JPH065202U - Dielectric filter - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent electromagnetic field leakage and reduce external influences to improve filter characteristics. [Structure] Dielectric substrate 1 whose upper and lower surfaces are ground electrodes 13
2 on both sides of the I / O electrodes 2 through a substantially square-shaped insulating band 19.
1, 22 are formed. The input / output electrodes 21, 22 have a so-called through hole structure, and the upper land and the lower land of the upper surface of the dielectric substrate 12 are electrically connected. The cover 16 is not provided with a cutout, and the entire cover 16 is covered with the dielectric substrate 12.
Cover and completely shield. Therefore, the cover 16
Even if it is covered with the dielectric substrate 12, the side piece 18 of the cover 16 does not come into contact with the input / output electrodes 21 and 22, but comes into contact with the ground electrode 13 to complete the shield. Therefore, the electromagnetic field leakage can be prevented and the influence from the outside can be greatly reduced.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a dielectric filter for the microwave band used in mobile communication devices such as car phones and mobile phones.

[0002]

[Prior art]

 FIG. 8 shows an exploded perspective view of a conventional dielectric filter, which has, for example, a four-stage resonator structure. The four dielectric coaxial resonators 1 to 4 arranged side by side are arranged so that the inner conductor formed on the inner surface of the hole 5 of the dielectric body and the outer conductor formed on the outer surface of the dielectric body resonate at a predetermined frequency. Has become. The connection terminals 6 contacting the inner conductors inside are press-fitted into the holes 5 of the dielectric coaxial resonators 1 to 4, respectively, and the tips of the connection terminals 6 are coupling elements formed on the upper surface of the coupling substrate 7. The capacitor electrode films 8 to 11 are respectively connected.

The coupling substrate 7 and the dielectric coaxial resonators 1 to 4 are mounted on the upper surface of a flat dielectric substrate 12 made of a dielectric material, and the ground electrode 13 is formed on a part of the upper surface and the bottom surface. There is. Note that FIG. 9 shows a bottom view of the dielectric substrate 12. Input / output electrodes 14 and 15 for inputting / outputting signals are formed on both sides of the end portion of the dielectric substrate 12. The coupling substrate 7 and the dielectric coaxial resonators 1 to 4 are mounted on the upper surface of the dielectric substrate 12 by soldering or the like, and a box-shaped cover 16 made of metal and having an open lower surface is provided on the upper surface thereof. The cover 16 shields to prevent electromagnetic field leakage.

[0004]

[Problems to be solved by the device]

 In such a dielectric filter, the two input / output electrodes 14 and 15 are provided from the upper and lower ends of the dielectric substrate 12 from one end to the other so that the metal cover 16 and the metal cover 16 are not shown in FIG. As shown, the side piece 18 of the cover 16 is formed with a notch 17 so as not to contact the input / output electrodes 14 and 15. That is, the cutout portion 17 forms a so-called escape structure. Therefore, there is a problem that electromagnetic field leakage occurs from the cutout portion 17 of the cover 16 or electromagnetic waves enter from the outside to the inside, which is not preferable in terms of electrical characteristics.

The present invention has been provided in view of the above-mentioned points, and it is intended to prevent electromagnetic field leakage, reduce the influence from the outside, and improve the performance of a dielectric material. It provides a filter.

[0006]

[Means for Solving the Problems]

 The present invention provides a plurality of dielectric coaxial resonators that resonate at a predetermined frequency with an inner conductor formed on the inner surface of a hole of a dielectric and an outer conductor formed on the outer surface of the dielectric, and a plurality of the dielectric induction resonators. A dielectric substrate on which the body coaxial resonator is disposed, a coupling element connected to the tip of a connection terminal connected to the inner conductor of the dielectric coaxial resonator, and a dielectric substrate formed on the dielectric substrate. In a dielectric filter including an input / output electrode and a shield cover for covering the dielectric substrate, the input / output electrode is formed inside an end surface of the dielectric substrate.

[0007]

[Action]

 In the present invention, by forming the input / output electrodes inside the end surface of the dielectric substrate, the conventionally formed notch of the cover can be eliminated, and the shield can be completely shielded to prevent electromagnetic field leakage. It is possible to eliminate the influence from the outside. Therefore, the reliability can be improved and the filter characteristics can be improved.

[0008]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of a dielectric filter according to an embodiment of the present invention, in which the dielectric coaxial resonators 1 to 4, the coupling substrate 7 and the like are constructed in the same manner as the conventional one. The dielectric filter is used in mobile communication devices such as automobile phones and mobile phones. The dielectric coaxial resonators 1 to 4 have electrode film-shaped inner conductors formed on the inner peripheral surface of the dielectric hole 5 formed in a rectangular parallelepiped shape, and electrode film-shaped inner conductors formed on the surface of the dielectric material. It is composed of an outer conductor. Into the holes 5 of the dielectric coaxial resonators 1 to 4, metal connection terminals 6 each having one end formed in a substantially cylindrical shape are press-fitted, respectively, and contact with the inner conductor in the holes 5 to obtain conduction. . The other end of the connection terminal 6 is formed in a tongue shape and is connected to the plurality of capacitor electrode films 8 to 11 formed on the upper surface of the coupling substrate 7 by soldering or the like. The combined substrate 7 is made of a dielectric material. In addition, the capacitor electrode films 8 to 11 of the coupling substrate 7 constitute coupling elements.

Electrode film-shaped ground electrodes 13 are formed on the top and bottom surfaces of a dielectric substrate 12 which is flat and made of a dielectric material. Further, both sides of the end of the dielectric substrate 12 will be described later. , And film-shaped input / output electrodes 21 and 22 are formed, respectively. A capacitor electrode film is formed on the lower surfaces of the capacitor electrode films 8 and 11 on both sides of the coupling substrate 7, and the capacitor electrode film is connected to both input / output electrodes 21 and 22 of the dielectric substrate 12 by soldering or the like. It has become so. The dielectric coaxial resonators 1 to 4 are arranged on the dielectric substrate 12 and mounted on the ground electrode 13 of the dielectric substrate 12 by soldering or the like. The cover 16 made of metal and having an opening on the lower surface covers the dielectric coaxial resonators 1 to 4, and the side piece 18 of the cover 16 and the dielectric substrate 12 are joined by soldering.

FIG. 3 shows an equivalent circuit diagram of the dielectric filter shown in FIG. 1. C ₁ and C ₅ are formed between the capacitor electrode films 8 and 11 of the coupling substrate 7 and the capacitor electrode film on the lower surface. Capacita is shown. Further, C _{2 to} C ₄ indicate capacitors formed between the capacitor electrode films 8 to 11 of the combined substrate 7. The dielectric filter configured in this way acts as a bandpass filter. Further, such a dielectric filter is designed to be mounted on a wiring board as a surface mounting type.

Next, the gist of the present invention will be described in detail. As shown in FIG. 1 and FIG. 2, an electrode film serving as the ground electrode 13 is formed on the upper and lower surfaces of the dielectric substrate 12, and both sides of the dielectric substrate 12 on the end side have a substantially square shape. Input / output electrodes 21 and 22 are formed via the insulating band 19. Since the two input / output electrodes 21 and 22 have the same structure, only one input / output electrode 21 will be described. The input / output electrode 21 has a so-called through-hole structure as shown in FIG. 2, and the upper land 31 and the lower land 32 on the upper surface of the dielectric substrate 12 are the inner circumference of the hole 33 formed in the dielectric substrate 12. Conduction is obtained by the electrode film 34 formed on the surface. Further, unlike the conventional case, the cover 16 is not provided with a notch as shown in FIG. 1, but the dielectric substrate 12 is covered with the entire cover 16 so as to completely shield it. Further, the side piece 18 of the cover 16 is joined to the ground electrode 13 of the dielectric substrate 12 by soldering or the like, as shown in FIG.

With this structure, even if the cover 16 is provided on the dielectric substrate 12, the side pieces 18 of the cover 16 do not contact the input / output electrodes 21 and are not grounded as shown in FIG. By contacting the electrode 13, the shield can be perfect. Therefore, it is possible to prevent electromagnetic field leakage and reduce external influences. Further, since the input / output electrodes 21 and 22 are surrounded by the ground electrode 13, the electric characteristics of the filter are improved. Further, even if the cover 16 is covered up to the line a (see FIG. 1) written on the end surface of the dielectric substrate 12, the input / output electrodes 21 and 22 are not short-circuited. The cover 16 shown in FIG. 1 has a gap between the edges of the side pieces 18, but the cover 16 may have a gap-free structure.

FIG. 4 is a diagram showing a state in which the present dielectric filter is specifically mounted on the wiring board 40 by soldering. As shown in FIG. 4B, a terminal electrode 41 having a through-hole structure is formed on the portion of the wiring board 40 connected to the input / output electrodes 21 of the dielectric substrate 12. The land on the lower side of the terminal electrode 41 is connected to the hot line 42 for signal input / output. Incidentally, 43 is a ground electrode. Further, the dielectric filter, that is, the dielectric substrate 12 is mounted on the wiring substrate 40 by soldering with the solder 44.

In the above embodiments, the band pass filter is described as an example, but the present invention is not limited to this, and a high pass filter, a low pass filter, a band elimination filter, or a combination of these various types of filters to form an input / output electrode. It is also applicable when doing. Further, although the number of resonator stages is four, the number is not limited to this.

Example 2 FIG. 5 shows an example in which the resonator has a three-stage structure and the capacitor electrode films 8 to 10 are formed on the substrate 12. The input / output electrodes 21 and 22 are formed integrally with the capacitor electrode films 8 and 10. Here, when the substrate 12 is made of resin, the difference in linear expansion coefficient between the substrate 12 and the dielectric coaxial resonators 1 to 3 is large, so that thermal stress is apt to occur due to soldering, which may cause resonator cracking. is there. Further, in order to obtain the required stray capacitance in the capacitor electrode films 8 to 10 forming the coupling circuit, a highly accurate electrode pattern is required, and stable dielectric constant and temperature stability are required. This is a weak point of using the resin substrate.

Therefore, in the present embodiment, alumina is used for the substrate 12, the dielectric coaxial resonators 1 to 3 are arranged on the substrate 12, and the capacitor electrodes of the coupling circuit are formed on the alumina substrate 12 by pattern electrodes. The films 8 to 10 and the input / output electrodes 21 and 22 are formed.

[0017]

[Table 1]

Table 1 above shows various characteristics of alumina, and as shown in Table 1, the aluminum has very good dimensional accuracy. Further, since alumina has high rigidity and strength, the thin substrate 12 can be formed. Further, the linear expansion coefficient of alumina is almost the same as that of the dielectric coaxial resonators 1 to 3, and the difference is 1 to 2 ppm / ° C. The difference between the resin and the resonator is 6 to 9 ppm / ° C. Also, although the dielectric constant of alumina is considerably smaller than that of the resonator, that of resin is much smaller. However, in the case of resin, the dielectric loss tangent is considerably larger than that of alumina. Further, the thermal conductivity of alumina is higher than that of resin. For the above reason, in this embodiment, the alumina substrate 12 is used without using the resin, and the dielectric filter is formed on the basis of the alumina substrate 12.

As described above, since the substrate 12 is made of alumina instead of resin, thermal stress is reduced, the reliability of the filter is improved, and the stray capacitance of the capacitor electrode films 8 to 10 is set and adjusted. It can be done easily. Further, since the dimensional accuracy is good, the dimensional accuracy of the filter is improved, the thermal conductivity is high, and the efficiency of assembly by reflow soldering is improved. Furthermore, since the substrate 12 can be made thin, it is possible to reduce the size of the dielectric filter.

Example 3 By the way, when the dielectric filter is surface-mounted on the wiring board, soldering is performed while the input / output electrodes, earth terminals, etc. are aligned with the pattern of the wiring board. If you do not position the wiring board, the following problems will occur. That is, when a force is applied to the dielectric filter in the left-right direction, the front-rear direction, or the circumferential direction, the dielectric filter is displaced with respect to the wiring board pattern. In this case, the input / output electrodes and the ground terminal may not match the pattern on the wiring board, and soldering may not be possible or, in the worst case, a short circuit may occur.

Therefore, in this embodiment, when the dielectric filter is mounted on the wiring board, the dielectric filter is positioned with respect to the wiring board. That is, as shown in FIGS. 6 and 7, the ground terminal 20 formed on the side pieces 18 on both sides of the cover 16 of the dielectric filter and the notch 51 are formed in a part of the alumina substrate 12, and the notch 51 is formed. The positioning claw 52 is integrally projected from the side piece 18 of the cover 16 so as to project. Then, a hole 45 into which the claw 52 is fitted is bored in the wiring board 40, and the claw 52 is fitted into the hole 45 to position the dielectric filter on the wiring board 40. The claw 52 is dimensioned so as not to project to the lower surface of the wiring board 40 when fitted in the hole 45. Reference numeral 46 shown in FIG. 6 denotes a ground electrode which is soldered to the ground terminal 20 of the cover 16, and 47 is a terminal electrode which is soldered to the input / output electrodes of the dielectric filter.

As described above, by fitting the claws 52 of the cover 16 into the holes 45 of the wiring board 40, the dielectric filter is not displaced in either the front-rear direction or the left-right direction. Can be reliably and easily mounted at a predetermined position on the wiring board 40, and the mounting work can be simplified by introducing an automatic machine or the like. Further, since the ground can be surely dropped onto the wiring board 40 via the ground terminal 20, the filter characteristic becomes stable. Furthermore, even if vibration or shock is applied during mounting (reflow soldering), the dielectric filter does not shift its position, so the I / O electrodes and terminal electrodes can be reliably soldered and mounting reliability is improved. To do. Since the claw 52 does not project from the wiring substrate 40 to the lower surface, the lower surface can be used for mounting another component.

Although the claws 52 are formed on both sides of the cover 16 in this embodiment, they may be formed on the front and rear sides of the cover 16. Further, the number of the claws 52 is not limited to one, and an appropriate number can be formed. Further, the claw 52 may be provided on each side of the cover 16. Further, the dielectric filter shown in FIG. 6 shows an example of a combination of a band pass filter and a band elimination filter used in a car telephone or the like. Therefore, in this embodiment, the input and output electrodes for reception and transmission, and the input and output electrodes for the antenna connected to the antenna as the common terminal are formed. Three terminal electrodes 47 are formed on the wiring board 40 according to the number of these three input / output electrodes.

In addition to the above dielectric filters, the present embodiment and the above may be applied to the case where a high-pass filter, a low-pass filter, a band-pass filter, and a band elimination filter are independently configured, or when these various filters are combined. The invention of Example 2 can be applied.

[0025]

[Effect of device]

 As described above, the present invention provides a plurality of dielectric coaxial resonators that resonate at a predetermined frequency with the inner conductor formed on the inner surface of the hole of the dielectric and the outer conductor formed on the outer surface of the dielectric, And a coupling element connected to the tip of a connection terminal connected to the inner conductor of the dielectric coaxial resonator, and the dielectric substrate on which the dielectric coaxial resonator of FIG. In the dielectric filter having the input / output electrodes and a cover for shielding the dielectric substrate, the input / output electrodes are formed inside the end surface of the dielectric substrate. By eliminating the notch in the cover, the cover can be completely shielded to prevent electromagnetic field leakage, and the influence from the outside can be eliminated. Therefore, the reliability can be improved and the filter characteristics can be improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a dielectric filter according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of an essential part showing a portion of an input / output electrode.

FIG. 3 is an equivalent circuit diagram of the dielectric filter shown in FIG.

4A is a simplified plan view of a case where a dielectric filter is mounted on a wiring board, and FIG. 4B is an enlarged cross-sectional view of a main part.

FIG. 5 is an exploded perspective view of a dielectric filter according to a second embodiment.

FIG. 6 is an explanatory diagram for positioning a dielectric filter on a wiring board according to a third embodiment.

FIG. 7 is a cross-sectional view when the dielectric filter of Example 3 is mounted on a wiring board.

FIG. 8 is an exploded perspective view of a conventional dielectric filter.

FIG. 9 is a bottom view of a conventional dielectric substrate.

FIG. 10 is a perspective view of a main part of a conventional example.

[Explanation of symbols]

 1-4 dielectric coaxial resonator 5 holes 6 connection terminal 7 coupling substrate 8-11 capacitor electrode film 12 dielectric substrate 16 covers 21, 22 input / output electrodes

Claims (1)

[Scope of utility model registration request] 1. An inner conductor formed on an inner surface of a hole of a dielectric,
A plurality of dielectric coaxial resonators that resonate at a predetermined frequency with an outer conductor formed on the outer surface of the dielectric body, a dielectric substrate on which the plurality of dielectric coaxial resonators are disposed, and the dielectric body. A coupling element connected to a tip of a connection terminal connected to the inner conductor of the coaxial resonator, an input / output electrode formed on the dielectric substrate, and a shield cover for covering the dielectric substrate. In the above dielectric filter, the input / output electrodes are formed inside the end surface of the dielectric substrate.