JP4575312B2 - Microwave bandpass filter - Google Patents

Description

  The present invention relates to a multiband microwave bandpass filter having a plurality of pass frequency bands.

  A conventional multiband microwave bandpass filter is configured by separately preparing a plurality of bandpass filters having different pass frequencies and then connecting them appropriately.

  FIG. 9 is a circuit diagram of a conventional multiband microwave bandpass filter (see, for example, Patent Document 1). In FIG. 9, BPF 1b, BPF 2b, and BPF 3b are band-pass filters having different pass frequencies, and each band-pass filter includes a plurality of resonators.

  These band-pass filters BPF1b to BPF3b are connected in parallel via filter inductances (L31b, L41b), (L32b, L42b) and (L33b, L43b), thereby forming a multiband filter. Each set of inductors has a mutual inductance, and plays a role of improving frequency selectivity by forming an attenuation pole in the vicinity of each pass band on the frequency axis.

JP 2004-343390 A (page 8, FIG. 3)

  However, the prior art has the following problems. Since the conventional multiband microwave bandpass filter requires a plurality of bandpass filters having different pass frequencies, the resonators constituting each filter naturally have different resonance frequencies. Therefore, there has been a problem that the types of parts required for the multiband microwave bandpass filter are increased. Further, since it is necessary to arrange a plurality of band pass filters, there is a problem that the size of the entire circuit is sometimes increased.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a microwave bandpass filter that can reduce the types of necessary components and can be miniaturized.

  The band-pass filter according to the present invention is a microwave band-pass filter composed of a plurality of resonators coupled to each other by an electromagnetic effect generated in the vicinity or by direct connection using a transmission line. N unit resonator groups (N is an integer of 2 or more) arranged by coupling resonators having the same shape (two or more integers) are coupled to each other, and one resonator included in each unit resonator group is coupled. Coupling resonators included in the first-stage unit resonator group by coupling N unit resonator groups by coupling the coupling resonators of adjacent unit resonator groups to each other. Is an input terminal and a coupling resonator included in the Nth stage unit resonator group is an output terminal.

  According to the present invention, the unit resonator group formed by coupling adjacent M resonators having the same shape to each other is coupled in N stages to form a multiband microwave bandpass filter. It is possible to obtain a microwave bandpass filter that reduces the types of components and enables miniaturization.

  Hereinafter, preferred embodiments of a microwave bandpass filter of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a microwave bandpass filter according to Embodiment 1 of the present invention. In the microwave bandpass filter of FIG. 1, M coaxial line resonators 1 whose ends are short-circuited (M is an integer of 2 or more and corresponds to M = 3 in FIG. 1) It is covered with a metal casing 2. Further, a part of the metal casing 2 is provided with a coupling window 3 for electromagnetically coupling adjacent coaxial line resonators 1 to each other.

  A structure in which the tips of the M coaxial line resonators 1 are short-circuited can be realized in a combline shape (a shape of comb teeth) or an interdigital shape (a shape in which two comb teeth are alternately combined).

  In this way, the three coaxial line resonators 1 having the same shape are coupled to each other to form one unit resonator group. Furthermore, a microwave band pass filter is formed by coupling N such unit resonator groups (N is an integer of 2 or more, corresponding to N = 3 in FIG. 1).

  More specifically, in FIG. 1, three unit resonator groups 4a, 4b, and 4c are shown. Further, the microwave bandpass filter shown in FIG. 1 is configured such that one coaxial line resonator 1 included in each of the unit resonator groups 4a, 4b, and 4c is defined as a coupling resonator and coupled to each other. The resonator groups 4a, 4b, and 4c are connected to each other.

  A coaxial line probe 5a serving as an input terminal of the microwave bandpass filter is connected to the coupling resonator included in the first-stage unit resonator group 4a. Similarly, a coaxial line probe 5c serving as an output terminal of the microwave bandpass filter is connected to the coupling resonator included in the third-stage unit resonator group 4c. In addition, the figure seen from the side of the microwave band pass filter which has such a connection structure is shown on the right side of FIG.

  Next, the operation of the microwave bandpass filter according to Embodiment 1 of the present invention will be described. FIG. 2 is a circuit diagram for explaining the operation of the microwave bandpass filter according to Embodiment 1 of the present invention. FIG. 2A shows a general equivalent circuit diagram of the bandpass filter. A microwave bandpass filter is generally composed of a resonator and an admittance inverter that connects each resonance circuit. FIG. 2A shows a configuration of N resonators and N + 1 admittance inverters.

  The admittance inverter couples the resonators or the resonator and the input / output terminal, and a band pass filter having a pass band in the vicinity of the resonance frequency of the resonator is obtained. As shown in FIG. 2 (b), in a bandpass filter having a single-pass band that is widely used in general, the resonator includes a resonance circuit composed of one inductor and one capacitor as its equivalent circuit. Is done.

The pass characteristic of the resonator alone exhibits the characteristic that the pass amount is maximum at the resonance frequency of the resonator itself. However, as shown in FIG. 2C, when a resonator is configured by coupling two parallel (or series) resonance circuits having the same resonance frequency, the input admittance is expressed by the following equation. .
j × 2C {ω−ω ₀ + J / (2C)} {ω−ω ₀ −J / (2C)} / (ω−ω ₀ )

The resonance frequency at which the above equation becomes 0 is two different frequencies of ω = ω ₀ ± J / (2C). Therefore, the pass characteristic of the resonator shown in FIG. 2C has two peaks on the frequency axis. When such a resonator is used as a component of the filter shown in FIG. A bandpass filter having two different passbands can be obtained.

  Based on the same consideration, it is derived that a total of M resonance circuits coupled to each other have different M resonance frequencies, and a unit resonator group including M resonators is designated as the resonator shown in FIG. It can be seen that a bandpass filter having a total of M passbands can be obtained.

  The microwave bandpass filter according to the first embodiment shown in FIG. 1 includes one unit resonator group including three coaxial line resonators arranged in a comb line shape with M = 3. Corresponds to a total of three stages connected as the resonator of FIG. FIG. 3 is a circuit block diagram of the microwave passband filter according to Embodiment 1 of the present invention. Therefore, it can be seen that the first embodiment is a triple-band microwave bandpass filter having three different passbands as described above.

  As described above, according to the first embodiment, the unit resonator group including M coaxial line resonators coupled to each other is used as a constituent unit, and the unit resonator groups are connected in N stages to thereby form the microwave bandpass filter. By configuring this, a bandpass filter having M different passbands can be obtained. At this time, each coaxial line resonator alone can be a resonator having the same resonance frequency and the same shape.

  As a result, compared to conventional multi-band microwave bandpass filters that require resonators with different resonance frequencies, the number of required components can be reduced, and further, the effect of the filter can be increased. Even when N stages are connected, a microwave band-pass filter that can be miniaturized can be realized.

Embodiment 2. FIG.
FIG. 4 is a configuration diagram of the microwave bandpass filter according to the second embodiment of the present invention. The microwave bandpass filter in FIG. 4 includes a microstrip line 21, a through hole 22, microstrip lines 23a and 23b serving as input / output terminals, and a microstrip line 24 connecting them on a dielectric substrate 20.

  The microstrip line 21 functions as a microstrip line resonator by electrically short-circuiting the tip of the microstrip line 21 through the through hole 22. The microstrip lines 23a and 23b serve as input / output terminals. Further, the microstrip line 24 is a microstrip line that connects the microstrip lines 21 that function as resonators, or the microstrip lines 21 that function as resonators and the microstrip lines 23a and 23b that serve as input / output terminals.

  Next, the operation of the microwave bandpass filter according to Embodiment 2 of the present invention will be described. Compared with the microwave bandpass filter in the first embodiment, the microwave bandpass filter in the second embodiment is obtained by reducing the number of filter stages N from three to two and then changing the coaxial line resonator to a microstrip line. It is replaced with. Furthermore, the inter-resonator coupling obtained by arranging three (corresponding to M = 3) coaxial line resonators in a comb line shape is realized by a quarter wavelength line.

  FIG. 5 is a circuit block diagram of the microwave passband filter according to the second embodiment of the present invention. Since the quarter wavelength line is approximately equivalent to the admittance inverter included in FIG. 2A, the second embodiment is a multiband microwave band similar to the first embodiment. It exhibits the characteristics of a pass filter. Note that the microstrip lines 21 and 24 have a length of about a quarter wavelength at a frequency intermediate between the lowest pass center frequency and the highest pass center frequency.

  As described above, according to the second embodiment, the microwave band-pass filter is configured by connecting the unit resonator groups in N stages with the M microstrip line resonator groups coupled to each other as the structural unit. Thus, a bandpass filter having M different passbands can be obtained. At this time, each single microstrip line resonator can be a resonator having the same shape and the same resonance frequency.

  As a result, compared to conventional multi-band microwave bandpass filters that require resonators with different resonance frequencies, the number of required components can be reduced, and further, the effect of the filter can be increased. Even when N stages are connected, a microwave band-pass filter that can be miniaturized can be realized.

Embodiment 3 FIG.
FIG. 6 is a configuration diagram of a microwave bandpass filter according to Embodiment 3 of the present invention. In the microwave band pass filter of FIG. 6, the dielectric resonator 31 is covered with a metal casing 32 serving as an outer conductor. A coupling window 33 for electromagnetically coupling adjacent dielectric resonators 31 is provided on a part of the inner wall of the metal housing 32.

  In the microwave bandpass filter shown in FIG. 6, three dielectric resonators 31 (corresponding to M = 3) having the same shape are coupled to each other to form one unit resonator group. Furthermore, a microwave band pass filter is formed by coupling three unit resonator groups 34a, 34b, 34c (corresponding to N = 3) to each other.

  A coaxial line probe 35a serving as an input terminal of the microwave bandpass filter is disposed adjacent to one coupling resonator included in the unit resonator group 34a. Similarly, in one coupling resonator included in the unit resonator group 34c, a coaxial line probe 35c serving as an output terminal of the microwave bandpass filter is disposed in proximity.

  The support base 36 is a support base for fixing each dielectric resonator 31 to the metal casing 32, and is made of a material having a low dielectric constant and a low loss.

  Next, the operation of the microwave bandpass filter according to Embodiment 3 of the present invention will be described. Compared with the microwave bandpass filter in the first embodiment, the microwave bandpass filter in the third embodiment is obtained by replacing the resonator from the coaxial line resonator 1 to the dielectric resonator 31.

  Since the microwave bandpass filter in the third embodiment is electromagnetically coupled between the adjacent dielectric resonators 31 through the coupling window 33, the multiband microwave bandpass similar to that in the first embodiment is performed. It will exhibit the characteristics of the filter.

  As described above, according to the second embodiment, the microwave resonator bandpass filter is configured by connecting the unit resonator groups in N stages with the unit resonator group including M dielectric resonators coupled to each other as a constituent unit. By configuring this, a bandpass filter having M different passbands can be obtained. At this time, each dielectric resonator alone can be a resonator having the same resonance frequency and the same shape.

  As a result, compared to conventional multi-band microwave bandpass filters that require resonators with different resonance frequencies, the number of required components can be reduced, and further, the effect of the filter can be increased. Even when N stages are connected, a microwave band-pass filter that can be miniaturized can be realized.

Embodiment 4 FIG.
FIG. 7 is a configuration diagram of the microwave bandpass filter according to the fourth embodiment of the present invention. The microwave bandpass filter in FIG. 7 includes a rectangular waveguide resonator 41a having a length of about ½ wavelength and a rectangular waveguide resonator 41b having a length of about ¼ wavelength. 42 is configured inside. Further, an inductive metal post 43 is disposed in order to adjust the coupling amount between the rectangular waveguide resonators 41a and 41b.

  The microwave bandpass filter shown in FIG. 7 can be considered to be composed of two unit resonator groups 44a and 44b coupled to each other. A rectangular waveguide 45 a serving as an input terminal of the microwave bandpass filter is connected to one coupling resonator included in the unit resonator group 44 a via a coupling window 46. Similarly, a rectangular waveguide 45b serving as an output terminal of the microwave bandpass filter is connected to one coupling resonator included in the unit resonator group 44b via a coupling window 46.

  Next, the operation of the microwave bandpass filter according to Embodiment 4 of the present invention will be described. Compared with the microwave bandpass filter in the second embodiment, the microwave bandpass filter in the fourth embodiment is obtained by replacing the microstrip line resonator with rectangular waveguide resonators 41a and 41b.

  In addition, the microwave bandpass filter according to the fourth embodiment realizes the coupling between the resonators obtained by the quarter wavelength line and the input / output terminal by the inductive metal post 43 or the coupling window 46. Therefore, the characteristics of the multiband microwave bandpass filter similar to those of the second embodiment are exhibited.

  As described above, according to the fourth embodiment, the unit resonator group composed of M waveguide resonators coupled to each other is used as a structural unit, and the unit resonator groups are connected in N stages to pass through the microwave band. By configuring the filter, a bandpass filter having M different passbands can be obtained. At this time, each waveguide resonator unit can be a resonator having the same shape and the same resonance frequency.

  As a result, the circuit design can be made easier and the circuit scale can be reduced as compared with a conventional multiband microwave bandpass filter that requires resonators and filters having different resonance frequencies.

Reference Example FIG. 8 is a configuration diagram of a microwave bandpass filter in a reference example of the present invention. The microwave band pass filter in FIG. 8 is composed of cubic waveguide resonators 51 having the same length of the three sides, and notches 52a and 52b are formed at the corners of the respective waveguide resonators 51. Is provided.

  The two waveguide resonators 51 share a wall surface, and a coupling window 53a is formed on the wall surface. The two waveguide resonators 51 are connected to a rectangular waveguide 55a serving as an input terminal and a rectangular waveguide 55b serving as an output terminal via another coupling window 53b.

Next, the operation of the microwave bandpass filter in the reference example of the present invention will be described. Compared with the microwave bandpass filter in the fourth embodiment, the microwave bandpass filter in the present reference example is a triple mode in which unit resonator groups 44a and 44b composed of three waveguide resonators are composed of a single cavity. This is a substitute for the waveguide resonator 51 of FIG.

  Since each of the two waveguide resonators 51 has a cubic shape, a TE10 mode having electric field components in three directions of Ex, Ey, and Ez can propagate as shown in FIG. The resonance modes having Ey and Ez components are coupled to each other by the notch 52a, and the resonance modes having Ex and Ey components are coupled to each other by the notch 52b.

  Therefore, each of the two waveguide resonators 51 is equivalent to three single-mode resonators (corresponding to M = 3) coupled to each other, and between the two adjacent waveguide resonators 51. Then, the resonance modes having the Ey component are coupled through the coupling window 53a, and the mode is coupled to the rectangular waveguide 55a serving as the input terminal and the rectangular waveguide 55b serving as the output terminal through the coupling window 53b. To do.

Therefore, the microwave bandpass filter in this reference example is expressed by the block diagram of FIG. 5 used in the description of the second embodiment, and similarly to the second and fourth embodiments, it is a multiband filter. It exhibits the characteristics of a microwave bandpass filter.

As described above, according to the reference example , the unit resonator group composed of triple mode waveguide resonators corresponding to M = 3 is used as a constituent unit, and the unit resonator groups are connected in N stages to pass through the microwave band. By configuring the filter, a bandpass filter having three different passbands can be obtained.

  As a result, compared to a conventional multiband microwave bandpass filter that requires resonators having different resonance frequencies, the number of necessary components can be reduced and the circuit can be greatly reduced in size.

  When a dual mode waveguide resonator is used, a multiband microwave bandpass filter having two different passbands can be formed.

It is a block diagram of the microwave bandpass filter in Embodiment 1 of this invention. It is a circuit diagram for demonstrating operation | movement of the microwave band pass filter in Embodiment 1 of this invention. It is a circuit block diagram of the microwave bandpass filter in Embodiment 1 of this invention. It is a block diagram of the microwave band pass filter in Embodiment 2 of this invention. It is a circuit block diagram of the microwave bandpass filter in Embodiment 2 of this invention. It is a block diagram of the microwave bandpass filter in Embodiment 3 of this invention. It is a block diagram of the microwave bandpass filter in Embodiment 4 of this invention. It is a block diagram of the microwave bandpass filter in the reference example of this invention. It is a circuit diagram of the conventional multiband microwave bandpass filter.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Coaxial line resonator 2, 32, 42 Metal housing 3, 33, 46, 53a, 53b Coupling window, 4a-4c, 34a-34c, 44a, 44b Unit resonator group, 5a, 5c, 35a, 35c Coaxial line probe, 20 Dielectric substrate, 21, 23a, 23b, 24 Microstrip line, 22 Through hole, 31 Dielectric resonator, 36 Support base, 41a, 41b Rectangular waveguide resonator, 43 Metal post, 45a, 45b, 55a, 55b Rectangular waveguide, 51 Waveguide resonator, 52a, 52b Notch.

Claims (7)

In a microwave bandpass filter composed of a plurality of resonators coupled to each other by direct connection using electromagnetic effects or transmission lines generated in the vicinity,
N unit resonator groups (N is an integer of 2 or more) are formed by connecting adjacent M resonators (M is an integer of 2 or more) having the same shape, and are included in each unit resonator group. One resonator is defined as a coupling resonator, and the coupling resonators of adjacent unit resonator groups are coupled to each other so that N unit resonator groups are coupled to each other. A microwave band-pass filter comprising: a coupling resonator included in a group as an input terminal; and a coupling resonator included in an N-th unit resonator group as an output terminal. The microwave bandpass filter according to claim 1,
Each of the N unit resonator groups has a configuration in which M resonators including coaxial lines whose one ends are short-circuited are arranged in an interdigital form or a comb line form and coupled to each other. Microwave bandpass filter. The microwave bandpass filter according to claim 1,
Each of the N unit resonator groups has a configuration in which M resonators composed of microstrip lines whose one ends are short-circuited are arranged in an interdigital form or a comb line form and coupled to each other. A microwave bandpass filter. The microwave bandpass filter according to claim 1,
Each of the N unit resonator groups has a configuration in which M dielectric resonators housed in a cut-off metal cavity are arranged side by side, and a coupling window is provided in each metal cavity to be coupled to each other. A microwave bandpass filter characterized by comprising: The microwave bandpass filter according to claim 1,
Each of the N unit resonator groups has a configuration in which M waveguide cavity resonators are arranged side by side, and a coupling window is provided on each cavity wall surface to be coupled to each other. Bandpass filter. The microwave bandpass filter according to claim 4 or 5,
Each of the N unit resonator groups uses a dual mode resonator as each resonator when M = 2. The microwave bandpass filter according to claim 4 or 5,
Each of the N unit resonator groups uses a triple mode resonator as each resonator when M = 3.

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