KR20010038222A - A ceramic filter - Google Patents

Abstract

PURPOSE: A ceramic filter is provided to generate an inductive coupling between an input terminal and an output terminal by using an inductive bar provided between the input terminal and the output terminal. CONSTITUTION: A ceramic filter(100) comprises a ceramic body section(110), a conductive body coating(120), an input terminal(130), and an output terminal(140). A plurality of resonance holes(111) which penetrate the lower surface(110b) from the upper surface(110a) of the ceramic body section(110) are capacitive coupled to input terminals(130) and output terminals(140). The ceramic body section(110) is coated with the conductive body coating(120) except for the upper surface(110a) of the ceramic body section(110).

Description

Ceramic Filter {A CERAMIC FILTER}

The present invention relates to a ceramic filter, and more particularly, to provide an inductive bar between an input terminal and an output terminal so that transmission zero can be present in a pass band so that it can be usefully used at the transmitting end of a communication system. The present invention relates to a ceramic filter having a trim portion that slows the role of a bar so that transmission zero may exist below a pass band, which may be useful for a receiving end of a communication system.

In general, the filter is a frequency selective device (Frequency Selective Device) performs a very important function in electronic equipment. Such filters should be designed to have a predetermined frequency response, depending on the particular application and application.

In this case, measurement values such as bandwidth, stopband, insertion loss, and return loss other than the predetermined center frequency should satisfy the circuit conditions to be used.

In addition, as the level of characteristics to be satisfied due to the maturation of the telecommunications market increases, filter designers can find ways to maximize the electrical characteristics while keeping the manufacturing process simple and increase the production efficiency. Should be proposed.

Particularly, in case of 900MHz Bandpass Filter (BPF) used in home cordless telephones, the size of the product is smaller, the characteristics are improved, and the price is reduced due to the decrease of the terminal price and the entry of the Surface Acoustic Wave (SAW) filter. Must be able to respond to requests for

In addition, the design of the filter should satisfy the characteristics of appropriate stop band and selectivity while satisfying the insertion loss and distortion in the pass band within an acceptable range. do.

On the other hand, filters at receivers remove unwanted interference from out-of-band and define the front-end noise band to affect the sensitivity of the receiver. . The filter at the transmitter reduces the magnitude of the unwanted signal spurious and suppresses the noise of the transmitter at the reception frequency. It also eliminates unwanted mixing products from transmitters and receivers.

Ceramic filters are the best to meet these requirements, and they have been widely used in cordless telephones and cellular phones operating in the 900 MHz band, and recently, personal communication systems operating in 2 System. ) The use of the phone is also increasing.

Specific examples of the ceramic filter will be described with reference to FIGS. 1 and 2 as follows.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view including a partial stripping showing a ceramic filter according to the prior art, and Fig. 2 is a sectional view showing a ceramic filter according to the prior art.

As shown in FIGS. 1 and 2, the general ceramic filter 10 includes a ceramic body part 12 having a cylindrical resonance hole 11 therein and inducing electric polarization by an electric field, and the ceramic body part. A conductor coating 13 plated on the surface of (12), an input terminal 14 and an output terminal 15 which are implemented through partial grinding processing of the conductor coating 13 and connected to a circuit board, An inner surface of the plurality of resonance holes 11 is ground to form a trim 16 having a predetermined capacitance C _S.

At this time, the dielectric constant of the ceramic body 12 is about 20 or more and about 90 or less. In addition, the plurality of resonance holes 11 are horizontally formed in the longitudinal direction of the ceramic body part 12 and are formed through the cylindrical shape, the surface of the resonance hole 11 is plated with a conductor coating (13) The conductor coating 13 is partially cut into a ring shape through the grinding process. Here, the diameter of the resonance hole 11 has an inductive capacitance, and the distance from the inner circumference of the resonance hole 11 to the conductor coating 13 generally has a capacitance.

In addition, the length of the ceramic body portion 12 is λ / 4, and λ is defined as the wavelength of the frequency signal to be passed, and the input terminal 14 and the output terminal 15 are soldered to the circuit board for use. do.

On the other hand, the filter must satisfy a specific frequency response, which includes a predetermined center frequency and bandwidth, and the stop band and return loss that the designer must improve. (return loss).

Recently, as the demand for a filter having a very small size and excellent characteristics increases, the situation has been engrossed in the development of the ceramic filter 10 having the maximized electrical characteristics as a minimized size.

On the other hand, the electrical characteristics of the filter may improve the selectivity of the material or increase the number of resonance holes 11 so that a transmission zero appears in the frequency response curve. This is implemented by a method of plating or removing metal on a specific portion and a method of changing the shape of the ceramic body 12.

According to the present invention, an inductive bar is provided between an input terminal and an output terminal so that transmission zero can exist on a pass band, and the selectivity can be greatly improved, and conversely, a trim part which slows the role of the inductive bar is transmitted. It is to provide a ceramic filter that allows zero to exist below the passband.

1 is a perspective view including partial stripping showing a ceramic filter according to the prior art;

2 is a cross-sectional view showing a ceramic filter according to the prior art.

3 is a perspective view including a part stripping from the front of the ceramic filter according to the first embodiment of the present invention;

4 is a perspective view of the ceramic filter according to the first embodiment of the present invention as viewed from the rear side thereof;

5 is a frequency response curve for explaining a ceramic filter according to an embodiment of the present invention.

6 is an equivalent circuit diagram showing a ceramic filter according to the present invention.

7 is a front perspective view of a ceramic filter according to a second embodiment of the present invention;

8 is a perspective view of the ceramic filter according to the second embodiment of the present invention as viewed from the rear side thereof;

9 is a perspective view of the ceramic filter according to the third embodiment of the present invention as viewed from the rear thereof;

* Description of the symbols for the main parts of the drawings *

100: ceramic filter 110: ceramic body

110a: upper surface 110b: lower surface

110c: front 110d: back

110e: Left side 110f: Right side

111 resonant hole 120 conductor coating

130: input terminal 140: output terminal

150: inductive bar 160: pattern portion

170: trim

The present invention for achieving the above object, having a plurality of resonant holes in parallel with each other and at the same time to induce electrical polarization by the electric field and the ceramic body of the rectangular shape of the top and bottom, front, back, left, right side And a conductive coating plated on a surface other than the upper surface of the ceramic body portion, and the conductor coating in a shape of a rectangular plate bent from a portion of the left side of the ceramic body portion to a portion of the front surface, leaving the conductive coating portion partially. And an output terminal implemented by leaving the conductor coating in a shape of a rectangular plate bent from a portion of the right side of the ceramic body portion to a portion of the front surface of the ceramic body and leaving the surroundings. Inductive coupling between the input terminal and the output terminal (Inductive Coupling) The output terminal present on the right side of the output terminal passing through the rear surface from the position parallel to the input terminal existing on the left side of the ceramic body to have a transmission zero above the over-band to improve the attenuation characteristics of the upper pass band And an inductive bar implemented by partially leaving the conductor coating in the form of a bent plate and stripping the surroundings of the conductor coating to a position spaced from parallel to the parallel.

Hereinafter, a preferred embodiment of the ceramic filter according to the present invention will be described with reference to FIGS. 3 to 9.

Filters are known to greatly attenuate signals with frequencies outside of a particular frequency range and very small attenuation of signals in the frequency range of interest.

In addition, such a filter is made of a ceramic material having a high dielectric constant 20 to 90 having one or more resonant holes 111. For example, the ceramic filter 100 can be made to provide the functionality of a low-pass, high-pass or band-pass filter.

As these filters become more mature due to the maturity of the telecom market, designers must find ways to maximize the electrical characteristics while keeping the manufacturing process simple. In particular, the demand for miniaturization, frequency selectivity and low cost is increasing day by day.

In a bandpass filter, the signals to be passed are spanned within a fairly narrow specific frequency range, and the signals in this region must have very small loss values and elsewhere, i.e., the signals in the blocking region, must have very large loss values. .

The specifications of the filter should be designed to meet the specific passband and stopband requirements. In general, the wider the passband, the lower the insertion loss (Insertion Loss), which is an important electrical variable, but the wider the bandwidth, the worse the cutoff band's ability to attenuate rejection frequencies. An additional resonator can also be used to improve the frequency selectivity of the filter, but this has the problem of increasing the size of the filter.

Therefore, the above problems have to be limited to the size of the ceramic body 110 and the number of the resonant holes 111, it is good to seek a method that can greatly improve the characteristics of the pass band while satisfying the required pass band characteristics. . Therefore, the present invention is to propose a ceramic filter 100 that can improve the attenuation characteristics of the cut-off band by forming a transmission zero in the unwanted frequency signal.

3 is a perspective view including a partial stripping of the ceramic filter according to the first embodiment of the present invention as viewed from the front, and FIG. 4 is a perspective view of the ceramic filter according to the first embodiment of the present invention as viewed from the rear side thereof.

As shown in FIGS. 3 and 4, the ceramic filter 100 according to the present invention includes a plurality of resonant holes 111 parallel to each other and at the same time induces electric polarization by an electric field, and has an upper surface 110a and a lower surface. The ceramic body 110 having a rectangular shape of 110b, the front surface 110c, the rear surface 110d, the left surface 110e, and the right surface 110f, and the upper surface 110a of the ceramic body 110 The conductor coating 120 plated on the surface except for the above, and the conductor coating 120 in the shape of a rectangular plate bent from a portion of the left side 110e of the ceramic body portion 110 to a portion of the front surface 110c. The conductor coating 120 was formed in the shape of a rectangular plate bent over a portion of the input terminal 130 and the right side 110f of the ceramic body 110 from a portion of the front surface 110c. The output terminal 140 is implemented by leaving a portion and leaving the surroundings.

Here, the plurality of resonance holes 111 penetrating from the upper surface 110a to the lower surface 110b of the ceramic body 110 are capacitively coupled to the input terminal 130 and the output terminal 140, respectively. All surfaces except the upper surface 110a of the ceramic body 110 are covered with the conductor coating 120. The conductor coating 120 serves as a case for encapsulating energy in the filter (Encapsulated Casing).

In addition, an upper portion of the plurality of resonance holes 111 may be expected to have an effect of extending a resonant length substantially by forming a tapered diameter. Thus, two transmission lines having different characteristic impedances are formed. Each of the resonant holes 111 can realize a reduction in length substantially than the resonant holes 111 having the same impedance, and can greatly improve the harmonic suppression ability.

5 is a frequency response curve for explaining a ceramic filter according to an embodiment of the present invention.

The ceramic filter 100 according to the present invention has an inductive coupling between the input terminal 130 and the output terminal 140 to have a transmission zero above the pass band so as to have a line A in the frequency response curve of FIG. 5. As shown in the right side 110f through the rear surface 110d from the position spaced in parallel from the input terminal 130 existing on the left side 110e of the ceramic body 110 to improve the attenuation characteristics of the upper pass band. It includes an inductive bar (150) implemented by leaving the conductor coating 120 from the output terminal 140 to the parallel spaced portion to be bent in the form of a plate and stripped around the portion.

The input terminal 130 and the output terminal 140 are capacitively coupled to each other by a predetermined distance from the inductive bar 150, and the inductive bar 150 exhibits an inductance value as shown in FIG. 6.

6 is an equivalent circuit diagram showing a ceramic filter according to the present invention.

As shown in FIG. 6, the input terminal 130 and the output terminal 140 are capacitively coupled to the plurality of resonant holes 111 with a C _e value, and the adjacent resonant holes 111 are electromagnetically coupled to each other. Are electromagnetically coupled. In addition, the input terminal 130 and the output terminal 140 are connected to the inductor L of the two C _b and the inductive bar 150.

7 is a perspective view of the ceramic filter according to the second embodiment of the present invention, viewed from the front, and FIG. 8 is a perspective view of the ceramic filter according to the second embodiment of the present invention, viewed from the back side thereof.

As shown in FIGS. 7 and 8, the ceramic filter 100 according to the present invention is spaced apart between the input terminal 130 and the inductive bar 150 and between the output terminal 140 and the inductive bar 150. Capacitive couple between the input terminal 130 and the inductive bar 150 and the output terminal 140 and the inductive bar 150 by extending the conductor coating 120 located in the upper and lower portions of the space facing each other. It further includes a plurality of pattern portions 160 to improve the selectivity by reducing the value of the ring (Capacitive Coupling) so that the position of the transmission zero close to the pass band as shown by the line 'A' shown in FIG.

Here, the plurality of pattern units 160 may include a ground pattern and a conductor coating 120 in a space between the input terminal 130 and the inductive bar 150 and a space between the output terminal 140 and the inductive bar 150. ) Extends in mutually opposite directions, reducing the capacitive coupling value (C _b ) shown in FIG. 6 to reduce the width of the bandwidth and at the same time tilting the transmission zero closer to the passband. The selectivity of is greatly improved.

As shown in FIG. 5, it can be seen that the frequency response curve of the filter has a transmission zero above the pass band, thereby improving attenuation characteristics above the pass band. Therefore, it can be used for the transmitting end in the communication system to reduce the size of the unwanted signal and to act to suppress the noise of the transmitter at the reception frequency.

9 is a perspective view of the ceramic filter according to the third embodiment of the present invention as viewed from the rear side thereof.

As shown in FIG. 9, the ceramic filter 100 according to the present invention has a top surface of the conductive coating 120 existing on the center of the inductive bar 150 positioned on the rear surface 110d of the ceramic body 110. Partial stripping up to 110a slows the role of the inductive bar 150 and causes strong capacitive coupling between the plurality of resonant holes 111 to occur so that transmission zero is realized below the passband. The unit 170 further includes.

The trim unit 170 slows the role of the inductive bar 150 and causes strong capacitive coupling between the resonance holes 111 to generate transmission zero at the bottom of the pass band, as shown in FIG. 5. Make it appear. As such, the transmission unit 170 may exist below the pass band by the trim unit 170, thereby greatly improving the attenuation characteristics under the pass band, and such a filter may be utilized at a receiving end in a communication system, thereby causing unwanted interference. By removing the interference (interference) and defining the front-end noise bandwidth (bandwidth) to improve the sensitivity of the receiver (Sensitivity) is to work.

As described above, according to the ceramic filter 100 according to the present invention, the right surface passes through the rear surface 110d from a position spaced in parallel from the input terminal 130 existing on the left surface 110e of the first ceramic body 110. The conductive coating 120 from the output terminal 140 present at 110f to the parallel spaced position is partially left in a bent plate shape and is simply provided with an inductive bar 150 which is implemented by peeling around the input. Inductive coupling is generated between the terminal 130 and the output terminal 140 to have a transmission zero above the pass band.

Secondly, the conductor coating 120 located in the upper and lower portions of the spaced space between the input terminal 130 and the inductive bar 150 and between the output terminal 140 and the inductive bar 150 extends in a direction facing each other. By implementing the plurality of pattern portions 160, the capacitive coupling value between the input terminal 130 and the inductive bar 150 and the output terminal 140 and the inductive bar 150 is reduced. As a result, the position of the transmission zero can be inclined so as to be close to the pass band, thereby having an excellent effect of greatly improving the selectivity.

Third, the trim portion 170 is peeled off by partially peeling the conductive coating 120 existing on the center of the inductive bar 150 located on the rear surface 110d of the ceramic body 110 to the upper surface 110a. As a result, the role of the inductive bar 150 is slowed down, and strong capacitive coupling is generated between the plurality of resonant holes 111 so that transmission zero is implemented under a pass band.

That is, the ceramic filter 100 according to the present invention includes an inductive bar 150 having a simple structure between the input terminal 130 and the output terminal 140 so that transmission zero may exist above the pass band. In addition to being useful in the transmitting terminal, a plurality of pattern units 160 are provided between the input and output terminals 130, 140 and the inductive bar 150, so that the frequency selectivity can be greatly improved. By providing a trim 170 that slows the role of the inductive bar 150, the transmission zero can be present under the passband, so that the receiving end of the communication system can be used very effectively.

Claims (3)

It has a plurality of resonant holes 111 in parallel with each other and at the same time induces electrical polarization by an electric field, the upper surface (110a) and the lower surface (110b), the front surface (110c), rear surface (110d), left surface (110e), The ceramic body 110 having a rectangular shape of the right side 110f, the conductor coating 120 plated on the surface except the upper surface 110a of the ceramic body 110, and the ceramic body 110 The input terminal 130 and the ceramic body, which are implemented by leaving the conductor coating 120 partly in the shape of a rectangular plate bent from a part of the left side surface 110e to a part of the front surface 110c and peeling it around. The output terminal 140 is formed by leaving the conductor coating 120 partly in the shape of a square plate bent from a part of the right side 110f of the part 110 to a part of the front part 110c and peeling it around. In the ceramic filter 100 comprising a, The ceramic body 110 may have an inductive coupling between the input terminal 130 and the output terminal 140 to have a transmission zero above the pass band to improve attenuation characteristics above the pass band. From the position spaced in parallel from the input terminal 130 existing on the left side surface 110e of the through the rear surface 110d to the position spaced in parallel from the output terminal 140 present on the right surface 110f Ceramic filter 100, characterized in that it comprises an inductive bar (150) implemented by leaving the conductor coating 120 in a bent plate shape and peeling around it. The method of claim 1, In the direction facing each other the conductor coating 120 located between the input terminal 130 and the inductive bar 150 and the upper and lower portions of the spaced space between the output terminal 140 and the inductive bar 150. Extends the capacitive coupling value between the input terminal 130 and the inductive bar 150 and the output terminal 140 and the inductive bar 150 to reduce the position of the transmission zero. Ceramic filter 100, characterized in that it further comprises a plurality of pattern portion 160 to improve the selectivity by approaching the pass band. The method of claim 1, The inductive bar 120 may be partially peeled off to the upper surface 110a of the conductive coating 120 existing at the center of the inductive bar 150 positioned on the rear surface 110d of the ceramic body 110. It further comprises a trim unit 170 to slow the role of 150 and to generate a strong capacitive coupling between the plurality of resonant holes 111 so that the transmission zero is implemented below the pass band. Ceramic body portion 110 to be.