JPH0461501A - Surface mount type dielectric filter - Google Patents

Abstract

PURPOSE:To make a characteristic of the filter stable by providing plural ground terminals to a conductive frame fixed to a major face at the mount side of the filter in parallel with a throughhole. CONSTITUTION:In the case of mounting a dielectric filter 1 onto a printed circuit board with a prescribed circuit pattern formed thereto, a lower frame 3b of the dielectric filter 1 is placed face to face onto the printed circuit board 21. Each ground terminal 16 of the dielectric filter 1 arranged on the printed circuit board 21 is soldered to a prescribed position of the prescribed circuit pattern 23 on the printed circuit board 21. Since each terminal 16 is prolonged on the same plane as that for the lower frame 3b, the terminal is easily adhered onto the surface of the printed circuit board 21 and soldered in a stable state. Moreover, since lots of the ground terminals 16 are arranged, the ground effect is improved and the attenuation characteristic of the dielectric filter 1 is made stable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dielectric filter, and particularly to a surface-mounted dielectric filter.

[Conventional technology]

As a surface-mounted dielectric filter that can be directly mounted on a circuit board, for example, a dielectric filter described in Japanese Patent Application Laid-Open No. 120703/1983 is known. This dielectric filter is constructed by integrating a plurality of dielectric resonators each having a conductor layer arranged on the outer peripheral surface thereof, and is mounted on a circuit board using an L-shaped spring fitting. Here, one side of the 1L-shaped spring fitting is soldered to the conductor layer of the dielectric block, and the other side is inserted into, for example, a through hole of the circuit board and soldered. Further, the input/output bins of the dielectric filter are connected to the wiring pattern on the circuit board by bonding wires.

[Problem to be solved by the invention]

The conventional dielectric filter has the following problems.

■ Filter characteristics (attenuation characteristics for polarized dielectric filters) are unstable due to poor grounding efficiency due to the spring fittings. Furthermore, if the L-shaped spring fitting is misaligned, it becomes difficult to attach it to a predetermined location on the circuit board. Furthermore, when mounting on a multilayer circuit board, the degree of freedom in internal wiring of the multilayer circuit board is reduced due to the formation of through holes for fixing the L-shaped spring fittings.

(2) When fixing an L-shaped spring fitting to mount a dielectric filter on a circuit board, the preset resonant frequency of the resonator constituting the filter may shift.

■ It is said that it is better to connect the input/output bin of a dielectric filter and the wiring pattern on the circuit board closer together to reduce the deterioration of the filter characteristics. Since the input/output bin and the wiring pattern are connected to each other, the filter characteristics are likely to change.

A first object of the invention is to provide a surface-mounted dielectric filter that is easy to attach to a circuit board and has stable filter characteristics.

A second object of the invention is to provide a surface-mounted dielectric filter whose resonance frequency does not change even after the filter is fixed to a frame.

A third object of the invention is to provide a surface-mounted dielectric filter that can suppress deterioration of filter characteristics due to mounting.

[Means to solve the problem]

In the surface-mounted dielectric filter according to the first invention, a through hole is formed in a dielectric block, and a conductive layer is formed on the outer surface of the dielectric block except for one opening surface of the through hole and on the inner wall surface of the through hole. The filter characteristics are fixed to a conductive frame. This surface-mounted dielectric filter is characterized in that a plurality of ground terminals are provided on a conductive frame fixed to the main surface on the mounting side of the filter parallel to the through holes.

In the surface-mounted dielectric filter according to the second invention, a through hole is formed in a dielectric block, and a conductive layer is formed on the outer surface of the dielectric block except for one opening surface of the through hole and on the inner wall surface of the through hole. Furthermore, a filter body in which a conductive layer removed portion for frequency adjustment is formed on the outer surface of the dielectric block is fixed to a conductive frame. This surface-mounted dielectric filter is characterized in that a window portion through which the conductive layer removed portion is exposed is formed in the conductive frame.

A surface-mounted dielectric filter according to a third aspect of the present invention includes forming a through hole in a dielectric block, and forming a conductive layer on the outer surface of the dielectric block except for one opening surface of the through hole and on the inner wall surface of the through hole. , a filter body provided with input/output means for connection to an external circuit is fixed to a conductive frame. This surface-mounted dielectric filter has at least: a window portion for connecting an external circuit and the input/output means formed in a conductive frame fixed to the main surface on the mounting side of the filter parallel to the through hole; It is characterized by

[Effect]

The surface-mounted dielectric filter according to the first invention is mounted on a predetermined circuit board by means of a conductive frame fixed to the main surface on the mounting side of the filter body. In the dielectric filter according to the present invention, the ground terminal is connected to the ground pattern arranged on the circuit board. Here, multiple ground terminals extending from the frame body parallel to the main surface on the mounting side are connected to the ground pattern, so the fixation of the dielectric filter to the circuit board is stable, and the grounding efficiency of the dielectric filter is improved. improves. As a result, the dielectric filter according to the present invention has stable filter characteristics.

In the surface-mounted dielectric filter according to the second invention, the conductive layer removed portion for frequency definition is exposed in the window portion of the conductive frame. Thereby, even if the dielectric filter of the present invention is fixed to a conductive frame, fluctuations in resonance frequency can be suppressed.

Furthermore, by removing the conductor layer of the dielectric filter through the window, it is possible to correct a shift in the resonance frequency that occurs during mounting on a circuit board.

A dielectric filter according to a third aspect of the invention includes a conductive frame having a window portion as described above.

Therefore, in the third invention, the wiring pattern on the circuit board and the input/output means can be connected as close as possible. Therefore, in the present invention, deterioration of filter characteristics due to changes in inductance and impedance occurring at the connection portion between the input/output means and the wiring pattern of the circuit board is less likely to occur.

〔Example〕

FIGS. 1 and 2 show a surface-mounted dielectric filter according to an embodiment of the present invention. FIG. 1 is a front perspective view of the dielectric filter, and FIG. 2 is a back perspective view.

In the figure, a dielectric filter 1 includes a filter body 2,
It mainly consists of a frame 3 surrounding a filter body 2.

The details of the filter body 2 will be explained with reference to FIG.

The filter body 2 includes five dielectric resonators 4. Each resonator 4 has a rectangular parallelepiped dielectric block 5.
have. A through hole 6 is provided in the dielectric block 5 from the top surface in the figure to the open bottom surface. An inner conductor 7 made of a conductive layer of silver, copper, or the like is arranged on the inner peripheral surface of the through hole 6 . Further, on the outer peripheral surface of the dielectric block 5, an outer conductor 8 made of a conductive layer made of the same material as the inner conductor 7 is arranged except for the upper surface (open end surface). This outer conductor 8 is short-circuited to the inner conductor 7 at the bottom surface (short-circuited end surface) of the dielectric block 5. Note that for ease of understanding, the thicknesses of the inner conductor 7 and outer conductor 8 are emphasized in the drawings.

The resonators 4 are lined up and joined so that the through holes 6 are straight and the open ends where the outer conductor 8 is not placed are on the upper side of the figure. In addition, for joining the resonators 4 to each other,
Solder or conductive adhesive is used. At the junction between each resonator 4, there is a
An angular coupling hole 9 is formed to obtain coupling capacity. Both ends of the coupling hole 9 are open, and the dielectric block 5 is exposed on the inner surface thereof. In addition, in order to adjust the resonant frequency of each resonator 4, the outer conductor 8 corresponding to each resonator 4 has a tuning part 8a with a part of the open end surface removed (see Fig. 1). ). Each resonator 4 is integrated into the filter body 2 after the resonance frequency is adjusted to a desired frequency.

A polarized substrate 1 is attached to the open end of the filter body 2 described above.
1 is placed. The polarized substrate 11 is formed in a rectangular shape that almost matches the open end surface of the filter body 2,
Made of ceramic material. The polarized substrate 11 includes
Resonators that make up the filter body 2 (1. 2 from the left in the figure)
．． 4. It has a fitting hole 12 at a position corresponding to the through hole 6 of the fifth resonator). Further, on the top surface of the polarized substrate 11 in the drawing, electrodes 13 are arranged around the insertion holes 12 at both ends at a slight interval. This electrode 13 becomes an input/output electrode for the filter body 20. Note that, on the back surface of the polarized substrate 11, a predetermined conduction pattern and a capacitance pattern are formed (not shown).

The above-mentioned polarized substrate 11 is connected to the inner conductor 7 of a predetermined resonator 4 of the filter body 2 through a conduction pin 10 .

The conduction bottle 10 is a generally cylindrical member made of a conductive material, and has a diameter-reduced fitting portion 10a at both ends.

In each conduction bottle 10, the fitting portion 10a on the lower side of the figure is connected to each through hole 6.
The polarized substrate 1 is inserted into the insertion part 10a on the upper side of the figure.
] By being fitted into the fitting hole 12, the filter main body 2 and the polarized substrate 11 are connected with a predetermined interval provided therebetween.

As is clear from FIGS. 1 and 2, the conductive frame 3
is a U-shaped member composed of an upper frame 3a, a lower frame 3b, and a connecting portion 3c that connects both frames 3a and 3b. This frame 3 has an upper frame 3a and a lower frame 3b disposed on both sides parallel to the through hole 6 of the filter body 2, and a connecting portion 3C is disposed around the open end of the filter body 2. It is fixed to the main body 2. Here, the upper frame 3a and the lower frame 3b are respectively connected to the filter main body 2.
is connected to the outer conductor 8 on the main surface of.

Further, the connecting portion 3c is arranged at a constant distance from the capacitor substrate 1 arranged on the open end surface of the filter body 2 (see FIG. 6).

As shown in FIG. 1, the upper frame 3a has a connecting portion 3.
Five windows 15 are provided at equal intervals on the c side. Each window portion I5 is provided at a portion where a tuning portion 8a with each resonator 4 constituting the filter body 2 is exposed. Further, as shown in FIG. 2, the lower frame 3b is provided with ground terminals 16 that protrude from both sides and the edge of the connecting portion 30 side.

Each ground terminal 16 extends on the same plane as the lower frame 3b.

L-shaped openings 17 are provided at both ends of the connecting portion 3C in the longitudinal direction between the connecting portion 3C and the lower frame 3b. An L-shaped terminal 14 is arranged in each opening 17 . This terminal 14 has an electrode 13 formed on the polarized substrate 11 on one side.
The other side is flush with the lower frame 3b (see Figure 6).The frame 3 is formed by bending a metal plate 18 as shown in Figure 4. .

The metal plate I8 is provided with five punched portions 15a arranged in the width direction near the central portion in the elongated direction. Further, two punched portions 17a are formed on the right side of the punched portion 15a in the figure, with a bending line 20 (imaginary!! 9I) extending in the width direction being separated therebetween. A bending line 20a (imaginary line) parallel to the bending line 20 is provided in the punched portion 17a. A U-shaped punched portion 19 is formed between the punched portions 17a, 17a, and a protrusion 16a is formed therein. Furthermore, three protrusions 16a are provided on each side edge on the right side of the figure than the punched part 17a.
stands out. Such metal plates are manufactured, for example, by punching conductive metal.

The frame 3 is made by bending the metal plate 18 at a line 20.2.
It is composed of l by bending at 0a.

At this time, the punched portion 15a, the punched portion 17a, and the protrusion 16a become the window portion 15, the opening portion 17, and the ground terminal 16, respectively.

In FIG. 5, which shows an equivalent circuit of the dielectric filter I, each resonator A corresponds to a resonator 4. In FIG. Note that the resonators A are mutually connected by magnetic field coupling (indicated by "○" in the figure).

This coupling is realized by each coupling hole 9.

In addition, input capacitor B1 and output capacitor B8
correspond to a capacitor constituted by the electrodes 13 at both ends of the polarized substrate 11 and the conductive pin 10, respectively. Polarized capacitors C1 and C! are formed between the fitting hole 12 at the left end of the polarized substrate 11 in FIG. 3 (corresponding to the first resonator) and the fitting hole 12 third from the left (corresponding to the fourth resonator), respectively. capacitor configured between the second fitting hole 12 from the third opening (corresponding to the second resonator) and the rightmost fitting hole l2 (corresponding to the fifth resonator). (The wiring pattern is formed on the back surface 1 of the polarized substrate 11, so it does not appear in the figure). Furthermore, the ground terminals correspond to each ground terminal 16 provided on the frame 3.

Next, the effects of the above embodiment will be explained.

The dielectric filter 1 is mounted, for example, on a circuit board on which a predetermined circuit pattern is arranged. At this time, the dielectric filter 1 is arranged so that the lower frame 3b faces the circuit board 21, as shown in FIG.

The dielectric filter l arranged on the circuit board 21 has each ground terminal I6 connected to a predetermined circuit pattern 23 on the circuit board 21.
is soldered to a predetermined location.

Here, since each ground terminal 16 extends on the same plane as the lower frame 3b, it can easily come into close contact with the surface of the circuit board 21 and be soldered in a stable state. Furthermore, since a large number of ground terminals 16 are arranged, the grounding effect is good. Therefore, the attenuation characteristics of the dielectric filter l are stabilized.

Also, when mounting the dielectric filter 1, the polarized substrate 11
The terminal 1"4.14 attached to the circuit board 21 is soldered to the microstrip line 22 on the circuit board 21 (FIG. 6). By the way, in general, the connection between the electrode 13 of the polarized board 11 and the microstrip line 22 is It is said that it is preferable to connect the two as close together as possible.This is because if the two are connected far apart, impedance matching cannot be performed accurately, and power is consumed due to the resistance of the connection part, which may cause signal interference. This is because transmission loss occurs and the characteristics of the filter deteriorate.

In this embodiment, as shown in FIG. 6, the microstrip line 22 is drawn into the frame 13 through the opening 17.17, and the connection between the microstrip line 22 and the terminal 14 can be made within the frame 3. 13 and the microstrip line 22 can be connected sufficiently close to each other. Therefore, in this embodiment, deterioration of filter characteristics is less likely to occur.

By the way, when the filter body 2 is fixed with the frame 3, the resonant frequency of the resonator 4 may vary from the pre-adjusted resonant frequency. However, in this embodiment, since the tuning section 8a is exposed in the window section 15 of the frame 3, the characteristics of the dielectric filter 1 do not change. Further, by appropriately removing the outer conductor 8 through this window portion 15, the resonant frequency of the dielectric filter 1 can be corrected again. Note that the outer conductor 8 can be removed using, for example, a laser.

Note that the dielectric filter 1 of this embodiment has a filter main body 2.
Since the coupling hole 9 is shielded by the frame 3, it is difficult for external noise to enter the coupling hole 9, and the coupling hole 9 is less likely to be affected by noise. In addition, since noise from the coupling hole 9 is also shielded by the frame 3 and is less likely to leak to the outside, the dielectric filter 1 is less likely to have an adverse effect on other electronic components.

[Other Examples]

(a) In the embodiment described above, the filter main body 2 is formed of five resonators 4, but the number of resonators can be set as appropriate depending on the filter characteristics. In addition, although a single (b) polarized substrate provided with a capacitor was used in the above embodiment, a polarized substrate provided with a reactance element such as a coil may also be used. Further, the dielectric filter may be a normal dondobus dielectric filter that does not use polarization means.

〔Effect of the invention〕

A surface-mounted dielectric filter according to a first aspect of the invention includes a conductive frame having a ground terminal as described above. Therefore, according to the present invention, it is possible to realize a surface-mounted dielectric filter that can be stably fixed to a circuit board and has stable attenuation characteristics.

A surface-mounted dielectric filter according to a second aspect of the invention includes a conductive frame having a window portion as described above. Therefore, according to the present invention, it is possible to realize a surface-mounted dielectric filter in which fluctuations in resonance frequency are less likely to occur and the resonance frequency can be modified.

A surface-mounted dielectric filter according to a third aspect of the invention includes a conductive frame having holes as described above. Therefore, according to the present invention, it is possible to realize a surface-mounted dielectric filter that can suppress deterioration of filter characteristics during mounting.

[Brief explanation of the drawing]

FIG. 1 is a front perspective view of a dielectric filter according to an embodiment of the present invention, FIG. 2 is a back perspective view thereof, FIG. 3M is an exploded perspective view of the filter body adopted in the embodiment, and FIG. FIG. 5 is a plan view of a metal plate for manufacturing the frame adopted in the above embodiment, FIG. 5 is an equivalent circuit diagram of the above embodiment, and FIG. 6 is a diagram of FIG. 1 when the above embodiment is mounted on a circuit board. ■-■ It is a sectional view. 1... Dielectric filter, 3... Frame, 3a...
・Upper frame, 3b...Lower frame, 3C...
Connecting portion, 5... Dielectric block, 6... Through hole, 8
...Outer conductor, 10...Conducting pin, 11...Polarized board, 13...Electrode, 4...Terminal, 5...Window part, 6...Earth terminal, 7. ...opening, 8...metal plate.

Claims (3)

[Claims] (1) A filter body in which a through hole is formed in a dielectric block and a conductive layer is formed on the outer surface of the dielectric block except for one opening surface of the through hole and the inner wall surface of the through hole,
A surface-mounted dielectric filter fixed to a conductive frame, characterized in that a plurality of ground terminals are provided on the conductive frame fixed to the main surface on the mounting side of the filter body parallel to the through hole. Surface-mounted dielectric filter. (2) forming a through hole in a dielectric block; forming a conductive layer on the outer surface of the dielectric block except for one opening surface of the through hole; and on the inner wall surface of the through hole; In a surface-mounted dielectric filter in which a filter body having a conductive layer removed portion for frequency adjustment formed on the outer surface is fixed to a conductive frame, the conductive frame has a window portion through which the conductive layer removed portion is exposed. A surface-mounted dielectric filter characterized by the following: (3) Forming a through hole in a dielectric block, forming a conductive layer on the outer surface of the dielectric block except for one opening surface of the through hole, and on the inner wall surface of the through hole to connect to an external circuit. In a surface-mounted dielectric filter in which a filter body provided with an input/output means is fixed to a conductive frame, the conductive frame is fixed to a main surface on the mounting side of the filter body parallel to at least the through hole, A surface-mounted dielectric filter characterized in that a window portion is formed for connecting the external circuit and the input/output means.