JPH0793523B2 - Dielectric band stop filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dielectric filter mainly used in a microwave band, and more specifically, to an integrated dielectric multistage coaxial resonator, in which each resonator is connected to each other. The present invention relates to a band elimination filter having a fixed capacitor substrate provided with most or all of lumped constant elements to be coupled.

[Prior Art] As a multistage band stop filter using a high dielectric constant ceramic material, as shown in FIG.
The individual dielectric prismatic resonators 10 are arranged in parallel and are coupled by an appropriate lumped element. The dielectric resonator 10 is formed by penetrating a resonator hole 14 in the center of a prism 12 made of a high dielectric constant material. A conductor film is attached to the inner wall surface of the resonator hole 14 and the outer surface of the prism 12 excluding the open surface (upper surface), which serves as a center conductor and an outer conductor, respectively. Coupling capacitors C ₁ , C ₂ and C ₃ are respectively connected to the open ends of the central conductors, and the capacitors are connected by inductance elements L ₁ and L ₂ . The equivalent circuit is shown in FIG. Each dielectric resonator 10 has a resonance frequency determined by its prismatic height, relative permittivity, capacitor capacity, etc., and a 1/4 wavelength coaxial resonance type band elimination filter is obtained by the above configuration.

[Problems to be Solved by the Invention] Since the band elimination filter shown in FIG. 15A has a plurality of single resonators 10 arranged, the number of parts is increased, so that the number of assembling steps is increased and the positioning between the resonators is increased. The demands on the accuracy of the outer conductor surface will also increase. Further, there is a problem in that mechanical strength and environmental resistance reliability are deteriorated because the resonators need to be joined together. Further, since a lumped element is attached to the upper part of each resonator, there is a drawback that it is difficult to assemble and handle.

Since the LC network composed of the lumped constant coupling capacitors C ₁ , C ₂ and C ₃ and the inductance elements L ₁ and L ₂ has a low-pass filter configuration, in the vicinity of 3f ₀ (third resonance frequency) A certain degree of damping characteristic can be obtained. But given
With an element constant exhibiting f ₀ characteristics, the cutoff frequency is 2f ₀
Since it is close to, only a few dB of attenuation can be obtained.

The object of the present invention is to solve these problems in the prior art, to improve the manufacturability and designability, to obtain stable electric / mechanical properties, and to exhibit a dielectric band stop exhibiting excellent attenuation characteristics at frequencies of 2f ₀ or higher. To provide a filter.

[Means for Solving the Problems] The present invention uses an integrated multi-stage coaxial dielectric resonator, forms a part or all of an appropriate lumped element on a capacitor substrate, and uses the capacitor substrate as a dielectric resonator. It is a dielectric filter that is attached to the notch step portion and integrated with it so as to exhibit a band elimination filter characteristic.

In a dielectric resonator, a rectangular parallelepiped dielectric block is provided with a plurality of resonator holes and coupling blocking holes located between them, which are short-circuited at both open ends, and a notch step near one open surface. Parts are provided. The capacitor substrate has a flat plate-type grounding capacitor portion having a plurality of front surface electrodes and back surface ground electrodes corresponding to the resonator holes. The capacitor substrate is attached to the stepped part so that the ground capacitor part projects, and the surface electrodes of each ground capacitor part are coupled by an inductance element, and the conductor film of each resonator hole and each surface electrode are coupled by a coupling capacitor. Connecting.

The coupling capacitor can have various configurations. For example, it is formed by the conductor pattern provided near the resonator hole on the open surface of the dielectric block and the surface electrode of the capacitor substrate facing vertically, or the gap of the conductor pattern provided near the resonator hole on the open surface of the dielectric block. It may be formed by. Further, it may be formed by the surface electrode of the capacitor substrate and the second surface electrode provided with a gap therebetween, or a chip capacitor mounted between these two surface electrodes. Further, it may be formed of a conductor film on the inner wall surface of the resonator hole, a conductor pattern provided on the step portion, and a dielectric block material between them.

[Operation] Each resonator hole constitutes a 1/4 wavelength type coaxial resonator. Since the coupling blocking holes provided between the resonator holes are short-circuited at both open ends, the electromagnetic coupling is blocked by blocking the propagation of electromagnetic waves between the resonators. Therefore, even though it is an integrated structure, it is electromagnetically equivalent to a single resonator arrayed.

A band stop filter can be obtained by additionally connecting an appropriate lumped constant element (coupling capacitor and inductance element) to this dielectric resonator. The grounding capacitor part formed on the capacitor substrate sets the capacitance to an appropriate value to make the attenuation above 2f ₀ large and steep.

The notch step portion formed in the dielectric block has a function of positioning the capacitor substrate, so that both can be easily integrated.

[Embodiment] FIG. 1 is a perspective view showing an embodiment of a dielectric band elimination filter according to the present invention, FIG. 2 is an exploded perspective view of the dielectric resonator and a capacitor substrate, and FIG. It is a figure. This embodiment is a case of three stages.

The dielectric resonator 20 is a substantially rectangular parallelepiped dielectric block.
Two through holes, which are resonator holes 24, and two through holes, which are located between them and serve as coupling blocking holes 26, are arranged in parallel in 22 and one of the surfaces where these through holes are open is an open surface. , A narrow notch step near one open side of the dielectric block 22
28 is formed, and a conductor film having a predetermined shape is attached to the dielectric block 22. The conductor film is provided on almost all surfaces except the inner wall surfaces of all the through holes and the open surface (the front surface in FIG. 1 and the upper surface in FIG. 2). Conductor film 30 on the inner wall surface of resonator hole 24
Serves as the central conductor, and the conductor film on the outer surface of the dielectric block 22 serves as the outer conductor 32. In the vicinity of the coupling prevention hole 26 on the open surface, a conductor pattern 34 for connecting the conductor film on the inner wall surface and the outer conductor 32 is formed.
Is provided, and the conductor film on the inner wall surface of the coupling blocking hole 26 is short-circuited (connected to the outer conductor 32) at both open ends thereof. The dielectric block 22 is made of a sintered body of a high dielectric constant material (for example, barium titanate or the like). The conductor film is a layer of an extremely thin conductive material formed by, for example, baking a silver paste.

The coupling blocking hole 26 located between the resonator holes 24 has its inner wall surface covered with a conductor film and is electrically connected to the outer conductor 32 at both opening ends. Propagation is blocked, and the dielectric resonator 20 is electromagnetically equivalent to a state in which each resonator is independent.

The capacitor substrate 40 has a dielectric plate 42 having a length substantially equal to the length of the dielectric resonator 20, and a flat-plate type ground capacitor portion formed by three front surface electrodes 44 and a rear surface whole surface ground electrode 46. . The capacitor substrate 40 is attached to the step portion 28 of the dielectric resonator 20 by a conductive adhesive or soldering so that the ground capacitor portion projects. In addition, the elongated conductor pattern 48 on the surface side formed on the capacitor substrate 40.
Is bonded to the conductor film formed on the step portion 28 of the dielectric resonator 20.

Then, the surface electrodes 44 of each grounding capacitor part are coupled by the coil 50, and the conductor film on the inner wall surface of each resonator hole 24 and the surface electrode
44 is connected by a coupling capacitor. This results in a dielectric bandstop filter. Reference numeral 52 is an input / output terminal.

Here, the coupling capacitor is formed by the conductor pattern 52 provided in the vicinity of the resonator hole on the open surface of the dielectric block and the surface electrode 44 of the capacitor substrate 40 facing each other at a right angle. The equivalent circuit of the filter thus obtained is the fourth
It becomes like the figure. In the figure, Ca, Cb and Cc represent ground capacitors, and C ₁ , C ₂ and C ₃ represent coupling capacitors.
L ₁ and L ₂ are coils 50.

In this manner, the dielectric resonator 20 is used and the appropriate lumped constant elements (C ₁ , ..., C ₃ , L ₁ , L ₂ ) are additionally connected to form a dielectric band elimination filter. Grounding capacitor Ca,…,
Cc is determined by the dielectric constant and thickness of the dielectric plate 42 and the area of the surface electrode 44, and by selecting it to an appropriate value, the attenuation characteristic at frequencies of 2f ₀ or higher is improved. An example of filter characteristics is shown in FIG.

The step of the notch step portion 28 formed in the dielectric constant block 22 is
Match the thickness of the capacitor substrate 40. Positioning is performed by aligning the capacitor substrate 40 with the step portion 28, and an integrated structure can be easily obtained.

Various configurations are conceivable for the coupling capacitor. 6 and 7, the coupling capacitance is provided by the gap between the conductor patterns 56, 58 provided in the vicinity of the resonator hole 24 on the open surface of the dielectric block 22. Conductor pattern 58 is a dielectric block
It reaches the end portion of 22 and, as shown in FIG. 7, that portion is brought into contact with the surface electrode 44 and soldering or the like is performed to achieve electrical connection.

8 to 10 show an example in which a coupling capacitor portion is also formed on the capacitor substrate 40. Surface electrode 44 of capacitor board 40
The second surface electrode 60 provided with a gap therebetween provides the coupling capacitance. Dielectric block
The conductor pattern 62 connected to the conductor film of the resonator hole 24 at the open surface of 22 extends to the end of the dielectric block 22 and contacts the second surface electrode 60 there. Also in this case, electrical connection is made by soldering or the like. In the example shown in FIG. 11, the chip capacitor 64 is mounted not in the gap between the surface electrode 44 of the capacitor substrate 40 and the second surface electrode 60 but in the gap to make it a coupling capacitance. This is preferable when a large coupling capacity is required.

In the example shown in FIGS. 12 to 14, the capacitor is formed by directly using the material of the dielectric block by the center conductor of the resonator hole 24 of the dielectric block 22 and the conductor film 68 formed in the notch step portion 28. is doing.

In each of the above-described embodiments, the resonator hole is formed in the dielectric block.
This is an example of a three-stage structure in which the resonator holes are two.
It goes without saying that the present invention can be applied to the case of four pieces or more. Although the coil is used as the inductance element, it is possible to form the inductance pattern on the capacitor substrate instead of the coil.
Also, in each drawing that shows the appearance of the dielectric resonator,
The portion shown with small dots shows the surface where the dielectric substrate is exposed, and the shaded portion shows the surface to which the conductor film is attached.

[Advantages of the Invention] As described above, the present invention is basically a dielectric block-integrated type and has a simple structure, so that manufacturability is good and stable electrical and mechanical properties are easily obtained. Further, since the coupling is performed by the lumped element, the design is easy and the frequency and coupling can be easily adjusted. Since all or most of the lumped element is formed on the capacitor substrate, it can be easily manufactured, and the coupling between the capacitor substrate and the dielectric resonator is performed by utilizing the notch step formed on the dielectric resonator. It can be positioned and easily installed. Since the capacitor substrate is provided with the grounded capacitor section, the amount of attenuation in the frequency region of 2f ₀ or higher is large, and good band stop filter characteristics can be obtained. In the present invention, since the dielectric resonator and the capacitor substrate are fixedly integrated with each other, surface mounting is possible and a caseless configuration is possible.

[Brief description of drawings]

1 is a perspective view showing an embodiment of a dielectric band elimination filter according to the present invention, FIG. 2 is an exploded perspective view of its dielectric resonator and a capacitor substrate, FIG. 3 is its sectional view, and FIG. Is an equivalent circuit diagram thereof, and FIG. 5 is a filter characteristic diagram. Sixth
FIG. 7 is a partial perspective view showing another embodiment of the present invention, and FIG. 7 is a partial sectional view thereof. FIG. 8 is a partial perspective view showing another embodiment of the present invention, FIG. 9 is an exploded perspective view of the dielectric resonator and the capacitor substrate, and FIG. 10 is a partial sectional view thereof. First
FIG. 11 is a partial sectional view showing another embodiment of the present invention. First
12 is a perspective view showing still another embodiment of the present invention, FIG. 13 is an exploded perspective view of the dielectric resonator and the capacitor substrate, FIG.
FIG. 14 is a partial plan view of the dielectric resonator. Fig. 15A
Is an explanatory view showing an example of a conventional filter, and B is an equivalent circuit diagram thereof. 20 ... Dielectric resonator, 22 ... Dielectric block, 24 ... Resonator hole, 26 ... Coupling blocking hole, 28 ... Step, 40 ... Capacitor substrate, 42 ... Dielectric plate, 44 ... … Surface electrode, 46 ……
Backside ground electrode, 50 ...... coil, Ca, Cb, Cc ...... grounding _{capacitor, C 1, C 2, C} 3 ...... coupling capacitor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-103001 (JP, A) JP-A 61-179603 (JP, A) JP-A 62-23204 (JP, A) JP-A 60- 114004 (JP, A) JP 61-193501 (JP, A) Actually opened 57-133102 (JP, U) Actually opened 63-181002 (JP, U) Actually opened 62-17201 (JP, U)

Claims (6)

[Claims] 1. A dielectric block is provided with a plurality of resonator holes and a coupling blocking hole located between the resonator holes and short-circuited at both opening ends.
A dielectric multi-stage coaxial resonator having a notch step portion on one side closer to the open surface is used, and a plurality of surfaces having a plate thickness corresponding to the step of the notch step portion and corresponding to each resonator hole. A capacitor substrate having a flat-plate type grounding capacitor part consisting of an electrode and a backside ground electrode is attached to the step so that the grounding capacitor part projects from the open surface of the dielectric block, and the inductance between the surface electrodes of each grounding capacitor part is reduced. A dielectric band elimination filter, which is coupled by an element, and the conductor film of each resonator hole and each surface electrode are connected by a coupling capacitor. 2. The filter according to claim 1, wherein the coupling capacitor is formed by a conductor pattern provided in the vicinity of the resonator hole on the open surface of the dielectric block and a surface electrode of the capacitor substrate facing vertically. 3. The filter according to claim 1, wherein the coupling capacitor is formed by a gap of a conductor pattern provided near the resonator hole on the open surface of the dielectric block. 4. The filter according to claim 1, wherein the coupling capacitor is formed by a gap between a surface electrode of the capacitor substrate and a second surface electrode provided at a distance from the surface electrode. 5. The filter according to claim 1, wherein the coupling capacitor comprises a chip capacitor provided between a surface electrode of the capacitor substrate and a second surface electrode provided at a distance from the surface electrode. 6. A coupling capacitor is formed by a conductor film provided on the inner wall surface of a resonator hole and a wall surface of a step portion, and a dielectric block material between them, and the conductor pattern is formed on the surface of a capacitor substrate. The filter according to claim 1, which is connected.