JPH08250905A - Dielectric filter circuit and its configuration method - Google Patents

Abstract

PURPOSE: To suppress interference between circuit elements without the use of a special additional member and to obtain a further larger attenuation in excess of a noise level. CONSTITUTION: An attenuation pole circuit 12a(12c, 12b) forming an attenuation pole comprising a reactive element such as a capacitor or a coil and a dielectric resonator 11a(11c, 11b) is connected between coupling circuit elements 13a and 13b (between coupling circuit elements 13b and 13d and between coupling circuit elements 13c and 13b) which are components of the dielectric filter circuit consisting of the cascade connection of the four coupling circuit elements 13a, 13b, 13d and 13c in this order each being a reactive element such as a capacitor or a coil. Then the attenuation pole circuits 12a, 12b whose frequencies are close to each other are located apart among the attenuation pole circuits 12a, 12c and 12b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter circuit mainly used in electronic equipment for communication and the like and a method for constructing the same.

[0002]

2. Description of the Related Art Conventionally, this type of dielectric filter circuit has been
Generally, it is used as a bandpass filter to obtain large attenuation near the pass band. As shown in FIG. 3, a dielectric filter circuit for such a bandpass filter has four coupling circuit elements 13a, 13b, 13c, 13d using reactance elements of capacitors or coils.
(However, capacitors are used for the coupling circuit elements 13a, 13b, 13c, and coils are used for the coupling circuit element 13d), and the coupling circuit elements 13a, 13a are connected in series in this order.
Reactance elements and dielectric coaxial resonators 11a, 11b, 1 are provided between adjacent ones of 13b, 13c, 13d.
Three attenuation pole circuits 12a, 12 forming an attenuation pole from 1c
b and 12c (however, capacitors are used for the attenuation pole circuits 12a and 12b, and coils are used for the attenuation pole circuit 12c), which are vertically connected in this order.

FIG. 4 shows the characteristics of a dielectric filter circuit having such a circuit structure as frequency [MHz] and loss [dB].
It is shown in the relationship with. In general, the dielectric filter circuit is required to have a smaller insertion loss in the signal pass band and a larger attenuation in the signal stop band.

Therefore, in order to achieve the standard line A in the signal stop band in accordance with the characteristic curve C in this dielectric filter circuit, the two attenuation poles 21a and 21b are arranged side by side in a narrow band to reduce the attenuation. Pole 21a,
21b is combined to obtain a large amount of attenuation to satisfy the standard line A in the signal stop band. That is, in the dielectric filter circuit, in order to satisfy such a condition, the normal attenuation pole 21
Attenuation pole circuits 12a and 12b forming a and 21b are arranged adjacent to each other.

[0005]

In the case of the dielectric filter circuit described above, if it is used under the condition that the noise level exceeds the noise level and large attenuation is required, a sufficient attenuation amount may not be obtained in terms of the circuit configuration.

FIG. 5 shows the noise level characteristic of the dielectric filter circuit shown in FIG. 3 in terms of the relationship between frequency [MHz] and attenuation [dB]. Here, it can be seen that the amount of noise level attenuation changes depending on the frequency, and increases as the frequency increases. Incidentally, the noise level characteristics generally change depending on the characteristics of the circuit elements and dielectric coaxial resonators used in the circuit configuration, and it is expected that the amount of attenuation itself will differ, but the relationship with frequency shows a similar tendency. Show.

FIG. 6 shows the relationship between the characteristic curve C1 of the actual measurement value shown by the solid line and the characteristic curve C2 of the theoretical value shown by the dotted line, showing the characteristics of the above-mentioned dielectric filter circuit when a large attenuation is taken over the noise level. It is shown. From FIG. 6, in comparison of the attenuation poles 21a and 21b, the characteristic curve C2
It can be seen that in the characteristic curve C1, that is not actually achieved although the sufficient attenuation is obtained. If you try to achieve a large amount of attenuation above the noise level,
It is presumed that interference is caused between the circuit elements and a large amount of attenuation cannot be obtained.

Specifically, in the dielectric filter circuit shown in FIG. 3, although the interference between the attenuation pole circuits 12a and 12b is large, the interference between the attenuation pole circuits 12b and 12c and the interference between the attenuation pole circuits 12a and 12c. The interference is almost negligible. That is, the interference itself consists of three attenuation pole circuits 12
Despite the fact that they occur between a, 12b and 12c respectively, the two attenuation poles 21a and 21b arranged in a narrow band with respect to the adjacent attenuation pole circuits 12a and 12b have different logical values and measured values. While the influence of the interference is large, the theoretical value and the measured value are almost the same in the attenuation pole 21c arranged with the pass band separated in the attenuation pole circuit 12c, and the influence of the interference is small. There is.

Further, such interference between the circuit elements causes the coupling circuit element 13 in the dielectric filter circuit shown in FIG.
When b is removed, the signal system between the input terminal and the output terminal is cut off in the middle, and the attenuation should be infinite. However, the existence of electromagnetic waves that actually propagate in the air It can also be seen from the fact that it does not become infinite.

FIG. 7 shows an equivalent circuit in the case where interference occurs between circuit elements in the above-mentioned dielectric filter circuit. That is, in this equivalent circuit, in addition to the coupling shown by the solid line, the coupling shown by the dotted line occurs due to the interference between the circuit elements.

If the interference between the circuit elements is simply eliminated, additional measures such as providing a metal plate between the interfering circuit elements may be taken, but such additional measures are effective. On the other hand, it is not only difficult to arrange other basic circuit elements, but also causes a large size, or there is a problem that productivity is deteriorated due to complicated assembly. Since it increases, it is not preferable as a measure against interference between circuit elements.

The present invention has been made to solve such a problem, and its technical problem is that interference between circuit elements can be suppressed without using a special additional member, and
It is an object of the present invention to provide a dielectric filter circuit that can obtain a larger amount of attenuation over a noise level and a method of configuring the dielectric filter circuit.

[0013]

According to the present invention, a plurality of coupling circuit elements connected in series and a plurality of coupling circuit elements adjacent to each other are vertically connected to each other, and
In a dielectric filter circuit that includes a plurality of attenuation pole circuits that include a dielectric resonator and that form an attenuation pole, a plurality of attenuation pole circuits can be obtained by a dielectric filter circuit in which adjacent frequencies are separated from each other. To be

On the other hand, according to the present invention, a plurality of attenuation pole circuits each including a dielectric resonator and forming an attenuation pole are vertically connected between adjacent ones of a plurality of series-connected coupling circuit elements. In a method of configuring a dielectric filter circuit that forms a body filter circuit, a method of configuring a dielectric filter circuit that separates adjacent ones of frequencies of a plurality of attenuation pole circuits from each other is obtained.

[0015]

In general, the phenomenon that the attenuation pole circuits forming the attenuation poles interfere with each other greatly appears when the attenuation poles are formed at frequencies close to each other. However, the characteristic of the attenuation poles separated from the signal pass band is characteristic. Interference between them is almost negligible. Therefore, in the method of constructing the dielectric filter circuit of the present invention, attention is paid to this, and those of the respective attenuation pole circuits whose frequencies are close to each other are separated from each other. In such a case, interference between circuit elements occurs between adjacent ones of the respective attenuation pole circuits, but since the attenuation poles are not placed at frequencies close to each other across the pass band, the influence of interference is small enough to be ignored. Become. As a result, in the dielectric filter circuit, the interference between the respective circuit elements can be ignored, and the attenuation poles whose frequencies are close to each other are combined to exceed the noise level and a sufficiently large attenuation amount can be obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The dielectric filter circuit of the present invention and the method of constructing the same will be described in detail below with reference to the drawings.

First, the outline of the method of constructing the dielectric filter circuit of the present invention will be briefly described. This dielectric filter circuit is constructed by connecting a plurality of attenuation pole circuits, each including a dielectric resonator and forming an attenuation pole, vertically between adjacent ones of a plurality of coupling circuit elements connected in series. Although the point of forming a filter circuit is the same as that of the conventional one, in the present invention, the circuits of the respective attenuation pole circuits whose frequencies are close to each other are separated from each other.

FIG. 1 shows the basic structure of a dielectric filter circuit according to an embodiment of the present invention to which this method of forming a dielectric filter circuit is applied.

In this dielectric filter circuit, four coupling circuit elements 13a, 13b, 13d and 13c using reactance elements such as capacitors or coils (however, here as well, each coupling circuit element 13a, 13b, 13c has a capacitor,
A coil is used as the coupling circuit element 13d), a reactance element of a capacitor or a coil, and dielectric coaxial resonators 11a, 11c, and 11b form an attenuation pole, and
Each coupling circuit element 13a, 13 connected in series in this order
b, 13d, 13c, three attenuation pole circuits 12a, 12c, 12 which are vertically connected in series with each other.
b (however, a condenser is used for the attenuation pole circuits 12a and 12b, and a coil is used for the attenuation pole circuit 12c here as well), and each of the attenuation pole circuits 12a, 12c, 1
In 2b, the attenuation pole circuits 12a and 12b, which have frequencies close to each other, are separated from each other.

Incidentally, this dielectric filter circuit has 400
400MHz for band pass filter of MHz band
The noise level attenuation amount at z is 45 dB according to the noise level characteristic shown in FIG.

In this dielectric filter circuit, the attenuation pole circuit 12a and the attenuation pole circuit 12 which form attenuation poles at frequencies close to each other.
An attenuation pole circuit 12c is arranged in the center so as to separate it from b. Therefore, interference occurs between the circuit elements between the attenuation pole circuits 12a and 12c and between the attenuation pole circuits 12c and 12b, but the attenuation poles of the attenuation pole circuits 12a, 12c, and 12b are close to each other across the pass band. Since it is not placed in frequency, the effect of interference is negligible.

FIG. 2 shows the characteristics of the conventional dielectric filter circuit shown in FIG. 3 (shown by the solid line as a characteristic curve C3) when the dielectric filter circuit has a large attenuation exceeding the noise level (indicated by the dotted line). This is shown by the relationship between the frequency [MHz] and the loss [dB] in comparison with the characteristic curve C4).

From FIG. 2, the standard line B in the insertion loss region of the signal pass band is 3 dB, and the standard line A in the signal stop band is 63 d.
In the case of B, it can be seen that the characteristic curve C4 cannot achieve the standard line A in the conventional characteristic, whereas the characteristic curve C3 can achieve the standard line A in the characteristic of the present embodiment.

In the dielectric filter circuit of the embodiment, 4
3 coupling circuit elements 13a, 13b, 13d, 13c and 3
Although the configuration including the individual attenuation pole circuits 12a, 12c, 12b has been described, the number of each of these circuit elements may be greater than that.

[0025]

As described above, according to the dielectric filter circuit and the method of constructing the same of the present invention, the interference between the respective circuit elements can be ignored even when a large attenuation is required beyond the noise level. Therefore, it is possible to obtain a large amount of attenuation in the signal stop band by disposing a plurality of attenuation poles. In particular, since interference between circuit elements can be suppressed by the configuration of only basic circuit elements without using a special additional member such as a metal plate, the dielectric filter circuit does not become large and productivity is not deteriorated. It has the advantage.

[Brief description of drawings]

FIG. 1 shows a basic configuration of a dielectric filter circuit for a bandpass filter according to an embodiment of the present invention.

2 is a graph showing characteristics of the dielectric filter circuit shown in FIG. 1 when a large attenuation is taken over a noise level, as compared with the characteristics of the conventional dielectric filter circuit shown in FIG. 3, in frequency [MHz] and loss [dB]. ] Is shown in the relationship with.

FIG. 3 shows a basic configuration of a conventional dielectric filter circuit for a bandpass filter.

FIG. 4 shows the characteristics of the dielectric filter circuit shown in FIG. 3 in terms of the relationship between frequency [MHz] and loss [dB].

5 shows the noise level characteristic of the dielectric filter circuit shown in FIG. 3 as a relationship between frequency [MHz] and attenuation [dB].

FIG. 6 is a graph showing the characteristics of the dielectric filter circuit shown in FIG. 3 when a large attenuation is achieved in excess of the noise level, in terms of the relationship between measured values and theoretical values.

7 shows an equivalent circuit in the case where interference occurs between circuit elements in the dielectric filter circuit shown in FIG.

[Explanation of symbols]

 11a, 11b, 11c Dielectric coaxial resonator 12a, 12b, 12c Attenuation pole circuit 13a, 13b, 13c, 13d Coupling circuit element 21a, 21b, 21c Attenuation pole A Standard line at signal stop band B Standard at insertion loss band line

Claims (2)

[Claims] 1. A plurality of coupling circuit elements connected in series,
A plurality of attenuating poles, each of which is vertically connected between adjacent ones of the plurality of coupling circuit elements and includes a plurality of attenuating pole circuits which form attenuating poles by including a dielectric resonator. The circuit is a dielectric filter circuit characterized in that those having frequencies close to each other are separated from each other. 2. A dielectric which forms a dielectric filter circuit by vertically connecting a plurality of attenuation pole circuits including a dielectric resonator and forming an attenuation pole between adjacent ones of a plurality of coupling circuit elements connected in series. In the method of constructing the body filter circuit,
A method of constructing a dielectric filter circuit, characterized in that among the plurality of attenuation pole circuits, those having a close frequency are separated from each other.