JP6265478B2 - Tunable dual-band bandpass filter - Google Patents

Description

  The present invention relates to a frequency tuning and banding of a dual-band bandpass filter used for transmitting and receiving signals in a device using high frequency or microwave, for example, mobile communication, satellite communication, fixed microwave communication, and other communication technology fields. The present invention relates to a technique for simultaneously improving the internal passage characteristics.

  In recent years, data communication such as video has increased explosively, and network capacity and frequency resources are expected to become a global problem. On the other hand, there is a need for the development of a microwave filter for mobile communication base stations that can simultaneously realize high-speed, large-capacity communication and effective use of frequency resources. Furthermore, in recent years, communication devices that support a plurality of frequency bands are desired.

  As a method for realizing high-speed and large-capacity communication, a method of communicating using two frequency bands at the same time has been proposed, and as its elemental technology, a dual-band bandpass filter that allows two frequency bands to pass simultaneously has been proposed. Yes.

Conventionally, a dual-band bandpass filter characterized by having two passbands has the following configuration method.
As shown in FIG. 1, a plurality of dual-band resonators N1, N2, and N3 that resonate at two frequencies are subordinately coupled, and coupled to input / output ports M1 and M2 at both ends of the subordinate coupling, respectively, thereby forming the filter 100. (Non-patent document 1).

  The dual-band resonators N1, N2, and N3 have an even / odd mode, and a dual-band resonator having two pass bands is configured by controlling these two modes. In this filter 100, the input / output ports M1 and M2 are directly coupled to the dual-band resonators N1 and N3 at both ends, and it is necessary to determine a connection position at which desired characteristics can be simultaneously obtained in both of the two passbands.

On the other hand, a bandpass filter having a steep cutoff characteristic is required for effective use of frequency resources. In general, a steep cut-off characteristic can be realized by increasing the number of resonators. However, since normal conductors such as copper have resistance, the insertion loss increases as the number of stages increases, making it impossible to achieve both low loss and sharp cutoff characteristics. As one method for solving this problem, for example, a superconducting bandpass filter has been proposed (Patent Document 1). Superconductors have a surface resistance that is 2 to 3 orders of magnitude lower than that of copper in the microwave band, so even if the number of stages is increased, insertion loss can be kept small, thus realizing both low loss and sharp cutoff characteristics. be able to.
As a method corresponding to a plurality of frequency bands, a center frequency tunable band pass filter capable of changing the center frequency of the band pass filter has been proposed.
FIG. 2 is a configuration example of a conventional superconducting tunable bandpass filter. A dielectric plate S10 is disposed above the microstrip filter pattern S1 formed on the dielectric substrate S5. By changing the distance h between the dielectric S10 and the filter pattern S1 using an actuator such as a piezoelectric element, the electric field distribution radiated from the filter pattern S1 is changed to vary the center frequency (Patent Document 2).

JP 2002-57506 A Japanese Patent No. 3535469

Jia-Sheng Hong, Wenxing Tang, “Dual-band filter based on non-degenerate dual-mode slow-wave open-loopresonators,” IEEE MTT-S International Microwave Symposium Digest, pp.861-864, 2009.

The dual-band bandpass filter realizes a dual-band bandpass filter using a dual-band resonator that realizes resonance frequencies of two passbands with one resonator. The center frequency of each band of the dual-band bandpass filter shown in FIG. 1 is determined by the even / odd mode generated in each dual-band resonator N1, N2, and N3. Since the odd-mode portions of the dual-band resonators N1, N2, and N3 are common to the even mode, adjusting the odd mode also affects the even mode. The bandwidth of each band is controlled by the distance between the resonators of the dual-band resonators N1, N2, and N3. When center frequency tuning is performed using the dielectric plate S10 for the dual-band bandpass filter, The dielectric plate covers the entire upper surface of the pass filter. Therefore, since it affects both the even and odd modes of the dual-band bandpass filter, the center frequency can be tuned, but it is difficult to tune the even and odd modes independently. In addition, since the entire filter is covered with a dielectric plate, the electromagnetic field distribution between the dual-band resonators is also affected, so that the bandwidth also changes. Further, when the shift amount of the center frequency is increased, the in-band pass characteristic is deteriorated. Therefore, a trimming mechanism for adjusting the resonator frequency of each resonator is required separately from the frequency tuning mechanism. Here, trimming is a method for improving the in-band pass characteristics.
The subject of this invention is made | formed in order to solve the subject of the above prior arts. In other words, the center frequency of each of the two passbands can be tuned (varied) independently, and the in-band pass characteristics that deteriorate after center frequency tuning can be tuned without using a new trimming mechanism. It is to realize a center frequency tunable dual band bandpass filter that can be improved.

As shown in FIG. 3, a typical dual-band resonator used in the present invention basically has a plane of symmetry AB of a dual-band resonator having a structure in which a stub 11 is added to a half-wave resonator 10. / A dual-band resonator that forms a magnetic wall and operates in two frequency bands by odd-mode resonance and even-mode resonance, in which the half-wave resonator 10 becomes an odd-mode resonator, and the half-wave resonator and the stub are even It becomes a resonator by mode, and the resonator length can be adjusted so that the odd mode resonates on the low frequency side and the even mode on the high frequency side, or the odd mode can resonate on the high frequency side and the even mode on the low frequency side. A dual-band resonator in which a ground conductor is disposed on a lower surface of a dielectric having a predetermined thickness, a strip conductor is disposed on an upper surface, and the strip conductor has an open end (a strip is not connected) A thin strip conductor having a width g that penetrates deeply, and a front end portion of the groove and an end surface of the strip conductor have a width d. An odd-mode resonator having a shape made of a conductor and an even-mode resonator having a shape in which a stub 11 having a length l is connected to an end surface on the side opposite to the open end;
When a current flows into the plane of symmetry A-B, it functions as an odd mode resonator, and when a current does not flow into the plane of symmetry A-B, it functions as an even mode resonator. It has been found that this dual band resonator has a tunable structure.

That is, according to the present invention, as shown in FIG. 3, the plane of symmetry AB of the dual-band resonator having a structure in which the stub 11 is added to the half-wave resonator 10 forms an electric / magnetic wall, and the odd-mode resonance and even A dual-band resonator operating in two frequency bands by mode resonance, in which the half-wave resonator 10 becomes an odd-mode resonator, the half-wave resonator and the stub become an even-mode resonator, and the odd-mode resonator has a low frequency. The dual-band resonator can adjust the resonator length so that the even mode resonates on the high frequency side, or can resonate the odd mode on the high frequency side and the even mode on the low frequency side,
A ground conductor is disposed on the lower surface of a dielectric having a predetermined thickness, a strip conductor is disposed on the upper surface, and the strip conductor is cut at an open end (where the strip is not connected). An odd-mode resonator having a groove having a width g that penetrates deeply, a tip portion of the groove and an end surface of the strip conductor having a width d and a single symmetrical strip conductor, and a length When the current flows into the plane of symmetry AB, it functions as an odd mode resonator, and the plane of symmetry AB plane. A tunable dual characterized in that a dielectric rod 25 is provided in the upper space of the stub 11 in the dual band resonator characterized in that it functions as an even mode resonator when no current flows into the stub. It is a band resonator.
Further, according to the present invention, in the tunable dual band resonator described above, the dielectric 25 is moved, and the position of the dielectric 25 is half-wave resonance at an intermediate portion of the length combining the half-wave resonator 10 and the stub 11. This is a tunable dual band resonator provided in the upper space of the resonator 10 and capable of frequency tuning independently of the resonant frequency of the even mode and the odd mode.

Further, according to the present invention, the plane of symmetry AB of the dual-band resonator having a structure in which the stub 11 is added to the half-wave resonator 10 forms an electric / magnetic wall, and two frequencies are generated by odd-mode resonance and even-mode resonance. A dual-band resonator operating in a band, in which the half-wave resonator 10 is an odd-mode resonator, the half-wave resonator and the stub are even-mode resonators, the odd mode is on the low frequency side, and the even mode is the high frequency side. A dual-band bandpass filter capable of adjusting the resonator length so as to resonate on the side or resonating the odd mode on the high frequency side and the even mode on the low frequency side, and having a predetermined thickness of dielectric A ground conductor is disposed on the lower surface, a strip conductor is disposed on the upper surface, and the strip conductor is a single thin strip conductor cut at an open end (where the strip is not connected). An odd-mode resonator having a groove having a width g that penetrates deeply, a tip portion of the groove and an end surface of the strip conductor having a width d and a symmetrical strip conductor, When the current flows into the plane of symmetry AB, it functions as an odd mode resonator, and the plane of symmetry AB is formed. A dual-band bandpass filter that functions as an even mode resonator when current does not flow into the surface, and is provided with dielectric rods 25 in the upper spaces of the half-wave resonator 10 and the stub 11 respectively. In dual-band bandpass filter,
A tunable dual band characterized in that a dielectric rod 25 is provided in the upper space of the stub 11 or in the upper space of the half-wave resonator 10 in the middle of the length of the half-wave resonator 10 and the stub 11 combined. It is a band pass filter.

Further, according to the present invention, the plane of symmetry AB of the dual-band resonator having a structure in which the stub 11 is added to the half-wave resonator 10 forms an electric / magnetic wall, and two frequency bands are obtained by odd-mode resonance and even-mode resonance. The half-wave resonator 10 is an odd-mode resonator, the half-wave resonator and the stub are even-mode resonators, the odd mode is on the low frequency side, and the even mode is on the high frequency side. A dual-band bandpass filter that can adjust the resonator length so as to resonate or resonate the odd mode on the high frequency side and the even mode on the low frequency side. Is a thin strip conductor in which a strip conductor is disposed on the upper surface, and the strip conductor is cut at an open end (where the strip is not connected). Thus, the odd-mode resonator having a groove g of a deep width and having a width d, the end of the groove and the end surface of the strip conductor having a width d, and an odd mode resonator having a length l When the current flows into the plane of symmetry AB, it functions as an odd mode resonator, and the plane of symmetry AB is in the plane of symmetry AB. Between the dual-band resonator, which functions as an even-mode resonator when current does not flow, and the same dual-band resonator whose direction is changed by 180 degrees at a constant interval m, the waveguide end A dual-band bandpass filter having a structure in which an H-type waveguide 12 having a length of n is provided, and a tunable dual-band in which dielectric rods 25 are respectively provided in the upper spaces of the half-wave resonator 10 and the stub 11 Band In the pass filter, dielectric rods 25 are respectively provided in the upper space of the stub 11 or in the upper space of the half-wave resonator 10 in the middle portion of the combined length of the half-wave resonator 10 and the stub 11. It is a tunable dual band bandpass filter.
Further, according to the present invention, the plane of symmetry AB of the dual-band resonator having a structure in which the stub 11 is added to the half-wave resonator 10 forms an electric / magnetic wall, and two frequencies are generated by odd-mode resonance and even-mode resonance. A dual-band resonator operating in a band, in which the half-wave resonator 10 is an odd-mode resonator, the half-wave resonator and the stub are even-mode resonators, the odd mode is on the low frequency side, and the even mode is the high frequency side. A dual-band bandpass filter capable of adjusting the resonator length so as to resonate on the side or resonating the odd mode on the high frequency side and the even mode on the low frequency side, and having a predetermined thickness of dielectric A ground conductor is disposed on the bottom surface, a strip conductor is disposed on the top surface, and the thin strip conductor is a thin strip that is cut at the open end (where the strip is not connected). An odd-mode resonator having a groove having a width g which penetrates deeply and having a grooved end and a strip conductor having a width d, the shape of the odd-mode resonator having a symmetrical shape; When the stub 11 having the length l is connected to the end face opposite to the open end, the even mode resonator has a shape, and when a current flows into the plane of symmetry AB, it functions as an odd mode resonator, and the plane of symmetry A- When current does not flow into the B-plane, between the dual-band resonator that functions as an even-mode resonator and the same dual-band resonator that changes the direction by 180 degrees at a fixed interval m, A dual-band bandpass filter having a structure provided with an H-type waveguide 12 having a length n at the end of the waveguide, wherein the coupling coefficient of the even-mode passband is adjusted by changing m, and then n By adjusting the even A dual-band bandpass filter capable of individually adjusting only the coupling coefficient of the odd-mode passband while keeping the coupling coefficient of the mode passband constant, and is an upper space of the half-wave resonator 10 and the stub 11 In the tunable dual-band bandpass filter in which the dielectric rods 25 are respectively provided, the upper space of the stub 11 or the upper space of the half-wave resonator 10 in the middle of the length of the half-wave resonator 10 and the stub 11 combined. The tunable dual-band bandpass filter is characterized in that each is provided with a dielectric rod 25.

Furthermore, the adjustment method of the frequency tuning shift amount in the two-stage tunable dual-band bandpass filter of the present invention is such that only each dielectric rod 25 provided in the upper space of each half-wave resonator 10 is tunable dual. This is a method of adjusting the shift amount of frequency tuning in which only the odd-mode passband characteristics are adjusted by adjusting all the distances to the bandband pass filter to the same height.
Furthermore, the adjustment method of the frequency tuning shift amount in the two-stage tunable dual-band bandpass filter of the present invention is such that only each dielectric rod 25 provided in the upper space of each stub 11 is tunable dual-band bandpass filter. The frequency tuning shift amount adjustment method adjusts the passband characteristics only in the even mode by adjusting all the distances to the same height.

Furthermore, the method (trimming) for improving the degradation of the in-band pass characteristic that occurs after frequency tuning in the two-stage tunable dual-band bandpass filter of the present invention (trimming) is provided in each upper space of each half-wave resonator 10. This is a method for improving the in-band pass band characteristic of only the odd mode by individually adjusting the distance between only the dielectric rod 25 and the tunable dual band band pass filter.
In addition, the method (trimming) for improving the degradation of the in-band pass characteristic that occurs after frequency tuning in the two-stage tunable dual band bandpass filter of the present invention is obtained by using each dielectric rod provided in the upper space of each stub 11. No. 25 is a method for improving the in- band pass band characteristics of only the even mode by individually adjusting the distance to the tunable dual band band pass filter.

Further, according to the present invention, the plane of symmetry AB of the dual-band resonator having a structure in which the stub 11 is added to the half-wave resonator 10 forms an electric / magnetic wall, and two frequencies are generated by odd-mode resonance and even-mode resonance. A dual-band resonator operating in a band, in which the half-wave resonator 10 is an odd-mode resonator, the half-wave resonator and the stub are even-mode resonators, the odd mode is on the low frequency side, and the even mode is the high frequency side. A dual-band bandpass filter capable of adjusting the resonator length so as to resonate on the side or resonating the odd mode on the high frequency side and the even mode on the low frequency side, and having a predetermined thickness of dielectric A ground conductor is disposed on the bottom surface, a strip conductor is disposed on the top surface, and the thin strip conductor is a thin strip that is cut at the open end (where the strip is not connected). An odd-mode resonant waveguide having a groove with a width g that penetrates deeply, and a tip end portion of the groove and an end surface of the strip conductor each having a width d and a symmetrical strip conductor. When the current flows into the plane of symmetry AB, the stub 11 having a length l is connected to the end face on the opposite side of the open end. A dual-band resonator characterized by acting as an even-mode resonant waveguide when no current flows into plane A-B, and the same dual-band resonator whose direction is changed by 180 degrees at a constant interval m And a dual-band resonator having a structure in which an H-type waveguide 12 having a length n at the end of the waveguide is provided, and the same dual-band whose direction is changed by 180 degrees at a fixed interval m Between the resonator, the waveguide end Having a structure including a total of three dual-band resonators including a dual-band resonator having a structure in which an H-type waveguide 12 having a length n is provided, and the first dual-band resonator and the third dual-band resonator. A characteristic is that a feeding conductor line 13 is provided along the odd-mode resonant waveguide 10 of the dual-band resonator, one feeding conductor line 13 is set as an input side, and the other feeding conductor line 13 is set as an output side. A tunable dual band bandpass filter having a dielectric rod 25 in the upper space of each of the half-wave resonator 10 and the stub 11 in the multistage dual band bandpass filter having the upper space of the stub 11 or the half wavelength A tunable characterized in that dielectric rods 25 are provided in the upper spaces of the half-wave resonator 10 in the middle part of the length of the resonator 10 and the stub 11 combined. It is a dual band bandpass filter.
Furthermore, the adjustment method of the frequency tuning shift amount in the three-stage tunable dual-band bandpass filter according to the present invention is such that only the dielectric rods 25 respectively provided in the upper spaces of the half-wave resonators 10 are tunable dual-band. By adjusting the distance from the band pass filter, the pass band characteristic can be adjusted only for the odd mode .
The method of adjusting the amount of frequency tuning shift in the three-stage tunable dual-band bandpass filter according to the present invention is such that only each dielectric rod 25 provided in the upper space of each stub 11 is tunable dual-band bandpass filter. By adjusting the distance, the passband characteristic can be adjusted only in the even mode .

Further, a method (trimming) for improving the degradation of the in-band pass characteristic that occurs after frequency tuning in the three-stage tunable dual-band bandpass filter of the present invention (trimming) is provided in each of the upper spaces of the half-wave resonators 10. This is a method for improving the in-band pass band characteristic of only the odd mode by individually adjusting the distance between only the dielectric rod 25 and the tunable dual band band pass filter.
Further, the method (trimming) for improving the degradation of the in-band pass characteristic that occurs after frequency tuning in the three-stage tunable dual-band bandpass filter according to the present invention is obtained by using each dielectric rod provided in the upper space of each stub 11. No. 25 is a method for improving the in-band pass band characteristics of only the even mode by individually adjusting the distance to the tunable dual band band pass filter.

According to the present invention, the design freedom of the center frequency, bandwidth, and input / output matching of each of the two pass bands is high, and the center frequencies of the two pass bands can be independently tuned. It is possible to provide a tunable dual-band resonator capable of improving in-band pass characteristics that deteriorate after tuning, and a tunable dual-band bandpass filter using the tunable dual-band resonator.

Conventional example Conventional example Structure of dual band resonator used in the present invention Sectional view of a dual-band resonator used in the present invention Current distribution diagram of dual-band resonator used in the present invention Arrangement position of dual band resonator and dielectric rod used in the present invention Frequency characteristics when the dielectric rod 25 is disposed at the open end of the stub 11 and when the dielectric rod 25 is not provided Arrangement position of dual band resonator and dielectric rod used in the present invention Frequency characteristics when the dielectric rod 25 is arranged at the center of the even-mode resonator and when the dielectric rod 25 is not provided Adjustment of shift amount by height of dielectric rod in tunable dual-band resonator of the present invention (Example 2) Example 3 Adjustment of Shift Amount according to Height of Dielectric Rod in Tunable Dual Band Resonator of the Present Invention Structure of a two-stage dual-band bandpass filter used in the present invention (Example 4) Relationship between inter-resonator distance m and coupling coefficient k when waveguide 12 is not used A change in coupling coefficient k of each pass band when the distance m between the resonators is constant and the length of n of the waveguide 12 is changed (Example 3) Structure of three-stage dual-band bandpass filter used in Example 5 Frequency characteristics of the three-stage dual-band bandpass filter used in Example 5 Arrangement position of dielectric rod of dual band bandpass filter when adjusting only center frequency of even mode (Example 6) Frequency characteristics of a tunable dual band bandpass filter when only the center frequency of the even mode is adjusted (Example 6) Arrangement position of dielectric rod of dual band bandpass filter when adjusting only center frequency of odd mode (Example 7) Frequency characteristics of a tunable dual-band bandpass filter when only the center frequency of the odd mode is adjusted (Example 7) Reflection characteristics in even mode (near 5.0 GHz) in Fig. 18 (S11) Side view of FIG. Reflection characteristics (S11) of odd mode (around 3.5 GHz) in Fig. 20 (Example 8) 19 side view Example 10: Change in frequency shift amount when the dielectric rod 25 is arranged and the radius r of the dielectric rod is changed FIG. 19 is a top view (Example 11). Example 11 Changes in Frequency Shift Amount When Ellipsoidal Dielectric Rod 25 is Arranged and Dielectric Rod Length s is Changed

As the dielectric substrate used in the present invention, a known dielectric can be used, and a substrate excellent in moldability is preferable. In order to suppress dielectric loss, a material having a low dielectric loss tangent is desirable. Also, a material with high thermal conductivity is desirable in order to suppress temperature rise.
As the normal conductor and the superconductor used for the strip conductor and the microstrip line, any known one can be used.
The structure as a typical structural unit of the resonator used in the present invention is shown in the center of FIG. The left side of FIG. 3 shows a half-wave resonator (odd mode resonance) 10, which basically has a hairpin-shaped symmetrical microstrip line structure. The right side of FIG. 3 shows a stub.
In the center of FIG. 3, the plane A-B of the dual-band resonator, which is a structure in which the stub 11 is added to the half-wave resonator 10 having a hairpin shape, forms an electric / magnetic wall, and is formed by odd mode resonance and even mode resonance. A dual-band resonator operating in two frequency bands, in which the half-wave resonator 10 is an odd-mode resonator, the half-wave resonator 10 and the stub 11 are even-mode resonators, A dual-band resonator that can adjust the resonator length so that the even mode resonates on the high frequency side, or can resonate the odd mode on the high frequency side and the even mode on the low frequency side, and has a predetermined thickness. A ground conductor is disposed on the bottom surface of the dielectric, a strip conductor is disposed on the top surface, and the strip conductor having the hairpin shape is cut at the open end (where the strip is not connected). A thin strip conductor having a deep groove g having a width g, and the end of the groove and the end surface of the strip conductor are formed of a single symmetrical strip conductor having a width d. When an odd-mode resonator is composed of an even-mode resonator having a shape in which a stub 11 having a length l is connected to the end surface opposite to the open end, and current flows into the plane of symmetry AB, the odd-mode resonator is It is a dual-band resonator that functions as an even mode resonator when no current flows into the plane of symmetry AB.
The dual band resonator can be used alone or in combination to form a dual band bandpass filter.
Next, the structure will be described in detail. However, since those skilled in the art can make a dual band bandpass filter having a similar structure by taking this structure into consideration, the present invention is limited to this structure only. Should not.

The rod 25 is preferably made of a material having a high dielectric constant and a low dielectric loss tangent, and examples thereof include sapphire and Kyocera SV380. (See FIGS. 6 and 8)
Further, the shape of the rod 25 is not particularly limited in the shape of the cross section, but in the case of a structure in which the rod 25 is pushed by rotation of a screw, a circular cross section is preferable. Further, in the case of a structure in which the rod 25 is brought close to the strip conductor without being rotated, any cross-sectional shape may be used. However, when performing odd-mode frequency tuning, even if the cross section is circular, if the circular cross section of the rod to be approached exceeds the width of the strip conductor, an ellipse is used so as not to exceed the width of the strip conductor. (See Figure 26)
In order to increase the maximum shift amount in even-mode frequency tuning, the radius of the dielectric rod 25 may be increased.
Further, in order to increase the maximum shift amount in the frequency tuning of the odd mode, the dielectric rod 25 may be elliptical and the size of the dielectric rod 25 may be increased in the length direction of the dual band resonator.

The resonator according to the embodiment of the present invention has a microstrip line structure. FIG. 3 is a plan view of one embodiment of a dual-band resonator constructed in accordance with the present invention, and FIG. 4 is a cross-sectional view of FIG. In these drawings, reference numeral 22 denotes a dielectric having a predetermined thickness. A ground conductor 21 is disposed on the lower surface of the dielectric 22, and a strip conductor 23 constituting a dual-band resonator is disposed on the upper surface. (This dielectric 22 is preferably formed using a material having a low dielectric loss tangent in order to suppress dielectric loss, and is preferably formed using a material having high thermal conductivity in order to suppress temperature rise. The ground conductor 21 is a material with a small conductor loss and is preferably a superconductive material.The strip conductor is also a material with a small conductor loss and particularly a superconductive material.) This explanation is based on a resonator using the following microstrip line structure. The same applies to all drawings showing filters.
If necessary, a switch can be provided between 10 and 11 in FIG. 3, but in this embodiment, a switch is not provided.
The AB plane of the dual-band resonator of FIG. 3 forms an electric / magnetic wall and becomes a dual-band resonator that operates in two frequency bands by odd-mode resonance and even-mode resonance. The basic structure is a structure in which a stub 11 is added to the half-wave resonator 10. The half-wave resonator 10 is an odd-mode resonator, and the half-wave resonator 10 and the stub 11 are even-mode resonators.
FIG. 5 shows the current distribution of the dual-band resonator of the present invention. In the case of the odd mode, as shown in FIG. 5A, the current flowing through the dual band resonator flows only through the half-wave resonator 10 and operates as an odd mode resonator. At this time, the bent portion of the half-wave resonator 10 is the central portion of the half-wave resonator 10, and since the voltage is 0 and the current is maximum, it can be regarded as GND. Does not affect. In the even mode, a current flows through the half-wave resonator 10 and the stub 11 as shown in FIG. 5B, and the device operates as a half-wave straight line resonator.
When current flows into the plane of symmetry AB from the above current distribution, it functions as an odd mode resonator, and when current does not flow into the plane of symmetry AB, it functions as an even mode resonator to provide dual-band resonance. Can act as a container.
In this resonator, the resonator length is adjusted so that the odd mode resonates on the low frequency side and the even mode resonates on the high frequency side. In some cases, it is possible to adjust the resonator length so that the odd mode resonates on the high frequency side and the even mode on the low frequency side. By making the half-wave resonator 10 and the stub 11 into a step impedance structure, it is possible to reduce the size.
FIG. 6 is a perspective view of one embodiment of a dielectric rod 25 for performing frequency tuning with a dual-band resonator constructed in accordance with the present invention. The dielectric rod 25 is disposed above the dual band resonator. (This dielectric rod 25 is preferably formed using a material having a low dielectric loss tangent in order to suppress dielectric loss. Also, since the frequency shift amount changes depending on the dielectric constant, the dielectric constant is desired. It is desirable to select the power supply line 24 for inputting / outputting signals to / from the dual-band resonator.
A major feature of the present invention is that the dielectric rod 25 is used so that the resonant frequency of the even mode and the odd mode can be adjusted completely independently. The frequency tuning method using the dielectric rod 25 is performed by changing the capacitance C distributed in the resonator. The most distributed capacitance C of the resonator is at the open end of the resonator. On the other hand, the portion where there is almost no distribution of the capacitance C is the central portion of the half-wave resonator where the current concentration is the largest. In the case of the odd mode, it is a bent portion of the half-wave resonator 10 of FIG. 5A, and in the case of the even mode, the center portion of the half-wave resonator 10 and the half-wave straight line resonator of the stub 11 in FIG. It becomes. Therefore, the frequency is not shifted by the dielectric rod 25 because the capacitance C is not distributed at the place where the current concentration is maximum.
Considering the arrangement position of the dielectric rod 25 in order to independently adjust the resonance frequency in the even / odd mode based on these, in order to adjust only the resonance frequency of the even mode, a dielectric is provided at the open end portion of the stub 11. By arranging the rod, the resonance frequency can be adjusted without affecting the odd mode. On the other hand, when only the odd-mode resonance frequency is adjusted, a dielectric rod is arranged in the central portion of the even-mode resonator (the central portion of the half-wavelength straight line resonator of the half-wave resonator 10 and the stub 11). Since the even-mode current concentration is the maximum, the even-mode resonance frequency does not change, and only the odd-mode resonance frequency can be adjusted.
In order to confirm this, a simulation was performed using a three-dimensional electromagnetic field analysis simulator MW-studio (manufactured by AET). The resonance frequency of the dual-band resonator is 3.5 GHz for the odd mode and 5.0 GHz for the even mode. FIG. 7 shows frequency characteristics when the dielectric rod 25 is arranged at the open end of the stub 11 as shown in FIG. 6 and when the dielectric rod 25 is not present. The dielectric rod 25 has a dielectric constant of 39, and the diameter of the dielectric rod 25 is the same as the width of the dual-band resonator. The diameter of the dielectric rod 25 at this time was 1.0 mm. The length of the dielectric rod 25 was 4.0 mm. The distance between the dual band resonator and the dielectric rod 25 was 0.01 mm.
From FIG. 7, it was confirmed that when there is no dielectric rod 25, the resonance frequencies are 3.5 GHz and 5.0 GHz, and the device operates as a dual-band resonator. When the dielectric rod 25 is disposed at the open end of the stub of the dual-band resonator as shown in FIG. 6, the odd-mode resonance frequency does not change and only the even-mode resonance frequency is lower than that without the dielectric rod 25. It can be seen that there is a large shift.
Next, the frequency when the dielectric rod 25 is arranged at the center of the even mode resonator (half wavelength straight line resonator of the half wavelength resonance 10 and the stub 11) as shown in FIG. 8 and when the dielectric rod 25 is not present. The characteristics are shown in FIG. The dielectric rod 25 has a dielectric constant of 39, and the diameter of the dielectric rod 25 is the same as the width of the dual-band resonator. The diameter of the dielectric rod 25 at this time was 1.0 mm. The length of the dielectric rod 25 was 4.0 mm. The distance between the dual band resonator and the dielectric rod 25 was 0.01 mm. As can be seen from FIG. 9, the even-mode resonance frequency does not change, and only the odd-mode resonance frequency is shifted to a lower frequency than when the dielectric rod 25 is not provided.

FIG. 10 is a diagram illustrating a change in the resonance frequency of the even mode with respect to the height h between the dielectric rod 25 and the dual-band resonator when the dielectric rod 25 is disposed at the open end of the stub 11. From FIG. 10, the resonant frequency of the even mode shifts to a low frequency as the dielectric rod 25 approaches the dual-band resonator. The closer the dielectric rod 25 is to the dual band resonator, the greater the tuning frequency of the even mode can be tuned. At this time, the resonance frequency of the odd mode does not change.

FIG. 11 shows the dielectric rod 25 and the dual band resonator when the dielectric rod 25 is arranged at the center of the even mode resonator (half-wave resonance 10 and half-wave straight line resonator of the stub 11) as shown in FIG. It is a figure which shows the change of the resonant frequency of the odd mode with respect to height h between. From FIG. 11, as the dielectric rod 25 approaches the dual-band resonator, the odd-mode resonance frequency shifts to a low frequency. The closer the dielectric rod 25 is to the dual band resonator, the greater the tuning of the odd mode resonance frequency. At this time, the resonant frequency of the even mode does not change.

FIG. 12 is a plan view of one embodiment of a two-stage dual-band bandpass filter constructed in accordance with the present invention, using a microstrip line structure. In the two-stage dual-band bandpass filter, two dual-band resonators shown in FIG. 3 are arranged, and a waveguide 12 is arranged at the center of the two dual-band resonators. Design conditions are required to design the filter. Here, a dual band bandpass filter having the same ratio bandwidth that is difficult to design in two passbands in the dual band bandpass filter will be described with an example. A Chebyshev function type filter was used for the design. Design conditions are: center frequency on the low frequency side is 3.5 GHz, specific bandwidth 70 MHz (2%), ripple 0.1 dB, center frequency on the high frequency side is 5.0 GHz, specific bandwidth 100 MHz (2%), ripple 0.1
dB. At this time, the coupling coefficient representing the coupling strength between the resonators that determine the specific bandwidth in the two passbands has the same value (0.018).
A major feature of the present invention is that the degree of freedom in designing the bandwidth of the two passbands of the odd mode and the even mode is increased by using the waveguide 12 and extremely reducing the coupling of the half-wave resonator 10. .
In general, the coupling coefficient between resonators is treated as a combined effect of a magnetic field coupling component and an electric field coupling component, and is adjusted by the distance between the resonators. FIG. 13 shows the relationship between the inter-resonator distance m and the coupling coefficient k when the waveguide 12 is not used. From FIG. 13, when the distance m between the resonators is changed, it is difficult to realize the same coupling coefficient in the two pass bands. In other words, if a certain distance m between the resonators is determined, the coupling coefficient between the two passbands is uniquely determined.
To solve this problem, the present invention adjusts the bandwidth of the even-mode passband by the inter-resonator distance m, and then adjusts the bandwidth of the odd-mode passband by the waveguide 12. At that time, it is important to arrange the waveguide at a position where the waveguide 12 does not affect the bandwidth of the even mode pass band. Since the waveguide 12 is coupled to the resonator through a gap, the electric field coupling component is affected. Therefore, in order to prevent the waveguide 12 from affecting the even mode, the waveguide can be ignored by disposing it in the portion where the magnetic field coupling component is the largest. The even-mode resonator portion having the largest even-mode magnetic field corresponds to the portion with the largest current, and is therefore the central portion of the even-mode resonator (half-wavelength resonance 10 and half-wave straight line resonator of the stub 11).
Further, in order to allow the bandwidth of the odd mode passband to be adjusted only by the waveguide 12, it is important not to depend on the inter-resonator distance m, and the half-wave resonator 10 has an open end portion. It is important to make the gap g closer. In general, when the current directions of two adjacent strip lines are opposite to each other, the magnetic field radiated to the outside decreases as the distance between the two adjacent strip lines decreases. By utilizing this fact, it is possible to reduce the coupling of the odd-mode passband by the half-wave resonator 10 and to reduce the dependency due to the inter-resonator distance m.
The reason why the odd mode coupling coefficient in FIG. 13 is extremely small with respect to the even mode and the amount of change with respect to the inter-resonator distance m is small is that the gap g at the open end of the half-wave resonator 10 is narrowed. It is. That is, it is necessary to select the gap g of the open end portion of the half-wave resonator 10 in which the change amount of the odd mode coupling coefficient is small with respect to the inter-resonator distance m.
FIG. 14 shows the coupling coefficient k of each passband when the distance m between the resonators of FIG. 12 is constant and the length of n of the waveguide 12 is changed. From FIG. 14, it can be seen that when the coupling coefficient in the odd-mode passband is significantly changed and n = 4.6 mm, the target coupling coefficient can be adjusted to 0.018. In addition, since the coupling coefficient of the even mode does not change at all when adjusting the coupling coefficient of the odd mode, the coupling coefficient of the even mode is affected by arranging the waveguide 12 in the center of the half-wave straight line resonator. It became clear not to give.
From the above, by using the present invention, it is possible to individually adjust the coupling coefficient of the even-odd mode, and it is possible to easily realize the same coupling coefficient in two bands, which has been difficult in the past. Revealed.

FIG. 15 is a schematic diagram of a three-stage dual-band bandpass filter designed under the design conditions of Example 4, and uses a microstrip line structure. FIG. 16 shows the frequency characteristics of the dual band bandpass filter of FIG. FIG. 16 clearly shows that a good dual-band bandpass filter having two passbands can be designed, and that a dual-band bandpass filter having the same specific bandwidth in the two passbands can be designed. I know that there is.

First, when the dielectric rod 25 is disposed at the open end of the stub 11 as shown in FIG. 17 in order to confirm whether the frequency tuning of only the even mode of the dual-band bandpass filter is possible by the dielectric rod. The pass characteristic (S21) when there is not is calculated by a three-dimensional electromagnetic field analysis simulator MW-studio (manufactured by AET), and the calculation result is shown in FIG. The diameter of the dielectric rod 25 was set to 1.0 mm, which is the same as the width of the dual band resonator. The height of the dielectric rod 25 was 4.0 mm. When the dielectric rod was used, the distance between the dielectric rod 25 and the dual band resonator was 0.01 mm. As shown in FIG. 18, it can be seen that the center frequency of the even mode is shifted to the low frequency side by using the dielectric rod 25. At that time, since the center frequency of the odd mode is not shifted, it has become clear that only the center frequency of the even mode can be independently tuned. In order to change the shift amount of the center frequency, the shift amount can be adjusted by adjusting the height of the dielectric rod as shown in FIG.

Next, in order to confirm whether only the odd mode of the dual-band bandpass filter can be tuned by the dielectric rod, an even mode resonator (half wavelength straight line resonator of half wavelength resonance 10 and stub 11) as shown in FIG. The pass characteristic (S21) with and without the dielectric rod 25 in the center is calculated by the three-dimensional electromagnetic field analysis simulator MW-studio (manufactured by AET), and the calculation results are shown in the figure. 20 shows. The diameter of the dielectric rod 25 was set to 1.0 mm, which is the same as the width of the dual band resonator. The height of the dielectric rod 25 was 4.0 mm. When the dielectric rod was used, the distance between the dielectric rod 25 and the dual band resonator was 0.01 mm. As shown in FIG. 20, it can be seen that the center frequency of the odd mode is shifted to the low frequency side by using the dielectric rod 25. At that time, since the center frequency of the even mode was not shifted, it became clear that only the center frequency of the odd mode could be frequency tuned independently. In order to change the shift amount of the center frequency, the shift amount can be adjusted by adjusting the height of the dielectric rod as shown in FIG.
As described above, it has been clarified that the center frequencies of the two bands of the dual-band bandpass filter can be independently tuned by using the present invention in the sixth and seventh embodiments.

FIG. 21 shows the reflection characteristic (S11) in the even mode (around 5.0 GHz) of FIG. As can be seen from FIG. 21, when the frequency tuning dielectric rod 25 is used in a dual-band resonator, the center frequency shifts to the low frequency side, but the reflection characteristic (S11) is higher than when the dielectric rod 25 is not used. This increases and the in-band pass characteristics deteriorate. This is because the resonance frequency of each resonator deviates from the design condition for realizing the optimum filter characteristics due to the shift of the center frequency. In order to improve this deteriorated reflection characteristic, it is important to align the resonance frequencies of the resonators. Here, this method of improving frequency characteristics is called trimming. Generally, the frequency tuning mechanism and the trimming mechanism exist separately, and adjustment is very complicated. However, the present invention has an advantage that the configuration is very simple in that the dielectric rod 25 used for frequency tuning is also used for trimming as it is. Specifically, first, for frequency tuning, the dielectric rod 25 is disposed on the dual band resonator as shown in FIG. 22 (side view of FIG. 17). At that time, the distance between the dielectric rod 25 and the dual-band resonator is the same distance (h1 = h2 = h3 = 0.01 mm). From this point, in this case, changing h1 and h3 to 0.02 mm improves the reflection characteristics as shown in FIG. Accordingly, it has been clarified that the dielectric rod 25 used in the present invention can realize even-mode frequency tuning and improvement (trimming) of reflection characteristics at the same time.

FIG. 23 shows the reflection characteristic (S11) of the odd mode (around 3.5 GHz) in FIG. As can be seen from FIG. 23, when the dielectric rod 25 for frequency tuning is used in a dual-band resonator, the center frequency shifts to the low frequency side, but the reflection characteristic (S11) is higher than when the dielectric rod 25 is not used. This increases and the in-band pass characteristics deteriorate. This is because the resonance frequency of each resonator deviates from the design condition for realizing the optimum filter characteristics due to the shift of the center frequency. In order to improve this deteriorated reflection characteristic, it is important to align the resonance frequencies of the resonators. Here, trimming is performed as described in the eighth embodiment. First, for frequency tuning, the dielectric rod 25 is disposed on the dual band resonator as shown in FIG. 24 (side view of FIG. 19). At that time, the distance between the dielectric rod 25 and the dual-band resonator is the same distance (h1 = h2 = h3 = 0.010 mm). From this point, in this case, changing h2 to 0.022 mm improves the reflection characteristics as shown in FIG. Therefore, it has been clarified that the dielectric rod 25 used in the present invention can simultaneously realize the odd-mode frequency tuning and the reflection characteristic improvement.

When increasing the maximum shift amount of frequency tuning in the even mode, the shift amount increases by increasing the dielectric constant used for the dielectric rod 25. Further, the frequency shift amount can be increased by increasing the radius of the cylindrical dielectric rod 25. FIG. 25 summarizes changes in the frequency shift amount when the dielectric rod 25 is arranged and the radius r of the dielectric rod is changed as shown in FIG. As can be seen from FIG. 25, when the dielectric rod 25 is used and the radius r of the dielectric rod 25 is increased as compared with the case without the dielectric rod 25, the shift amount of the even-mode center frequency increases.

  When the maximum shift amount of frequency tuning in the odd mode is increased, the shift amount is increased by increasing the dielectric constant used for the dielectric rod 25. In the odd mode, unlike the even mode, the frequency shift amount cannot be increased while maintaining good characteristics even if the radius of the dielectric rod 25 is simply increased. FIG. 26 is a top view of FIG. If the radius of the dielectric rod 25 is simply increased, the dielectric rod 25 affects the waveguide 12 and the feed conductor line 13 and the frequency characteristics are deteriorated. Therefore, as a method for increasing the shift amount of the odd mode frequency without affecting the waveguide 12 and the feed conductor line 13, an elliptical dielectric rod 25 is used as shown in FIG. FIG. 27 summarizes changes in the amount of frequency shift when the elliptical dielectric rod 25 is arranged and the length s of the dielectric rod is changed as shown in FIG. At this time, the width direction of the dielectric rod 25 is fixed to 1.0 mm which is the same as that of the dual band resonator. As can be seen from FIG. 27, when the dielectric rod 25 is used and the length s is increased as compared with the case without the dielectric rod 25, the shift amount of the odd-mode center frequency increases.

The tunable dual-band resonator of the present invention and the tunable dual-band bandpass filter using the same can independently adjust the center frequency of each band, and can simultaneously improve in-band characteristics that deteriorate after center frequency tuning. Therefore, it can be diverted to all kinds of communication filters and contributes to the development of the communication industry.

8 Open end (where the strip is not connected)
DESCRIPTION OF SYMBOLS 10 Half wavelength resonator 11 Stub 12 Waveguide 13 Feeding conductor line 21 Grounding conductor 22 Dielectric 23 Strip conductor 24 Feeding line 25 Dielectric rod

Claims (14)

A dual-band resonator having a structure in which a stub 11 is added to the half-wave resonator 10 has a plane A-B which is an electric / magnetic wall, and operates in two frequency bands by odd-mode resonance and even-mode resonance. The half-wave resonator 10 is a resonator based on an odd mode, the half-wave resonator and the stub are resonators based on an even mode, and the odd mode is resonated on the low frequency side and the even mode is resonated on the high frequency side. A dual-band resonator that can adjust the resonator length or resonate the odd mode on the high frequency side and the even mode on the low frequency side,
A ground conductor is disposed on the lower surface of a dielectric having a predetermined thickness, a strip conductor is disposed on the upper surface, and the strip conductor is cut at an open end (where the strip is not connected). An odd-mode resonator having a groove having a width g that penetrates deeply, a tip portion of the groove and an end surface of the strip conductor having a width d and a single symmetrical strip conductor, and a length When the current flows into the plane of symmetry AB, it functions as an odd mode resonator, and the plane of symmetry AB plane. A tunable dual characterized in that a dielectric rod 25 is provided in the upper space of the stub 11 in the dual band resonator characterized in that it functions as an even mode resonator when no current flows into the stub. Band resonator. The tunable dual band resonator according to claim 1, wherein the dielectric 25 is moved, and the position of the dielectric 25 is set to the half-wave resonator 10 at the middle portion of the length of the half-wave resonator 10 and the stub 11. A tunable dual-band resonator that can be tuned independently of the resonant frequency of the even mode and the odd mode. A dual-band resonator having a structure in which a stub 11 is added to the half-wave resonator 10 has a plane A-B which is an electric / magnetic wall, and operates in two frequency bands by odd-mode resonance and even-mode resonance. The half-wave resonator 10 is a resonator based on an odd mode, the half-wave resonator and the stub are resonators based on an even mode, and the odd mode is resonated on the low frequency side and the even mode is resonated on the high frequency side. A dual-band bandpass filter that can adjust the resonator length, or can resonate the odd mode on the high frequency side and the even mode on the low frequency side, with a ground conductor on the bottom surface of the dielectric with a predetermined thickness. A strip conductor is arranged on the upper surface, and the strip conductor is a thin strip conductor that is cut at an open end (where the strip is not connected). An odd-mode resonator having a groove having a width g and having a grooved tip and an end surface of the strip conductor, each having a width d, formed of a single symmetrical strip conductor, and a stub 11 having a length l. Are connected at the end face opposite to the open end, and when current flows into the plane of symmetry AB, when the current flows into the plane of symmetry AB, it functions as an odd mode resonator, and current flows into the plane of symmetry AB. A tunable dual-band bandpass filter having dielectric rods 25 in the upper spaces of the half-wave resonator 10 and the stub 11, respectively. In
A tunable dual band characterized in that a dielectric rod 25 is provided in the upper space of the stub 11 or in the upper space of the half-wave resonator 10 in the middle of the length of the half-wave resonator 10 and the stub 11 combined. Bandpass filter. A dual-band resonator having a structure in which a stub 11 is added to the half-wave resonator 10 has a plane A-B which is an electric / magnetic wall, and operates in two frequency bands by odd-mode resonance and even-mode resonance. The half-wave resonator 10 is a resonator based on an odd mode, the half-wave resonator and the stub are resonators based on an even mode, and the odd mode is resonated on the low frequency side and the even mode is resonated on the high frequency side. A dual-band bandpass filter that can adjust the resonator length, or can resonate the odd mode on the high frequency side and the even mode on the low frequency side, with a ground conductor on the bottom surface of the dielectric with a predetermined thickness. The strip conductor is disposed on the upper surface, and the strip conductor is a thin strip conductor that is cut at the open end (where the strip is not connected). An odd-mode resonator formed of a single symmetrical strip conductor having a width d on the front end of the groove and the end surface of the strip conductor and a stub 11 having a length l. When the current flows into the plane of symmetry AB, it functions as an odd mode resonator and no current flows into the plane of symmetry AB. Sometimes, the length of the end of the waveguide is between a dual-band resonator characterized by acting as an even-mode resonator and the same dual-band resonator whose direction is changed by 180 degrees at a fixed interval m. A dual-band bandpass filter having a structure in which an n-type H-type waveguide 12 is provided, which is a tunable dual-band bandpass filter in which dielectric rods 25 are respectively provided in the upper spaces of the half-wave resonator 10 and the stub 11. A dielectric rod 25 is provided in the upper space of the stub 11 or in the upper space of the half-wave resonator 10 in the middle part of the length of the half-wave resonator 10 and the stub 11 combined. Bull dual-band bandpass filter. A dual-band resonator having a structure in which a stub 11 is added to the half-wave resonator 10 has a plane A-B which is an electric / magnetic wall, and operates in two frequency bands by odd-mode resonance and even-mode resonance. The half-wave resonator 10 is a resonator based on an odd mode, the half-wave resonator and the stub are resonators based on an even mode, and the odd mode is resonated on the low frequency side and the even mode is resonated on the high frequency side. A dual-band bandpass filter that can adjust the resonator length, or can resonate the odd mode on the high frequency side and the even mode on the low frequency side, with a ground conductor on the bottom surface of the dielectric with a predetermined thickness. A strip conductor is disposed on the upper surface, and the thin strip conductor is a single thin strip conductor cut at an open end (where the strip is not connected), An odd-mode resonator having a groove having a width g and having a width d, the tip of the groove and the end surface of the strip conductor having a width d, and a symmetric stub 11 having a length l. Are connected at the end face opposite to the open end, and when current flows into the plane of symmetry AB, when the current flows into the plane of symmetry AB, it functions as an odd mode resonator, and current flows into the plane of symmetry AB. If not, the length of the end of the waveguide is between the dual-band resonator, which functions as an even-mode resonator, and the same dual-band resonator whose direction is changed by 180 degrees at a fixed interval m. A dual-band bandpass filter having a structure in which an n-shaped H-type waveguide 12 is provided, wherein the coupling coefficient of the even-mode passband is adjusted by changing m, and then n is adjusted by adjusting n. Mode passband A dual-band bandpass filter that can individually adjust only the coupling coefficient of the odd-mode passband while keeping the coupling coefficient constant, and is a dielectric rod in the upper space of the half-wave resonator 10 and the stub 11 respectively. In the tunable dual-band bandpass filter provided with 25, dielectric rods are respectively placed in the upper space of the stub 11 or in the upper space of the half-wave resonator 10 in the intermediate length of the combined length of the half-wave resonator 10 and the stub 11. 25 is a tunable dual band bandpass filter. 6. The two-stage tunable dual-band bandpass filter according to claim 4 or 5, wherein only each dielectric rod 25 provided in the upper space of each half-wave resonator 10 is a distance from the tunable dual-band bandpass filter. A method of adjusting the amount of shift in frequency tuning that adjusts the passband characteristics only in the odd mode by adjusting all to the same height. 6. The two-stage tunable dual-band bandpass filter according to claim 4 or 5, wherein only each dielectric rod 25 provided in the upper space of each stub 11 has the same distance from the tunable dual-band bandpass filter. A frequency tuning shift adjustment method that adjusts the passband characteristics only in the even mode by adjusting the height. A method (trimming) for improving deterioration of in-band pass characteristics generated after frequency tuning in the two-stage tunable dual-band bandpass filter according to claim 4 or 5 is provided in an upper space of each half-wave resonator 10. A method of improving the in-band passband characteristics of only the odd mode by individually adjusting the distance between each of the obtained dielectric rods 25 and the tunable dual-band bandpass filter individually. The method (trimming) for improving the degradation of the in-band pass characteristic that occurs after frequency tuning in the two-stage tunable dual-band bandpass filter according to claim 4 or claim 5 is provided in each upper space of each stub 11. A method of improving the in- band passband characteristic of only the even mode by individually adjusting the distance between only the dielectric rod 25 and the tunable dual-band bandpass filter . A dual-band resonator having a structure in which a stub 11 is added to the half-wave resonator 10 has a plane A-B which is an electric / magnetic wall, and operates in two frequency bands by odd-mode resonance and even-mode resonance. The half-wave resonator 10 is a resonator based on an odd mode, the half-wave resonator and the stub are resonators based on an even mode, and the odd mode is resonated on the low frequency side and the even mode is resonated on the high frequency side. A dual-band bandpass filter that can adjust the resonator length, or can resonate the odd mode on the high frequency side and the even mode on the low frequency side, with a ground conductor on the bottom surface of the dielectric with a predetermined thickness. A strip conductor is disposed on the upper surface, and the thin strip conductor is a single thin strip conductor cut at an open end (where the strip is not connected), An odd-mode resonant waveguide having a groove having a width g and having a grooved tip and a strip conductor having a width d at the end of the groove and a width d, and a stub having a length l 11 is an even-mode resonant waveguide having a shape connected to the end surface opposite to the open end, and when current flows into the plane of symmetry AB, it functions as an odd-mode resonant waveguide, and the plane of symmetry AB Between the dual-band resonator, which functions as an even-mode resonance waveguide when no current flows, and the same dual-band resonator whose direction is changed by 180 degrees at a constant interval m Between a dual-band resonator having a structure in which an H-type waveguide 12 having an end length n is provided, and the same dual-band resonator whose direction is changed by 180 degrees at a constant interval m, H-shaped guide with length n at the end of the waveguide Odd-mode resonance of a first dual-band resonator and a third dual-band resonator having a structure including a total of three dual-band resonators including a dual-band resonator having a structure provided with a waveguide 12 A multistage dual-band bandpass filter characterized in that a feed conductor line 13 is provided along the waveguide 10, one feed conductor line 13 is an input side, and the other feed conductor line 13 is an output side. In the tunable dual band bandpass filter in which the dielectric rod 25 is provided in the upper space of the half-wave resonator 10 and the stub 11, respectively, the upper space of the stub 11 or the half-wave resonator 10 and the stub 11 are combined. A tunable dual-band band characterized in that dielectric rods 25 are respectively provided in the upper spaces of the half-wave resonator 10 in the middle of the length. Pass filter. 11. The three-stage tunable dual-band bandpass filter according to claim 10, wherein only each dielectric rod 25 provided in the upper space of each half-wave resonator 10 adjusts the distance from the tunable dual-band bandpass filter. The adjustment method of the shift amount of the frequency tuning for adjusting the passband characteristic only in the odd mode. The three-stage tunable dual-band bandpass filter according to claim 10, wherein only each dielectric rod 25 provided in the upper space of each stub 11 is adjusted by adjusting the distance from the tunable dual-band bandpass filter. A method of adjusting the amount of frequency tuning shift that adjusts the passband characteristics only in the mode. The method (trimming) for improving the degradation of the in-band pass characteristic generated after frequency tuning in the three-stage tunable dual-band bandpass filter according to claim 10 is performed by each dielectric provided in the upper space of each half-wave resonator 10. A method of improving the in-band passband characteristics of only the odd mode by individually adjusting the distance between only the body rod 25 and the tunable dual-band bandpass filter. The method (trimming) for improving the degradation of the in-band pass characteristic generated after frequency tuning in the three-stage tunable dual-band bandpass filter according to claim 10 is performed by using each dielectric rod 25 provided in the upper space of each stub 11. The only way to improve the in-band passband characteristics of even mode only by individually adjusting the distance with the tunable dual band bandpass filter.

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