JP2006340043A - Coaxial filter, duplexer, and manufacturing method of coaxial filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coaxial filter providing strong connection without closely arranging respective coaxial resonators, and desired filter characteristics by a simple adjusting process without requesting high accuracy for the installation position of the coaxial resonator, and also to provide a duplexer, and a manufacturing method of the coaxial filter. <P>SOLUTION: In the coaxial filter composed of: a plurality of resonance conductors 2; an external conductor 1 surrounding them; and a conductor plate 5 arranged between the resonance conductors 2, when installing the conductor plate 5, the thickness of the conductor plate to obtain a desired connection coefficient is decided on the basis of the relation of the connection coefficient for the thickness of the conductor plate and the length of the conductor plate, then the length of the conductor plate is finely adjusted, and the desired filter characteristics are provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a coaxial filter, a diplexer, and a method for manufacturing a coaxial filter that allow a signal in a desired frequency band to pass therethrough.

The resonator mainly in the microwave band is configured using a coaxial resonator, and has a structure in which at least one resonance conductor and an outer conductor arranged so as to surround the resonance conductor are arranged at a predetermined distance. Have taken. Since this coaxial resonator is particularly advantageous in terms of its size, a quarter-wave resonator in which one end is open and the other is short-circuited is generally used. Conventionally, as a configuration of a coaxial filter using this type of coaxial resonator, for example, there is one shown in Patent Document 1.

7A and 7B are diagrams showing the structure of this conventional coaxial filter, in which FIG. 7A is a side view and FIG. 7B is a top view excluding the top conductor of the outer conductor.

As shown in FIG. 7, this conventional coaxial filter is a four-stage comb line BPF having two attenuation poles on both sides of the pass band, skipping two coaxial resonators, and a metal case (outer conductor) 101 and a resonance The conductor 102, the input terminal 103, the output terminal 104, the input / output coupling loop 105, and the polarized coupling loop 106 are configured.
Japanese Patent Laid-Open No. 06-291512

However, in such a coaxial filter using a conventional coaxial resonator, the electric field energy concentrates on the fringing capacity of the open portion of the resonant conductor, so that the electric field / magnetic field energy can be transferred simply by placing the resonant conductor adjacent to each other. There is a problem that they occur equally and the apparent coupling amount becomes low with respect to the spread of the electromagnetic field.

In order to solve this problem, the coaxial resonators can be arranged close to each other to increase the coupling amount in the coaxial line portion of each coaxial resonator, but the interval between the coaxial resonators is reduced. Accordingly, the coupling amount of the coaxial line portion of each coaxial resonator increases exponentially, so that a high accuracy is required for the installation position of the coaxial resonator, and at the same time, it causes a Q-down.

The present invention has been made in view of such a problem, and it is possible to obtain strong coupling without arranging the coaxial resonators close to each other and to require high accuracy when adjusting the filter characteristics of the coaxial filter. It is an object of the present invention to provide a coaxial filter, a diplexer, and a method for manufacturing a coaxial filter that can obtain desired filter characteristics by a simple adjustment process.

In order to solve the above problems, the present invention provides a plurality of resonant conductors continuously arranged from an input position to an output position of a frequency signal, an outer conductor surrounding the plurality of resonant conductors, and the plurality of resonant conductors. And a conductive plate disposed in at least one gap of the conductive plate having a desired characteristic based on a relationship between a coupling coefficient with respect to the thickness of the conductive plate and a length of the conductive plate. The thickness and length were determined.

This is because when the conductor plate that blocks the electromagnetic field in the coaxial line section is designed to be near the midpoint of the coaxial resonator, the coupling coefficient between the coaxial resonators can be increased and the coupling to the change in the length of the conductor plate can be obtained. The relationship between the coupling coefficient with respect to the thickness of the conductor plate shown in FIG. 3 and the length of the conductor plate, which can reduce the coefficient change amount, is used.

More specifically, in the present invention, after first determining the thickness of the conductor plate that provides a desired coupling coefficient, the length of the conductor plate that does not require relatively high adjustment accuracy is adjusted to obtain the desired filter characteristics. A coaxial filter is obtained.

In the present invention, the conductor plates are arranged in at least one gap between the continuously arranged resonant conductors to block the electromagnetic field generated in the coaxial line portion. It becomes possible to obtain strong coupling in the coaxial line portion without arranging them.

In the present invention, the outer conductor is formed so that the distance between the side surface of the resonant conductor and the outer conductor is substantially constant. As a result, the loss of the coaxial resonator alone can be reduced.

In the present invention, the plurality of resonant conductors, the outer conductor, and the conductor plate are arranged so that the input position and the output position of the frequency signal are close to each other. Thereby, the freedom degree of the circuit arrangement | positioning at the time of product mounting can be improved.

According to the present invention, when the conductor plate is installed between the resonant conductors, the thickness and length of the conductor plate having desired characteristics based on the relationship between the coupling coefficient with respect to the thickness of the conductor plate and the length of the conductor plate. By determining the length, it is possible to obtain a desired filter characteristic by a simple adjustment process without requiring high adjustment accuracy for adjusting the filter characteristic of the coaxial filter.

In the present invention, the conductor plates are arranged in at least one gap between the continuously arranged resonant conductors to block the electromagnetic field generated in the coaxial line portion. It is possible to obtain strong coupling in the coaxial line portion without arranging, and to obtain an effect that the shape of the coaxial resonator can be designed with a relatively large degree of freedom.

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
1A and 1B are diagrams showing an example of the configuration of a coaxial filter according to Embodiment 1 of the present invention. FIG. 1A is a side view, and FIG. 1B is a top view excluding an upper conductor of an outer conductor. is there.
In FIG. 1, the coaxial filter according to the first embodiment of the present invention includes an outer conductor 1, a resonant conductor 2, an input terminal 3, an output terminal 4, and a conductor plate 5.

The outer conductor 1 surrounds the resonant conductor 2 with a certain distance from the resonant conductor 2. The resonant conductor 2 is continuously arranged from the input terminal 3 that is the input position of the frequency signal toward the output terminal 4 that is the output position. The outer conductor 1 and the plurality of resonant conductors 2 constitute a coaxial filter.
The input terminal 3 is a terminal to which a frequency signal is input, and the output terminal 4 is a terminal to which a frequency signal is output.

The conductor plate 5 flows in the gap between the continuously disposed resonant conductors 2 from the position of the outer conductor 1 on the open end side of the resonant conductor 2 toward the short-circuited side of the resonant conductor 2. It is formed so as to block. The material of the conductor plate 5 is not particularly limited, but it is preferable to use the same material as that of the outer conductor 1. In addition, since the conductor plate 5 should just be what can interrupt the electromagnetic field which arises in a coaxial line part, the inside of the conductor plate 5 may be hollow, and each conductor plate 5 is arrange | positioned in C shape. For example, the conductor plates 5 are not necessarily provided in parallel.

FIG. 2 is an explanatory diagram for explaining the relationship between the coupling coefficient and the length of the conductor plate with respect to the thickness of the conductor plate between the coaxial resonators. The two coaxial resonators each have an outer conductor 1 of 30 mm in length and width, The length is 50 mm, the length of the resonant conductor is 38.3 mm, and the radius is 10 mm.

FIG. 3 is a diagram showing the relationship between the length L from the outer conductor surface on the open end side to the thickness t of the conductor plate and the coupling factor in the configuration of FIG.
As shown in FIG. 3, the relationship between the length L from the position of the outer conductor 1 on the open end side and the coupling coefficient gradually increases as the length L increases up to about L = 25 mm. After that, it gradually decreases as the length L increases.

This is because, of the resonator energy, the electric field energy is concentrated on the open end side from the middle, and the magnetic field energy is concentrated on the short-circuit side from the middle. When the length L is larger than the intermediate point, the electric field and magnetic field energy is concentrated. Since a phenomenon occurs in which energy cancels out, such a change point of the coupling coefficient occurs.

In the present invention, attention is paid to a physical phenomenon in which the coupling coefficient is large near the change point, and the change amount of the coupling coefficient is extremely small even when the length L is changed. For example, assuming t = 3 mm and L = 25 mm as the design center, even if the length L fluctuates by ± 5 mm, the amount of change in the coupling coefficient is about 0.1%, which hardly affects the filter characteristics.

Therefore, this is taken into consideration in the design. First, the thickness of the conductor plate 5 is determined from the relationship between the length of the conductor plate with respect to the thickness of the conductor plate 5 and the coupling coefficient, and then the filter characteristic is adjusted by adjusting the length of the conductor plate 5. A fine adjustment was made. Thereby, even if the processing accuracy of the conductor plate 5 is somewhat poor, it is possible to easily finely adjust the filter characteristics.

The thickness of the conductor plate 5 to be selected is preferably selected so that the desired coupling coefficient between the coaxial resonators can be obtained and the amount of change in the coupling coefficient with respect to the length change of the conductor plate 5 is small. Thus, fine adjustment of the filter characteristics can be facilitated.

As described above, according to the coaxial filter and the manufacturing method of the coaxial filter according to the first embodiment of the present invention, the outer conductor 1 on the open end side of the resonant conductor 2 is disposed in the gap between the continuously disposed resonant conductors 2. A conductor plate 5 that blocks the flow of the electromagnetic field generated in the gap is provided from the short circuit side to the short-circuit side. When the conductor plate 5 is installed, the conductor is determined based on the relationship between the length of the conductor plate 5 and the coupling coefficient. After the thickness of the plate 5 is determined, the length of the conductor plate 5 is finely adjusted, thereby obtaining a desired coupling coefficient between the coaxial resonators, and a simple adjustment process that does not require high precision processing accuracy. Thus, desired filter characteristics can be obtained.

In addition, even when a diplexer is configured using the coaxial filter according to the first embodiment of the present invention, high processing accuracy is not required for adjusting the filter characteristics, so that it is possible to easily obtain a diplexer having desired characteristics. become.

In the coaxial filter according to the first embodiment of the present invention, the conductor plate 5 is provided between all the resonant conductors 2, but the same applies to the case where the conductor plate 5 is provided in at least one gap. An effect can be obtained.

Further, in the coaxial filter according to the first embodiment of the present invention, the open end side of the resonant conductor 2 is completely blocked using the conductor plate 5, but the shape of the conductor plate 5, the outer conductor 1 and the conductor plate 5 The contact position is not particularly limited, and the conductor plate 5 only needs to be able to block a part of the electromagnetic field generated in the coaxial line portion.

In the coaxial filter according to Embodiment 1 of the present invention, the conductor plate 5 is installed from the position of the outer conductor 1 on the open end side of the resonant conductor 2 toward the short-circuit side of the resonant conductor 2. For example, the conductor plate 5 may be installed from the position of the outer conductor 1 on the short-circuit side of the resonant conductor 2 toward the open end side of the resonant conductor 2.

(Embodiment 2)
Next, a coaxial filter according to Embodiment 2 of the present invention will be described.
In the coaxial filter according to the second embodiment of the present invention, as shown in FIG. 4, the shape of the outer conductor 1 surrounding each resonant conductor 2 is a cylindrical shape.

In general, in a coaxial resonator, even if the impedance is the same, if the outer conductor 1 and a part of the resonant conductor 2 are extremely close to each other, the current concentrates there, and the loss increases. Therefore, in the coaxial filter according to the second embodiment, the outer conductor 1 surrounding each resonance conductor 2 is formed in a cylindrical shape so as to reduce the loss of the coaxial resonator alone.

In the present invention, as described in the first embodiment, since the conductor plate 5 shaped in a predetermined procedure is provided between the resonant conductors 2, strong coupling is achieved even if the resonant conductors 2 are somewhat apart. It becomes possible to take. Therefore, according to the present invention, the shape of the coaxial filter can be relatively freely designed, and the shape of the outer conductor 1 surrounding each resonance conductor 2 can be easily made cylindrical.

As described above, according to the coaxial filter according to the second embodiment of the present invention, the shape of the outer conductor 1 surrounding each resonance conductor 2 is made cylindrical, so that the loss of each coaxial resonator alone can be reduced. It becomes possible.

In the second embodiment of the present invention, the outer conductor 1 surrounding each resonant conductor 2 is shown as an example of a cylindrical shape. However, the outer conductor 1 surrounding each resonant conductor 2 is shaped like a resonant conductor. For example, the shape of the outer conductor 1 surrounding each resonance conductor 2 may be a regular polygonal column as long as the distance between the two side surfaces and the outer conductor 1 is substantially constant.

(Embodiment 3)
Next, a coaxial filter according to Embodiment 3 of the present invention will be described.
The coaxial filter according to the third embodiment of the present invention is formed by forming a coaxial filter so that the input position and output position of the frequency signal are close to each other.

5 and 6 are top views of the coaxial filter according to Embodiment 3 of the present invention with the top conductor removed.
As shown in FIGS. 5 and 6, the input terminal 3 and the output terminal 4 can be arranged close to each other while taking a strong coupling coefficient by making the shape of the coaxial filter into a quadrangular prism shape or a hexagonal prism shape. It becomes possible.

As described above, according to the coaxial filter according to the third embodiment of the present invention, the plurality of resonant conductors 2, the outer conductor 1, and the conductor plate 5 are arranged so that the input terminal 3 and the output terminal 4 are close to each other. By arranging, the degree of freedom of circuit arrangement at the time of product mounting can be improved.

In the third embodiment of the present invention, a description has been given of a case where square or equilateral triangular coaxial resonators are arranged in a quadrangular shape or a hexagonal shape and the shape of the coaxial filter is a quadrangular prism shape or a hexagonal prism shape. The shape of the coaxial filter may be any shape as long as the input position and the output position of the frequency signal are close to each other. For example, the coaxial resonator may be arranged in a substantially U shape or a substantially circular shape.

The figure which shows an example of a structure of the coaxial filter by Embodiment 1 of this invention. Explanatory drawing for demonstrating the relationship between the coupling coefficient with respect to the thickness of the conductor plate between coaxial resonators, and the length of the conductor plate Figure showing the relationship between the length from the outer conductor surface on the open end side and the coupling coefficient with respect to the thickness of the conductor plate The perspective view which shows an example of a structure of the coaxial filter by Embodiment 2 of this invention. The top view in the state which removed the upper surface conductor of the coaxial filter by Embodiment 3 of this invention Top view showing another example of the coaxial filter according to Embodiment 3 of the present invention. The figure which shows an example of a structure of the conventional coaxial filter

Explanation of symbols

1 Outer conductor 2 Resonant conductor 3 Input terminal 4 Output terminal 5 Conductor plate

Claims (7)

A plurality of resonant conductors continuously arranged from the input position of the frequency signal toward the output position;
An outer conductor surrounding the plurality of resonant conductors;
A conductor plate disposed in at least one gap of the plurality of resonant conductors,
A coaxial filter, wherein the thickness and length of the conductor plate having desired characteristics are determined based on the relationship between the coupling coefficient with respect to the thickness of the conductor plate and the length of the conductor plate. The coaxial filter according to claim 1, wherein
A coaxial filter, wherein the thickness and length of the conductor plate are determined by adjusting the length of the conductor plate after determining the thickness of the conductor plate having desired characteristics. The coaxial filter according to claim 1 or 2,
The coaxial filter, wherein the conductor plate is installed from the outer conductor position on the open end side of the resonant conductor toward the short-circuit side of the resonant conductor. The coaxial filter according to any one of claims 1 to 3,
The coaxial filter, wherein the outer conductor is formed so that a distance between the side surface of the resonant conductor and the outer conductor is substantially constant. The coaxial filter according to any one of claims 1 to 4,
The coaxial filter, wherein the plurality of resonant conductors, the outer conductor, and the conductor plate are arranged so that an input position and an output position of the frequency signal are close to each other. A plurality of resonant conductors continuously arranged from the input position of the frequency signal toward the output position;
An outer conductor surrounding the plurality of resonant conductors;
A diplexer comprising a coaxial filter comprising a conductor plate disposed in at least one gap between the plurality of resonant conductors,
A diplexer characterized in that the thickness and length of the conductor plate having desired characteristics are determined based on the relationship between the coupling coefficient with respect to the thickness of the conductor plate and the length of the conductor plate. A plurality of resonant conductors arranged continuously from an input position to an output position of a frequency signal, an outer conductor surrounding the plurality of resonant conductors, and at least one gap between the plurality of resonant conductors A method of manufacturing a coaxial filter comprising a conductor plate,
After determining the thickness of the conductor plate having desired characteristics based on the relationship between the coupling coefficient with respect to the thickness of the conductor plate and the length of the conductor plate, the thickness of the conductor plate is adjusted by adjusting the length of the conductor plate. And a method for producing a coaxial filter, wherein the length is determined.

Images