JPH0648963Y2 - Dielectric filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a dielectric filter using a dielectric ceramic for microwaves as a material.

[Prior Art] In a high frequency circuit of equipment such as a radio and a television, a dielectric filter or a SAW is used instead of the conventional LC resonance circuit using a coil and a capacitor in accordance with downsizing of the equipment and an IC of a circuit element. A filter is adopted.

Examples of the dielectric filter include a first conventional example shown in FIG. 7 and a second conventional example shown in FIG. In each of these, a dielectric body made of ceramic is molded into a block body 11 having a predetermined length related to the wavelength of a target high frequency wave, a through hole 12 is formed in the length direction, and a conductor film 13 is formed inside the through hole 12. To form an internal electrode 13, and the outer surface and the bottom surface to be covered with a conductor film 14 to form an external electrode 14 to form a resonant element that resonates in a TEM mode at a target high frequency. The resonance element and the capacitor are combined to form a bandpass filter that allows a specific frequency to pass.
The conventional example is a capacitance substrate 15 in which a dielectric plate is sandwiched between conductor plates.
(Or a chip capacitor) is formed separately from the resonance element, and the second conventional example is a block body of the resonance element.
A conductor pattern 16 connected to the internal electrodes 13 is formed on the upper surface of 11 to form a capacitor.

[Problems to be Solved by the Invention] However, in the above-described first conventional example, since it is necessary to prepare a separate capacitor and connect the capacitor and the resonance element by wiring, the number of parts and the number of steps are reduced. Will increase. In particular, when a capacitive substrate is used, defects due to substrate cracking are likely to occur, and it is necessary to devise a method for supporting and fixing the substrate. Further, in the second conventional example, when forming the pattern of the capacitive electrode, an etching or pattern printing step is added, and high dimensional accuracy is required. Therefore, there is a problem that the manufacturing cost is increased in any case.

The present invention aims to provide a dielectric filter having a simple structure and a low manufacturing cost.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a columnar dielectric block with a plurality of through holes vertically penetrating the inner surface of the through holes. In a dielectric filter in which a conductor film is provided on the outer surface of the dielectric block as electrodes and one end of which is an open end, a groove is provided at the one end of the dielectric block so as to leave a part of each through hole. As a result, the capacitor is formed integrally with the block body that forms the resonance element.

Here, the capacitance of the capacitor can be set by changing the depth of the groove, and the method of connecting the capacitor and the resonant element can be changed by changing the position where the groove is formed or how the internal electrode is left on the inner surface of the through hole. Can be changed.

[Operation] In the dielectric filter configured as described above, the resonant element is formed between the electrodes in the portion of the dielectric block body set to the predetermined length, and the other extension portion is A capacitor is constructed. Therefore, the filter in which the inductor and the capacitor are combined is integrally formed only by appropriately machining the block body.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, reference numeral 1 is a block body formed of a dielectric ceramic in a rectangular parallelepiped shape. As the ceramic material, for example, barium oxide, titanium oxide, or the like is appropriately adopted. In addition, the dimensions of the block body 1 are set so that the electrical constants required for the dielectric filter can be expressed for each item, as will be described later.

The block body 1 has a pair of through holes 2, which vertically penetrate the block body 1.
2 is formed, and a conductor film 3 of metal or the like is formed on the inner surface of the through hole 2 to cover the through hole, and the conductor film 3 constitutes the internal electrode 3. On the other hand, the outer side surface and the bottom surface of the block body 1 are covered with the conductor film 4, which constitutes the outer electrode 4. These film formation methods are
Appropriate ones among known techniques such as plating, vapor deposition, and sputtering are adopted.

The upper surface 1a of the block body 1 has a pair of through holes 2,2.
A groove 5 having a width shorter than the diameter of the through hole 2 is formed along a line connecting the centers of the two. In this case, the distance 1 between the bottom surface 5a of the groove 5 and the bottom surface 1b of the block body 1 is set so that l <λ / 4, where λ is the target frequency of the filter. Further, the depth and width of the groove 5 are such that the internal electrode 3 and the external electrode 4 are formed on both sides of the groove 5.
The capacitance increases between the capacitor and the capacitor. The capacitance increases as the depth of the groove 5 increases and the width of the groove 5 decreases and the area of the internal electrode 3 increases.

In the dielectric filter having such a configuration, the resonance element is formed between the internal electrode 3 and the external electrode 4 in the same manner as in the conventional case in the portion of the block body 1 having the height 1 below the groove 5.
Capacitors C ₁ and C ₂ having a predetermined capacitance are formed between the electrodes 3 and 4 on both sides of the groove 5 above them. Therefore, the equivalent circuit of this embodiment is as shown in FIG. 3, and a bandpass filter is constructed by the combination of the resonant element and the capacitors C ₁ and C ₂ .

FIG. 4 shows a second embodiment of the present invention, in which two parallel grooves 5, 5 go straight to the line passing through the center of one through hole 2 and connecting the centers of both through holes 2. In this case, the capacitances of the capacitors C ₁ and C ₂ are not so different from those of the first embodiment, but the capacitor C ₃ is formed between the internal electrodes 3 and 3. The equivalent circuit is as shown in FIG.

FIG. 6 shows a third embodiment of the present invention, in which the width of the groove 5 is expanded to one side in the second embodiment and the area of the internal electrode 3 at the position corresponding to the groove 5 is reduced. This equivalent circuit corresponds to the one in FIG. 5 in which the values of the capacitors C ₁ and C ₂ are reduced. In this case, if the external electrode 4 in the groove 5 is removed, the capacitors C ₁ and C _{2 in} FIG.
Capacitor becomes 0 and the capacitor C ₃ is only between the internal electrodes _3.
Is the set circuit.

[Advantages of the Invention] As described in detail above, according to the present invention, a plurality of vertically extending through holes are formed in a columnar dielectric block, and conductors are formed on the inner surface of the through hole and the outer surface of the dielectric block. In a dielectric filter in which a film is provided as each electrode and one end is an open end, a groove is provided at the one end of the dielectric block so that a part of each through hole is left, thereby making it relatively simple. The capacitor can be configured in the dielectric block simply by machining, and the excellent effect that the dielectric filter can be integrally manufactured without increasing the number of parts and man-hours is achieved. .

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a sectional view thereof, FIG. 3 is an equivalent circuit diagram thereof, FIG. 4 is a perspective view of the second embodiment, and FIG. 5 is an equivalent circuit thereof. FIG. 6 is a perspective view of the third embodiment, and FIGS. 7 and 8 are perspective views of a conventional example. 1 ... Block body, 2 ... Through hole, 3 ... Conductor film (internal electrode), 4 ... Conductor film (external electrode), 5 ... Groove.

Claims (1)

[Scope of utility model registration request] 1. A columnar dielectric block is provided with a plurality of through holes penetrating vertically and a conductor film is provided on an inner surface of the through hole and an outer surface of the dielectric block to form electrodes, and one end is opened. In the dielectric filter having an end, a groove is provided at the one end of the dielectric block so that a part of each of the through holes is left.