KR100314086B1 - A ceramic filter - Google Patents

Abstract

The present invention relates to a ceramic filter, and further extends and strips the conductor coating (120) peeled upward and downward on the left end of the input terminal (130) present on the left side (110e) of the ceramic body (110). At the same time, the conductor coating 120 peeled upward and downward on the right end of the output terminal 140 present on the right side 110f of the ceramic body 110 is extended further in the downward direction so as to be extended according to the extension length and extension width. The harmonic characteristic adjusting unit 150 is provided to arbitrarily adjust the height and the slope of the parasitic pass band, so that the coupling between the input terminal 130 and the output terminal 140 and the resonance hole 111 are opened. The height and inclination of the parasitic passband by the generated parasitic coupling can be easily adjusted by the harmonic characteristic adjusting unit 150 to freely implement the desired frequency response characteristics.

Description

Ceramic Filter {A CERAMIC FILTER}

The present invention relates to a ceramic filter, and more particularly to a harmonic that can arbitrarily adjust the height and inclination of the parasitic pass band by the parasitic coupling generated from the coupling between the input terminal and the output terminal and the resonance hole is opened. The present invention relates to a ceramic filter having a characteristic adjusting unit which can freely implement a desired frequency response characteristic.

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 in terminal price and the entry of 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.

A specific example of such a 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.

The present invention is to provide a ceramic filter having a harmonic characteristic control unit that can arbitrarily adjust the height and the slope of the parasitic pass band by the parasitic coupling to freely implement the desired frequency response characteristics.

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.

Figure 3 is a perspective view of the peeling of the ceramic filter according to the first embodiment of the present invention, respectively, seen from the left and right sides.

Figure 4 is a perspective view including the stripping of the ceramic filter according to the second embodiment of the present invention, respectively viewed from the left and right sides.

FIG. 5 is a perspective view of a stripping part of the ceramic filter according to the third embodiment of the present invention viewed from left and right sides, respectively.

FIG. 6 is a perspective view of a stripping part of the ceramic filter according to the fourth embodiment of the present invention viewed from left and right sides, respectively.

7 is a perspective view showing a ceramic filter according to a fifth embodiment of the present invention.

8 is a perspective view showing a ceramic filter according to a sixth embodiment of the present invention.

Figure 9 is a graph showing the harmonic frequency (Harmonic frequency) size according to the length and area of the harmonic characteristics adjusting unit for explaining the ceramic filter according to the present invention.

10 is a graph showing a frequency response characteristic for explaining the ceramic filter according to the present invention.

* 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: harmonic characteristics control unit

ℓ: length

W: width

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 A portion, the conductor coating plated on the surface except the upper surface of the ceramic body portion, and the conductor coating in the 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 part of the conductor coating in its surroundings. 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. In the upper and lower left end of the input terminal present on the left side of the ceramic body portion Extends and strips the conductor coating peeled off in the downward direction further, and further strips the conductor coating peeled upward and downward on the right end of the output terminal existing on the right side of the ceramic body portion in the downward direction. It is a basic feature of the technical configuration that comprises a harmonic characteristic control unit that can arbitrarily adjust the height and the slope of the parasitic pass band according to l) and the extension width (W).

Hereinafter, a preferred embodiment of the ceramic filter according to the present invention will be described with reference to FIGS. 3 to 10.

Such 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 one or more resonant holes 111 and having a high dielectric constant 20 to 90. 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 blocking 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.

On the other hand, the band pass filter has a parasitic pass band in the higher frequency region in addition to the pass band to be satisfied. In general, it is possible to manufacture a filter that can satisfy the passband specifications, but research on this is important because it is difficult to control the parasitic passband. In particular, as various communication schemes and types of frequencies are used, demands for attenuation characteristics in spurious as well as passbands are greatly amplified.

In the design of such a filter, the structure of the filter mainly forms a TEM (Transverse Electromagnetic Wave) mode wave so as to satisfy specifications of a desired passband. Therefore, in defining the operation of the filter, if the TEM Guided Waves theory and the Transmission Line Theory are used, the characteristics of the filter can be predicted and the structure can be applied in various ways. However, outside of the passband, all of the filters will have areas with slightly severe parasitic passbands and poor attenuation values. In addition, parasitic passbands incorporating this problem are evident above the desired passband and often occur below it.

From a practical point of view, this parasitic passband would cause serious problems if it matches the 2nd or 3nd harmonics of the TEM mode passband. This is because a strong harmonic signal of a transmitter frequency is applied to the antenna as it is.

Potential problems provided by these unwanted parasitic passbands result in interference or unwanted noise to the signal.

If the interference is very strong, it can result in the call being disconnected. Furthermore, the transmission of higher frequency harmonics may present issues for carriers as much as they must be addressed by the Federal Communication Commission (FCC).

As a result, many system designers, such as cellular telephones, have no choice but to have filters with better attenuation values than those provided by conventional filters. To solve this, designers often use a low-pass filter to suppress unwanted harmonic responses. Unfortunately, this solution is expensive and labor intensive, and is a costing factor.

Therefore, the above problems have a limited size of the ceramic body portion 110 and the number of the resonant holes 111, it is good to find a method that can greatly improve the characteristics of the pass band while satisfying the required pass band characteristics. . Accordingly, the present invention proposes to provide a filter that can arbitrarily adjust the height and slope of the unwanted parasitic passband.

3 is a perspective view of a part of the ceramic filter according to the first embodiment of the present invention including peeling portions viewed from left and right sides, respectively.

As shown in FIG. 3, the ceramic filter 100 according to the first embodiment of the present invention includes a plurality of resonance 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 ceramic body portion 110 having a rectangular shape of a lower surface 110b, a front surface 110c, a rear surface 110d, a left surface 110e, and a right surface 110f, and an upper surface 110a of the ceramic body portion 110. The conductor coating 120 plated on the surface except for the portion, and the conductor coating 120 in the shape of a rectangular plate bent from a portion of the left surface 110e of the ceramic body portion 110 to a portion of the front surface 110c. The conductor coating 120 in the shape of the input terminal 130 and the rectangular plate bent from a portion of the right side 110f of the ceramic body portion 110 to a portion of the front surface 110c by leaving the surroundings peeled off. The output terminal 140 is implemented by leaving a portion thereof 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 with 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.

In addition, the ceramic filter 100 according to the first embodiment of the present invention is vertically disposed at the left end of the input terminal 130 existing on the left surface 110e of the ceramic body 110 as shown in FIG. 3. The stripped conductor coating 120 further extended downward, and at the same time, the conductor coating 120 peeled up and down at the right end of the output terminal 140 present on the right side 110f of the ceramic body 110. The apparatus further includes a harmonic characteristic adjusting unit 150 to further extend downward in the downward direction to arbitrarily adjust the height and inclination of the parasitic pass band according to the extension length (l) and the extension width (W).

The degree of movement of the parasitic pass band is also changed according to the physical size of the harmonic characteristic adjusting unit 150, that is, the extension length L and the extension width W. For example, the harmonic characteristics shown in FIG. As can be seen from the graph showing the magnitude of the harmonic frequency according to the length (l) and the area of the control unit 150, the frequency of the parasitic passband according to the width and length (l) of the harmonic characteristic control unit 150 is determined. The amount of movement will be different.

That is, as the width of the harmonic characteristic adjusting unit 150 is wider and the length (l) is longer, it can be seen that the frequency of the parasitic passband becomes lower. In addition, as the harmonic characteristic adjusting unit 150 is formed as the upper surface 110a of which the resonance hole 111 is opened, the frequency of the parasitic pass band is further lowered.

10 is a graph showing the frequency response characteristic for explaining the ceramic filter according to the present invention.

For example, the ceramic filter 100 according to the related art shown in FIG. 1 is represented by a frequency response curve as shown by the solid line A of FIG. 10.

The ceramic filter 100 according to the related art has a parasitic pass band H1 as well as a pass band P1 as shown in the solid line A of FIG. 10. At this time, if the insertion loss to be satisfied at the 'X' position in FIG. 10 is required, the filter without the harmonic characteristic adjusting unit 150 of the present invention will not be able to easily satisfy the above-described specifications.

On the other hand, in the ceramic filter 100 according to the present invention, since the harmonic characteristic adjusting unit 150 exists, a frequency response curve such as the thick solid line B shown in FIG. 10 appears.

That is, the frequency response curve can be greatly changed by adding the harmonic characteristic adjusting unit 150 according to the present invention. For example, the frequency response curve of the ceramic filter 100 having the harmonic characteristic adjusting unit 150 as in the first embodiment of the present invention shown in FIG. 3 is undesired with the passband P01 as shown in FIG. Will have a passband H01. By adding the harmonic characteristic adjusting unit 150, the position of the parasitic pass band can be changed.

In this case, the addition of the harmonic characteristic adjusting unit 150 can move only the frequency of the parasitic passband without affecting the passband characteristic of the filter, and thus is accepted as a very important fact of the filtering characteristic.

That is, as shown in FIG. 10, the insertion loss designated at the 'X' position can be easily satisfied through the addition of the harmonic characteristic adjusting unit 150, thereby moving the position of the unwanted parasitic passband. The ability to do so will be a very valuable technology for RF (Radio Frequency) design engineers.

This fact allows designers to satisfy the specification in two steps. That is, first, after satisfying the pass band, the harmonic characteristic adjusting unit 150 is added to move the position of the unwanted parasitic pass band so as to simply obtain the desired frequency response characteristic.

In general, the parasitic passband is known to be due to the coupling between the input terminal 130 and the output terminal 140 and the parasitic coupling in the open side of the resonance hole 111. Therefore, the parasitic coupling can freely implement the desired frequency response characteristics by allowing the frequency of the pass band to be lowered by the harmonic characteristic adjusting unit 150 formed around the input terminal 130 and the output terminal 140. It can be confirmed through the present invention.

Meanwhile, as the size of the harmonic characteristic adjusting unit 150 increases, the frequency decrease becomes larger. The harmonic characteristic adjusting unit 150 may exist in both the input terminal 130 and the output terminal 140, and may exist only on any surface of the ceramic body 110. Also, it can be modified in various forms according to the design specifications and any arrangement can be made. However, starting from the region where the metal of the input terminal 130 and the output terminal 140 is removed, it should extend in parallel with the resonance hole 111.

Referring to the design process of the ceramic filter 100 using the harmonic characteristic control unit 150, first design the filter to satisfy the desired passband, and then check the frequency response of the filter while the input terminal 130 and the output terminal If the harmonic characteristic control unit 150 is made around 140 to satisfy the desired parasitic passband characteristics, the production can be completed simply. This tuning process can be completed by increasing the length (l) of the harmonic characteristic adjusting unit 150 until the parasitic passband satisfies the desired specification.

In addition, the harmonic characteristic adjusting unit 150 may be designed in various various structures as shown in FIGS. 4 to 8 based on the theoretical background as described above.

That is, based on the theoretical background as described above, the harmonic characteristic adjusting unit 150 applied to the ceramic filter 100 according to the present invention has a ceramic body part (as shown in FIG. 4). At the same time, the conductor coating 120 peeled up and down on the left end of the input terminal 130 existing on the left side 110e of the 110 is extended further upward, and at the same time, the right side 110f of the ceramic body 110 is provided. The conductor coating 120 peeled up and down at the right end of the output terminal 140 existing at the upper side is further peeled off in the upward direction, and the height and the slope of the parasitic pass band according to the extension length (L) and the extension width (W) are obtained. It may be made of a structure that can be arbitrarily adjusted, as in the third embodiment of the present invention shown in Figure 5, the ceramic body portion 110 is peeled off the conductor coating 120 in the horizontal direction at the lower end of the input terminal 130 Conductor sheath 120 from the edge of At the same time, the conductor coating 120 is further extended and peeled downward from the edge of the ceramic body portion 110 in which the conductor coating 120 is peeled off in the horizontal direction at the lower end of the output terminal 140. The height and inclination of the parasitic passband may be arbitrarily adjusted according to the extension length (l) and the extension width (W).

In addition, the harmonic characteristic adjusting unit 150 of the ceramic body 110 is peeled off the conductor coating 120 in the horizontal direction at the upper end of the input terminal 130, as in the fourth embodiment of the present invention shown in FIG. At the same time, the conductor coating 120 is extended upward and away from the corner, and at the same time, the conductor coating 120 is peeled off in the horizontal direction on the upper end of the output terminal 140. It is possible to make the structure further capable of arbitrarily adjusting the height and inclination of the parasitic passband according to the extension length (L) and the extension width (W) by further extending the strip 120, and the fifth of the present invention shown in As in the embodiment, the conductor body 120 peeled upward and downward on the right end of the input terminal 130 existing on the front surface 110c of the ceramic body portion 110 further upwards and away from the ceramic body portion ( Outgoing present in the front surface 110c of the 110 By stripping the conductor coating 120 peeled up and down at the left end of the terminal 140 in an upward direction, the height and inclination of the parasitic pass band can be arbitrarily adjusted according to the extension length (L) and the extension width (W). 8, the conductors peeled up and down at the right end of the input terminal 130 present in the front surface 110c of the ceramic body 110, as in the sixth embodiment of the present invention illustrated in FIG. 8. At the same time, the coating 120 is further extended to the lower side, and at the same time, the conductor coating 120 peeled up and down on the left end of the output terminal 140 present on the front surface 110c of the ceramic body 110 is downward. It can be made to a structure that can arbitrarily adjust the height and inclination of the parasitic passband according to the extension length (l) and the extension width (W).

Through the various structures of the harmonic characteristic adjusting unit 150, the ceramic filter 100 according to the present invention can freely change the position of the parasitic passband, which can be applied to a circuit requiring various filtering characteristics more effectively. It can be seen that there is an action.

As described above, the ceramic filter 100 according to the present invention has the following beneficial effects.

First, the harmonic characteristic control unit adjusts the height and slope of the parasitic pass band by the parasitic coupling generated from the coupling between the input terminal 130 and the output terminal 140 and the upper surface 110a of which the resonance hole 111 is opened. By simply configured to be adjusted by 150 there is an excellent effect that can freely implement the desired frequency response characteristics.

Second, the harmonic characteristic adjusting unit 150 is present in both the input terminal 130 and the output terminal 140 by using the characteristic that the frequency decreases as the size of the harmonic characteristic adjusting unit 150 increases. The ceramic filter 100 having the desired frequency response characteristics can be realized by simply presenting only one surface of the 110 to implement various frequency response characteristics through a structure from various harmonic characteristic adjusting units 150 according to design specifications. There is a beneficial effect that can be produced very easily.

That is, first, the filter is designed to satisfy the desired passband, and then the harmonic characteristic control unit 150 is formed around the input terminal 130 and the output terminal 140 while checking the frequency response of the filter. It is possible to simply complete the manufacture of the filter while satisfying the characteristics, there is an effect that the productivity and precision is very good.

Claims (6)

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, At the same time, the ceramic body 120 further extends and peels off the conductor coating 120 peeled upward and downward on the left end of the input terminal 130 existing on the left side 110e of the ceramic body 110. Extending and stripping the conductor coating 120 peeled upward and downward on the right end of the output terminal 140 existing on the right side 110f of the 110 in the downward direction, the extension length L and the extension width W Ceramic filter 100, characterized in that it comprises a harmonic characteristic adjusting unit 150 to arbitrarily adjust the height and the slope of the parasitic passband. The method of claim 1, The harmonic characteristic adjusting unit 150, At the same time, the conductive body 120, which is peeled up and down on the left end of the input terminal 130 existing on the left surface 110e of the ceramic body 110, is further extended and peeled upward. The conductor coating 120 peeled up and down on the right end of the output terminal 140 existing on the right side 110f of the 110 is further extended and peeled upward, and its extension length (l) and extension width (W). Ceramic filter 100, characterized in that consisting of a structure capable of arbitrarily adjusting the height and the slope of the parasitic passband. The method of claim 1, The harmonic characteristic adjusting unit 150, At the same time, the output terminal is further extended from the corner of the ceramic body portion 110 in which the conductive coating 120 is peeled off in the horizontal direction at the lower end of the input terminal 130 and extended further downward. Extending and stripping the conductor coating 120 further downward in the downward direction from the edge of the ceramic body portion 110 in which the conductor coating 120 is peeled off in the horizontal direction at the lower end of the 140. Ceramic filter 100, characterized in that made of a structure that can arbitrarily adjust the height and the slope of the parasitic passband according to the width (W). The method of claim 1, The harmonic characteristic adjusting unit 150, At the same time, the output terminal is further extended from the corner of the ceramic body portion 110 in which the conductive coating 120 is peeled off in the horizontal direction at the upper end of the input terminal 130 and extended upward. An extension length (L) and an extension of the conductor coating 120 are further extended and peeled upward from an edge of the ceramic body 110 in which the conductor coating 120 is peeled off in the horizontal direction at an upper end of the 140. Ceramic filter 100, characterized in that made of a structure that can arbitrarily adjust the height and the slope of the parasitic passband according to the width (W). The method of claim 1, The harmonic characteristic adjusting unit 150, At the same time, the conductive body 120, which is peeled up and down on the right end of the input terminal 130 existing on the front surface 110c of the ceramic body 110, is further extended and peeled upward. An extension length (L) and an extension width (W) of the conductor coating 120 peeled upward and downward on the left end of the output terminal 140 existing on the front surface 110c of the 110 are extended further upward. According to the ceramic filter 100, characterized in that made of a structure capable of arbitrarily adjusting the height and slope of the parasitic passband. The method of claim 1, The harmonic characteristic adjusting unit 150, At the same time, the conductor body 120, which is peeled up and down on the right end of the input terminal 130 existing on the front surface 110c of the ceramic body 110, is further extended and peeled downward. An extension length (L) and an extension width (W) of the conductor coating 120 peeled up and down on the left end of the output terminal 140 existing on the front surface 110c of the 110 are further extended in a downward direction. According to the ceramic filter 100, characterized in that made of a structure capable of arbitrarily adjusting the height and slope of the parasitic passband.