JPH05327314A - Dielectric filter - Google Patents

Abstract

PURPOSE:To provide a compact dielectric filter by composing one capacitor, for which one terminal of the dielectric filter is connected to the ground, of conductive patterns provided on the both surfaces of an insulated board mounting a dielectric resonator at least. CONSTITUTION:On the same surface of a ceramic board 2, two capacitors are formed by a gap 3 of conductive patterns 4 and 5. At the same time, a conductive pattern 5 is formed on the other surface of the ceramic board 2 corresponding to the real back of the common conductive pattern 4. The capacitors are formed like this, and other ground faces 11 of both of the resonators are conductively fixed to the bottom or side face of a case 6 by soldering 8 after one of the ground faces 11 of resonators 1' and 1' is adhered each other. At the same time, a hot terminal 10 is conductively fixed to the prescribed part of the conductive pattern on the ceramic board 2 by soldering 8. As a result, the gap of the dielectric resonators is eliminated, these resonators can be closely arranged, and the miniaturized dielectric filter can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a dielectric filter, and more particularly to a high frequency and narrow band dielectric filter of a type in which a plurality of dielectric resonators are connected in series.

[0002]

2. Description of the Related Art Conventionally, when a plurality of dielectric resonators are cascaded in parallel and used as a bandpass filter (hereinafter referred to as BPF), a capacitive coupling type B using a capacitor as a coupling element.
PF was commonly used. FIG. 2 is a diagram showing an equivalent circuit of a capacitive coupling type BPF using two dielectrics,
A capacitor C _C is inserted as a coupling element between the terminals of two dielectrics 1 and 1 having equivalent characteristics. At this time, it is known that the capacitance value of the coupling capacitor C _C is given by the equation 1. Here, K is an element constant determined by the response characteristic of the filter, f _{B is a} pass band width, Z ₀ is a characteristic impedance of the dielectric resonator, f ₀ is a center frequency. Conventionally, a designing method based on this formula has been designed and manufactured to have a center frequency of several hundred MHz and a specific bandwidth of about 3 to 4%.

However, higher frequency and narrow band BPF,
For example, a BPF having a Butterworth characteristic (K = 1) with a specific bandwidth of about 1%, such as f ₀ = 1.9 GHz and f _B = 20 MHz.
2 is configured by the circuit of FIG. 2 using a general dielectric resonator of about Z ₀ = 10Ω, the value of C _C is 0.
It becomes 07 pF. However, this capacitance value is extremely small and difficult to realize, and even if it can be realized, reproducibility is poor,
It was impossible to use it industrially as it is.

Therefore, in order to make the coupling capacitance a feasible capacitance value, for example, C _C and the equivalent capacitance of the dielectric resonator are appropriately converted into an equivalent circuit to realize a BPF having desired characteristics. Figure 4 is a circuit diagram showing an example of, first dielectric resonator 1 the equivalent capacitance of the dielectric resonator 1, 1 in Figure 2 as shown in FIG. 3 ', 1' equivalent capacitor C ₁ and capacitor C of _The circuit is equivalently converted by replacing it with a parallel circuit consisting of _X, and a π-type circuit composed of C _C and two C _X is composed of two capacitors C _C1 and C _C2 as shown in FIG. Π-T conversion may be performed so as to obtain a T-type circuit. At this time, C _C1 and C _C2 can be set to a realizable capacitance value by selecting C _X at an appropriate value.
Can be realized. For example, in the above example, C _X = 0.2
If it is set to 1 pF, the coupling capacitors C _C1 and C _C2 after conversion have a feasible capacitance value of 1.05 pF and 0.35 pF, respectively.

However, when actually manufacturing the BPF having the structure shown in FIG. 4, as shown in FIG. 5, the capacitor C _C2 is provided in order to further shorten the wiring to the ground and suppress the stray capacitance with the resonator hot terminal. Since it is arranged between the dielectric resonators 1'and 1'on the ceramic substrate 2, as compared with the case where there are no components to be inserted in parallel with the two dielectric resonators 1 and 1 as shown in FIG. Then, there is a defect that the shape is enlarged by the amount of the space provided between the dielectric resonators.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to eliminate the defects of the conventional dielectric filter as described above, and is a dielectric filter comprising a plurality of dielectric resonators.
It is an object of the present invention to provide a more compact dielectric filter that eliminates the gap between the dielectric resonators and allows them to be arranged close to each other.

[0007]

SUMMARY OF THE INVENTION In a dielectric filter having a plurality of dielectric resonators, at least one of the capacitors, one terminal of which constitutes the dielectric filter, is connected to ground,
The dielectric resonator is formed of conductive patterns provided on both sides of an insulating substrate. Further, at least 3 coupling capacitors are used when the dielectric resonators are cascaded in parallel.
A T-shaped circuit composed of a plurality of capacitors, wherein one of the capacitors to be inserted in parallel with the resonator is constituted by a conductive pattern arranged on both surfaces of an insulating substrate.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings showing the embodiments. 1 (a) and 1 (b) are a plan view and a front view showing a configuration of an embodiment of a dielectric filter according to the present invention, in which two capacitors C _C1 are electrically conductive on the same surface of a ceramic substrate 2. The capacitor C _C2 is realized by forming the conductive pattern 5 on the other surface of the ceramic substrate corresponding to the back side of the common conductive pattern 4 while being formed by the pattern gap 3.
This ceramic substrate 2 is fixed to a supporting member 7 made of an insulating material provided on the bottom surface of a metal case 6, and at this time, the conductive pattern 5 is arranged so as to face the bottom surface of the case 6, and both are electrically fixed by solder 8. To do. Figure 1
As shown in (c), the dielectric resonator is a hot terminal 1 in which a metal rod is embedded in one end surface of a square pole-shaped dielectric material 9 to a predetermined depth.
0, and the ground terminals (surfaces) 11 are formed on all other five surfaces by metal plating or the like. As shown in FIGS. 1 (a) and 1 (b), the dielectric resonators 1'and 1'are grounded. One of the surfaces 11 is brought into close contact with each other, and the other grounding surfaces 11 are electrically connected and fixed to the bottom surface or the side surface of the case 6 with solder (not shown), and the hot terminal 10 is connected to the ceramic substrate 2.
The conductive pattern is fixed to a predetermined position by soldering (not shown).

With the above-described structure, the two dielectric resonators can be arranged in close contact with each other, so that the useless space is limited and the high-frequency narrow-band dielectric filter can be miniaturized. Although the present invention has been described with reference to the example in which two dielectric resonators are connected in series,
The present invention is not limited to this, and may have a structure in which a plurality of three or more dielectric resonators are cascade-connected or a structure other than cascade connection. Therefore, the dielectric resonators are used. If one terminal of the capacitors constituting the filter is connected to the ground, it may be applied not only to the coupling capacitor but also to the matching capacitor or the like. or,
Regarding C _C1 , a gap type capacitor with a conductive pattern on a ceramic substrate has advantages such as ease of assembly in manufacturing and reduction of the number of parts, but it is not always necessary to adopt this configuration, and a discrete or chip type capacitor is required as in the past. Obviously, it may be a capacitor, and the ceramic substrate may be a substrate made of another insulating material.

[0010]

Since the present invention is constructed as described above, when a dielectric filter is constructed using a plurality of dielectric resonators, they can be arranged in close contact with each other. This has a remarkable effect in limiting the wasted space and realizing a miniaturization particularly in a high frequency and narrow band dielectric filter.

[0011]

[Brief description of drawings]

1A and 1B are a plan view and a front view showing a configuration of an embodiment of a dielectric filter according to the present invention, and FIG. 1C is a diagram showing a configuration of a dielectric resonator.

FIG. 2 is a diagram showing an equivalent circuit of a conventional capacitive coupling type dielectric filter using two dielectric resonators.

FIG. 3 is a diagram illustrating a process of converting to a dielectric filter equivalent to that in FIG.

FIG. 4 is a circuit diagram of a dielectric filter equivalent to FIG.

FIG. 5 is a plan view showing the configuration of a conventional dielectric filter.

[Explanation of symbols]

1, 1 '... Dielectric resonator 2 ... Ceramic substrate 3 ... Gap 4, 5 ... Conductive pattern C _C1 , C _C2 ... Coupling capacitor

[Formula 1]

Claims (3)

[Claims] 1. A dielectric filter having a plurality of dielectric resonators, wherein at least one of capacitors having one terminal constituting the dielectric filter connected to ground is insulated by mounting a dielectric resonator. A dielectric filter comprising a conductive pattern provided on both surfaces of a substrate. 2. A dielectric filter in which a plurality of dielectric resonators are cascade-connected in parallel, wherein a coupling capacitor between the dielectric resonators is a T-type circuit composed of at least three capacitors, 2. The dielectric filter according to claim 1, wherein a capacitor that is inserted in parallel with the resonator is formed of a conductive pattern provided on both surfaces of the insulating substrate. 3. A capacitor other than a capacitor composed of conductive patterns arranged on both surfaces of the insulating substrate, wherein a gap between conductive patterns formed on the same surface of the insulating substrate is used. Item 1. The dielectric filter according to item 1 or 2.