JPH04304004A - Band pass filter - Google Patents

Abstract

PURPOSE:To realize a band pass filter with a wide pass band and less insertion loss at the pass band. CONSTITUTION:First stage and last stage resonance elements R1C and R8C among resonator elements incorporated in a common shield case S are made up of coaxial resonance elements, and intermediate resonance elements R2D-R7D are made up of TE01delta mode dielectric resonance elements. The center axis of the 1st stage coaxial resonance element R1C and the center axis of the final stage coaxial resonance element R8C are made orthogonal to each other, and the center axis of the final stage coaxial resonance element R8C and the center axis of the pre-stage coaxial resonance element R2D in the TE01delta mode are made orthogonal to each other. The center axes of the TE01delta mode dielectric resonance elements R2D-R7D are kept in parallel.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to mobile communication systems such as car telephones, in which the transmitting antenna and receiving antenna of a base station are relatively close to each other, or when a shared transmitting and receiving antenna is used. The characteristics required of the bandpass filter that constitutes the reception amplification system are that the passband width of the reception frequency is relatively wide, the amount of attenuation in the transmission frequency band is extremely large, and the bandpass has low insertion loss in the passband. It concerns a filter.

0002

[Prior Art] Conventionally, as a band-pass filter that meets the above-mentioned characteristics requirements, a band-pass filter constructed by connecting a plurality of TE01 alternator mode dielectric resonators in series has been used. is used.

0003

[Problem to be Solved by the Invention] When configuring a bandpass filter by connecting a plurality of TE01 alternator mode dielectric resonators in series, it is necessary to It is impossible to increase the degree of coupling between the resonator at the final stage and the output coupling circuit, and it is difficult to realize a bandpass filter with a wide passband width.

0004

[Means for Solving the Problems] The present invention provides a first-stage coaxial resonator comprising a coaxial resonant element coupled to an input coupling element housed in a common shield case, and a final stage coaxial resonator comprising a coaxial resonant element coupled to an output coupling element installed in the TE01, and an appropriate number of TE01s installed in the common shield case between the first and final stage coaxial resonators. The present invention attempts to eliminate the drawbacks of the prior art by realizing a bandpass filter with an appropriate number of TE01 alternating dielectric resonators comprising alternating alternating dielectric resonators.

[0005]

[Operation] The input coupling element and the first stage coaxial resonant element are electromagnetically coupled, and this coupling coefficient can be varied over a wide range from close coupling to loose coupling by changing the distance between the input coupling element and the first stage coaxial resonant element. changes over time. The coupling between the final stage coaxial resonant element and the output coupling element is also exactly the same as that on the input side. First-stage coaxial resonant element and second-stage TE01 alternator
A coaxial resonant element and a TE01 rotor motor are coupled to each other by electric field coupling and magnetic field coupling.
By changing the distance from the dielectric resonant element, the coupling can be varied over a wide range from close coupling to loose coupling. The coupling between the coaxial resonant element at the final stage and the TE01 alternator mode dielectric resonant element at the preceding stage is also the same as on the input side. TE0
In a 1-telter mode dielectric resonant element, the coupling between adjacent resonant elements is mainly magnetic field coupling, so the coupling ranges from medium to loose coupling depending on the spacing between the resonant elements. Varies in range.

[0006]

[Embodiment] FIG. 1(a) is a cross-sectional view showing a main part of an embodiment of the present invention {BB cross-sectional view of FIG. 1(b)}, and FIG. In both figures, S is a common shield case, R1C and R8C are rod-shaped or cylindrical resonant elements forming a coaxial resonator, and R2D to R7D are TE01 alternator mode dielectrics. The body resonant elements are arranged so that their central axes are parallel to each other (the directions may be the same or opposite), and the directions of the central axes of the coaxial resonant elements R1C and R8C are parallel to each other. TE01 alternator mode dielectric resonant element R2
The central axis directions of D and R7D are arranged so as to be perpendicular to each other.

CI is an input coupling element, and in the figure, one end of a metal plate of an appropriate width is connected to an input terminal TI, the other end is connected to a common shield case S, and its longitudinal direction is connected to the first stage coaxial Although a case is illustrated in which the coupling line is provided parallel to the central axis direction of the resonant element R1C, the rule
It may also be formed using a loop or a capacitive element. CO is an output coupling element and has the same configuration as the input coupling element CI. TO is an output terminal. Hereinafter, a case where the input coupling element CI and the output coupling element CO are formed by coupling lines will be described. In addition, in Figure 1,
The illustration of the resonant frequency fine adjustment element provided for each resonant element is omitted.

FIG. 2 is a partially enlarged sectional view for explaining the coupling between the input coupling line and the first-stage coaxial resonant element and the coupling between the resonant elements in the band-pass filter of the present invention shown in FIG. , FIG. 2(a) is a sectional view taken along line BB in FIG. 2(b), and FIG. 2(b) is a sectional view taken along line AA in FIG. 2(a). Figure 2 (
The solid line with an arrow in a) indicates the electric field, and the solid line with an arrow in Fig. 2(b)
) The dashed line in ) indicates the magnetic field. The symbols in Figure 2 are the same as those in Figure 1.
Although FIG. 2 shows the distribution of the electric field and magnetic field on the input side, the distribution of the electric field and magnetic field on the output side is also the same as that on the input side.

FIG. 3 is an equivalent circuit diagram of the band-pass filter of the present invention shown in FIG. 1, where EI1, E12, E78 and E8O are electric field coupling coefficients, MI1, M12, M23
, M34 , M45 , M56 , M67 , M78
and M8O is the magnetic field coupling coefficient.

In the bandpass filter of the present invention, as shown in FIG. 2, the input coupling line CI and the first stage coaxial resonant element R
The coupling with 1C is electromagnetic coupling, and the degree of coupling can be varied over a wide range from close coupling to loose coupling depending on the distance between the input coupling line CI and the first stage coaxial resonant element R1C. Final stage coaxial resonant element R8C and output coupling line C
The connection with O is also the same as on the input side. The first-stage coaxial resonant element R1C and the next-stage TE01-mode dielectric resonant element R2D are coupled by electric field coupling and magnetic field coupling.
It is possible to vary it over a wide range from close coupling to loose coupling depending on the spacing between the mode dielectric resonant elements R2D. TE01 alter mode dielectric resonant element R7
The coupling between D and the coaxial resonant element R8C is also the same as that on the input side. TE01 alter mode dielectric resonant element R2D
to R7D, since magnetic field coupling is the main coupling between adjacent resonant elements, the coupling varies from medium to loose coupling depending on the spacing between the resonant elements.

The bandpass filter of the present invention has an input coupling line C
The coupling between I and the first stage coaxial resonant element R1C and the coupling between the final stage coaxial resonator R8C and the output coupling line CO can be made tighter. Since the resonant element disposed between the TE01 and TEL mode dielectric resonant elements is formed by a TE01 alternator mode dielectric resonant element, the pass band width can be widened and the insertion loss in the pass band can be reduced.

[0012] When configuring a bandpass filter by connecting a plurality of resonant elements in series, by appropriately distributing the Q of each resonator when loaded according to its order, it is possible to However, even in the band-pass filter of the present invention, if the order is 8 as shown in FIG.
In the case of L, the first and final stage resonant elements R1C and R
The Q of the resonator made of 8C when loaded is approximately 0.3QL.
In addition, the Q of the resonator composed of resonant elements R2D and R7D when loaded is approximately 0.63QL, and the Q of the resonator composed of resonant elements R3D and R6D when loaded is approximately 0.79QL.
Furthermore, the ripple can be reduced by selecting the load Q of the resonator consisting of the resonant elements R4D and R5D to approximately 0.82QL.

TE01 constituting the bandpass filter of the present invention
Delta mode dielectric resonant element R2D to R7D
The unloaded Q (QU) of a resonator consisting of
The Q (QU) at no load of the resonator consisting of coaxial resonant elements R1C and R8C in the first and final stages has a maximum value of approximately 8300, which is approximately 1/1 of that of the resonator consisting of TE01 alternator mode dielectric resonant elements. 3, but there is no risk of affecting the insertion loss of the bandpass filter.

The insertion loss for each resonator formed by each resonant element and a common shield case can be determined by the following equation.

[Math 1] In the above formula, LQk: Resonator insertion loss QUk: Q at no load QLk: Q at load k: from 1 to 8

In the band-pass filter of the present invention, as shown by the broken line in FIG. 1, one end of the sub-coupling line SL27 made of a suitable transmission line is connected to an electric field (or magnetic field) made of a capacitive element or a loop, etc. It is sub-coupled to the resonant element R2D via the sub-coupling element C2 (L2), and the other end is connected to an electric field (or magnetic field).
A sub-coupling line S is sub-coupled to the resonant element R7D via the sub-coupling element C7 (L7) and has the same configuration as the sub-coupling line SL27.
One end of L36 is connected to electric field (or magnetic field) sub-coupling element C3 (L3
) and sub-coupling the other end to the resonant element R6D via the electric field (or magnetic field) sub-coupling element C6 (L6), thereby forming a polarized bandpass filter. Can be configured.

When the electrical lengths of the sub-coupled lines SL27 and SL36 are determined appropriately, the cascade-connected resonant element R1C
The main circuit consisting of R8C is transmitted to the resonant element R7.
The phase of the signal reaching D and the phase of the signal reaching the resonant element R7D via the sub-coupling line SL27 are opposite to each other, and similarly, the phase of the signal transmitted through the main circuit and reaching the resonant element R6D, Resonant element R6 via sub-coupling line SL36
The phases of the signals reaching D can be made to be opposite to each other.

Therefore, the sub-coupling elements C2 (L2), C
3 (L3), C6 (L6), and C7 (L7) and the resonant element, and connect the main circuit and sub-coupling line SL.
By making the amplitudes of the two signals that reach the resonant element R7D after each transmission of 27 equal to each other, an attenuation pole is generated at the frequency position of this signal in the attenuation region, and similarly, the main circuit and the sub-coupling line SL36 are transmitted. By making the amplitudes of both signals reaching the resonant element R6D equal to each other, an attenuation pole can be generated at the frequency position of this signal in the attenuation range.

Although the above example uses two sub-coupled lines, the present invention can be implemented by increasing or decreasing the number of sub-coupling lines as necessary.If necessary, the order of the band-pass filter can be increased to The number of lines may be increased. In either case, an attenuation pole can be generated in the attenuation region by sub-coupling opposing resonant elements through two resonant elements or an integral multiple thereof.

FIG. 4 is a diagram showing essential parts of another embodiment of the present invention, and FIG. 4(a) is a sectional view taken along line BB in FIG. 4(b).
(b) is a sectional view taken along line AA in FIG. 4(a). In both figures, SU is a common shield case, and SS is a partition wall made of a metal plate, which partitions the inside of the shield case SU into a U-shape. TI is the input terminal, CI is the input coupling line, R1C
is a coaxial resonant element, R2D to R7D is TE01
The alternator mode dielectric resonant element, R8C is a coaxial resonant element, CO is an output coupling line, TO is an output terminal, and these are arranged in a U-shape in a U-shaped space partitioned by a partition wall SS. The central axes of the resonant elements R1C and R2D are perpendicular to each other, and the central axes of the resonant elements R8C and R7D are perpendicular to each other.
This is similar to the embodiment shown in FIG. 1 in that the central axes of D are arranged in parallel. SC18 is a sub-coupling capacitance element, which is formed by attaching electrodes that form a capacitance between each of the resonant elements R1C and R8C to both ends of a conductor inserted through a hole bored in the partition wall SS. SH27 is a sub-coupling hole drilled in the partition wall SS, SC36 is a sub-coupling capacitance element,
It has the same configuration as element SC18.

FIG. 5 is an equivalent circuit diagram of the band-pass filter of the present invention shown in FIG. 4, where E18 and E36 are sub-electric field coupling coefficients, M27 is a sub-magnetic field coupling coefficient, and other symbols are the same as in FIG. 3. It is.

The coupling effect between the resonant elements and the formation of attenuation poles in the attenuation region in this embodiment are similar to those in the embodiment shown in FIG. Since the circuit is arranged in a U-shape, the entire circuit can be miniaturized, and sub-coupling is performed by the sub-coupling capacitance elements SC18 and SC36 provided through the partition wall SS and the sub-coupling hole SH27 bored in the partition wall. Therefore, the configuration of the sub-coupling circuit can be simplified compared to the case where the sub-coupling circuit is formed using a sub-coupling line and an electric field (or magnetic field) sub-coupling element as in the embodiment shown in FIG. can do. Figure 4
It goes without saying that even in the embodiment shown in FIG.

FIG. 6 is a curve diagram showing an example of the transmission characteristics of the bandpass filter of the present invention, and FIG. 7 is an enlarged diagram of the passband portion in FIG. 6. In both figures, the horizontal axis represents the transmission frequency f ( M
Hz), and the vertical axis is the attenuation amount ATT (dB).

[0023]

Effects of the Invention In the bandpass filter of the present invention, the first and final stage resonant elements are formed by coaxial resonant elements, and the intermediate resonant element is formed by a TE01 alternator mode dielectric resonant element. By increasing the degree of coupling between the coupling line and the first-stage resonant element and the degree of coupling between the last-stage resonant element and the output coupling line, it is possible to widen the passband width and reduce insertion loss in the passband. It can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing essential parts of an embodiment of the present invention.

FIG. 2 is a diagram showing electric field and magnetic field distributions in the bandpass filter of the present invention.

FIG. 3 is an equivalent circuit diagram of the bandpass filter of the present invention.

FIG. 4 is a sectional view showing essential parts of another embodiment of the present invention.

FIG. 5 is an equivalent circuit diagram of the bandpass filter of the present invention.

FIG. 6 is a curve diagram showing an example of the transmission characteristics of the bandpass filter of the present invention.

FIG. 7 is a curve diagram showing an example of the transmission characteristics of the bandpass filter of the present invention.

[Explanation of symbols]

S Common shield case R1C Resonant element R2D Resonant element R3D Resonant element R4D Resonant element R5D Resonant element R6D Resonant element R7D Resonant element R8C Resonant element CI Input coupling element CO Output coupling element TI Input terminal TO Output terminal SL27 Sub-coupling line SL36 Sub-coupling line C2 (L2) Sub-coupling element C3 (L3) Sub-coupling element C6 (L6) Sub-coupling element C7 (L7) Sub-coupling element SU Common shield case SS
Partition wall SC18 Sub-coupling element SC36 Sub-coupling element SH27 Sub-coupling element EI1 Electric field coupling coefficient E12 Electric field coupling coefficient E78 Electric field coupling coefficient E8O Electric field coupling coefficient MI1 Magnetic field coupling coefficient M12 Magnetic field coupling coefficient M23 Magnetic field coupling coefficient M34 Magnetic field coupling coefficient M45 Magnetic field coupling coefficient M56 Magnetic field coupling coefficient M67 Magnetic field coupling coefficient M78 Magnetic field coupling coefficient M8O Magnetic field coupling coefficient E18 Sub-electric field coupling coefficient E36 Sub-electric field coupling coefficient M27 Sub-magnetic field coupling coefficient

Claims (6)

[Claims] Claim 1: A first stage coaxial resonator comprising a coaxial resonant element coupled to an input coupling element housed in a common shield case, and an output coupling element housed in the common shield case. a final stage coaxial resonator comprising coaxial resonant elements to be coupled, and an appropriate number of TE01 alternator mode dielectric resonant elements housed in the common shield case between the first stage and final stage coaxial resonators. A bandpass filter comprising an appropriate number of TE01 alternator mode dielectric resonators. [Claim 2] The axial direction of the coaxial resonant element in the first-stage coaxial resonator and the axial direction of the TE01 alternator mode dielectric resonator in the TE01 alternator mode dielectric resonator adjacent to this coaxial resonator are different. The axial direction of the coaxial resonant element in the final stage coaxial resonator is orthogonal to the axial direction of the TE01 alternator mode dielectric resonator in the TE01 alternator mode dielectric resonator adjacent to this coaxial resonator. 2. The bandpass filter according to claim 1, wherein the TE01 alternator mode dielectric resonant elements in each TE01 alternator mode dielectric resonator are arranged in parallel. 3. A bandpass filter according to claim 1, wherein the common shield case is linear. 4. The bandpass filter according to claim 1, wherein the opposing resonant elements are sub-coupled via two resonant elements or an integral multiple thereof. 5. Claim 1, wherein a common shield case is partitioned by partition walls made of metal plates to form a U-shaped space, and a plurality of resonant elements are arranged in a U-shape within this space. A bandpass filter as described in . 6. The bandpass filter according to claim 5, wherein the opposing resonant elements are sub-coupled via two resonant elements or an integral multiple thereof.