JPH05152806A - Voltage controlled filter - Google Patents

Abstract

PURPOSE:To obtain a capacitor whose static capacitance is selected without a parasitic inductance by arranging dielectric resonators while their side faces are in contact with each other and providing a part having no conductor to contact faces between the dielectric resonators. CONSTITUTION:Dielectric resonators DR1, DR2 are arranged while the side faces are in contact with each other, and a part having no conductor is provided to the contact faces. A coupling capacitor is formed by the static capacitance between inner conductors 16, 17 while the dielectric resonators DR1, DR2 are in contact with each other. The capacitance of the coupling capacitor depends on the distance between the inner conductors 16, 17, the dielectric constant of the dielectric resonators DR1, DR2 and the area of the part having no conductor of the contact faces between the dielectric resonators DR1, DR2 or the like, and the capacitance of the coupling capacitor is set to a desired value by varying the area of the part having no conductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled filter capable of changing the center frequency of a pass band by changing a bias voltage applied to a varactor diode.

[0002]

2. Description of the Related Art A conventional example of a voltage control filter composed of a varactor diode, a dielectric resonator and a capacitor on a dielectric substrate is, as shown in FIG. 2, a chip as a coupling capacitor and a variable frequency width adjusting capacitor. I was using a capacitor.

[0003]

In such a conventional example, a chip capacitor is used as a coupling capacitor for connecting the dielectric resonators, but it is necessary because the type of capacitor capacitance is determined. There was a defect that the chip capacitor could not be realized because there was no capacity or the required capacity was too small. Further, since the chip capacitor has an inductance component in addition to the capacitance, there is a drawback that the characteristics deteriorate due to the influence of the inductance component as the frequency increases, and the characteristics as designed cannot be obtained.

The present invention eliminates such drawbacks by arranging dielectric resonators so that their side surfaces are in contact with each other, and providing a non-conductor portion on the contact surface between dielectric resonators. An object of the present invention is to provide a voltage controlled filter that uses the capacitance between the inner conductors of a body resonator as a coupling capacitor.

[0005]

SUMMARY OF THE INVENTION According to the present invention, an input terminal for inputting a signal, an output terminal for outputting a signal, a dielectric having a side surface covered with a conductor, and a dielectric which penetrates the dielectric and projects outward from an end surface thereof. A plurality of dielectric resonators each having an internal conductor, and a first coupling capacitor connected between one of the internal conductors protruding from one end face of the dielectric resonator and the input terminal. A second coupling capacitor connected between the output terminal and another one of the inner conductors protruding from one end face of the dielectric resonator, and protruding from one end face of the dielectric resonator. A third coupling capacitor connected between the inner conductors, a varactor diode connected via a capacitor to the inner conductor projecting from the other end face of the dielectric resonator, and this varactor diode. And a means for changing the capacitance of the capacitor, the third coupling capacitor is arranged such that the side surfaces of the adjacent dielectric resonators are in contact with each other and the contacting surface has no conductor. It is a capacitor formed by providing a portion.

[0006]

[Function] The side surfaces covered by the respective conductors of the two dielectric resonators are brought into contact with each other, and a portion having no conductor is provided on the contact surface, and electrostatic capacitance is provided between the inner conductors penetrating the two dielectric resonators. To have As a result, the capacitance value can be selected to a desired value without any parasitic inductance.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment (two-stage bandpass filter) of the present invention.

In this embodiment, as shown in FIGS. 1 and 3, an input terminal 1 for inputting a signal, an output terminal 2 for outputting a signal, a dielectric whose side surface is covered with a conductor and this dielectric are penetrated. A dielectric resonator DR1 and a dielectric resonator DR2 each having an inner conductor protruding outward from its end face;
A coupling capacitor C1 connected between an internal conductor protruding from one end face of the dielectric resonator DR1 and the input terminal 1, an internal conductor protruding from one end face of the dielectric resonator DR2, and an output terminal. 2 and a coupling capacitor C2 connected between the internal conductor protruding from one end surface of the dielectric resonator DR1 and an internal conductor protruding from one end surface of the dielectric resonator DR2. The coupled capacitor C3, the varactor diodes X1 and X2 connected to the internal conductors protruding from the other end faces of the dielectric resonator DR1 and the dielectric resonator DR2 via the capacitors C4 and C5, respectively. The bias supply resistors R1 and R2 and the bias supply terminals 3 and 4 which are means for changing the electrostatic capacities of the varactor diodes X1 and X2. For example, here, the coupling capacitor C3
Is a capacitor formed by contacting and arranging the side surface of the dielectric resonator DR1 and the side surface of the dielectric resonator DR2, and providing a portion without a conductor on the contacting surface.

Next, the operation of this embodiment will be described. A signal input from the input terminal 1 propagates through the microstrip line 12 provided on the surface of the dielectric substrate 10, and passes through the coupling capacitor C1 to which the internal conductor 16 of the dielectric resonator DR1 is connected. 13, the coupling capacitor C3, the microstrip line 14 to which the internal conductor 17 of the dielectric resonator DR2 is connected, the coupling capacitor C2, and the microstrip line 15
And is output from the output terminal 2. Dielectric resonator DR1
(Or DR2) is connected to the microstrip line 13 (or 14) of the inner conductor 16 (or 17) of the internal conductor 16 at the opposite end to the varactor diode X1 (or X).
2) is connected to the bias supply resistor R1 (or R2), and the capacitance of the varactor diode X1 (or X2) is the bias supply terminal provided at the other end of the bias supply resistor R1 (or R2). It can be changed by the voltage applied to 3 (or 4).

FIG. 1B is a dielectric resonator DR1 shown in FIG.
And the structural details of DR2. Dielectric resonator DR1
(Or DR2) has an inner conductor 16 (or 17) penetrating the center of the dielectric and protruding to the outside at both ends, and has a coaxial structure in which the side surface is covered with the conductor. Dielectric resonator D
The R1 and the dielectric resonator DR2 are arranged in a state where one side surface is in contact with each other, and the contacting surface is provided with a portion having no conductor. Dielectric resonator DR1 and dielectric resonator DR
When they are in contact with each other, the capacitance between the inner conductor 16 and the inner conductor 17 forms a coupling capacitor C3. The capacitance of the coupling capacitor C3 is determined by the distance between the inner conductors 16 and 17, the dielectric constants of the dielectric resonators DR1 and DR2, the dielectric resonator DR1 and the dielectric resonator DR2.
The capacitance value of the coupling capacitor C3 can be set to a desired value depending on the area of the conductor-free portion of the contact surface between and.

The center frequency of the pass band of the band pass filter is the combined capacitance of the capacitance of the varactor diode X1 and the capacitor C4, the combined capacitance of the capacitance of the varactor diode X2 and the capacitor C5, and the resonance frequency of the dielectric resonators DR1 and DR2. The center frequency can be varied by changing the capacitance of the varactor diodes X1 and X2. The capacitors C4 and C5 are capacitors for adjusting the variable range of the center frequency, and the variable range of the capacitances of the varactor diodes X1 and X2 cannot be freely selected. Therefore, by selecting the capacitance values of the capacitors C4 and C5, Change the change range of the combined capacitance of the capacitor C4 and C5,
The variable range of the center frequency can be adjusted.

[0012]

As described above, according to the present invention, since the coupling capacitor is formed by the electrostatic capacitance between the inner conductors of the dielectric resonator, there is no parasitic inductance component like that of a chip capacitor, which is high. There is an effect that the characteristic does not deteriorate even at the frequency. Further, there is an effect that the capacitance of the coupling capacitor having a desired value can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the structure of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a structure of a conventional example.

FIG. 3 is a connection diagram showing a circuit configuration of the voltage controlled filter shown in FIGS. 1 and 2.

[Explanation of symbols]

 1 Input Terminal 2 Output Terminal 3, 4 Bias Supply Terminal 10 Dielectric Substrate 11 Grounding Conductor 12, 13, 14, 15 Microstrip Line 16, 17 Internal Conductor X1, X2 Varactor Diode R1, R2 Bias Supply Resistance DR1, DR2 Dielectric resonator C1, C2, C3 Coupling capacitor C4, C5 capacitor

Claims (2)

[Claims] 1. A dielectric having an input terminal for inputting a signal, an output terminal for outputting a signal, a dielectric having a side surface covered with a conductor, and an internal conductor penetrating the dielectric and projecting outward from an end surface thereof. A plurality of body resonators, a first coupling capacitor connected between one of the inner conductors protruding from one end face of the dielectric resonator and the input terminal, and one of the dielectric resonators. Connected between the other one of the inner conductors projecting from the end face of the output terminal and the second coupling capacitor and the inner conductor projecting from one end face of the dielectric resonator. A third coupling capacitor, a varactor diode connected via a capacitor to an internal conductor projecting from each of the other end faces of the dielectric resonator, and the capacitance of this varactor diode is changed. In the voltage-controlled filter having means for causing the third coupling capacitor, the third coupling capacitor is formed by arranging adjacent dielectric resonators so that the side surfaces of the dielectric resonators are in contact with each other and a contactless surface is provided. A voltage-controlled filter characterized by being a capacitor. 2. The voltage controlled filter according to claim 1, wherein the number of the dielectric resonators is two.