JPH0897610A - Dielectric filter - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] A band-stop dielectric filter in which circuit elements such as a dielectric resonator, a capacitor, and a coil are mounted on a wiring board, and the circuit elements are covered with a metal case. In, the dielectric filter is excellent in attenuation characteristics of the center frequency and the bandwidth. [Structure] Dielectric resonator 1 mounted on wiring board 12,
Further, a metal plate 14 is arranged in a columnar shape at the position facing the circuit element inside the metal case 13 so as to be close to the circuit element 2 such as a capacitor, a coil, or a resistor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter used for communication electronic equipment and the like.

[0002]

2. Description of the Related Art FIG. 5 shows a general example of a conventional dielectric filter and its case. In particular, electronic components used in portable communication devices are mounted close to each other because it is necessary to miniaturize the devices, and interference due to electromagnetic noise and the like interfere with normal operation of electronic devices. . For this reason, the dielectric filter, as shown in FIG. 5, avoids obstacles due to the emission of electromagnetic waves to the outside and also protects against the obstacles of electromagnetic waves incident from the outside. Is a copper foil formed on the back surface of the wiring substrate 12 on which the dielectric resonator 1 and other circuit elements 2 are mounted, and the metal case 23 except the opening end surface 1a of the dielectric resonator 1.
It is covered and wrapped with metal such as.

FIG. 7 shows an equivalent circuit of a conventional dielectric filter, which includes a dielectric resonator 1, a capacitor 3 and a coil 4.
Consists of.

[0004]

The attenuation characteristic of a dielectric filter is required to have a smaller insertion loss for a signal in a signal pass frequency band and a larger attenuation amount in a stop band for a spurious signal. ing. At this time, the attenuation amount in the stop band requires a large attenuation characteristic even at a harmonic of twice or three times the center frequency, but the dielectric filter having the conventional structure has a large attenuation amount in the stop band. There was a problem that it was difficult to obtain.

An object of the present invention is to provide a dielectric filter which can eliminate the above-mentioned drawbacks and can obtain a large amount of attenuation in a high frequency band.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a dielectric filter in which a dielectric resonator and other circuit elements are covered with a metal case, and the potential of the metal case is grounded. The space between the metal case and the circuit element is filled, is electrically connected to the metal case by soldering or a conductive adhesive in the vicinity of the circuit element, and has a block shape on the inner surface of the case toward the circuit element, or By arranging partition-shaped metal, especially by arranging a metal case that is grounded close to the mounting parts of circuit elements such as coils and capacitors, high attenuation characteristics are achieved over a wide band at the center frequency. Is obtained. Further, in this structure, a U-shaped cutout is provided in the metal case, and the cutout is bent inward toward the inside so as to be substantially perpendicular to the upper surface of the metal case, and is arranged close to the circuit element. By forming a metal wall in the vicinity of the mounted circuit element, a dielectric filter having a large attenuation amount and a wide attenuation width is obtained.

That is, the present invention comprises a wiring board having a copper foil adhered to the outer surface for mounting a circuit element such as a capacitor, a coil, and a dielectric resonator, and a metal case covering the outer periphery of the circuit element. In a dielectric filter in which a metal case and the wiring board electrically wrap around a circuit element and the potential of the metal case is set to the ground potential, the metal case is electrically connected to the metal case, and a part of the metal case is It is a dielectric filter characterized in that a metal plate is arranged in a columnar shape inside a metal case so as to project close to the circuit element in a space formed by the circuit element and the metal case.

Further, the present invention is characterized in that the metal plate arranged inside the metal case is a partition-shaped metal wall formed so as to hang down from the upper surface of the metal case toward the inside of the metal case. It is the dielectric filter described above.

Further, according to the present invention, a part of the metal case is cut out in a U-shape, and the U-shaped cutout is substantially perpendicular to the upper surface of the metal case toward the inside of the metal case. The dielectric filter described above, characterized in that it comprises a partition-shaped metal wall formed by bending.

[0010]

The characteristics of the dielectric resonator and the dielectric filter in which the periphery of the circuit element is electromagnetically shielded by metal are such that the higher the frequency in the GHz band, the greater the amount of electromagnetic waves propagating in the space between the input and output terminals. Therefore, it becomes difficult to obtain a large amount of attenuation.
By installing a grounded metal plate or the like close to the circuit element in the metal case, the electromagnetic wave propagating in the space inside the metal case is weakened, the attenuation characteristic of the center frequency is improved, and the center frequency is doubled. And increase the attenuation in the triple harmonic band.

[0011]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an external perspective view of the dielectric filter using the metal case 13 according to the present invention as seen from the lower surface direction. The back surface of the wiring board 12 on which the dielectric resonator 1 and the circuit element 2 are mounted is covered with a copper foil surface except the input / output terminals 11, and the convex portion 13a of the metal case 13 and the wiring board 12 are covered.
The concave portions 12a of the metal case 13 are fitted to each other and soldered, the metal case 13 is electrically connected to the outer surface of the wiring board 12, and the metal case 13 and the wiring board 12 make the metal case 1
By grounding 3 or the wiring board 12, electromagnetic waves are almost completely shielded.

In the present invention, the inner surface of the metal case 13 is
A columnar metal plate 14 is formed at a position above the circuit element 2 arranged between the input / output terminals 11 along a corner inside the metal case 13 adjacent to the circuit element 2. The characteristic of the dielectric filter using the metal case of the present invention is shown in FIG. 4, and the characteristic of the dielectric filter using the conventional metal case 23 is shown in FIG.
Shown in. The characteristic of the dielectric filter using the conventional metal case 23 shown in FIG. 6 is that the attenuation amount at 3800 (MHz) is 25 (dB), while the metal case 13 according to the present invention shown in FIG. In the characteristics of the dielectric filter using, the attenuation amount at 3800 (MHz) is 38
(DB), an improvement of 13 (dB) was observed.

FIG. 2 is a view showing a second embodiment of the present invention. In the present invention shown in FIG. 2, the metal plate is replaced with a partition-shaped metal wall 31, and the embodiment shown in FIG. The same damping characteristic as the example can be obtained. At the same time, it is possible to reduce the cost of parts and reduce the weight.

Furthermore, in order to improve the manufacturing efficiency, as shown in the third embodiment of the present invention in FIG. 3, a partition-shaped metal wall 41 is formed inside the metal case 43 at the mounting position of the circuit element. . Usually, the frequency of the dielectric resonator is set in the metal case 43,
Alternatively, when a hole for adjusting the coil is provided, a conductive label is attached, but by installing the metal wall, a conductive part is provided in the hole portion on the upper surface of the metal case 43 having a hole. By attaching the label, the same result as when the metal plate was installed in the metal case was obtained.

Although the ordinary plate is used in the embodiment shown here, the same effect can be obtained even if the metal plate has a mesh shape. The material is not particularly limited, but a soft magnetic metal foil may be used on the outer peripheral surface and a metal case having a two-layer structure using copper and aluminum on the inner surface may be used.

[0017]

As described above, in the dielectric filter in which the dielectric resonator and the circuit element such as the capacitor and the coil are electromagnetically shielded by the metal case and the wiring board in which the copper foil is adhered on the entire surface, It is possible to obtain a large amount of attenuation in a high frequency band by providing a metal plate or a metal wall mounted on the wiring board on the inner surface of the metal case, particularly close to the circuit element and electrically conducting to the metal case. it can.
Further, when a part of the metal case is cut out and the cutout part is bent inward of the metal case so as to be close to the circuit element, it is possible to improve the damping characteristics without impairing the productivity. .

[Brief description of drawings]

FIG. 1 is an external perspective view from a lower surface direction of a dielectric filter using a metal case according to the present invention.

FIG. 2 is an external perspective view from the lower surface direction showing a second embodiment of the dielectric filter using the metal case according to the present invention.

FIG. 3 is an external perspective view from the bottom surface direction showing a third embodiment of the dielectric filter using the metal case according to the present invention.

FIG. 4 is a characteristic diagram showing frequency attenuation characteristics of the dielectric filter according to the present invention shown in FIG.

FIG. 5 is an external perspective view of a dielectric filter using a conventional metal case, viewed from the lower surface direction.

6 is a characteristic diagram showing frequency attenuation characteristics of the conventional dielectric filter shown in FIG.

FIG. 7 is an equivalent circuit diagram of a dielectric filter according to a conventional example.

[Explanation of symbols]

1 Dielectric Resonator 1a Open End Face 2 Circuit Element 3 Capacitor 4 Coil 11 I / O Terminal 12 Wiring Board 12a Recessed 13, 23, 33, 43 Metal Case 13a Convex 14 Metal Plate 31 (Metal Connected) Partition-shaped metal wall (connected to the case) 41 Partition-shaped metal wall (formed by notching and bending)

Claims (3)

[Claims] 1. A wiring board having an outer surface on which a dielectric resonator and a circuit element are mounted and a copper foil adhered to the wiring board, and a metal case covering the outer periphery of the dielectric resonator and the circuit element. In a dielectric filter in which a circuit element is electrically conducted and wrapped by a wiring board and the potential of the metal case is set to the ground potential, it is electrically connected to the metal case, and the circuit element and the metal are connected from a part of the metal case. A dielectric filter, characterized in that a metal plate is arranged in a columnar shape inside a metal case so as to protrude in the space formed by the case so as to be close to the circuit element. 2. The metal plate disposed inside the metal case,
2. The dielectric filter according to claim 1, which is a partition-shaped metal wall formed so as to hang down from the upper surface of the metal case toward the inside of the metal case. 3. A partition formed by cutting out a part of the metal case in a U-shape and bending the U-shaped cut-out toward the inside of the metal case so as to be substantially perpendicular to the upper surface of the metal case. The dielectric filter according to claim 1, wherein the dielectric filter is formed of a metal wall.