JPH05167309A - Dielectric filter - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a compact and inexpensive dielectric filter capable of obtaining a composite capacitor circuit with a simple structure, having a small number of parts. [Structure] Open surface 1 on one side of dielectric block 11
The step portion 15 is provided on the third side, and the capacitance pattern 16 is formed on the step portion 15. This capacitance pattern is configured by providing a conductor film-uncoated portion having a substantially U-shaped plane, the both ends of which communicate with the open surface 13. Then, the first conductor film 14a is formed in the internal space of the U-shaped portion 17 not coated with the conductor film, and the second conductor film 14b is formed outside the U-shaped portion. Then, a ground capacitance is formed between the first conductor film and the second conductor film and another adjacent conductor film 14. The three dielectric resonators 10 with the capacitance pattern are arranged side by side so that each capacitance pattern faces the same direction. Then, the capacitance patterns formed in the adjacent dielectric resonators are connected by the inductances L1 and L2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter, and more specifically, a discrete band stop filter constructed by connecting L and C circuits to a resonator made of a dielectric material. Regarding the improvement of.

[0002]

2. Description of the Related Art Dielectric filters are used as constituent parts of various communication circuits such as car phones, mobile phones and the like. Along with the downsizing of the mounted device, downsizing of the dielectric filter has been achieved. An example of the dielectric filter is shown in FIG. That is, the three cylindrical dielectric resonators 1 are arranged in parallel on the mounting plate 2 so that their open end faces 1a are located on the same plane. Then, the open end surface 1 of the dielectric resonator 1
One end of the connecting rod 3 is inserted into the opening 1b on the a side, and the other end of the connecting rod 3 is arranged so as to project to the outside. At the other end of the connecting rod 3, a chip capacitor C1,
C2, C3 are connected, and chip capacitors C1, C2, C
3 and the capacitance pattern CA formed on the capacitance substrate 5 in series.
, CB, CC are connected. Then, the respective capacitance patterns CA, CB and CC are dropped to the ground of the substrate 2.
In addition, the capacitance patterns CA, CB and CC are connected by the inductances L1 and L2. As a result, FIG.
The equivalent circuit diagram shown in FIG. 7 is constructed, and the frequency characteristics shown in FIG. 7 are obtained.

[0003]

However, in the above-mentioned conventional dielectric filter, the three chip capacitors C1 to C3, the capacitor substrate 5 and the two inductances L are used.
1, L2, and a large number of parts such as a connecting rod 3 for connecting to the chip capacitors C1 to C3 are required. Further, since the dielectric filter is required to be miniaturized as described above, each component must be miniaturized, but it is not only difficult to form such a small component, and the assembling work is complicated. Become. As a result, there is a problem such as an increase in cost.

The present invention has been made in view of the above background, and an object of the present invention is to reduce the number of parts and to make the dielectric filter extremely small and simple in structure and easy to assemble. To provide.

[0005]

In order to achieve the above object, in a dielectric filter according to the present invention, a dielectric block having a resonance hole and an inner surface of the resonance hole and a predetermined portion of the dielectric block are formed. And a plurality of dielectric resonators each including a conductor film forming a ground pattern, and LC coupling between the plurality of dielectric resonators. Among the side faces of the resonator, a stepped portion is formed on the open side of the side face that does not face the other adjacent dielectric resonator, a stepped portion is formed, a capacitance pattern is formed on the stepped portion, and the inductance between the capacitance patterns is formed. I joined it with.

[0006]

Since a capacitance pattern is formed at a predetermined position on the dielectric resonator, a desired dielectric filter can be constructed simply by arranging a plurality of such dielectric resonators and coupling the capacitance patterns with an inductance. It That is,
There is no need for an externally attached component such as a grounding capacitance, which was conventionally required. Then, the capacitance is changed only by adjusting the shape and size of the capacitance pattern, and the desired filter characteristic is obtained. Also,
Since it has a step portion, for example, an inductance may be inserted and arranged in the step portion, or a coupling member or the like to another circuit may be inserted and arranged.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a perspective view showing an example of a resonator constituting a dielectric filter according to the present invention, FIG. 2 is an equivalent circuit diagram of the dielectric filter of FIG. 1, and FIG. 3 shows such a dielectric resonator. 1 shows a first embodiment of the present invention configured using the same. As shown in the figure, the dielectric resonator 10
First, a resonance hole 12 extending in the axial direction is provided in a substantially rectangular parallelepiped dielectric block 11 made of a dielectric ceramic, and the resonance hole 12 is opened on one surface (open surface 13).
Other than the five surfaces and the inner surface of the resonance hole 12 are the conductor film 1
The coating is formed by 4.

Here, in the present invention, the stepped portion 15 which is lowered by one step is formed at one end of the side surface covering the conductor film 14 on the side of the open surface 13. The step portion 15 includes a low step surface 15a parallel to the side surface and one step lower, and the low step surface 15a.
And a back surface 15b connecting the side surface and the side surface. Then, the capacitance pattern 16 is formed on the step portion 15.
The capacitance pattern 16 is formed by providing a conductor film uncoated portion having a substantially U-shaped plane when the conductor film 14 is formed on one side surface thereof. That is, specifically, both sides of the lower step surface 15a and the entire inner surface 15b are the conductor film uncoated portions, and both ends 1 of the U-shaped portion 17 not coated with the conductor film are
7a and 17a are communicated with the open surface 13, and the side edges of the U-shaped portion 17 are aligned with both sides of one side surface of the dielectric block 11. As a result, on this one side surface, the first conductor film 14a located in the internal space of the U-shaped portion 17 (the central portion of the lower step surface 15a) and the first conductor film 14a formed outside the U-shaped portion 17 are formed. The two conductor film 14b is formed. Then, the capacitance is changed by changing the width of the U-shaped portion 17. The conductor film 14 formed on the other side surface and the second conductor film 14b are ground planes.

More specifically, if the widths t1 and t2 of the two straight line portions of the U-shaped portion 17 communicating with the open surface 13 formed on the low step surface 15a are changed, the capacitance changes greatly, On the other hand, even if the width t3 of the straight line portion formed on the inner surface 15b connecting the two straight line portions is changed, the change in capacitance is small. Therefore, it is possible to perform rough adjustment with the former and fine adjustment with the latter. The widths t1 and t2 are not necessarily the same width. Then, after forming a pattern in a predetermined shape by design in advance, the applied conductive films 14, 14a, 14
A desired capacity can be obtained by appropriately cutting a predetermined position of b.

An equivalent circuit of the dielectric resonator 10 having the above structure is shown in FIG. The capacitance C1 is formed between the peripheral edge of the resonance hole 12 located on the open surface 13 and the outer peripheral edge of the open surface 13, and the capacitance CA is formed by the capacitance pattern 16 as described above.
Then, this capacitance CA forms the U-shaped portion 17
Capacities CA1, CA2, CA3 generated in the straight parts of the book
Are connected in parallel.

The capacitance C1 can be changed along with the resonance frequency by cutting the peripheral edge of the resonance hole 12 on the open surface 13 side. Further, when it is desired to change only the capacitance C1, this can be done by cutting off the side edge communicating with the open surface 13 of the first conductor film 14a. Further, when it is desired to change only the resonance frequency, the capacitance pattern 1
This can be done by scraping off the side edges that communicate with the open surface 13 of the conductor film 14 that is formed on the other three side surfaces on which 6 is not formed.

Then, as shown in FIG. 3, a plurality (three in this example) of dielectric resonators 10 having the above-mentioned structure are used and they are provided side by side. At this time, the open surfaces 13 and the capacitance patterns 16 provided on the dielectric resonators 10 are arranged so as to face the same direction. Then, the capacitance patterns 16 formed on the adjacent dielectric resonators 10 are connected by the inductances L1 and L2. As a result, an equivalent circuit as shown in FIG. 6 is obtained, and the band rejection filter having the characteristics shown in FIG. 10 is configured by appropriately setting the capacitance formed in the dielectric resonator 10.

In order to mount the dielectric filter 18 having such a structure on a printed circuit board on which an actual circuit pattern is formed, although not shown, for example, the dielectric resonator 10 is formed on the ground pattern formed on the printed circuit board. The second conductor film 14b formed in the above can be brought into surface contact. As a result, the ground surface of the dielectric filter 18 and the ground surface of the printed circuit board are substantially aligned with each other, and the ground can be obtained in an ideal state. In addition, the step 15
Even if the dielectric filter 18 is grounded in a state in which is directed to the printed circuit board side, the stepped portion 15 forms a predetermined space between the surface of the printed circuit board and the low step surface 15a. It is possible to easily connect the capacitance pattern 16 provided on the step portion 15 and the circuit pattern formed on the printed circuit board by utilizing the above. The inductances L1 and L2 provided on the capacitance patterns 16 and 16 are
It may be directly attached to the capacitance pattern 16. Alternatively, it may be mounted on the printed circuit board side and connected to the capacitance pattern 16 via a wiring pattern or the like formed on the printed circuit board, and various configurations can be taken. Note that, conversely to the above, the stepped portion 15 may face upward.

As described above, in this example, when mounting the dielectric resonator on the mounting substrate 20, only three dielectric resonators and two inductances L1 and L2 are required. The area can be reduced.

FIG. 4 shows a second embodiment of the present invention.
In this example, the dielectric resonator 10 shown in FIG.
They are used individually and are installed together as in the first embodiment. Then, the opposing side surfaces of the adjacent dielectric resonators 10 are bonded to each other to be integrated. Then, in the step portion 15 provided in the integrated dielectric resonator 10,
A flat board 20 is mounted.

The substrate 20 is made of a dielectric material, and its thickness h is set to be equal to or smaller than the width of the inner surface 15b provided on the dielectric resonator 10, and the depth D is set. Is set longer than that D1 of the low step surface 15a of the dielectric resonator 10. As a result, when the substrate 20 is mounted on the dielectric resonator 10, the bottom surface thereof does not protrude outward from the side surface of the dielectric resonator 10, and the front end side 20a of the substrate 20 has the dielectric resonance. It is located so as to project outward from the open surface 13 of the container 10.

Further, at a predetermined position on the upper surface of the substrate 20,
Three terminal patterns 22 are formed, and adjacent terminal patterns 22 are connected to each other by inductances L1 and L2. When the board 20 is mounted on the dielectric resonator 10 as described above, the terminal patterns 22 provided on the board 20 are in surface contact with the capacitance patterns 16 formed on the dielectric resonators 10. As a result, the respective capacitance patterns 16 are connected by the inductances l1 and L2.

The dielectric resonators 10 and the dielectric resonator 10 and the substrate 20 can be joined to each other by various means such as simultaneous baking or soldering. By integrating the components 10 and 20 in this manner, the one-chip dielectric filter 25 having a simple structure and high mechanical strength is formed. In this example, since the one-chip type is used as described above, the actual mounting on the circuit board becomes easy.

Although not shown, the outer periphery of the dielectric filter having the above-mentioned structure is covered with a box-shaped metal case having an opening at the bottom, if necessary, to suppress the leakage of radio waves to other circuits. May be. Further, in this example, the ground capacitance CA (CB, CC) is formed on the dielectric resonator 10, so it is necessary to obtain the ground capacitance by using the coupling substrate 5 as in the conventional example shown in FIG. There is no board 2
0 may be made of a material having a low dielectric constant such as alumina or forsterite.

Further, in this example, the inductance L1,
Although each of L2 is formed by winding a lead wire a predetermined number of times, for example, the above-mentioned substrate 20 is formed by using a multilayer printed circuit board and an interactance pattern is formed in an intermediate layer thereof. You may do it. In such a case, since the inductance portion does not protrude to the outside, for example, the planar shape of the substrate is changed to the dielectric resonator 10.
It is possible to set the step shape 15 to be substantially equal to or smaller than the planar shape of the step portion 15, and further downsizing can be achieved. The rest of the configuration and operation (method of adjusting the capacity, etc.) are the same as those in the first embodiment described above, and therefore their explanations are omitted.

In each of the above-mentioned embodiments, 3
Although an example in which a dielectric filter is configured by using one dielectric resonator 10 has been described, the present invention is not limited to this and may be configured with two or four or more. Further, although the adjacent dielectric resonators 10 are bonded and integrated in each of the above-described embodiments, a predetermined gap may be provided between the opposing side surfaces of the adjacent dielectric resonators. However, in that case, each dielectric resonator 10 is placed on a mounting plate or placed directly on a mounting substrate on which a circuit pattern is formed, as in the conventional case.

Furthermore, the shape of the capacitance pattern formed on one side surface of the dielectric resonator 10 is not limited to the above-mentioned U-shape, but may be, for example, a U-shape, an arc-shape, or other various patterns. The point is that both ends of the uncoated portion of the conductor film communicate with the open surface, and a conductor film (corresponding to the first conductor film 14a) is formed on the portion defined by the uncoated portion and the open surface. Good. Further, the side edges of the uncoated portion do not coincide with the sides of the one side surface of the dielectric block as in the above-described embodiment, but are separated by a predetermined distance, that is, between the uncoated portion and the side. The conductor film (earth pattern) may be located. Furthermore, it is not necessary to provide an uncoated portion over the entire back surface, and the conductor film (either the first or second conductor film) may be located on the back surface.

[0023]

As described above, in the dielectric filter according to the present invention, since the capacitance pattern is formed at the predetermined position of the dielectric resonator, a plurality of such dielectric resonators are arranged and the capacitance thereof is increased. A desired dielectric filter can be constructed only by coupling the patterns with an inductance. As a result, it is possible to reduce the size by eliminating the need for an external component for the grounding capacitance, which has been essential in the past. Moreover, the structure is simple, and the assembly (mounting) work is also simplified, resulting in a low cost. Furthermore, since the capacitance pattern is provided at the step portion provided at the predetermined position of the dielectric resonator, it is possible to insert an inductance in the step portion or insert and arrange a connecting member to another circuit. The height in the mounted state can be kept low.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a dielectric resonator used in a dielectric filter according to the present invention.

FIG. 2 is an equivalent circuit diagram of the dielectric resonator shown in FIG.

FIG. 3 is a perspective view showing a first embodiment of a dielectric filter of the present invention constructed by using the dielectric filter shown in FIG.

FIG. 4 is a perspective view showing a second embodiment of the dielectric filter according to the present invention.

FIG. 5 is a perspective view showing an example of a conventional dielectric filter.

6 is an equivalent circuit diagram of the dielectric filter shown in FIG.

7 is a graph showing frequency characteristics of the dielectric filter shown in FIG.

[Explanation of symbols]

 10 Dielectric Resonator 11 Dielectric Block 14 Conductor Film (Earth Pattern) 14a First Conductor Film (Capacitance Pattern) 14b Second Conductor Film (Earth Pattern) 15 Step Part 16 Capacitance Pattern 17 U-Shaped Section (Capacitance Pattern) 20 Base plate 22 Terminal pattern L1, L2 Inductance

Claims (2)

[Claims] 1. A plurality of dielectric resonators provided with a dielectric block having a resonance hole and a conductor film forming an earth pattern formed on the inner surface of the resonance hole and a predetermined portion of the dielectric block. In addition, in a dielectric filter configured by LC coupling between the plurality of dielectric resonators, an open surface of a side surface of each of the dielectric resonators that does not face another adjacent dielectric resonator. A dielectric filter characterized in that a step portion lowered one step is formed on the side, a capacitance pattern is formed on the step portion, and the capacitance patterns are coupled by an inductance. 2. A plurality of dielectric resonators provided with a dielectric block having a resonance hole and a conductor film forming an earth pattern formed on the inner surface of the resonance hole and a predetermined portion of the dielectric block. In addition, in the dielectric filter configured by LC coupling between the plurality of dielectric resonators, a side surface of each of the dielectric resonators that is not opposed to another adjacent dielectric resonator is opened. Form a stepped portion lowered by one step on the surface side, form a capacitance pattern on the stepped portion, and
A dielectric filter, wherein a substrate having a plurality of terminal patterns connectable to the capacitance pattern and an inductance connecting the terminal patterns is mounted on the step portion.