JPH0770883B2 - Dielectric filter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter having a band elimination characteristic in which a resonant circuit mainly composed of a dielectric resonator is connected via a coupling inductor.

2. Description of the Related Art As a dielectric filter having a band elimination characteristic, one having a circuit configuration shown in FIG. 6 is known. This filter consists of a dielectric resonator 14 and a capacitor for external coupling.
A configuration is provided in which a plurality of resonance circuits in which a storage capacitor 15 is connected in parallel to a series circuit with 13 and adjacent resonance circuits are connected by a coupling inductor 11 are connected.

As shown in FIG. 7, such a filter assembling structure has a structure in which a plurality of resonators 14 are housed in a case 20 with the inner conductor 14a being horizontal and soldered to the inner conductor 14a and exposed to the outside. With respect to the terminal 16, the tip side bent portion 17a of the earth plate 17 having the base end portion sandwiched between the inner bottom surface of the case 20 and the outer conductor 14b of the resonator 14 is horizontally opposed to each other, and the opposing coupling terminals are opposed to each other. 16
Capacitors 13 and 15 are attached between the bent portion 17a and the bent portion 17a by soldering 18 or the like. Also, the resonator 14
Is clamped and supported by the spring 19 interposed between the base end side of the wavy ground plate 17 and the case 20 above the resonator 14. Reference numeral 12 in the figure is a transmission line including a coupling inductor 11 interposed between capacitors 13 and 15, and a cross section is shown.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By the way, in the above-mentioned configuration, the capacitors 13 and 15 separated from each other are used, and in order to obtain a desired filter characteristic, Since it is necessary to set C to a predetermined value, and all the values are generally different, it has been difficult in the past to manage a large number of parts having various capacities by capacity.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a dielectric filter that facilitates component management.

Means for Solving the Problems A dielectric filter according to the present invention includes a resonance circuit in which a capacitor for storage capacitance is connected in parallel to a series circuit of a dielectric resonator and a reactance element for external coupling, and adjacent resonance circuits are In the dielectric filter connected by the coupling inductor, at least two capacitors for storage capacitance of the resonance circuit share the substrate.

Function In the present invention, at least two of the capacitors for storage capacitance share the substrate, so that the number of parts of this capacitor is reduced.

Example 1 FIG. 1 is a perspective view showing a band elimination filter to which the present invention is applied, FIG. 2 is a sectional view taken along line II-II, and FIG. 3 is a front view showing an essential part of the present invention. The same parts as those in FIG. 7 are designated by the same reference numerals. The equivalent circuit of this filter is the same as the circuit shown in FIG. The structure of the filter itself is as follows. For example, four prism-shaped dielectric resonators 14 are housed in the case 20 with the inner conductor 14a being horizontal, and four outer conductors 14b of each resonator 14 are housed in the case 20.
It is provided in contact with the. The case 20 is grounded, and each outer conductor 14 is also grounded.

The inner conductor 14a of the resonator 14 is formed in a cylindrical shape, and a coupling terminal 6 made of a conductive material and having a base end portion 6b formed in a cylindrical shape is attached by fitting the base end portion 6b therein. The tip portion 6a of the coupling terminal 6 is oriented substantially horizontally and vertically faces the inner bottom surface of the case 20.

Three storage capacitor elements 1, 2, 3 are provided on the inner bottom surface of the case 20 facing the tip 6a of the coupling terminal 6. Of the elements 1 and 3 at both ends, the whole electrodes 1b and 3b are formed on the lower surface of the substrates 1a and 3a made of a dielectric material, and the electrodes 1c and 3c are formed on the upper surface below the tip 6a of the coupling terminal 6. Electrodes 1b and 1c, 3b and 3c facing each other.
Capacitors C1 and C4 are formed between the lower surface electrodes 1b,
3b contacts case 20 and is grounded.

In the remaining element 2 in the central portion, the entire surface electrode 2b is formed on the lower surface of the substrate 2a made of a dielectric material, and the electrodes 2c and 2d are formed on the upper surface below the tip portions 6a of the two intermediate coupling terminals 6. Capacitors C2 and C3 are formed between the opposing electrodes 2b and 2c, 2b and 2d, and the entire surface electrode 2b is grounded in contact with the case 20 on the lower side.

The electrodes 1c, 2c, 2d, formed on the upper surfaces of the three elements 1, 2, 3
An external coupling reactance element, for example, a capacitor 13 is mounted on each of 3c and electrically connected thereto, and a coupling inductor 11 is connected between adjacent electrodes. Note that these connections may be soldered separately, but VP
It may be done at once by reflow soldering such as S. The external coupling reactance element is for adjusting the Q value.

The tip 6a of the coupling terminal 6 is connected to the upper surface electrode of the external coupling capacitor 13 to form the filter of the present invention.

Despite the similar configuration, the storage capacitor elements 1, 2, and 3 are separated because the capacitors at the first stage and the last stage on both sides need to have large capacitances. This is because the element 2 having a dielectric constant different from that of the substrate 2a is used.

With respect to the mounting angle of the coupling terminal 6, it may be mounted so that the tip portion 6a faces in any direction in the circumferential direction of the inner conductor 14a, such as the capacitor elements for storage capacitors 1, 2, 3 and the external coupling capacitor 13. It may be formed according to the total height. For example, as shown in FIG. 4, the coupling terminal 6 may be attached so that the tip portion 6a is located on the upper side.

FIG. 5 is a perspective view showing another embodiment of the present invention. In this filter, an external coupling coil 13 'is attached instead of the external coupling capacitor 13. Even in this case, the present invention can be applied.

In the above embodiment, the capacitor elements for storage capacitance 1, 2,
Although the lower surface of 3 is the whole surface electrodes 1b, 2b, 3b, the present invention is not limited to this, the upper electrode 1c, 2c, 2d, 3c is the same size and the electrode is formed only in the lower part of the counter electrode. May be

Further, although the above embodiment is applied to a filter having four stages, the present invention is not limited to this, and it is needless to say that the present invention can be applied to a filter having more or less stages.

Furthermore, although the prismatic dielectric resonator is used in the above embodiments, the present invention is not limited to this, and it goes without saying that a cylindrical resonator can be used.

EFFECTS OF THE INVENTION As described in detail above, according to the present invention, since at least two of the capacitors for storage capacitance share the board, the number of parts of this capacitor can be reduced and the parts management can be facilitated. In addition to the effect that it is possible, even if it is necessary to make the capacitance of the strain capacitance capacitors at both ends different from the capacitance of the strain capacitance capacitors at the other ends, by using substrates with different dielectric constants Since the capacitance can be changed without changing the size of the electrodes in the capacitor for capacitance and without changing the thickness of the substrate, it can be manufactured in the same manufacturing process as the capacitor for strain capacitors other than both ends, and it does not take much time to manufacture. The effect is added.

[Brief description of drawings]

FIG. 1 is a perspective view showing a band elimination filter to which the present invention is applied, FIG. 2 is a sectional view taken along the line II-II, FIG. 3 is a front view showing an essential part of the present invention, and FIG. FIG. 5 is a perspective view showing an example of mounting terminals, FIG. 5 is a front view showing another embodiment of the present invention, FIG. 6 is an equivalent circuit diagram of a band elimination filter, and FIG. 7 is a configuration of a conventional band elimination filter. FIG. 1,2,3 …… Stress capacitor element, 1a, 2a, 3a ……
Substrate, 1b, 2b, 3b …… Full surface electrode, 1c, 2c, 2d, 3c …… Electrode, 1
1 …… Coupling capacitor, 13 …… External coupling capacitor, 1
3 '... coil for external coupling, 14 ... dielectric resonator, 14a ...
… Inner conductor, 14b …… Outer conductor, 20 …… Case.

Claims (1)

[Claims] 1. A series circuit comprising a dielectric resonator and a reactance element for external coupling is provided with at least four resonance circuits in which a capacitor for storage capacitance is connected in parallel, and adjacent resonance circuits are connected by a coupling inductor. In the dielectric filter, the storage capacitor for at least two resonance circuits except for the resonators at both ends is formed by using a common first substrate, and the storage capacitor for the resonators at both ends is connected to the substrate. A dielectric filter formed by using a second substrate having a common thickness but a different dielectric constant.