JPS6251803A - Microwave filter - Google Patents

Abstract

PURPOSE:To provide a polar characteristic by providing an input/output terminal connected simultaneously to an input stage resonance element and a resonance element of next stage adjacent to the input stage resonance element. CONSTITUTION:An input terminal 4 is formed between the input stage resonance element 21 and the resonance element 22 of the next stage adjacent to the element 21. Since the resonance element 22 of the next stage is connected to the input terminal 4 while skipping the resonance element 21 of the input stage in this way, when the output terminal 5 is arranged similarly as above even in the output stage, a polar characteristic is obtained similarly. The polar filter having a pole at the attenuation region is constituted easily by having only to arrange the input/output terminals 4, 5 at the midpoint between the resonance elements in this way, even in a comb-line filter of microstrip line structure where the resonance elements 21-24 are formed on the same major surface of the dielectric substrate 1.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to microwave filters.

<Prior Art> FIG. 6 is an equivalent circuit diagram of an example of a microwave filter. In FIG. 6, IN is an input terminal, OUT is an output terminal, and GND is a ground terminal. al+a2+...+a
@ is the adjacent coupling capacitor, b,, b,,..., bs
is a resonant element. C is an interlaced coupling capacitor that couples the input stage resonant element b1 to the fourth stage resonant element b4.

In a microwave filter with such a configuration, the coupling capacitor C has a ball (pole) in the attenuation region of the filter characteristics.
It has the effect of forming

<Problems to be Solved by the Invention> Some conventional microwave filters of this type are formed on a dielectric monolithic substrate. This formation will be explained in conjunction with the equivalent circuit diagram of the microwave filter shown in FIG. That is, this microwave filter includes a dielectric substrate. On one main surface of this dielectric substrate, a plurality of mutually parallel resonant elements are arranged by electrodes.
..., b5 is formed.

Adjacent resonant elements, b, ..., b, are
Capacitance at + as + a4 + via dielectric substrate
Joined with as.

Further, the input stage resonant element a1 and the fourth stage resonant element a4 are coupled by a capacitance C through an electrode formed on one main surface of the dielectric substrate.

By the way, in the structure of such a microwave filter,
It is difficult to form electrodes that act as interlaced coupling capacitors.

An object of the present invention is to simply provide a microwave filter having balls (poles) in the attenuation region.

<Means for Solving the Problems> In order to achieve such an object, the present invention provides a substrate,
A plurality of resonant elements are arranged in parallel from the input side to the output side on one main surface of the substrate and electrically coupled to each other, and an input terminal and an input terminal formed on the one main surface of the substrate. The input terminal is arranged so as to be simultaneously electrically coupled to the resonant element of the input stage and the resonant element of the next stage adjacent to it, or the resonant element of the output stage and the resonant element of the adjacent previous stage It is characterized in that the output terminal is arranged so as to be electrically coupled to the resonant element at the same time.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a schematic plan view of a microwave filter according to an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of this microwave filter.

1 is a dielectric substrate. 21 to 24 are a plurality of resonant elements arranged in parallel on one main surface of the dielectric substrate 1 by electrodes from the input side to the output side.

Each of the resonant elements 21 to 24 is commonly connected to a guard electrode 10 formed at an end of the dielectric substrate 1.

A ground electrode (not shown) is formed entirely on the other main surface of the dielectric substrate l. Such a structure becomes a combline type filter.

Each resonant element 21 to 24 is connected to a capacitor 3 via a dielectric substrate l.
2, 33, and 34.

Reference numeral 4 denotes an input terminal formed of an electrode on one main surface of the dielectric substrate 1 so as to be electrically coupled to the input stage resonant element 21 and the adjacent next stage resonant element 22 at the same time. Specifically, the input terminal 4 is formed between the resonant element 21 and the next stage resonant element 22, as shown in FIG.

Reference numeral 5 designates an output terminal formed on one main surface of the dielectric substrate 1 so as to be electrically coupled to the output stage resonant element 24 and the adjacent previous stage resonant element 23 at the same time. Specifically, the output terminal 5 is formed between the resonant element 24 and the preceding resonant element 23.

The input terminal 4 formed at this position couples the input terminal 4 and the resonant element 21 through a capacitor 31 .

Furthermore, the output terminal 5 formed at this position couples the output terminal 5 and the resonant element 24 through a capacitor 35 .

Similarly, the input terminal 4 connects the input terminal 4 and the resonant element 22.
and is coupled with a capacitance of 6. Furthermore, the output terminal 5 is coupled to the resonant element 23 through a capacitor 7 .

FIG. 3 is a circuit diagram of a portion A surrounded by a chain line in FIG. 4 is an equivalent circuit diagram of FIG. 3, and FIG. 5 is a diagram for explaining the operating characteristics of the circuit of FIG. 4. When the portion B surrounded by the one-dot chain line in FIG. 4 is in an anti-resonance state, the microwave filter becomes a bandpass filter. Further, when the portion B is in a resonant state, the microwave filter operates so as to form a ball in the attenuation region.

In this case, the capacitance C of the capacitor in the part B surrounded by the one-dot chain line in FIG. 4, the electrical angle θ of the resonant element, and the characteristic impedance Z are so that the circuit in FIG.
is determined. Correspondingly, the capacitances of the adjacent coupling capacitors 31 and 32 and the interlaced coupling capacitor 6 of the circuit shown in FIG. 3 are determined.

In addition, in the embodiment, the capacitance for the interlaced coupling capacitor is obtained through the dielectric substrate l, but the present invention is not limited to this. For example, the resonant element may be interlaced coupled by inductive coupling using a coil. You can.

<Effects of the Invention> As described above, according to the present invention, the resonant element is formed on one main surface of the substrate so as to be electrically coupled to the resonant element of the input stage and the resonant element of the next stage adjacent thereto at the same time. an output terminal formed on one main surface of the substrate so as to be electrically coupled simultaneously to a resonant element of the output stage and a resonant element of the preceding stage adjacent thereto; It is equipped with As a result, a polarized filter can be constructed simply by changing the shapes of the input terminal and output terminal. Therefore, the desired pole can be easily obtained in the attenuation region by changing the installation position of the terminal.

[Brief explanation of the drawing]

1 to 5 are diagrams according to embodiments of the present invention. Fig. 1 is a schematic plan view of the embodiment, Fig. 2 is an equivalent circuit diagram of Fig. 1, Fig. 3 is a circuit diagram of the chain line portion A in Fig. 2, Fig. 4 is an equivalent circuit diagram of Fig. 3, FIG. 5 is an operational characteristic diagram of the circuit of FIG. 4. FIG. 6 is a conventional equivalent circuit diagram. ■...Substrate, 21-24...Resonant element, 31-35...Capacitor for adjacent coupling, 4...Input terminal, 5...Output terminal, 6.7... Capacitor for interlaced coupling.

Claims (1)

[Claims] (1) a substrate; a plurality of resonant elements arranged in parallel from an input side to an output side on one main surface of the substrate and electrically coupled to each other; and on one main surface of the substrate; an input terminal formed on the substrate; and an output terminal formed on one main surface of the substrate. A microwave filter comprising at least one of an input terminal or an output stage resonant element electrically coupled to an input terminal or an output stage resonant element and an output terminal electrically coupled simultaneously to an adjacent previous stage resonant element.