JPH07283610A - Dielectric filter - Google Patents

Abstract

PURPOSE:To provide the dielectric filter which has a small number of parts and is low-cost, small-sized, and low-height and is easy to adjust and has a stop band and a pass band and has attenuation characteristics in both of the low band and the high band. CONSTITUTION:At least three notch circuits 115 to 117, at least one inter-stage coupling capacitor 112, and at least one inter-stage coupling inductor 113 are provided, and notch circuits are cascaded with the inter-stage coupling capacitor 112 or the inter-stage coupling inductor 113 between them. At least one dielectric resonator (103 to 105), a shield cover, a terminal substrate, and a coupling circuit part consisting of circuit elements formed or mounted on the terminal substrate are provided, and dielectric resonators 103 to 105 are electrically connected to the coupling circuit part to constitute a filter circuit. The shield cover covers the surface of the terminal substrate including the coupling circuit part but not including dielectric resonators 103 to 105.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter mainly used for wireless communication equipment such as mobile phones.

[0002]

2. Description of the Related Art In recent years, there has been a demand for miniaturization of dielectric filters with the spread of portable terminals of mobile communication equipment, and therefore, there has been a strong demand for both excellent performance and compact shape. In terms of performance, in addition to having a pass band and a stop band as the original filter function, in order to remove unnecessary signal components emitted from the radio device or jumping into the radio device, both low and high frequencies are removed. It is required that the transfer characteristic obtain an attenuation amount. In addition, as a compact shape, in order to effectively use the mounting space of the component, it is strongly desired to reduce the height of the component.

An example of a conventional dielectric filter will be described below with reference to the drawings. FIG. 5A shows a circuit diagram of a conventional dielectric filter. Figure 5
In (a), 601, 602 are input / output terminals, 603
˜605 is a dielectric resonator, 610-612 series coupling capacitors, 613-615 are parallel ground capacitors, 61
Reference numerals 6 and 617 denote inter-stage coupled inductors. The operation of the conventional dielectric filter will be described below.

The dielectric resonators 603 to 605 and the series coupling capacitors 610 to 612 are respectively connected in series to form a one-stage notch circuit having series resonance characteristics and parallel resonance characteristics. The interstage coupling inductor 616 and the parallel ground capacitors 613 and 614, and the interstage coupling inductor 617 and the parallel ground capacitors 614 and 615 respectively form a J inverter that is a resonator coupling circuit. For J inverter, refer to the literature (GLMatthaei et al., "Microwave fi
lters, impedance-matching networks, and coupling s
tructures ", McGraw-Hill, 1964), etc. Each notch circuit is cascaded by a J inverter, and multistage band rejection that shows large attenuation in transfer characteristics at the series resonance frequency of each notch circuit. In addition, since the impedance of the notch circuit becomes infinite at the parallel resonance frequency of each notch circuit, it is connected in cascade with the J inverter to show the band pass characteristic. Is a J-inverter and a π-type low-pass filter when viewed in a wide band, and thus exhibits a low-pass characteristic, so that this filter has the following characteristics as shown by the solid line in FIG.
It has a stop band and a pass band, and has a low-pass characteristic.

Further, FIG. 5B shows a circuit diagram of a modified dielectric filter of the conventional example. In FIG. 5B, 618 to 620 are parallel ground inductors, 621 and 6
22 is an inter-stage coupling capacitor. The configuration of the modified dielectric filter of the conventional example is almost the same as that of the above-described conventional dielectric filter, and only the configuration of the J inverter is different. Therefore, although the same operation as the conventional example is performed, J
The capacitors and inductors that make up the inverter are J inverters, and at the same time, they are π-type high-pass filters when viewed in a wide band, so this shows high-pass characteristics. Therefore, this filter has a stop band and a pass band as shown by the broken line in FIG. 5C, and has a high-pass characteristic.

On the other hand, FIG. 6 is an external perspective view of the above-mentioned conventional dielectric filter. In FIG. 6, 6
01 is an input terminal, 603-605 are dielectric resonators, 60
6 is a shield cover, 607 is a terminal board, 608, 60
Reference numeral 9 is an adjustment window. The structure of the conventional dielectric filter will be described below.

First, on the terminal substrate 607 on which the dielectric resonators 603 to 605 and the circuit element for connecting them are mounted, the shield cover 6 is provided to prevent electromagnetic interference with an external circuit.
It is covered with 06. The shield cover 606 has a top surface and side surfaces in three directions, and covers the entire area of the dielectric resonator except the short-circuited end portion. The bottom edge of each side surface of the shield cover 606 is fixed to the terminal substrate 607 by soldering, and the dielectric resonators 603 to 605 are fixed by soldering the top surface and the edge portions of the two side surfaces on both sides. In the shield cover 606,
Square-shaped adjustment windows 608 and 609 are provided, and adjustment rods are inserted from there to adjust the interstage coupling inductor and the like.

[0008]

However, in the above-mentioned structure, for example, in order to form the conventional three-stage filter, six capacitors and two inductors are required, and the number of parts is large, so that the cost is reduced. Is high and the shape becomes large. In addition, the circuit configuration is complicated and there are many adjustment points after mounting, and it is difficult to simultaneously achieve the attenuation characteristics in the low and high frequencies necessary to suppress the spurious components generated in the radio. There was a point. Furthermore, because the shield cover covers almost the entire surface, the height of the component is the total height when the thickness of the terminal board and the dielectric resonator are added to the thickness of the shield cover and the thickness of the solder for fixing. It had many problems such as high cost.

In view of the above problems, the present invention has a small number of parts, a low cost, a small size, a low profile, easy adjustment, a stop band and a pass band, and a low band and a high band. An object is to provide a high-performance dielectric filter having an attenuation characteristic.

[0010]

In order to solve the above problems, a dielectric filter according to the present invention, in claim 1, has at least three notch circuits and at least one interstage coupling capacitor. At least one interstage coupling inductor is provided, and the notch circuits are connected in cascade via the interstage coupling capacitor or the interstage coupling inductor.

Alternatively, in claim 2, in addition to this, a parallel ground capacitor or a parallel ground inductor is provided,
The connection point to which only the interstage coupling capacitor is connected is grounded via the parallel ground inductor, and the connection point to which only the interstage coupling inductor is connected is grounded via the parallel ground capacitor. The connection point to which both the capacitor and the interstage coupling inductor are connected is configured such that neither the parallel ground inductor nor the parallel ground capacitor is connected.

Alternatively, in claim 3, a parallel ground capacitor is provided, and a connection point to which only the interstage coupling inductor is connected is grounded via the parallel ground capacitor, and a connection to which the interstage coupling inductor is connected. The point is such that the parallel ground capacitor is not connected.

Alternatively, in the present invention, a parallel ground inductor is provided, and the connection point to which only the interstage coupling capacitor is connected is grounded via the parallel ground inductor, and the connection to which the interstage coupling capacitor is connected. The point is such that the parallel ground inductor is not connected.

Further, in claim 5, these are limited to the first notch circuit, the second notch circuit, the third notch circuit, the interstage coupling capacitor, the interstage coupling inductor, and the parallel ground. A capacitor is provided, and an interstage coupling capacitor is connected between the first notch circuit and the second notch circuit, and an interstage coupling inductor is provided between the second notch circuit and the third notch circuit. The third notch circuit is connected, the third notch circuit is grounded by the parallel ground capacitor, and the first notch circuit and the third notch circuit are respectively connected to the input / output terminals.

According to a sixth aspect of the present invention, the notch circuit is limited to a circuit in which a series coupling capacitor is connected in series to the dielectric coaxial resonator.

Further, according to a seventh aspect of the present invention, the structure has at least one dielectric resonator, a shield cover, a terminal board, and a coupling circuit section formed by a circuit element formed or mounted on the terminal board. The dielectric resonator is electrically connected to the coupling circuit unit to form a filter circuit, the shield cover includes the coupling circuit unit on the terminal substrate, and the dielectric resonance is provided. The container is a structure that covers the area not included.

Further, in the eighth aspect, this is limited, and the height of the top surface of the shield cover is equal to or lower than the height when the dielectric resonator is mounted.

Similarly, in claim 9, the shield cover is limited to this, and the shield cover has a top surface and side surfaces in three directions, of which two side surfaces at both ends are formed with joint arm portions, respectively. The joining arm portion is joined to the outermost two side surfaces of the dielectric resonator arranged as described above, and the shield cover is fixed.

Similarly, in claim 10, this is limited to
The height of the upper side of the joining arm portion is made lower than the height of the top surface of the shield cover to form a stepped structure.

Similarly, in claim 11, this is limited,
By inserting the fixing protrusion provided below the tip of the joining arm into the fixing hole provided in the terminal board,
The shield cover is fixed to the terminal board.

Similarly, claim 12 limits this,
The shield cover is fixed to the terminal board by soldering a bent portion provided below the tip of the joining arm portion to a ground electrode pattern provided on the terminal board.

Similarly, claim 13 limits this,
A structure in which the shield cover is fixed to the terminal board by inserting a fixing projection provided below a side surface of the shield cover that is not in contact with the dielectric resonator into a fixing hole provided in the terminal board. Is.

Similarly, claim 14 limits this,
A structure in which the shield cover is fixed to the terminal board by soldering a bent portion provided below a side surface of the shield cover that is not in contact with the dielectric resonator to a ground electrode pattern provided on the terminal board. It was done.

Similarly, in claim 15, this is limited,
A notch is provided on a side of the side surface of the shield cover which is in contact with the terminal board, so that the shield cover and the terminal board are not in contact with each other at the corner.

Similarly, claim 16 limits this,
The shield cover has a structure in which a round adjustment window is provided on the top surface.

[0026]

According to the present invention, the impedance of the interstage coupling capacitor increases at a low frequency due to the combination of the interstage coupling capacitor and the interstage coupling inductor in the configurations of claims 1 to 5, and Since the impedance of the coupled inductor increases at high frequencies, attenuation characteristics can be realized at the same time in the low band and high band in addition to the stop band and pass band. Further, with the configurations of claims 2 to 6, the circuit configuration is simplified, and the number of parts that configure the circuit can be reduced. Further, in the configurations of claims 7 to 16, since the dielectric resonator is not covered with the shield cover, the height of the component is reduced accordingly. Further, in the configurations of claims 9 to 14, by providing the structure such as the joining arm portion, the fixing projection, and the bent portion, the shield cover can be reliably grounded, and sufficient mechanical strength can be obtained. The structure can be obtained. In addition, claim 15
With this configuration, the corners of the shield cover can be effectively used for mounting circuit elements, and the size can be reduced. According to the sixteenth aspect, the opening area of the adjustment window can be reduced without impairing the workability of the adjustment work, and the excellent shielding property and the processing cost can be reduced.

[0027]

【Example】

(Embodiment 1) A dielectric filter according to a first embodiment of the present invention will be described below with reference to the drawings. First, Fig. 1
1A is a circuit diagram of a dielectric filter according to the first embodiment of the present invention, and FIG. 1B is a graph showing transfer characteristics.
In FIG. 1A, 101 and 102 are input / output terminals and 10
3 to 105 are dielectric resonators, 109 to 111 are series coupling capacitors, 112 is an inter-stage coupling capacitor, 113 is an inter-stage coupling inductor, 114 is a parallel ground capacitor, 11
Reference numeral 8 is a parallel ground inductor. For example, quarter-wavelength tip short-circuit type dielectric coaxial resonators are used as the dielectric resonators 103 to 105, parallel plate capacitors are used as the series coupling capacitors 109 to 111, and the interstage coupling capacitor 11 is used.
2. A chip capacitor is used as the parallel ground capacitor 114, and an air core coil is used as the interstage coupling inductor 113 and the parallel ground inductor 118. First notch circuit 11
Reference numeral 5 is composed of a dielectric resonator 103 and a series coupling capacitor 109 connected in series. In addition, the second notch circuit 1
Reference numeral 16 is a dielectric resonator 104 and a series coupling capacitor 110.
The third notch circuit 117 is formed by serially connecting the dielectric resonator 105 and the series coupling capacitor 111. These notch circuits exhibit very low impedance at the series resonant frequency and very high impedance at the parallel resonant frequency. Input / output terminal 101
And the first notch circuit 115 are connected, the first notch circuit 115 and the second notch circuit 116 are connected through the interstage coupling capacitor 112, and the second notch circuit 116 and the third notch circuit 116 are connected.
Of the third notch circuit 117 and the input / output terminal 102 by connecting the notch circuit 117 of FIG.
Connect. The first notch circuit 115 is grounded via the parallel ground inductor 118, and the third notch circuit 117 is grounded via the parallel ground capacitor 114.

The operation of the dielectric filter having the above structure will be described below. The basic operation principle of the dielectric filter having the structure of the present invention is almost the same as that of the conventional example and the modification of the conventional example described above. What is different from the conventional example is a method of constructing a J inverter in which each notch circuit is connected in cascade. The configuration method of the J inverter is as described in the above-mentioned conventional example and the modified configuration of the conventional example.
Two configurations are possible: a three-element π-type high-pass filter type that uses an inductor for parallel grounding and a three-element π-type low-pass filter type that uses a capacitor for parallel grounding. With the configuration of the present invention, first, by adopting a combination of both, it is possible to realize a dielectric filter having attenuation characteristics in both the low band and the high band.

Next, the central notch circuit 116 is originally connected to both the parallel ground inductor of the J inverter including the interstage coupling capacitor 112 and the parallel ground capacitor of the J inverter including the interstage coupling inductor 113. There must be. However, the interstage coupling capacitor 112
By properly selecting the element value of the interstage coupling inductor 113, the admittance values of the parallel ground inductor and the parallel ground capacitor can cancel each other at or near the series resonance frequency of the notch circuit. In such a state, the notch circuit 11
It is possible to eliminate the parallel grounding element originally connected to 6. Therefore, the number of parts can be reduced without substantially deteriorating the filter characteristic.

Therefore, in the dielectric filter of this embodiment, as shown in FIG. 1B, the dielectric filter has the characteristics of having a stop band and a pass band and having an attenuation characteristic in both the low band and the high band. Can be realized.

As described above, by combining the J inverter connecting the notch circuits with a three-element π-type low-pass filter and a high-pass filter, the amount of attenuation can be secured in both the low band and the high band. Moreover, since it is possible to reduce the number of inductors and capacitors for grounding the connection points of two types of J inverters in parallel, it is possible to realize a small-sized, low-cost and high-performance dielectric filter.

The structure of the dielectric filter of this embodiment will be described below. FIG. 2 is an external perspective view of the dielectric filter according to the first embodiment of the present invention, and FIG. 3 is an exploded perspective view. Since the circuits shown in FIGS. 2 and 3 have the configuration shown in FIG. 1, the same components are designated by the same reference numerals. 2 and 3, 101 and 102 are input / output terminals and 10
3 to 105 are dielectric resonators, 106 is a shield cover,
107 is an adjustment window, 108 is a terminal substrate, 201 is a ground electrode pattern, 202 is a fixing hole, 301 is a joining arm portion, 302 is a fixing projection, 303 is a bent portion, 304
Is a notch.

For the dielectric resonators 103 to 105, for example, quarter-wavelength tip short-circuit type dielectric coaxial resonators are used. The dielectric resonators 103 to 1 are provided on the terminal board 108.
A circuit element for coupling 05 is mounted, or the circuit element is formed with an electrode pattern to form a coupling circuit section 119. Unlike the conventional example, the metal seal cover 106 covers only the coupling circuit section 119 and does not cover the dielectric resonators 103 to 105 in this embodiment. The shield cover 106 is composed of a top surface and side surfaces in three directions including A surface, B surface, and C surface. The surface A is a side surface that does not contact the dielectric resonator, and the bonding arm portions 301 are formed on the two side surfaces at both ends, that is, the surfaces B and C, respectively.

Since the circuit elements other than the dielectric resonator are capacitors or inductors, they are easily affected by the electromagnetic field energy emitted from the circuit element or the electromagnetic field energy reaching from the outside. Therefore, the shield cover has a shield function of preventing the filter characteristics from being deteriorated by them. On the other hand, the dielectric resonator has a shield function by itself because the outer peripheral surface is covered with a metal film except for the open end surface connected to the coupling circuit section.

If the dielectric resonator is not covered with the shield cover as in the present embodiment, the height of the top surface of the shield cover can be set to be equal to or lower than the height when the dielectric resonator is mounted. . Therefore, the height as a component can be set to the height from the bottom surface of the terminal board to the top surface of the dielectric resonator, so that the shield cover covering the dielectric coaxial resonator of the conventional structure and the thickness of soldering can be omitted, and the low profile can be achieved. Becomes possible.

The joining arms of the B and C faces of the shield cover are joined by soldering to the outermost two side faces of the dielectric resonator arranged and mounted in parallel on the terminal board.
This ensures the stability of grounding and joining. Furthermore, by providing a step from the top surface in this portion, the length of the side in contact with the dielectric resonator can be expanded, and thus sufficient grounding and bonding stability can be ensured.

Further, by providing a fixing projection 302 below the tip of the joining arm and fitting it into the fixing hole 202 of the shield cover formed on the terminal board, the stability of alignment and fixing with the terminal board is improved. Can be increased. In addition, the bent portion 3 is provided below the A surface of the shield cover.
03, the ground electrode pattern 201 is formed along the edge on the terminal board, and both are soldered,
Grounding and fixing can be ensured and stable filter characteristics can be secured.

On the other hand, the input / output terminal patterns 101 and 102
Are provided at the corners on the terminal board respectively, so that the corners of the A surface and the B surface of the shield cover and the A surface and the C surface of the shield cover.
The corners of the surface can be effectively used for mounting the circuit element, and the degree of freedom in component placement is increased. For that purpose, it is necessary to provide cutouts on the sides of these corners that come into contact with the terminal board so that the shield cover and the terminal board do not come into contact with each other at the corners. By doing so, the shield cover does not come into contact with the circuit element and the input / output terminal pattern, and the mounting area can be effectively used, so that the size can be reduced.

A circular adjustment window is provided on the top surface of the shield cover. Insert the adjusting rod from there to adjust the inter-stage coupling inductor. By making the adjustment window round, the window processing die can be manufactured more easily and can be manufactured at a lower cost than a square processing mold, so that the window drilling cost can be reduced. In addition, in the round shape, the opening area can be reduced without impairing the workability of the adjustment work, and good shielding performance can be realized.

As described above, according to this embodiment, the combination of the interstage coupling capacitor and the interstage coupling inductor allows
It is possible to realize a high-performance dielectric filter having a stop band and a pass band and having attenuation characteristics in both the low band and the high band. Also, with a simple circuit configuration with a small number of parts, a large amount of attenuation in the low and high frequencies can be obtained, adjustment is easy, downsizing and cost reduction can be achieved, and a dielectric filter optimal as a transmission filter for mobile phones is available. realizable.

Further, by preventing the dielectric resonator from being covered with the shield cover, the height of the parts can be reduced by the thickness of the shield cover and the solder, and a low-profile dielectric filter can be obtained. realizable. Further, the shield arm and the dielectric resonator and the terminal board can be securely connected and fixed to each other by the joining arm portion, the fixing projection and the bent portion, which has good filter characteristics and sufficient mechanical strength can be obtained. It is possible to realize a dielectric filter. Further, the corner portions of the shield cover can be effectively used for mounting circuit elements, and a small dielectric filter can be realized. Also, adjustment work is easy,
It is possible to realize a dielectric filter with excellent shielding properties and low processing costs.

In the description of the present embodiment, a fixing projection 302 is provided below the tip of the joining arm and is fitted into a fixing hole 202 of the shield cover formed on the terminal board. The bent portion 303
It is said that the soldering is performed on the ground electrode pattern 201 on the terminal board by soldering, but a bent portion is provided on the lower end of the joining arm portion and the soldering is performed on the ground electrode pattern formed on the terminal board. It is also possible to provide a fixing projection on and to fit it into the fixing hole of the terminal board. It goes without saying that the same effect can be obtained in this case as well.

(Embodiment 2) A dielectric filter according to a second embodiment of the present invention will be described below with reference to the drawings. First, FIG. 4A is a circuit diagram of a dielectric filter in the second embodiment of the present invention, and FIG. 4B is a graph showing transfer characteristics. The circuit shown in FIG. 4 has the first circuit shown in FIG.
The same components as those of the circuit of the embodiment are given the same numbers. This embodiment is different from the first embodiment in that the parallel ground inductor 118 is removed in the configuration of the first embodiment.

The parallel-grounded inductor 118 connected in parallel to the first notch circuit 115 can secure a certain amount of low-frequency attenuation with the inter-stage coupling capacitor 112 unless a large amount of attenuation is required in the low frequency range. There is no problem even if it is deleted in order to make the circuit simpler than the configuration of the first embodiment. By properly selecting other circuit element values,
Good filter characteristics can also be realized with the configuration of this embodiment. Such a configuration is also possible for a dielectric filter composed of four or more stages of notch circuits. In this case, the circuit can be composed of only capacitors without using an inductor as a parallel ground element. Therefore, the circuit configuration is simplified, and the number of inductors formed by the air-core coil that need to be adjusted can be reduced, which facilitates the adjustment work.

As described above, according to this embodiment, in addition to the same effects as the first embodiment, the circuit structure can be made simpler and the number of parts can be reduced and the size can be reduced as compared with the first embodiment. Therefore, the cost can be reduced, and the adjustment work can be facilitated.

Since the external structure of this embodiment is the same as that of the first embodiment, this embodiment has the same effect as that of the first embodiment with respect to the structure. .

In the description of this embodiment, the parallel ground inductor connected in parallel with the notch circuit is deleted, but similarly, the parallel ground capacitor connected in parallel with the notch circuit may be deleted. It is possible. In this case, the amount of attenuation in the high frequency band is somewhat reduced, but the effect that the circuit configuration can be simplified as in the present embodiment is obtained.

[0048]

As described above, according to the present invention, in the structure of claim 1, the combination of the inter-stage coupling capacitor and the inter-stage coupling inductor has a stop band and a pass band, and has a low band and a high band. It is possible to realize a high-performance dielectric filter having both attenuation characteristics.

Further, in the structure of claim 2, in addition to the same effect as the structure of claim 1, a simple circuit structure with a small number of parts can obtain a large amount of attenuation in the low range and high range, and adjustment can be performed. It is easy, and it is possible to realize downsizing and cost reduction.

Further, in the structure of claim 3, in addition to the same effect as the structure of claim 1, the circuit structure is simpler than the structure of claim 2, the number of parts is small, and the high-frequency attenuation is large. An obtainable dielectric filter can be realized.

Further, in the structure of claim 4, in addition to having the same effect as the structure of claim 1, the circuit structure is simpler and the number of parts is smaller than that of the structure of claim 2, and the amount of low-frequency attenuation is large. An obtainable dielectric filter can be realized.

Further, in the structure of claim 5, in addition to the same effects as those of the structures of claims 1 and 3, it is possible to realize a compact and low-cost dielectric filter optimal as a transmission filter of a mobile phone.

In addition, the structure of claim 6 has the same effect as any one of the structures of claims 1 to 5, and can realize downsizing and cost reduction with a simple circuit structure.

Further, in the structures of claims 7 and 8, the height of the component is reduced by the thickness of the shield cover and the solder so that the dielectric resonator is not covered with the shield cover. It is possible to realize a low-profile dielectric filter.

The structure of claim 9 has the same effect as that of the structure of claim 7, and the connection arm portion ensures the connection of the shield cover and the dielectric resonator, and has a good filter characteristic. In addition, it is possible to realize a dielectric filter having sufficient mechanical strength.

In the structure of claim 10, the effect obtained by the structure of claim 9 can be made more reliable.

In addition, the structures of claims 11 to 14 have the same effect as that of the structure of claim 7, and can reliably connect the shield cover and the terminal substrate, and have good filter characteristics. Moreover, it is possible to realize a dielectric filter having sufficient mechanical strength.

Further, in the structure of the fifteenth aspect, the corner portions of the shield cover can be effectively used for mounting the circuit element, and a small dielectric filter can be realized.

Further, in the structure of claim 16, it is possible to realize a dielectric filter which is easy to adjust and has a good shielding property and a low processing cost.

[Brief description of drawings]

1A is a circuit diagram of a dielectric filter according to a first embodiment of the present invention, and FIG. 1B is a graph showing transfer characteristics of a dielectric filter according to a first embodiment of the present invention.

FIG. 2 is an external perspective view of the dielectric filter according to the first embodiment of the present invention.

FIG. 3 is an exploded perspective view of the dielectric filter according to the first embodiment of the present invention.

FIG. 4A is a circuit diagram of a dielectric filter according to a second embodiment of the present invention, and FIG. 4B is a graph showing a transfer characteristic of the dielectric filter according to the second embodiment of the present invention.

5A is a circuit diagram of a dielectric filter of a conventional example, FIG. 5B is a circuit diagram of a dielectric filter in a modification of the conventional example, and FIG. 5C is a transfer characteristic of a dielectric filter in a conventional example and a modification of the conventional example. Showing the graph

FIG. 6 is an external perspective view of a conventional dielectric filter.

[Explanation of symbols]

 101, 102 Input / output terminals 103, 104, 105 Dielectric resonator 106 Shield cover 108 Terminal board 109, 110, 111 Series coupling capacitor 112 Interstage coupling capacitor 113 Interstage coupling inductor 114 Parallel grounding capacitor 115, 116, 117 Notch circuit 118 Parallel Ground Inductor 119 Coupling Circuit Section 201 Grounding Electrode Pattern 202 Fixing Hole 301 Joining Arm Section 302 Fixing Protrusion 303 Bending Section 304 Notch

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Shoji Tanaka, Shoji Tanaka, Kyoto, Tsubaki-cho, Oita 55-12 Ozumi, Matsushita Nitto Electric Co., Ltd. Ozumi Kojihama 55-12 Matsushita Nitto Electric Co., Ltd.

Claims (16)

[Claims] 1. At least three notch circuits, at least one inter-stage coupling capacitor, and at least one.
A dielectric filter comprising: a plurality of inter-stage coupled inductors, wherein the notch circuits are connected in series via the inter-stage coupled capacitors or the inter-stage coupled inductors. 2. At least three notch circuits, at least one inter-stage coupling capacitor, and at least one.
A plurality of interstage coupling inductors and a parallel ground capacitor or a parallel ground inductor are provided, and the notch circuits are connected in cascade via the interstage coupling capacitors or the interstage coupling inductors, respectively, and only the interstage coupling capacitors are provided. Is connected to the ground via the parallel ground inductor, the connection point to which only the interstage coupling inductor is connected is grounded via the parallel ground capacitor, and the interstage coupling capacitor and the interstage coupling are connected. A dielectric filter, wherein a connection point to which both inductors are connected does not connect either the parallel ground inductor or the parallel ground capacitor. 3. At least three notch circuits, at least one interstage coupling capacitor, and at least one.
A plurality of interstage coupling inductors and a parallel ground capacitor are provided, and the notch circuits are connected in cascade via the interstage coupling capacitors or the interstage coupling inductors, respectively, and only the interstage coupling inductors are connected. A dielectric filter, wherein a connection point is grounded via the parallel ground capacitor, and the parallel ground capacitor is not connected to the connection point to which the interstage coupling inductor is connected. 4. At least three notch circuits, at least one interstage coupling capacitor, and at least one.
A plurality of interstage coupling inductors and a parallel ground inductor are provided, and the notch circuits are connected in cascade via the interstage coupling capacitors or the interstage coupling inductors, respectively, and only the interstage coupling capacitors are connected. A dielectric filter characterized in that a connection point is grounded via the parallel grounded inductor, and the parallel grounded inductor is not connected to the connection point to which the interstage coupling capacitor is connected. 5. A first notch circuit, a second notch circuit, a third notch circuit, an interstage coupling capacitor, an interstage coupling inductor, and a parallel ground capacitor, wherein the first notch circuit is provided. An interstage coupling capacitor is connected between the circuit and the second notch circuit, and an interstage coupling inductor is connected between the second notch circuit and the third notch circuit, and the third notch circuit is connected. A dielectric filter, wherein the first notch circuit and the third notch circuit are respectively connected to input / output terminals while being grounded by the parallel ground capacitor. 6. The dielectric filter according to claim 1, wherein the notch circuit is composed of a circuit in which a series coupling capacitor is connected in series to a dielectric coaxial resonator. 7. A dielectric resonator comprising: at least one dielectric resonator, a shield cover, a terminal board, and a coupling circuit section formed of circuit elements formed or mounted on the terminal board. Is electrically connected to the coupling circuit section to form a filter circuit, the shield cover includes the coupling circuit section on the terminal substrate, and
A dielectric filter, characterized in that it covers a region that does not include the dielectric resonator. 8. The dielectric filter according to claim 7, wherein the height of the top surface of the shield cover is not more than the height when the dielectric resonator is mounted. 9. The shield cover has a top surface and side surfaces in three directions, and two joint side arm portions are formed on two side surfaces at both ends of the shield cover. The dielectric filter according to claim 7, wherein the shield arm is fixed by joining the joining arms to the outer two side surfaces. 10. The dielectric filter according to claim 9, wherein the height of the upper side of the joining arm portion is made lower than the height of the top surface of the shield cover to form a step. 11. A shield cover has a top surface and side surfaces in three directions, of which two joint side arm portions are formed on two side surfaces at both ends, and a fixing arm is provided below the tip end portion of the joint arm portion. 8. The dielectric filter according to claim 7, wherein the shield cover is fixed to the terminal substrate by inserting a projection for insertion into a fixing hole provided in the terminal substrate. 12. A shield cover has a top surface and side surfaces in three directions, two joint side arm portions are formed on two side surfaces at both ends, and a bending portion is provided below a tip end portion of the joint arm portion. 8. The dielectric filter according to claim 7, wherein the shield cover is fixed to the terminal board by soldering the portion to a ground electrode pattern provided on the terminal board. 13. The shield cover is fixed to the terminal board by inserting a fixing projection provided below a side surface of the shield cover that is not in contact with the dielectric resonator into a fixing hole provided in the terminal board. The dielectric filter according to claim 7, which is characterized in that. 14. The shield cover is fixed to the terminal board by soldering a bent portion provided below a side surface of the shield cover that is not in contact with the dielectric resonator to a ground electrode pattern provided on the terminal board. The dielectric filter according to claim 7, wherein: 15. A cutout is provided on a side of a side edge of the shield cover which is in contact with the terminal board, so that the shield cover and the terminal board are not in contact with each other at the corner. Dielectric filter. 16. The dielectric filter according to claim 7, wherein a round adjustment window is provided on the top surface of the shield cover.