JPH0832308A - Dielectric filter and characteristic adjustment method therefor - Google Patents

Abstract

PURPOSE:To provide a polarized type dielectric filter by simple structure and electrode pattern. CONSTITUTION:Plural dielectric resonators are coupled by inductive coupling M and connected to input/output terminals IN and OUT at an impedance matching point and a capacitance CT is connected to the grounding terminal of this dielectric filter connected to the grounding terminal. The capacitance CT is obtained by a conductor pattern integrally formed on a substrate with a wiring pattern for input/output. By adjusting the capacitance value CT, the position of a pole is adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter using a plurality of dielectric coaxial resonators, and more particularly to a dielectric filter which is coupled by inductive coupling to obtain a desired pass band characteristic. The present invention also relates to a method of adjusting its characteristics.

[0002]

2. Description of the Related Art Bandpass filters using a plurality of dielectric resonators are used in various fields in a high frequency range. Combined with a cylindrical or prismatic dielectric coaxial resonator, the input and output terminals are connected to the input and output terminals via capacitance, and the outer conductor and short-circuit conductor are connected to the metal case or grounded conductor pattern to ground. To be done. There is also one in which a plurality of dielectric resonators are integrally formed into a block.

When a band pass filter is constructed using such a dielectric filter, a pass band
In some cases, a polarized type having an attenuation pole on both sides of is required.

FIG. 5 shows an equivalent circuit diagram of an example of such a polar type bandpass filter, in which LC parallel resonators are coupled by inductive coupling M, and C between the input and output terminals. _IN and C _OUT are arranged to obtain the input / output coupling capacitance. The low potential side of the resonator, that is, the short-circuit conductor side is grounded.

[0005]

In order to make the dielectric filter utilizing such inductive coupling polar, it is necessary to connect the capacitor C _T on the hot side. This capacity C _T
Is obtained by forming a conductor pattern on the dielectric substrate that forms the input / output coupling capacitance or by mounting a chip capacitor, but both require a wiring pattern that requires a certain amount of area. There will be size restrictions.

The present invention provides a dielectric filter capable of forming a capacitor necessary for forming an attenuation pole without requiring a special element and without forming a complicated conductor pattern. In particular, even in a dielectric filter having no input / output coupling capacitance, the attenuation pole can be obtained.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above problems by utilizing a conductor pattern on the ground side and interposing a capacitance between the grounded potential and the ground potential.

That is, a plurality of dielectric coaxial resonators are coupled by inductive coupling, connected to the input / output terminals at the impedance matching point of the dielectric coaxial resonator at the input / output end, and their outer conductor and short-circuit conductor are grounded. In this dielectric filter, the outer conductor and the short-circuit conductor are characterized in that they are grounded via a capacitor.

Further, a plurality of dielectric coaxial resonators are coupled by inductive coupling and connected to the input / output terminals at the impedance matching points of the dielectric coaxial resonators at the input / output ends, and their outer conductor and short-circuit conductor are grounded. The characteristic adjusting method of the dielectric filter described above is characterized in that the outer conductor and the short-circuit conductor are grounded via a capacitance, and the attenuation pole is adjusted by adjusting the capacitance value.

[0010]

[Operation] By changing the capacity connected to the ground end,
The attenuation pole moves away from or near the passband. By utilizing this, the attenuation pole can be formed at a predetermined frequency by selecting the capacitance value.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an equivalent circuit diagram of an embodiment of the present invention. The dielectric resonators forming the LC parallel resonance circuit are coupled by inductive coupling M and tapped (impedance matching point)
To connect to the input / output terminals. In the present invention, the low potential side of the dielectric filter, that is, the short-circuit conductor side is grounded via the capacitor C _T. This capacitance C _T can be formed and arranged so as to be commonly connected to a plurality of resonators.

FIG. 2 is a perspective view showing an embodiment of the present invention. The dielectric filter 15 is mounted on the surface of the dielectric substrate 10. The dielectric filter 15 is formed by bonding two dielectric substrates, and the inner conductor 16 is inside the through hole, the outer conductor 17 is on the outer peripheral surface, and the through hole is further formed. A short-circuit conductor (not shown) is formed on one end face where the hole opens. From the impedance matching point of the inner conductor of the resonator at the input and output ends, the conductor pattern is formed on the bonding surface to the side surface and connected to the terminal electrode 18. Terminal electrode 18
Are connected to the conductor pattern formed on the surface of the dielectric substrate 10.

FIG. 3 is a partial plan view of an example of a coupling substrate used in the dielectric filter according to the present invention. An input / output conductor pattern 21 and a grounding conductor pattern 22 are formed on one surface of the dielectric substrate 20.
Reference numeral 21 is an impedance matching point of the dielectric resonator at the input / output end and is connected to the inner conductor of the dielectric resonator. The conductor pattern 22 for grounding is electrically connected to the outer conductor of the dielectric resonator. For connection with an external circuit, it is better to form a pattern for connection with the dielectric resonator on the back surface.

The conductor pattern 22 for grounding is not grounded as it is, but the conductor pattern 22 for grounding and the conductor pattern 23 separated and insulated are formed in close proximity to each other. A terminal is pulled out from this conductor pattern 23 and is grounded. As a result, a capacitance is formed between the conductor pattern 22 and the conductor pattern 23, and the capacitance C _T shown in FIG. 1 is added. Although only one of the input and output ends is shown in this embodiment, a normal dielectric filter can be formed by forming the input and output ends and using the common ground end.

FIG. 4 is a partial plan view showing another embodiment of the present invention, in which an input / output conductor pattern is formed on one surface of the printed circuit board 30.
31a and 31b are formed, and a conductor pattern for grounding
32 and the conductor patterns 33a and 33b for forming capacitors. Form a conductor pattern on the back of this board,
The connection with the dielectric resonator or the outer conductor is the same as in the above example.

The dielectric filter to which the present invention can be applied is not limited to the above-mentioned examples, but can be used for all block filters in which individual resonators are combined and a plurality of dielectric resonators are integrated. Further, it is also possible to form the capacitance on the dielectric substrate or the printed substrate on the front and back surfaces.
In addition, a polar filter can be obtained with a similar configuration even in a filter having three or more stages of elements. Further, the capacitance on the ground side can be obtained by a chip capacitor or the like.

In the dielectric filter according to the present invention,
When the capacitance value of the capacitance C _T to be grounded is increased, the attenuation pole is formed at a position apart from the pass band. When the capacitance value is reduced, the characteristic changes such that the attenuation pole approaches the pass band. By utilizing this, the frequency forming the pole can be arbitrarily adjusted. Also, adjustment is possible by trimming the conductor pattern.

[0019]

According to the present invention, a capacitance can be formed on a dielectric substrate or the like only by changing the shape of the ground electrode, whereby a polar type dielectric filter can be obtained. Therefore, a compact dielectric filter can be obtained which is easy to manufacture.

Further, the capacitance value can be set by adjusting the shape and area of the ground electrode, and the trimming thereof can be performed, so that the characteristics can be easily adjusted.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of an embodiment of the present invention.

FIG. 2 is a perspective view of an embodiment of the present invention.

FIG. 3 is a partial plan view of an embodiment of the present invention.

FIG. 4 is a partial plan view of another embodiment of the present invention.

FIG. 5 is an equivalent circuit diagram of a conventional dielectric filter.

[Explanation of symbols]

 21, 31: I / O conductor pattern 22, 32: Earth conductor pattern 23, 33: Capacitance forming conductor pattern

[Procedure amendment]

[Submission date] August 9, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

Claims (5)

[Claims] 1. A plurality of dielectric coaxial resonators are coupled by inductive coupling, connected to an input / output terminal at an impedance matching point of the dielectric coaxial resonator at an input / output end, and their outer conductor and short-circuit conductor are grounded. In the dielectric filter described above, the outer conductor and the short-circuit conductor are grounded via a capacitor. 2. The dielectric filter according to claim 1, wherein the capacitance is constituted by a conductor pattern formed on the surface of the dielectric substrate. 3. The dielectric filter according to claim 1, wherein the capacitance is obtained between a conductor pattern connected to the outer conductor and the short-circuit conductor and a conductor pattern facing the same plane. 4. The dielectric filter according to claim 1, wherein the capacitance is formed on a wiring board on which a dielectric resonator is mounted. 5. A plurality of dielectric coaxial resonators are coupled by inductive coupling, connected to an input / output terminal at an impedance matching point of the dielectric coaxial resonator at an input / output end, and their outer conductor and short-circuit conductor are grounded. In the method for adjusting the characteristics of the dielectric filter described above, the outer conductor and the short-circuit conductor are grounded via a capacitor,
A characteristic adjusting method for a dielectric filter, characterized in that the attenuation pole is adjusted by adjusting the capacitance value.