JPS61193501A - Filter - Google Patents

Abstract

PURPOSE:To attain miniaturization by conducting one of two capacitor electrodes to the center conductor of the open end side of a resonator and connecting the other electrode to the same kind of capacitor electrode of the next stage via an inductance element so as to eliminate the need for a strip line and a coaxial line. CONSTITUTION:The open end side center conductor of the resonator 1 is connected to a capacitor electrode 12 via a terminal 15. A capacitor 3 is realized by static capacitance formed between capacitor electrodes 11, 12, a capacitor 7 is realized by static capacitance formed between the capacitor electrodes 11 and 14 and the earth side capacitor electrode 14 is grounded by a proper means. For example, an elastic metallic piece is inserted between the electrode 14 and the case. The earth side capacitor electrode 14 is not required depending an operating frequency and the capacitor 7 is realized by a stray capacitance between the capacitor electrode 11 and the case. Thus, a large-sized transmission line is realized by a lumped constant and miniaturized. The capacitor connected in series with the resonator is realized by using a lumped constant circuit so as to miniaturize a band elimination filter.

Description

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

(Prior art) A conventional example of this type of filter is, for example,
It is disclosed in Publication No. 903. In other words, to explain the outline, a series connection of a capacitor and a dielectric coaxial resonator was connected between the transmission line and the ground at a 1/4 wavelength interval, and this transmission line was composed of a strip line. . There were also others where the transmission line was made up of coaxial lines.

Therefore, the strip line or coaxial line must be housed in a case, which limits how compact the filter can be made, and the filter inevitably remains larger than a bandpass filter with the same number of stages. In addition, the structure is complex, making it difficult to reduce costs.

(Problem to be Solved by the Invention) Therefore, an object of the present invention is to eliminate the need for strip lines and coaxial lines, reduce the size, and reduce costs. Filters can be provided.

(Means and effects for solving the problem) In the present invention, the transmission line is configured with a lumped constant circuit, and moreover, this lumped constant circuit is arranged in multiple numbers on a single dielectric substrate, which is often used in bandpass filters. is provided on a bonded substrate provided with capacitor electrodes. In other words, one of the two capacitor electrodes provided with a gap on one surface of this dielectric substrate is electrically connected to the center conductor on the open end side of the resonator, and the other electrode is connected to the same type of capacitor in the next stage via an inductance element. It is connected to the electrode and forms a capacitance between the other electrode and ground. Then, the center conductor on the open end side of the resonator is connected to the transmission line via the capacitance formed between two capacitor electrodes provided on one surface of the substrate, and the transmission line is inserted in series with the line. This is a π-type circuit composed of an inductance element having a shape of 1, and two capacitances formed between capacitor electrodes located at both ends of the inductance element and the ground.

(Embodiment) FIG. 1 is an equivalent circuit diagram of an embodiment of the present invention, and FIG. 2 is a schematic diagram of its specific configuration. In the figure, 1 is a 1/4 wavelength dielectric axis co-imager, 3 is a capacitor connected between the center conductor of the resonator 1 and the transmission line, 5 is a lumped transmission line, and an inductance element 6 ．． It is associated with a π-shaped circuit formed from capacitor 7.7. Capacitor 3. Inductance element 6. The capacitor 7 is configured as shown in FIG. 2, for example. Now, if we convert a transmission line with a characteristic impedance Za and an electrical angle θ□ into a π-type circuit with capacitance elements hanging at both ends of an inductance element, for example, the center frequency is 400 MH2, the characteristic Considering a line with an impedance of 50Ω, in the band elimination filter, θ is 90°, so such a value can be realized with the structure shown in Fig. 2 described below.In Fig. 2, 10 is a dielectric substrate, 11 and 12 are capacitor electrodes formed with a gap on one surface of the substrate 10, 13 is an inductance electrode formed integrally with the two capacitor electrodes 11.1111, and 14 is the substrate 10. a capacitor electrode 15 formed on the other surface to face the electrode 11;
is the terminal. The center conductor on the open end side of the resonator 1 is connected to a capacitor electrode 12 via a terminal 15. Capacitor 3 has capacitor electrodes 1j,, 12
This is realized by the capacitance formed between them. Capacitor 1 is realized by a capacitance formed between capacitor electrodes 11,14. The ground side capacitor electrode 14 is grounded by an appropriate means (not shown). For example, a springy metal piece may be interposed between the electrode 14 and the case. Depending on the frequency used, the ground side capacitor electrode 14 may not be necessary.
The capacitor 7 is realized by the stray capacitance between the capacitor electrode 11 and the case. The inductance element is the electrode 11
It may be realized by a coil component without using 13.

(Effects) As is clear from the above embodiments, according to the present invention, a band pass filter, for example,
A band elimination filter can be constructed using a process similar to that of a band pass filter having a configuration in which a plurality of coupling capacitors are formed on a single dielectric substrate, as is known in Japanese Patent No. 2. In other words, the large transmission line that was conventionally required has been reduced in size by using lumped constants, and the capacitors connected in series with the resonator can also be realized on the board used to form the lumped constant circuit. For these reasons, the band elimination filter can be made small and provided at low cost.

[Brief explanation of drawings]

FIG. 1 is an equivalent circuit diagram of an embodiment of the present invention, and FIG. 2 is a schematic diagram of its specific configuration. 1 is a dielectric coaxial resonator, 3 is a capacitor, 5 is a lumped transmission line, 6 is an inductance element, 7 is a capacitor, 10 is a dielectric T4M plate, 11° and 12 are capacitor electrodes, and 13 is an inductance electrode. Patent applicant

Claims (2)

[Claims] (1) In a band elimination filter in which a capacitance and a dielectric circumferential resonator are connected in series between a transmission line and ground, a dielectric substrate is placed on the open end side of the dielectric coaxial resonator, On one side of this board, two capacitor electrodes are provided for each resonator with a predetermined gap, one electrode is connected to the center conductor on the open end side of the resonator, and the other electrode is connected to the same type of the next stage. A filter characterized in that it is connected to a capacitor electrode via an inductance element, and a capacitance is formed between the other electrode and ground. (2) The filter according to claim (1), wherein the inductance element is an electrode film provided integrally with a capacitor electrode on the substrate.