JPH0595203A - Coaxial resonator filter - Google Patents

Abstract

PURPOSE:To obtain a small-sized coaxial resonator filter excellent in performance by providing an open stub whose tip is opened to an input output coupling element subjected to electric field coupling with input and output coaxial resonators so as to obtain attenuation at a harmonic band. CONSTITUTION:The filter is provided with an inner conductor 5 having a group of plural main bodies juxtaposed between metallic chassis 1, 2 at an interval so that the wave of the waveguide mode is sufficiently cut off at the pass band of the filter of the coaxial resonator main body 3 and with coupling elements 4A, 4B coupling the main body 3 and an external circuit. The elements 4A, 4B are connected to coaxial connectors 6A, 6B of the external circuit at coaxial coupling parts 6C, 6D at one end of the opening end, and an opening stub 7 having an opening end whose length is 1/4 wavelength at a prescribed harmonic band connected to the coaxial coupling parts 6C, 6D at one end of the opening end is added to the elements 4A, 4B. The stub 7 acts like a 1/4 wavelength resonator at a harmonic band at which the cut-off waveguide composed of the chassis 1, 2 is not interrupted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial resonator type road filter having an improved coupling portion with an external circuit of a coaxial connector attached to an end portion of a coaxial resonator body used in a microwave band.

[0002]

2. Description of the Related Art A conventional coaxial resonator is shown in FIGS.
As shown in the plan view and the external view as seen from the side, respectively, a metal chassis 1 to which the input and output coaxial connectors 6A and 6B are attached, a mating metal chassis 2 and a coaxial resonator body 3 are formed. Conductor 5, coaxial connectors 6A, 6
B coupling element 4A, 4B. As a structure for obtaining the coupling with the external circuit of such a coaxial resonator type bandpass filter, in the interdigital type bandpass filter, one end face is short-circuited and the other end is open.
A and 4B are installed at a constant distance from the coaxial resonator body 3 and are connected to an external circuit via coaxial connectors 6A and 6B from the vicinity of the open end.

[0003]

In this conventional coaxial resonator, the coaxial resonator operates as a quarter-wave resonator with one short-circuited one end and the other open-ended. The length direction of the resonator is slightly longer than a quarter wavelength of the center frequency of the pass band, and the unnecessary amount of the waveguide mode is excited in the length direction of the resonator in the amount of attenuation in the harmonic band. Therefore, only the attenuation of about 0 to 10 dB was obtained. In order to secure the attenuation in the harmonic band, it is necessary to connect the coaxial resonator type band pass filter and the low pass filter in cascade, which increases the mounting space and increases the manufacturing cost. Was becoming.

[0004]

The coaxial resonator type filter of the present invention is a coaxial resonator type filter having a structure in which at least one coaxial resonator is coupled to each other in a metal chassis. An open stub whose one end of the input / output coupling element for electric field coupling to the coaxial resonator is an open end in the harmonic frequency band is provided.

[0005]

The present invention will be described below with reference to the drawings. 1A and 1B are a plan sectional view and a side external view of an embodiment of the present invention, respectively. In FIG. 1, the same reference numerals as in the conventional example of FIG. 2 have the same configuration.

In this embodiment, a certain distance is provided between the metal chassis 1 and the metal chassis 2 so that the waveguide mode is sufficiently cut off in the pass band of the filter of the coaxial resonator body 3. A group of a plurality of coaxial resonator main bodies 3 arranged in parallel and an inner conductor 5 having coupling elements 4A and 4B for coupling the coaxial resonator main body 3 and an external circuit are included. Here, the coupling elements 4A and 4B are the coaxial connectors 6 of the external circuit.
An open stub 7 having an open end that is connected to A and 6B by coaxial coupling portions 6C and 6D at one end of the open end and has a quarter wavelength in a predetermined harmonic band is added at the same time. The open stub 7 operates as a quarter-wave resonator in a harmonic band in which the cutoff waveguide formed by the metal chassis 1 and the metal chassis 2 including the inner conductor 5 is not cut off. It is possible to improve the harmonic attenuation of the filter.

[0007]

As described above, according to the present invention, in an ultra-high frequency coaxial resonator in which at least a plurality of coaxial resonators are coupled to each other in a metal chassis, an input / output coupling for electric field coupling to the input and output coaxial resonators. By providing an open stub with an open tip on the element, attenuation can be obtained in the higher harmonic band that cannot be obtained in the conventional example, so there is an effect that it is possible to provide a compact coaxial resonator type filter with improved characteristics. is there.

[Brief description of drawings]

FIG. 1 is a plan sectional view (a) and a side external view (b) of an embodiment of the present invention.

FIG. 2 is a plan sectional view of a conventional coaxial resonator type filter (a).
And FIG.

[Explanation of symbols]

 1, 2 Metal chassis 3 Coaxial resonator 4A, 4B Coupling element 5 Inner conductor 6A, 6B Coaxial connector 6C, 6D Coaxial coupling part 7 Open stub

Claims (2)

[Claims] 1. A coaxial resonator type filter having a structure in which at least one or more coaxial resonators are coupled to each other in a metal chassis, and an input / output coupling element for electric field coupling to input and output coaxial resonators is provided. A coaxial resonator type filter characterized in that an open stub whose end is an open end in a harmonic frequency band is provided. 2. The length of the open stub has a length of approximately ¼ wavelength in a harmonic frequency band from the end of the coaxial connector for coupling to the outside to the open end. Coaxial resonator type filter.