KR20010047698A - Monoblock dielectric filter with an attenuation pole - Google Patents

Abstract

PURPOSE: A solid dielectric filter having a damping electrode is provided to achieve a small size and obtain frequency transfer characteristics having damping electrodes in frequency bands higher or lower than a pass band. CONSTITUTION: An outer electrode(414) covers the outer surfaces of a dielectric block(401) except only one opened surface. A plurality of resonant holes(402,403,404) are formed to pass through the dielectric block from the opened surface to a rear surface, and the internal surfaces of the resonant holes are filled with electrodes. I/O electrodes(412,413) are formed by insulating portions of the outer electrode from the other portions, and are extended toward the resonant holes on the opened surface. Electrode patterns(405,406,407) are extended from the electrodes within the respective resonant holes, and are spaced apart from each other by predetermined gaps. Ground electrodes(409,410,411) are formed in positions corresponding to the respective electrode patterns.

Description

MONOBLOCK DIELECTRIC FILTER WITH AN ATTENUATION POLE

The present invention relates to an integrated dielectric filter, and more particularly, to an integrated dielectric filter having an attenuation pole in a higher frequency or lower frequency region than a pass band.

In general, a dielectric filter is to obtain a desired passband characteristic by connecting a plurality of dielectric blocks provided with a coaxial resonator, and an integrated dielectric filter as an advanced filter in the dielectric filter is a plurality of coaxial resonators in one dielectric block. To simplify the structure.

Since the dielectric filter is used as a pass band filter to obtain a signal of a desired channel band only in a mobile communication device such as a car phone or a mobile phone using a high frequency band as a communication band, the dielectric filter is required to be small, light in weight, and high impact resistance. A passband characteristic of 20-30 MHz is required.

1 to 3 are diagrams illustrating a conventional integrated dielectric filter, and the conventional integrated dielectric filter illustrated in FIG. 1 forms coupling holes 9 between resonance holes 7 and 8 to form mutual inductance and mutual capacitance. As to adjust, the degree of binding was determined by the size, length, position and the like of the coupling hole (9). However, the increase in the coupling holes 9 causes problems such as difficulty in forming the dielectric filter and deterioration in mechanical strength, and therefore cannot be regarded as suitable for the requirements of the current mobile communication device. As another example, the integrated dielectric filter shown in FIG. 2 is made to be coupled by a characteristic impedance difference due to the difference in the inner diameter of the resonant holes 7 and 8 without changing the inner diameter of the resonance holes 7 and 8 in a specific part. Although there are improvements in the characteristics compared to the dielectric filter shown in FIG. 1, the manufacturing complexity is complicated and a difficulty in obtaining a uniform molded body is caused by changing the inner diameter of the small resonant holes. As another example, the integrated dielectric filter shown in FIG. 3 forms an external electrode on the entire surface of the dielectric block 1 without an open surface unlike other dielectric filters and forms an internal specific portion of the resonant holes 7 and 8. 17, 18) by removing the electrodes to form a coupling between the resonators, there was a problem that it is difficult to remove the electrode accurately at any position of the inner surface of the small resonance hole.

In addition, today's dielectric filters, where the spacing between communication channels are getting closer, are demanding higher attenuation characteristics, especially when they are quite close, such as transmit and receive channels, requiring higher attenuation ratios in certain bands. In the conventional dielectric filter, one more resonator is used to induce an attenuation pole, or a capacitance or an inductor has been used externally, which causes a problem that it is difficult to miniaturize the filter.

SUMMARY OF THE INVENTION An object of the present invention is to provide an integrated dielectric filter having an attenuation pole in a higher frequency or lower frequency region than a pass band, which is smaller than a conventional filter.

According to one embodiment of the invention, the integral dielectric filter is formed to pass through the dielectric block, an external electrode covering the outer surface except one open surface of the dielectric block, the rear surface from the open surface of the dielectric block A plurality of resonant holes in which an inner surface is filled with electrodes, a portion of the outer electrode is insulated from the other portions, and an input / output electrode formed by extending toward the resonant hole on the open surface and extending in the electrodes in the respective resonant holes; Electrodes of capacitors formed between the ground electrodes and the electrode patterns corresponding to the electrode patterns, the electrode patterns being spaced apart by a predetermined interval, and the ground electrodes formed at positions corresponding to the respective electrode patterns; Spacing, and the electrode spacing of the capacitor formed between the electrode patterns to adjust the amount of coupling. That is to be characterized.

According to still another aspect of the present invention, a capacitor formed between the electrode patterns for coupling between the resonance holes and a resonance frequency of a short transmission line coupled in parallel between the resonance holes exist in a frequency region lower than a pass band. Is designed.

According to another feature of the present invention, the resonant frequency of the capacitor formed between the electrode pattern for coupling between the resonant holes and the short-circuit transmission line coupled in parallel between the resonant holes is present in the frequency region higher than the pass band. Is designed.

1 is a perspective view of one embodiment of an integrated dielectric filter according to the prior art;

2A is a perspective view of another embodiment of an integrated dielectric filter in accordance with the prior art;

FIG. 2B is a cross-sectional view taken along the line A-A 'of the integrated dielectric filter shown in FIG. 2A;

Figure 3a is a perspective view showing another example of an integrated dielectric filter according to the prior art.

3B is a cross-sectional view taken along the line b-b 'of the integral dielectric filter shown in FIG. 3A.

4 shows the structure of an integrated dielectric filter in accordance with the present invention.

5 is an equivalent circuit diagram of an integrated dielectric filter in accordance with the present invention.

6 is a graph showing frequency transfer characteristics with attenuation poles in the frequency region higher than the pass band.

7 is a graph showing frequency transfer characteristics with an attenuation pole in the frequency region lower than the pass band.

FIG. 8 is a graph showing a change in capacitance value C01 according to a change in electrode spacing when a coupling capacitor formed between an external terminal and a resonator is fixed at 1 mm in width;

Fig. 9 is a graph showing a change in capacitance value Cg according to a change in electrode spacing when a capacitor formed between a resonator and a ground plane is fixed to 1 mm in width.

<Explanation of symbols for the main parts of the drawings>

401: dielectric block

402, 403, 404: resonance hole

405, 406, 407: electrode pattern

408: open face

409, 410, 411: ground electrode

412 and 413: input and output electrode

414: external electrode

Hereinafter, the present invention will be described with reference to the drawings.

Fig. 4 is a perspective view of an integrated dielectric filter according to the present invention, showing a structure in which a TEM mode spherical resonator having a quarter wavelength is arranged side by side and integrated.

Looking at the configuration in detail with reference to Figure 4, the dielectric block 401 has an open surface 408 on one side, a plurality of resonant holes 402, 403, 404 formed to penetrate in the rear direction from the open surface The electrode patterns 405, 406, and 407 are formed to extend in contact with each of the resonance holes 402, 403, and 404, and are spaced apart from each other by a predetermined interval, except for the open surface of the dielectric block 401. An outer electrode 414 covering the surface, an input / output electrode 412 and 413 formed by insulating a part of the outer electrode 414 from the other part, and the respective electrode patterns 405, 406 and 407. The ground electrodes 409, 410, and 411 formed at corresponding positions are formed. Here, the insides of the resonance holes 402, 403, and 404 are formed of metal electrodes.

Each resonator in the dielectric block according to the present invention makes its own electromagnetic coupling with an adjacent resonator, and basically the resonant frequency of each resonator is determined by the length of the filter and the dielectric constant of the dielectric material constituting the filter. Each resonator constituting one filter has a different resonant frequency and is adapted by the coupling capacitors C ₁₂ , C ₂₃ formed by the electrode patterns 409, 410, 411 disposed on the open surface 408. By combining the resonance period, a filter having a desired pass band is obtained. In the present invention, the capacitors C _g1 , C _g2 , and C _g3 formed between the electrode patterns 405, 406, 407 extending in contact with the resonator and the ground electrodes 409, 410, and 411 are configured on the open surface of the equivalent. By absorbing the negative impedance to be considered in the circuit design, the length of each resonator is the same, making it possible to manufacture the filter in one block. In addition, two input / output electrodes 412 and 413 are formed by removing a portion of the conductor from one side of the filter to allow surface mounting for connection with an external input / output terminal. The input / output electrodes 412 and 413 are electrodes Input and output capacitors C ₁ and C ₃₄ are formed between the patterns 405, 406, and 407 to achieve capacitance coupling.

FIG. 5 is an equivalent circuit diagram of the integrated dielectric filter shown in FIG. 4.

Referring to FIG. 5, Pin and Pout represent input / output terminals, C ₁ and C ₃₄ correspond to input / output coupling capacitors between the input / output electrodes 412 and 413 and the electrode patterns 405 and 407, and C ₁₂ and C ₂₃ C _g1 , C _g2 , and C _g3 represent capacitors designed between the resonators and the ground electrodes 409, 410, 411, and each resonator has a transmission line (Z ₁ , Z ₂ and Z). ₃ ). The characteristic impedance due to the coupling between these resonators is represented by Z ₁₂ and Z ₂₃ . That is, Z ₁₂ and Z ₂₃ respectively represent characteristic impedance due to coupling between resonators 1 and 2 and characteristic impedance due to coupling between resonators 2 and 3, which are formed between the electrode patterns for coupling between resonance holes. It is a short-circuit transmission line coupled in parallel between the capacitors C ₁₂ and C ₂₃ and the resonance holes.

The characteristic impedances of the resonators represented by the transmission lines Z ₁ , Z ₂ , and Z ₃ were calculated by calculating the right mode and pre-mode characteristic impedances by the two-dimensional finite element method. In this case, Z ₁₂ may be obtained by using Equation 1 below.

In this case, Z represents a characteristic impedance, Z _o represents an odd mode characteristic impedance, and Z _e represents an even mode characteristic impedance.

In the present invention, the resonant holes 402, 403, and 404 in the dielectric block 401 are all the same size, and since they are symmetrical, Z ₁ = Z ₃ and Z ₁₂ = Z ₂₃ . In FIG. 2, the capacity of each capacitor C ₁ , C ₁₂ , C ₂₃ , C ₃₄ , C _g1 , C _g2 , C _g3 is obtained by the following Equations 2 to 6.

Where J is the J-inverter, ω o is the central angular frequency of the pass band of the resonant filter, Y is the characteristic admittance of the transmission line, θ _r is the electrical length of the transmission line at the center angular frequency of the pass band, and G _A and G _B are input and output conductances. to be.

The C _g value was initially set up to absorb the negative impedance due to the coupling. Such a filter has an attenuation pole in the lower or higher frequency region than the pass band, where the resonance frequency of the capacitance of Z ₁₂ and Z ₂₃ and the capacitors C ₁₂ and C ₂₃ connected in parallel is the frequency of the attenuation pole. To determine.

Therefore, when the resonant frequency is designed to be higher than the pass band, as shown in FIG. 6, the resonant frequency exhibits a frequency transmission characteristic (denoted by the curve 600) in the frequency region higher than the pass band, and the resonant frequency is lower than the pass band. In the case of design, as shown in FIG.

8 and 9 illustrate changes in capacitance values according to electrode spacing changes of the electrode patterns 409, 410, and 411 in a state where the width of the capacitor is constant. A filter having a frequency transfer characteristic as shown in FIG. The allocation corresponds to a narrow band trend, and the size of the filter can be smaller than that of using one resonator or having an external capacitor or inductor to have an attenuation pole in the existing dielectric filter. In this way, the positions of the attenuation poles are opposite to each other, and two filters having different pass bands can be combined and used as a duplexer.

8 shows an electrode width of 1 mm with respect to the coupling capacitors C ₁₂ and C ₂₃ between the external terminal and the resonator on the open end 408 of one dielectric quarter wavelength TEM mode resonator. The change in the C ₁ value calculated using Equation 7 below represents the resonance frequency and notch frequency obtained when analyzed by the finite element method.

Where ω _n is the notch angular frequency, ω _o is the resonant angular frequency, θ _r is the electrical length of the resonator, and Z _A is the characteristic impedance of the resonator.

9 shows capacitors C _g1 , C _g2 , C _g3 implemented between the resonator and ground electrodes 409, 410, 411 above the open end of one dielectric quarter wave TEM mode resonator. The resonance frequency obtained when the width is 1mm and the electrode spacing is changed by the finite element method is used to represent the change in the C _g value calculated using Equation 8 below.

Where ω _o is the resonant angular frequency, θ _r is the electrical length of the resonator, and Z _A is the characteristic impedance of the resonator.

It is possible to determine the structure of a capacitor having a desired capacitance value from the graphs of FIGS. 8 and 9. Through this analysis, each coupling capacitance value obtained from the equivalent circuit of the passband filter can be implemented with a suitable structure.

As described above, the present invention has the advantage of obtaining a frequency transfer characteristic having an attenuation pole in the lower or higher frequency region than the pass band. In addition, there is an advantage that the size of the filter can be miniaturized while having an attenuation pole.

Claims (3)

In an integrated dielectric filter: Dielectric block, An external electrode covering an outer surface except for one open surface of the dielectric block, A plurality of resonance holes formed to penetrate in the rear direction from the open surface of the dielectric block and having an inner surface filled with electrodes; An input / output electrode formed by insulating a part of the external electrode from the other part and extending toward the resonance hole on the open surface; Electrode patterns extending from the electrodes in the resonance holes and spaced apart by predetermined intervals, respectively; With ground electrodes formed at positions corresponding to the respective electrode patterns, An integrated dielectric material configured to adjust an amount of coupling by adjusting an electrode gap of a capacitor formed between the ground electrodes and the electrode patterns corresponding thereto, and an electrode gap of a capacitor formed between the electrode patterns; filter. The method of claim 1, wherein the resonant frequency of the capacitor formed between the electrode pattern for coupling between the resonant holes and the short-circuit transmission line coupled in parallel between the resonant holes is designed to exist in a frequency region lower than the pass band. Integrated dielectric filter. The method of claim 1, wherein the resonant frequency of the capacitor formed between the electrode pattern for coupling between the resonant holes and the short-circuit transmission line coupled in parallel between the resonant holes is present in a frequency region higher than the pass band. Integrated dielectric filter.