JPH036103A - Dielectric filter - Google Patents

Abstract

PURPOSE:To enable surface packaging to be performed and to improve spurious characteristic by providing a through-hole with prescribed length at a rectangular parallelopiped dielectric, applying metallic films on the surfaces of five planes except for one plane where the through-hole is provided, and forming a land shape pattern at a prescribed place. CONSTITUTION:The through-hole 31 is provided at a rectangular parallelopiped block 3 consisting of a dielectric whose length in a longitudinal direction is d1=lambda/4, and also, the metallic films are applied on the surfaces of the five planes except for the plane B and the inner planes of the through-hole 31. The land shape patterns 32 and 33 are formed by eliminating part of the metallic film at an almost d1/3 from the plane B on the planes C and D along the through-hole 31. The patterns 32 and 33 are set as electrodes, and a capacitor formed between the patterns and the metallic film of the inner plane of the through-hole 31 is used as a coupling capacitor, and also, the land shape patterns 32 and 33 are used as input/output terminals.

Description

[Detailed Description of the Invention] [Summary] For example, regarding a dielectric filter used in a wireless device for a mobile phone in the several hundred MHz band, the present invention aims to provide a dielectric filter that can be surface mounted and has excellent spurious characteristics. A rectangular parallelepiped block made of a dielectric material has a through hole of length λ/4 (one in total), and five surfaces excluding one of the surfaces with the opening of the through hole and the through hole. A metal coating is applied to the inner surface of the pair of opposing surfaces, and from this one surface (B) along the through hole, d-
The metal coating is removed near the position of (λ/4).[(2m+1)/(2n+3)) to form an island pattern.

[Industrial application field]

The present invention relates to a dielectric filter used in radio equipment for car telephones in the several hundred MHz band, for example.

In recent years, there has been a demand for smaller mobile radio equipment, and this has led to a demand for smaller filters for splitting signals and filters that suppress unwanted waves that have three times the frequency of the desired signal. .

For this reason, a miniaturized semi-coaxial dielectric filter using a dielectric material with a high dielectric constant has been provided, but2 this filter does not have a structure that allows surface mounting.

Here, "surface mountable" means that it can be directly connected to a pattern on a printed board without making holes in the printed board.

Furthermore, since the above-mentioned semi-coaxial dielectric filter constituted by a λ/4) resonator resonates at three times the frequency, it is difficult to suppress this frequency.

Therefore, it is necessary to provide a dielectric filter that can be surface mounted and has excellent spurious characteristics.

[Conventional technology]

FIG. 6 is a configuration diagram of a conventional example, where FIG. 6(a) is a perspective view, FIG. 6(b) is a cross-sectional view taken along line A-A' in FIG. 6(a), and FIG.
The figure shows a configuration diagram of another conventional example. The operation of the conventional example will be explained below.

First, as shown in FIG. 6(b), one, for example, two through holes 12.
13 will be provided.

Then, a metal coating is applied to the four surfaces of this rectangular parallelepiped block 11 excluding the lower surface B, the upper surface 2, and the inner surfaces of the through holes 12.13, and input terminals 16 are provided at the openings on the lower surface of the two through holes 12.13. Coupling capacitor with 15. For example, the coupling capacitor 17 with the output terminal 18 is soldered. Note that the hatched areas in Figure 1 indicate metal coatings, and the dotted areas indicate dielectric areas.

In addition, in order to ensure that the metal coating applied to the four surfaces is grounded,
As shown in Figure 6(a), the dielectric filter is placed in the metal case 1.
4 and solder this metal coating and metal case 14. 2. Fix this to a printed board (not shown), and connect the input/output terminals to the patterns on the printed board.

Note that the first resonator and the second resonator are configured by the through holes 12.13 in FIG. 6(b), and the resonant wavelength is λ/4.

Further, the opening on the lower surface side of the first resonator is an open end.

Since the opening on the top side is a short-circuited end, the coupling capacitor is attached to the part where the electric field is maximum.

Here, since the dielectric filter is inserted into the metal case as described above, it cannot be made very compact and surface mounting is difficult.Also, since it is coupled to the output side at the open end, it is difficult to handle the third harmonic wave. The disadvantage is that the amount of attenuation cannot be taken.

Therefore, an outline of a dielectric filter that improves this will be explained with reference to FIG.

First, while providing the through hole 21 in the rectangular parallelepiped block 2,
A metal coating is applied to five surfaces other than eight surfaces of this rectangular parallelepiped block and to the inner surface of the through hole 21. Then, a part of the metal coating applied to the opposing surfaces 0 and 0 is removed to form a pair of island-like patterns 23 and 24, and these island-like patterns are used as electrodes of a capacitor.

A capacitor formed between this and the metal coating on the inner surface of the through hole 21 is used as a coupling capacitor, and the island pattern itself is used as an input/output terminal.

Here, the filter must be able to arbitrarily design the passband width, and this is achieved by changing the area of the island pattern. That is, in the case of a narrow band filter, the area of the island pattern is made small in order to weaken the coupling, and in the case of a wide band filter, the area of the island pattern is made large.

Furthermore, if the island pattern is located close to the open end in the longitudinal direction of the dielectric block, the electric field strength will be high and the coupling will be strong, resulting in a broadband filter. However, when a narrow band filter is required, either the area of the island pattern should be made small near the open end as shown above, or the island pattern with a relatively large area should be used on the opposite side near the short circuit side. do.

Now, the method for mounting such a dielectric filter is as shown in the figure, using an island pattern and a human output line 2 formed on a printed board.
2.25. By directly soldering the metal film and the ground plane, the metal case and coupling capacitor described above are unnecessary, allowing miniaturization and surface mounting.

[Problem to be solved by the invention]

Here, in addition to resonating at the fundamental resonant frequency, the λ/4 resonator also resonates at a frequency three times the fundamental resonant frequency, and the electric field is maximum at the open end.

On the other hand, since the coupling between the resonator and the input/output circuit is generally performed at the open end where the electric field is maximum, there is a problem in that the amount of attenuation for the frequency three times the above cannot be obtained. So, these 3
A separate low-pass filter must be added to suppress harmonics.

An object of the present invention is to provide a dielectric filter that can be surface mounted and has excellent spurious characteristics.

31 is the length λ/ provided in the rectangular parallelepiped block made of dielectric material.
In the through hole 4, 34 is a metal coating on five surfaces excluding one of the surfaces where the opening of the through hole is located and on the inner surface of the through hole.

In addition, 32.33 is a metal coating applied to the surfaces of a pair of opposing surfaces, from the first surface (B) along the through hole, d
=(λ/4) ・ [(2m+1)/(2n+3))
This is an island-like pattern formed by removing the metal coating near the position.

[Effect]

In general, a λ/4 resonator resonates at the fundamental resonant frequency as shown in Figure 2(a), and also resonates at an odd multiple of the fundamental frequency, for example, 3 times the fundamental resonant frequency as shown in Figure 2(b). They resonate even at twice the frequency, and the electric field is at its maximum at both open ends, resulting in good coupling with the resonator. However, since the electric field is at its minimum at point e in Figure 2, et al., coupling becomes difficult.

Therefore, in the present invention, d-(λ
/4) ・If it is combined with the electric field of the fundamental frequency using the A device of (2m+1)/(2n+3)), it will be difficult to combine with the electric field of the frequency that is an odd multiple of the fundamental frequency, and the spurious that is an odd multiple of the fundamental frequency will be suppressed. .

Note that as the island pattern shifts from the open end to the shorted end as shown in point e in Figure 2(b), the electric field at the fundamental resonance frequency becomes a little weaker, but if the area of the island pattern is slightly increased, Bye.

This makes it possible to provide a dielectric filter that can be surface-mounted and has excellent spurious characteristics.

[Embodiment] FIG. 3 is a configuration diagram of an embodiment of the present invention, FIG. 4 is an explanatory diagram of the operation of FIG. 3, and FIG. 5 is an explanatory diagram of implementation of FIG. 3. Here, the same reference numerals indicate the same objects throughout the figures. Below, n
=m=o, and the configuration and implementation of the embodiment of the present invention will be described using FIGS. 3 to 5.

First, the length of the camphor tree shown in Fig. 3 in the longitudinal direction is d, = λ/4.
A through hole 31 is provided in the rectangular parallelepiped block 3, and five surfaces of the rectangular parallelepiped block except for surface B and the through hole 3 are provided.
A metal coating is applied to the inner surface of 1, but then a part of the metal coating applied to the 0 side and on the 0 side at a position approximately (1/3) d from the B side along the through hole is removed. A pair of island-like patterns 32 and 33 are formed.

Then, this island-like pattern is used as an electrode of a capacitor, and the capacitor formed between this and the metal coating on the inner surface of the through hole 31 is used as a coupling capacitor, and this island-like pattern itself is used as an input/output terminal. .

Next, Fig. 4 shows the passage through the dielectric filter when the island pattern is provided almost at the open end (Fig. 7) and when it is provided approximately (1/3) d from the open end (Fig. 3). In the case of FIG. 7, there is almost no passing loss between the fundamental frequency r and the frequency 3f, which is three times the fundamental frequency, and there is almost no suppression of the third harmonic.

On the other hand, in the case of FIG. 3 (in the case of the present invention), 3f
This suppresses the third harmonic wave as it gives a considerable passing loss. Note that the reason why there is a concave portion at 3f is because there is a bond from the vicinity.

Further, FIG. 5(a) shows a dielectric filter constructed by providing a through hole 31 and island-like patterns 32 and 33 in a rectangular parallelepiped 3.
FIG. 5(b) shows the pattern of the printed board 38 to be mounted. In this pattern, an input/output line 34, 35 and two ground planes 36, 37 are formed, and the ground plane is connected to the ground plane on the back side of the printed board via a through hole or the like.

Then, as shown in FIG. 5C, the bottom surface of the outer conductor of the dielectric filter whose ground surface is coated with metal is connected by soldering or the like. An island pattern 32.33 (not shown) is also soldered to the input/output lines 34,35.

This makes it possible to provide a dielectric filter that can be surface-mounted and has excellent spurious characteristics.

Figure 6 is a configuration diagram of a conventional example. FIG. 7 shows a configuration diagram of another conventional example.

In the figure, 3 is a rectangular block, 31 is a through hole; 32 and 33 are island-like patterns, 34 indicates a metal coating.

〔Effect of the invention〕

As described in detail above, the present invention has the advantage of being able to provide a dielectric filter that can be surface mounted and has excellent spurious characteristics.

[Brief explanation of drawings]

FIG. 1 is a diagram of the principle configuration of the present invention. Figure 2 is an explanatory diagram of the operation of Figure 1; FIG. 3 is a configuration diagram of an embodiment of the present invention, Fig. 4 is an explanatory diagram of the operation of Fig. 3; Figure 5 is an illustration of the implementation of Figure 3; dice / times 3 leaps Spear Shi/'121's 1 Kamuike Akira Z Graduation 21211 4th eye 6th head

Claims (1)

[Claims] A rectangular parallelepiped block (3) made of a dielectric material has a length λ/4 (
λ is the resonant wavelength), at least one through hole (31) is provided, and one of the surfaces (B
) and the inner surface of the through hole are coated with metal coating (3).
4) is applied, but among the metal coatings applied to the surfaces of a pair of opposing surfaces, d=(λ/4)・[(2m+1)/( 2n+3)](m
, n is a positive integer including 0, and (2n+3)>(2m+1
) is removed to form an island pattern (32, 3).
3), and the island pattern is used as an input/output terminal.