JPS6360603A - Dielectric filter - Google Patents

Abstract

PURPOSE:To provide an attenuation pole to an optional frequency of a filter characteristic by connecting an open end of an adjacent dielectric resonator by a reactance element. CONSTITUTION:A coupling hole 6 is provided among dielectric resonators A1-A6 and adjacent resonators A1, A2... are coupled electromagnetically. A U-shaped electrode 5 is formed around the coupling hole 6. A static capacitance is formed between the open end of an innder conductor 3 and the electrode 5 by the presence of the electrode 5. Moreover, since the electrode 5 is formed as a U-shape, the inductive component is provided. A paralle resonance circuit is formed with a specific reactance elemetn equivalently and an attenuation pole is formed with the antiresonance state at a specific frequency. Thus, the attenuation pole is provided to an optional frequency of the filter characteristic.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a dielectric filter having a configuration in which a plurality of dielectric resonators are coupled to each other electromagnetically or via a coupling element. This paper relates to a bandpass filter with poles in the range.

('b) Conventional technology In band-pass filters, when configuring a filter that increases the amount of attenuation at frequencies that are a predetermined frequency away from the center frequency, multiple resonators, whether cavity resonators or dielectric resonators, are connected adjacently. In a filter configured such that two components are electromagnetically coupled or coupled via a coupling element, one possible method is to increase the number of resonator stages, or to directly electromagnetically couple resonators separated by one or more stages.

(C) Problems to be Solved by the Invention However, with conventional bandpass filters, it is difficult to form an attenuation pole at an arbitrary frequency of the filter characteristics. In addition, the polarization technology that creates a pole in the attenuation range of filter characteristics is already known for cavity resonator filters and semi-coaxial filters, but it has not yet been implemented for dielectric filters. It is.

An object of the present invention is to provide a dielectric filter that can have an attenuation pole at an arbitrary frequency in its filter characteristics.

(Means for Solving Problem d1) This invention provides a dielectric filter having a configuration in which a plurality of adjacent dielectric resonators are electromagnetically coupled or coupled via a coupling element. The open end of the device is connected by a reactance element.

FIG. 5 is a diagram showing an example of a dielectric filter composed of dielectric resonance blocks. An outer conductor made of a metal film is formed on the four sides of this block 1, and through holes 3 are formed in the dielectric block 1 at predetermined intervals. An inner conductor 4 made of a metal film is formed on the inner surface of the through hole 3 , and is short-circuited to the outer conductor 2 by a conductive film formed on the bottom surface of the dielectric block 1 . Dielectric resonators A1 to A6 are formed by each inner conductor 4, outer conductor 2, and dielectric block 1 existing therebetween. Further, coupling holes 6 are formed between the resonators A1 to A6 for coupling the resonators to each other, and adjacent resonators are electromagnetically coupled. In the present invention, for example, in such a dielectric filter, the open ends (the upper part of the inner conductor 4 in FIG. 5) of adjacent dielectric resonators are connected by a reactance element.

(e) Operation An equivalent circuit of the dielectric filter shown in FIG. 5 is shown in FIG. In this figure, 10a, 10b, . . . represent resonance elements, 11a, 11b, . . . represent specific actance elements, and a, b, . do. As described above, according to the present invention, by connecting the open ends of adjacent dielectric resonators by a reactance element, the reactance element and the specific reactance element are connected in parallel. Capacitors 12a and 12b are connected as reactance elements as shown in FIG.

12C1... are connected, the capacitor 12a and the intrinsic resistance element 11a form a parallel resonant circuit.

In this way, since a parallel resonant circuit is formed with each unique actance element in the equivalent circuit, anti-resonance can occur at the resonant frequency and attenuation poles can be formed at a plurality of arbitrary frequencies.

(f) Embodiment FIG. 1 shows a dielectric filter constructed of dielectric resonance blocks as an embodiment of the present invention.

Reference numeral 1 denotes a dielectric block made of a titanium oxide-based ceramic dielectric, etc. An outer conductor 2 made of a metal film is formed on the four sides of each block 1, and a plurality of through holes 3 are formed in the dielectric block 1 at predetermined intervals. It is formed. An inner conductor 4 made of a metal film is formed on the inner surface of each through hole 3, and is short-circuited to the outer conductor 2 by a conductive film (not shown) formed on the bottom surface of the dielectric block 1. In this way, each inner conductor 4, outer conductor 2, and dielectric block 1 existing between them
The dielectric resonators A1 to A6 are configured by the above. A coupling hole 6 is provided between the resonators A1 to A6 as a means for coupling the resonators to each other, and the adjacent resonators A
l, A2. ... are electromagnetically coupled.

The upper surface of the dielectric block 1 in the drawing is an open end surface on which no conductive film is formed, and a "U"-shaped electrode 5 is formed around the coupling hole 6 on the end surface. This electrode 5
is formed by printing silver paste or the like on the open end surface and firing it. Due to the presence of this electrode 5, the inner conductor 3
A capacitance is formed between the open end of the electrode 5 and the electrode 5. Further, since the electrode 5 is formed in a "U" shape, it also includes an inductive component. (See the parts of resonators A5 and A6 in the same figure.) By connecting the open ends of adjacent dielectric resonators with reactance elements as described above, the inherent resistance in the equivalent circuit is reduced as shown in Figure 4. A parallel resonant circuit is formed between the actance elements, and an attenuation pole is formed by entering an anti-resonant state at a specific frequency.

FIG. 2 is a diagram schematically showing the filter characteristics. In the same figure, the arrow part is the attenuation pole.As shown in Figure 1, in the 6-stage dielectric filter, the open ends of each dielectric resonator are connected by 5 quarter actance elements, so there are 5 attenuation poles. (arrow portion in the figure) is formed. The number of attenuation poles can be arbitrarily set depending on the number of electrodes 5 shown in FIG. 1, and the frequency can be set depending on the shape of the electrodes.

Although the above embodiment was an example in which a reactance element was provided by forming an electrode directly on the top surface of a dielectric block, it is also possible to directly connect a reactance element as a discrete component to the open end of a dielectric resonator. be.

FIG. 3 is a diagram showing an example of this, and as shown in the figure, a capacitor element 7 with a lead is connected to the open end of each resonator by soldering. Note that 8 is an input/output terminal.

According to this configuration, a capacitive reactance element with a relatively large capacity can be connected, and an attenuation region can be formed in a relatively low frequency region.

Although the actance element shown in FIG. 3 is a capacitive reactance element, it is also possible to use an inductive reactance element as required. Furthermore, by connecting a reactance element whose value can be adjusted, such as a variable capacitor, it is possible to move the frequency of the attenuation pole as necessary.

(g1 Effects of the Invention As described above, according to the present invention, any number of attenuation poles can be formed at any frequency, and bandpass filters having various filter characteristics can be easily constructed as required. be able to.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a dielectric filter as an embodiment of the present invention, FIG. 2 is a diagram schematically showing the filter characteristics, and FIG. 3 is a perspective view of a dielectric filter showing another embodiment.
FIG. 4 is a diagram showing an example of an equivalent circuit of a dielectric filter according to the present invention, and FIG. 5 is a perspective view showing the structure of a conventional dielectric filter. A1 to A6 - dielectric resonator, 5 - electrode, 7 - capacitor.

Claims (1)

[Claims] (1) In a dielectric filter having a configuration in which a plurality of adjacent dielectric resonators are electromagnetically coupled or coupled via a coupling element, the open ends of adjacent dielectric resonators are connected by a reactance element. A dielectric filter featuring: