JPS61192101A - Filter - Google Patents

Abstract

PURPOSE:To attain low cost and miniaturization by unifying the resonance frequency of a dielectric coaxial resonator in use and connecting a capacitor for frequency adjustment in parallel with the required resonator so as to allow each resonator to have a prescribed resonance frequency relation. CONSTITUTION:Resonators 11-15 have an identical resonance frequency f1 in equivalent circuit diagram (a). A static capacitors Cs1 for frequency adjust ment is provided between a center conductor at the open end of the resonator 12 and ground in order to bring the resonance frequency of the resonator 12 into f2. The resonator is treated similarly. A capacitor Cs2 is provided to the resonator 13 similary to obtain the resonance frequency of f43. Coupling capacitors C3, C3 are obtained respectively between capacitor electrodes 17 and 18 and between capacitor electrodes 18 and 19 in the actual constitution (figure b). Capacitors Cs1, Cs2, Cs1 are obtaind respectively between opposed capacitor electrodes 17 and 23, between capacitor electrodes 18 and 24, and between capacitor electrodes 19 and 25. Coupling capacitors C1, C2 are obtained between the electrodes 17 and 18 and between the electrodes 18 and 19 similarly through the construction. Since the resonance frequency of the resonators is unified in this way, cost-down is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bandpass filter using a dielectric coaxial resonator.

(Prior Art) An example of a bandpass filter using a dielectric coaxial resonator is disclosed in, for example, Japanese Patent Application Laid-Open No. 56-57302. An equivalent circuit of this kind of filter is shown, for example, in FIG. That is, a coupling capacitor is connected directly or via a suitable terminal to the center conductor on the open end side of the 1/4 wavelength dielectric coaxial co-installer. In the figure, C1, C2, and C3 are coupling capacitors, and 1 to 5 are dielectric coaxial resonators. Coupling capacitor C1, C2, C3
may be a single capacitor, or may have a structure in which a plurality of capacitor electrodes are formed on a single dielectric substrate. The resonant frequency of resonator 4 is the same as that of resonator 2 (-12), and the resonant frequency of resonator 5 is the same as that of resonator 1 (=f t ). and,
Since fl>f2>f3 must be satisfied, two resonators each tuned to three different resonance frequencies must be prepared for one filter, which is disadvantageous in terms of cost. Furthermore, the case dimensions must be determined in accordance with the longest resonator dimension, which is disadvantageous in terms of miniaturization.

(Problem to be solved by the invention) Therefore, this invention can reduce costs, and
The present invention aims to provide an efficient filter that can be miniaturized to the utmost, and is easy to assemble.

(Means and effects for solving the problem) In this invention, the resonant frequencies of the dielectric coaxial resonators used are unified,
A frequency adjustment capacitor is connected in parallel to the required resonators so that each resonator has a predetermined resonance frequency relationship.

(Example) FIG. 1 is an equivalent circuit diagram showing an embodiment of the present invention.

FIGS. 3 and 4 are schematic diagrams showing main parts of the actual configuration.

In FIG. 1, resonators 11 to 15 all have the same resonant frequency (=r 1). These resonators 11-1
5 may be independent dielectric coaxial resonators one by one as shown in FIGS. 3 and 4, or may be integrally formed with one dielectric block. In order to set the resonant frequency of the resonator 12 to 2, a capacitance C3t for frequency adjustment is provided between the center conductor on the open end side of the resonator 12 and the ground.

Similar measures are taken for the resonator 14. The resonator 13 has a similar frequency adjustment capacitor I in order to set its resonant frequency to C3.
C32 is provided. Now, if the characteristic impedance of the λ/4 resonator is 7a, the relative dielectric constant between the inner and outer conductors is εr, the axial length is the axis length, and the speed of light is CO, the bandpass filter using the λ/4 resonator will resonate. Axis length C3 of resonator 11.15 with frequency f1
It is sufficient to set 1. It would be good to define the same.

The same applies to filters using λ/2 resonators.

The capacitances C31 and C32 are configured as shown in FIGS. 3 and 4, for example. In FIG. 3, 16 is a dielectric substrate, 17, 18, and 19 are capacitor electrodes formed on one side of the substrate 16, 20, 21, and 22 are terminals.
23, 24, and 25 are capacitor electrodes formed on the other side of the substrate 16. Terminals 20, 21, 22 are conductively fixed to the open-ended central conductors of the resonators 12, 13, 14, respectively. Terminals 20, 21, 22 are soldered to capacitor electrodes 17, 18, 19, respectively. Coupling capacitance C3, C3 is capacitor electrode 11.18@
, respectively, between the capacitor electrodes 18 and 19. The capacitances tcs 1 , C8z, and C31 are obtained between the opposing capacitor electrodes 17.23111, 18.24, and 19.25, respectively. The coupling capacitance 11ct and C2 are also obtained by the same structure as between capacitor electrodes 11.18 and 18.19. FIG. 4 shows another configuration. The dielectric substrate 26 is similar to the substrate 1G, and a soldering iron-shaped capacitor electrode 21 is provided on one side of the substrate 26.
．． 28, 29 are formed, and capacitor electrodes 33, 34, 35 are formed inside each of the electrodes 21, 28, 29. Then, coupling capacities C3 and C3 are obtained between capacitor electrodes 27 and 28 and between capacitor electrodes 28 and 29, respectively. The capacitances C81, C82, and C81 are obtained between capacitor electrodes 27.33, capacitor electrodes 11128.34, and capacitor electrodes Fi29.35, respectively.

Coupling capacitances C1 and C2 are also connected between capacitor electrodes 27 and 28.
It is obtained with the same structure as between 8.29 and 29.

(Effects) As is clear from the above embodiments, according to the present invention, the resonant frequencies of the resonators to be prepared are unified, so it is possible to reduce costs, and the resonators are made smaller. can. In addition, the installation work is easy and efficiency is improved. Furthermore, it is also possible to employ a configuration in which all the resonators are composed of one dielectric block, and in this case, the above-mentioned effect is further emphasized.

In addition, when a coupling capacitor is composed of a single dielectric substrate with multiple capacitor electrodes, the unused space of the dielectric substrate originally required for forming the coupling capacitor is used for coupling. It is preferable that the present invention can be carried out simply by providing a capacitor electrode so that a frequency adjustment capacitance is generated between the capacitor electrode and grounding this electrode.

[Brief explanation of drawings]

Fig. 1 is an equivalent circuit diagram of an embodiment of the present invention, Fig. 2 is an equivalent circuit diagram of a conventional example, Fig. 3 is a schematic configuration diagram of an embodiment of the present invention, and Fig. 4 is an equivalent circuit diagram of an embodiment of the present invention.
The figure is a schematic configuration diagram of another embodiment. 11 to 15 are dielectric coaxial co-imagers, C1, C2, and C3 are coupling capacitors, and C81 and C32 are frequency adjustment capacitors.

Claims (2)

[Claims] (1) In a bandpass filter formed by coupling multiple dielectric coaxial resonators with coupling capacitance, the resonant frequencies of the dielectric coaxial resonators are unified, and each resonator has a predetermined resonant frequency relationship. A filter characterized in that a frequency adjustment capacitance to be set is connected in parallel to a required resonator. (2) Coupling capacitance is realized by forming a capacitor electrode on a single dielectric substrate, and by further providing a capacitor electrode on this dielectric substrate, there is a connection between the capacitor electrode and the capacitor electrode for forming the coupling capacitance. The filter according to claim (1), characterized in that a frequency adjustment capacitance is realized in the filter.