 at the outermost end of the filter and serve as input / output terminals of the filter.

  Further, the metal casing 101 is provided with coupling windows 131 to 141 for electromagnetically coupling the dielectric resonators 111 to 120. In particular, in a resonator group including dielectric resonators 115 to 120 arranged in 2 rows × 3 columns, coupling windows 135 to 141 are provided so that resonators in adjacent rows and columns are electromagnetically coupled to each other. ing.

Next, the operation of the bandpass filter according to the first embodiment having such a configuration will be described. All of the resonators constituting the band pass filter resonate in the TE _01δ mode, and the resonators are coupled by a magnetic field, so that their coupling coefficients are all positive. FIG. 2 is a diagram showing an equivalent circuit of the bandpass filter according to the first embodiment of the present invention. As shown in FIG. 2, the band-pass filter is generally configured by coupling a plurality of resonators to each other and further coupling an input / output terminal to any one of the resonators.

  The pass characteristic of the filter is determined by a coupling coefficient representing the degree of coupling between the resonators and an external Q which is a parameter corresponding to the degree of coupling between the input / output terminal and the resonator. In the first embodiment, the coupling coefficients between the resonators all have the same polarity, and the electromagnetic coupling between the resonators is all magnetic field coupling.

  FIG. 3 is a diagram conceptually disassembling the equivalent circuit of FIG. 2 in Embodiment 1 of the present invention into a plurality of element function circuits. As shown in FIG. 3, the band-pass filter according to the first embodiment can be regarded as being composed of an A part, a B part, and a C part. Here, the part A is a part in which a plurality of resonators are arranged in a line and form the center of the filter. The part B is a part composed of two resonator groups that can be regarded as branches connected to the resonators included in the part A. Furthermore, C part is a part which consists of a total of four resonator groups couple | bonded together with the resonator contained in A part.

  FIG. 4a is a diagram showing typical pass characteristics and group delay characteristics of part A of the element function circuit shown in FIG. 3 according to Embodiment 1 of the present invention. The circuit configuration shown in FIG. 4a is the same as that of the Chebyshev type filter in the RF band that is generally widely used, and the characteristics thereof also conform to those of the Chebyshev type filter as shown in FIG. 4a. That is, the pass characteristic exhibits a unimodal frequency characteristic, and the group delay characteristic exhibits a concave frequency characteristic.

  On the other hand, FIG. 4b is a diagram showing typical pass characteristics and group delay characteristics of part B of the element function circuit shown in FIG. 3 in the first embodiment of the present invention. Part B can be regarded as two resonators coupled to each other coupled to a resonator on the main path through which an input / output signal propagates. Considering that two resonators coupled to each other generally have two impedance zeros or poles on the frequency axis, the pass characteristic of the B section has two attenuation poles as shown in FIG. 4b. It is understood that it presents.

  FIG. 4c is a diagram showing typical pass characteristics and group delay characteristics of part C of the elemental function circuit shown in FIG. 3 in Embodiment 1 of the present invention. The circuit of part C can be regarded as a circuit in which the number of resonators is set to 4 in the circuit of part A described above and so-called interlaced coupling between the resonators at the input and output ends is added. When the coupling coefficient of the interlaced coupling is negative, a circuit such as part C has an attenuation pole in the pass characteristic, and the group delay characteristic has a concave frequency characteristic. On the other hand, when the coupling coefficient is positive, the frequency selectivity of the pass characteristic deteriorates, but the group delay characteristic exhibits a convex characteristic.

  Finally, the characteristics of the bandpass filter according to the first embodiment can be considered approximately when the characteristics shown in FIGS. 4a to 4c are superimposed. Therefore, it can be said that the resonator group including a total of six resonators arranged in 2 rows × 3 columns included in the first embodiment plays a role of forming an attenuation pole and a delay equalizer. This will be described next with reference to FIGS.

  FIG. 5 summarizes numerical examples of parameters in the equivalent circuit shown in FIG. 2 according to the first embodiment of the present invention. FIG. 6 is a diagram showing pass, reflection characteristics, and group delay characteristics when the parameter values shown in FIG. 5 are used for the passband filter according to Embodiment 1 of the present invention. The parameters here are the coupling coefficient k and the external Q.

  In FIG. 6, the solid line indicates the frequency characteristic of the passband filter of the present invention, and the broken line indicates the frequency characteristic of the conventional Chebyshev filter. As shown in FIG. 6, according to the bandpass filter according to the first embodiment, the attenuation pole is formed without using any negative coupling coefficient between the resonators, and the flatness of the group delay deviation is also achieved. You can see that it has improved.

  As described above, according to the first embodiment, dielectric resonators having the same shape are used as the plurality of resonators, and the resonators are arranged in 2 rows × 3 columns, and their coupling paths form a lattice shape. A resonator group composed of six dielectric resonators is included as a component of a plurality of resonators, and coupling between the resonator groups arranged in such a specific layout and all other dielectric resonators By configuring the bandpass filter with positive coefficients, a high-performance bandpass filter having an attenuation pole and delay equalization function can be obtained.

  Furthermore, in general, since there is no need for a negative inter-resonator coupling coefficient that must be realized by using separate parts, it is possible to avoid an increase in the number of parts at the time of manufacturing the filter and simplify the circuit configuration. it can.

Embodiment 2. FIG.
In the first embodiment, the band-pass filter using dielectric resonators as the plurality of resonators has been described. In the second embodiment, a band pass filter using a coaxial line resonator instead of a dielectric resonator will be described.

  FIG. 7 is a diagram showing a band-pass filter according to the second embodiment of the present invention. The band pass filter of FIG. 7 includes a metal casing 201, a metal screw 202, a plurality of coaxial line resonators 211 to 220, coupling windows 231 to 241 and coaxial line probes 251a and 251b.

  Here, the plurality of coaxial line resonators 211 to 220 all have the same shape. Among these, the six coaxial line resonators 215 to 220 are a total of six resonators arranged in 2 rows × 3 columns constituting the resonator group, and are arranged in a specific layout. Corresponds to the instrument group.

  The metal screw 202 is a screw for adjusting the resonance frequency of the coaxial line resonators 211 to 220. The coaxial line probes 251a and 251b are probes that excite the two coaxial line resonators 211 and 220 at the outermost end of the filter and serve as input / output terminals of the filter.

  Further, the metal casing 201 is provided with coupling windows 231 to 241 for electromagnetically coupling the coaxial line resonators 211 to 220. In particular, in a resonator group including coaxial line resonators 215 to 220 arranged in 2 rows × 3 columns, coupling windows 235 to 241 are provided so that resonators in adjacent rows and columns are electromagnetically coupled to each other. ing.

  Next, the operation of the bandpass filter according to the second embodiment having such a configuration will be described. In the second embodiment, a coaxial line resonator is used as a plurality of resonators instead of the dielectric resonator used in the first embodiment, and is configured as a so-called comb line filter. . In such a comb line filter, since the coaxial line resonators are magnetically coupled to each other, all the couplings between the resonators in the second embodiment are positive.

  Further, since the second embodiment includes a group of resonators coupled to each other in 2 rows × 3 columns as in the first embodiment, the second embodiment also has the same operation principle as described above. In addition, the formation of the attenuation pole and the delay equalization can be realized without using any negative coupling coefficient between the resonators.

  As described above, according to the second embodiment, coaxial line resonators having the same shape are used as the plurality of resonators, and the resonators are arranged in 2 rows × 3 columns, and their coupling paths form a lattice shape. A resonator group including six coaxial line resonators is included as a constituent element of a plurality of resonators, and the resonator group arranged in such a specific layout and all other coaxial line resonators are combined with each other. By arranging the bandpass filters in such a manner that the coupling coefficient between them is positive, a high-performance bandpass filter having an attenuation pole and a delay equalization function can be obtained.

  Furthermore, in general, the negative inter-resonator coupling coefficient that needs to be realized by using separate parts is not required at all, and therefore, it is possible to avoid an increase in the number of parts at the time of filter manufacture and simplify the circuit configuration. it can.

  In addition, although the above-mentioned FIG. 7 has illustrated about the case where a coaxial line is used, it is also possible to use a suspended line instead of a coaxial line. Furthermore, it is possible to configure not as a comb line filter but as an interdigital filter.

Embodiment 3 FIG.
In the first embodiment, the band-pass filter using dielectric resonators as the plurality of resonators has been described. In the second embodiment, the band-pass filter using coaxial line resonators as the plurality of resonators has been described. Next, in the third embodiment, a band-pass filter using a waveguide resonator as a plurality of resonators will be described.

FIG. 8 is a diagram showing a band-pass filter according to Embodiment 3 of the present invention. The band pass filter of FIG. 8 includes TE ₀₁₁ mode resonators 311 to 317 made of a cylindrical waveguide, coupling windows 331 to 338, 339a and 339b, and rectangular waveguides 351a and 351b.

Here, the plurality of TE ₀₁₁ mode resonators 311 to 317 all have the same shape. Among these, the six TE ₀₁₁ mode resonators 212 to 217 are a total of six resonators arranged in 2 rows × 3 columns constituting the resonator group, and are arranged in a specific layout. It corresponds to a resonator group.

Further, the rectangular waveguides 351a and 351b excite the two TE ₀₁₁ mode resonators 311 and 317 at the outermost end of the filter and serve as input / output terminals of the filter. The TE ₀₁₁ mode resonator 311 and the rectangular waveguide 351a, and the TE ₀₁₁ mode resonator 317 and the rectangular waveguide 351b are electromagnetically coupled by respective coupling windows 339a and 339b provided on the wall surface. .

_Furthermore, on the wall surface of the _{TE 011} mode resonator _311-317, coupling window 331 to 338 for electromagnetically coupling the _{TE 011} mode resonator 311-317 it is provided. In particular, in a resonator group including TE ₀₁₁ mode resonators 312 to 317 arranged in 2 rows × 3 columns, coupling windows 332 to 338 are provided so that resonators in adjacent rows and columns are electromagnetically coupled to each other. It has been.

Next, the operation of the bandpass filter according to the third embodiment having such a configuration will be described. In the third embodiment, a cylindrical waveguide is used instead of the dielectric resonator used in the first embodiment or the coaxial line resonator used in the second embodiment as a plurality of resonators. A TE ₀₁₁ mode resonator composed of a tube is used.

The TE ₀₁₁ mode has a uniform electric field distribution in the circumferential direction as indicated by a dotted line in the TE ₀₁₁ mode resonator 311 in FIG. From this, as shown in FIG. 8, by connecting a TE ₁₀ mode rectangular waveguide having an electric field component in the same direction as that, the TE ₀₁₁ mode resonance is excited, and between adjacent resonators Moreover, it will couple | bond together.

At this time, since all the TE ₀₁₁ mode resonators and their coupling mechanisms have the same shape, the coupling coefficients have the same polarity. Further, since the third embodiment includes a group of resonators coupled to each other in 2 rows × 3 columns, as in the first and second embodiments, the present embodiment is similar to the above-described operation principle. 3 can also realize attenuation pole formation and delay equalization without using any negative coupling coefficient between the resonators.

  As described above, according to the third embodiment, waveguide resonators having the same shape are used as the plurality of resonators, and the resonators are arranged in 2 rows × 3 columns, and the coupling path has a lattice shape. A resonator group composed of a total of six waveguide resonators is included as a component of a plurality of resonators, and the resonator group arranged in such a specific layout and all other waveguide resonators By configuring the bandpass filters so that the coupling coefficients have the same polarity, the high-performance bandpass filter having the attenuation pole and the delay equalization function can be obtained.

  Furthermore, in general, since there is no need for a negative inter-resonator coupling coefficient that must be realized by using separate parts, it is possible to avoid an increase in the number of parts at the time of manufacturing the filter and simplify the circuit configuration. it can.

It is a figure which shows the bandpass filter by Embodiment 1 of this invention. It is a figure which shows the equivalent circuit of the band pass filter by Embodiment 1 of this invention. FIG. 3 is a diagram conceptually disassembling the equivalent circuit of FIG. 2 in Embodiment 1 of the present invention into a plurality of element function circuits. It is a figure which shows the typical passing characteristic and group delay characteristic of the A section of the elemental function circuit shown in FIG. 3 in Embodiment 1 of this invention. It is a figure which shows the typical pass characteristic and group delay characteristic of the B section of the elemental function circuit shown in FIG. 3 in Embodiment 1 of this invention. It is a figure which shows the typical pass characteristic and group delay characteristic of the C section of the elemental function circuit shown in FIG. 3 in Embodiment 1 of this invention. FIG. 4 summarizes numerical examples of parameters in the equivalent circuit shown in FIG. 2 according to the first embodiment of the present invention. FIG. 6 is a diagram showing pass, reflection characteristics, and group delay characteristics when the parameter values shown in FIG. 5 are used for the passband filter according to Embodiment 1 of the present invention. It is a figure which shows the bandpass filter by Embodiment 2 of this invention. It is a figure which shows the bandpass filter by Embodiment 3 of this invention. It is a block diagram of the conventional band pass filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Metal housing, 102 Metal screw, 103 Support stand, 111-120 Dielectric resonator, 131-141 Coupling window, 151a, 151b Coaxial line probe, 201 Metal housing, 202 Metal screw, 211-220 Coaxial line resonator 231-241 Coupling window, 251a, 251b Coaxial line probe, 311-317 TE ₀₁₁ mode resonator (waveguide resonator), 331-338, 339a, 339b Coupling window, 351a, 351b Rectangular waveguide.

Claims (4)

In a bandpass filter composed of a plurality of resonators coupled to each other,
The plurality of resonators all have the same shape, and a resonator group including a total of six resonators arranged in 2 rows × 3 columns is included as a component of the plurality of resonators. The resonators included in the group are all coupled to the resonators in the adjacent rows and columns with the same polarity coupling coefficient, and the remaining resonators other than the resonator group also have the same polarity as the resonator group. A band-pass filter characterized by being coupled by a coupling coefficient. The bandpass filter according to claim 1, wherein
Each of the plurality of resonators includes a cylindrical or rectangular dielectric resonator housed in a metal casing, and the resonators are coupled to each other by a coupling window provided in the metal casing. A band-pass filter characterized by that. The bandpass filter according to claim 1, wherein
Each of the plurality of resonators is configured by a resonator including a coaxial line or a suspended line housed in a metal casing, and each resonator is electromagnetically coupled by a coupling window provided in the metal casing. A band-pass filter characterized by that. The bandpass filter according to claim 1, wherein
Each of the plurality of resonators is composed of a waveguide resonator, and each resonator is coupled by a coupling window provided on a wall surface of the waveguide resonator. .

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