GB1601857A - Feed-through capacitor - Google Patents
Feed-through capacitor Download PDFInfo
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- GB1601857A GB1601857A GB1355978A GB1355978A GB1601857A GB 1601857 A GB1601857 A GB 1601857A GB 1355978 A GB1355978 A GB 1355978A GB 1355978 A GB1355978 A GB 1355978A GB 1601857 A GB1601857 A GB 1601857A
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- 239000003990 capacitor Substances 0.000 title claims description 162
- 239000004020 conductor Substances 0.000 claims description 118
- 238000009826 distribution Methods 0.000 claims description 31
- 230000004048 modification Effects 0.000 claims description 19
- 238000012986 modification Methods 0.000 claims description 19
- 230000003247 decreasing effect Effects 0.000 claims description 17
- 239000003989 dielectric material Substances 0.000 claims description 17
- 238000009828 non-uniform distribution Methods 0.000 claims description 11
- 239000000463 material Substances 0.000 claims description 6
- 238000009827 uniform distribution Methods 0.000 claims description 3
- 239000000919 ceramic Substances 0.000 description 7
- 229910010293 ceramic material Inorganic materials 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 241000226585 Antennaria plantaginifolia Species 0.000 description 2
- 239000003985 ceramic capacitor Substances 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000010445 mica Substances 0.000 description 1
- 229910052618 mica group Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/35—Feed-through capacitors or anti-noise capacitors
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
- Control Of Motors That Do Not Use Commutators (AREA)
- Filters And Equalizers (AREA)
Description
(54) FEED-THROUGH CAPACITOR
(71) We, MURATA MANUFACTURING CO. LTD., a Japanese Corporation, of 26-10, Tenjin 2-chome Nagaokakyo-shi, Kyoto-fu, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:
The present invention relates to a feed-through capacitor.
One of the prior art documentations of particular interest to the present invention is
United States Patent No. 3,255,396, entitled "Feed-Through Capacitor" and issued June 7, 1966 to John B. Heron, Jr. et al. The referenced U.S. patent discloses a ceramic feed-through capacitor of a layered structure comprising a plurality of electrodes with a ceramic dielectric layer formed therebetween, wherein a feed-through conductor is provided extending in parallel with the plane of the plurality of electrode layers.
Another type of a prior art feed-through capacitor of a layered structure of interest to the present invention has also been proposed, wherein a feed-through conductor is provided in the direction orthogonal to the plane of a plurality of electrode layers. Such a type of feed-through capacitor is seen in Japanese Utility Model Laying-Open Gazette, Laying
Open No. 28607/1976.
Figure 1 is a sectional view of a layered type feed-through capacitor of the last mentioned type of structure. Figure 2 is a plan view of the Figure 1 capacitor. Figure 3 is a fragmentary sectional enlarged view of a portion of the Figure 1 capacitor. The layered feed-through capacitor as shown comprises a feed-through conductor 1 extending along the axis of the capacitor and a capacitor portion 2 formed therearound, and a flanged ground potential conductor 3 extending outwardly from the outer surface of the capacitor portion 2. The capacitor portion 2 comprises a dielectric layer 21 of such as ceramic divided into a plurality of layers extending in the direction orthogonal to the feed-through conductor 1.The capacitor portion 2 further includes a plurality of first inner electrode plates 22 sandwiched between the dielectric layers extending in the direction orthogonal to the feed-through conductor 1, and a corresponding plurality of second inner electrode plates 23 sandwiched between the dielectric layers 21 extending in the directon orthogonal to the feed-through conductor 1. The first and second inner electrode plates 22 and 23 are arranged alternately.
The outer and inner diameters of the first inner electrode plates 22 are selected to be smaller than the outer and inner diameters of the second inner electrode plates 23. An inner electrode 24 of a cylindrical shape having a diameter commensurate with the inner diameter of the first inner electrode plates 22 is provided extending through the arrangement of the first inner electrode plates 22 such that the inner diameter edges of the layered first inner electrode plates 22 are electrically connected to the cylindrical inner electrode 24.On the other hand, an outer electrode 25 of a cylindrical shape having a diameter commensurate with the outer diameter of the second inner electrode plates 23 is provided around the arrangement of the second inner electrode plates 23, such that the outer diameter edges of the second inner electrode plates 23 are electrically coupled to the outer electrode 25. Thus, the assembly of the first inner electrode plates 22 and the inner electrode 24 and the assembly of the second inner electrode plates 23 and the outer electrode 25 are interdigitated in section, as seen in Figures 1 and 2.Thus, it would be appreciated that in the capacitor portion 2 a plurality of capacitance elements are formed between each pair of adjacent first and second inner electrode plates 22 and 23, such that the capacitance elements are distributed in the axial direction. whereby a parallel connection of capacitance elements is formed as a whole. The gap between the feed-through conductor 1 and the inner electrode 24 is filled with a soldering material 4a, while the flange shaped grounding conductor plate 3 is soldered to the outer electrode 25. As a result, an inner capacitor electrode is formed by the electrically coupled feed-through conductor 1, inner electrode 24. and electrode plates 22, and an outer capacitor electrode is formd by the electrically coupled flange shaped grounding conductor 3, outer electrode 25, and electrode plates 23.
It would be appreciated that the feed-through conductor 1 and the grounding conductor 3 each constitute a terminal of the feed-through capacitor shown.
Now consider a resonance frequency characteristic of such a feed-through capacitor of a layered structure as described above. Figure 4 shows a frequency response curve illustrating the characteristics of a typical conventional feed-through capacitor of a layered structure, wherein the abscissa indicates the frequency and the ordinate indicates the attenuation characteristic. As seen in the figure. the conventional feed-through capacitor of a layered structure exhibits a single peak tuned frequency characteristic having an easy slope.The reason is that the conventional feed-through capacitor of a layered structure as shown in
Figure 1 is normallv structured such that each capacitance element is of substantially the same capacitance value, while the inductance value of the inductance component for each capacitance element with respect to the grounding conductor increases with the distance of the capacitance element from the grounding conductor 3, with the result that the resonance frequency determined by each capacitance element and the inductance comnonent corresponding to each such capacitance element decreases with increasing distance of the capacitance element from the grounding conductor 3 and that the frequency characteristic has an easy slope.In other words, the further each such capacitance element is from the grounding conductor 3. the lower the resonance frequency determined by a predetermined capacitance value of the capacitance element and the inductance value of the inductance component corresponding thereto. Therefore, it follows that the overall frequency characteristic of such a conventional feed-through capacitor of a layered structure exhibits a peak and an easy slope as seen in Figure 4.
Depending on applications. such as a filter circuit application. however, the requirements for the frequency characteristics of a feed-through capacitor would be different. More specifically, in some applications, a frequency characteristic of a uniform attenuation value throughout a relatively wide frequency range might be required, even if the attenuation value is relatively low, whereas in some other applications a frequency characteristic having a relatively high attenuation value in a relatively narrow frequency range might be required.
Thus, it would be appreciated that a conventional feed-through capacitor cannot meet such different requirements depending on the applications.
A conventional feed-through capacitor of such a structure causes another problem. More specifically, since the capacitance elements distributed in the axial direction of the capacitor are each adapted to be of the same capacitance value, a satisfactory frequency characteristic attained by such a feed-through capacitor in a relatively lower frequency range does not necessarily mean a desired frequency characteristic in a higher frequency range, inasmuch as an increase in the frequency causes a situation in which each capacitance element does not show a reactance characteristic of a pure capacitance, an undesired parallel resonance phenomenon occurs, a capacitance element comes to function as an inductance component, and the like. As a result, a satisfactory frequency characteristic throughout any frequency range is not attained by a conventional feed-through capacitor.Nevertheless, if such a feed-through capacitor is designed so as not to cause a parallel resonance phenomenon in a relatively high frequency region, so as to prevent each capacitance element from functioning as an inductance component, and so on, then the geometry of each capacitance element needs to be small sized; however, the reduction of the geometry of each capacitor element reduces the capacitance value of each capacitance element, with the result that a satisfactory frequency characteristic cannot be attained by such a feed-through capacitor in a relatively low frequency region.
A feed-through capacitor of the above described layered structure further entails another problem, when the same is utilized in a high frequency region. More specifically, in a high frequency region such as 1 to 10 GHz. for example, the inductance component of the outer electrode 25 becomes dominant and has a significant influence. As described previously, as the distance of the capacitance elements from off the grounding conductor 3 increases, the inductance values of the inductance components corresponding to such capacitance elements considerably increases in such a high frequency region. It is extremely difficult to reduce the inductance values of such inductance components in such a high frequency region.
In accordance with the invention there is provided a feed-through capacitor having an inner electrode comprising a feed-through conductor and an outer electrode comprising an outer conductor disposed around a length of the feed-through conductor, wherein there is, between said electrodes, a capacitance which is non-uniformly distributed along the length of the feed-through conductor, the distribution being such that the overall shape of the frequency response curve of the capacitor is substantially different from that of a feed-through capacitor of equivalent value with a uniform distribution.
In a preferred embodiment of the present invention, the non-uniform capacitance distribution is achieved by causing the dielectric constant of a dielectric material to vary along the axial direction of the feed-through conductor. In another preferred embodiment of the present invention. the non-uniform capacitance distribution is achieved by changing the distance between adjacent electrodes in the axial direction of the feed-through conductor. In a further preferred embodiment of the present invention, the non-uniform capacitance distribution is achieved by varying the opposing areas of adjacent electrodes constituting each capacitance element along the axial direction of the feed-through conductor.It is also preferred in some embodiments that the capacitance distribution be such that the resonance frequency determined by each capacitance element and the inductance value of the inductance component corresponding to the capacitance element may be constant throughout the length of the feed-through conductor in the capacitor. As a result. a feed-through capacitor exhibiting a frequency characteristic of a relatively large attenuation value in a relatively narrow frequency region is provided. In another preferred embodiment of the present invention, the capacitance distribution is such that the overall resonance frequency characteristic of the feed-through capacitor is relatively broade. As a result, a feed-through capacitor exhibiting a frequency characteristic of a relatively low attenuation value throughout a relatively wide frequency region is provided.
Arrangements embodying the invention will now be described by way of example with reference to the accompanying drawings, in which:
Figure 1 is a sectional view of a conventional feed-through capacitor of a layered structure:
Figure 2 is a plan view of the Figure 1 feed-through capacitor;
Figure 3 is a fragmentary sectional and enlarged view of a portion of the Figure 1 capacitor:
Figure 4 is a graph showing a frequency response curve of a conventional feed-through capacitor of a layered structure;
Figure 5 is a sectional view of one embodiment of the present invention
Figure 6 is a sectional view of another embodiment of the present invention
Figures 7 to 12 are sectional views of further embodiments of the present invention;
Figure 13 is a sectional view of a still further embodiment of the present invention; and
Figures 14 to 17 show frequency response curves attained by the embodiments of the present invention.
Figure 5 is a sectional view of one embodiment of the present invention. The Figure 5 feed-through capacitor is shown extending through a chassis 101 or the like. The chassis 101 is formed with a circular opening 106 for receiving a grounding conductor 102 of the feed-through capacitor. The grounding conductor 102 is of a generally cylindrical shape, with a flange 103 formed on the outer surface thereof at an approximately central position, this outer surface being formed with a thread 104 from the flange portion to one end of the cylindrical grounding conductor 102. upon which a nut 105 is threaded.The threaded portion 104 of the grounding conductor 102 is inserted through the opening 106 of the chassis 101 and the nut 105 is threaded on the threaded portion 104 of the grounding conductor 102. whereby the feed-through capacitor is fixed to the chassis 101, with the edge portion of the opening 106 sandwiched between the flange 103 and the nut 105. The feed-through capacitor is provided with a feed-through conductor 110 so as to extend through the cylindrical portion of the grounding conductor 102 in the axial direction thereof. whereby the feed-through conductor 110 is surrounded by the cylindrical portion of the grounding conductor 102.
In the embodiment shown. first, second and third capacitor elements 108, 107 and 109 are arranged in the axial direction of the feed-through conductor 110 and between the feed-through conductor 110 and the grounding conductor 102. Also in the embodiment shown. the second capacitor element 107 is adapted to exhibit a frequency characteristic suited for utilization in a high frequency region. To that end, a material such as ceramic, mica, plastics or the like is utilized as a dielectric material disposed between the feed-through conductor 110 and the grounding conductor 102. In the embodiment shown, a dielectric material of a cylindrical shape made of ceramic formed with electrode layers on the inner and outer surfaces thereof is employed.According to the embodiment shown, the first and third capacitor elements 108 and 109 are adapted to exhibit a frequency characteristic suited for a lower frequency region and are disposed coaxially with the second capacitor element 107 so as to be contiguous thereto at both ends of the second capacitor element 107 in the axial direction. The capacitor elements 108 and 109 intended for a lower frequency region may comprise a dielectric material such as a metal electrolytic oxidation coat, tantalum, semiconductor ceramic, or the like in order to achieve a large capacitance value with a reduced size of the capacitance elements. The frequency characteristic of the embodiment is as shown in Figure 14 and will be described in detail subsequently.
In the embodiment shown, the dielectric materials in these portions comprise a cylindrical ceramic dielectric material, with the inner and outer surfaces formed of electrode layers, whereby what are known as semiconductor ceramic capacitor elements are formed. The electrode layers formed on the inner surfaces of the capacitor elements 108, 107 and 109 are all in electrical contact with the feed-through conductor 110. Likewise, the electrode layers formed on the outer surfaces of the cylindrical dielectric materials are all in electrical contact with the grounding conductor 102. The end surfaces of the first and third capacitor elements 108 and 109 are covered with sealing resin materials 111 and 112.
It has been observed that in accordance with the shown structure a feed-through capacitor effective for a signal with a frequency component as wide as from a KHz order to a GHz order is provided by properly selecting the materials, geometry, the structure and the like of the respective capacitor elements disposed in the axial direction thereof.More specifically, three capacitor elements 107, 108 and 109 are coupled in parallel with each other between the feed-through conductor 110 and the grounding conductor 102, wherein the capacitor elements 108 and 109 are intended to provide a sufficient capacitance value, so that the feed-through capacitor shows a desired frequency characteristic even in a lower frequency region, while the capacitor element 107 has been selected to be of a capacitance value effective to show a desired frequency characteristic in a higher frequency region where the capacitor elements 108 and 109 no longer function as a capacitor, with the result that the feed-through capacitor is sufficiently effective to function in a wide frequency range from a lower frequency region to a higher frequency region.
Figure 6 is a sectional view of another embodiment of the present invention, wherein similar portions to those shown in the Figure 5 capacitor have been denoted by the same reference characters. The conductor 102a is substantially the same as the above described conductor 102, except that the inner diameter at the position of the flange 103 has been made small, such that the inner surface of the reduced diameter portion of the conductor 102a is in contact with an outer electrode layer of a cylindrical ceramic capacitor element 113. Capacitor elements 114 and 115 are similar to the capacitor elements 108 and 109 in the
Figure 5 embodiment and capacitor elements 116 and 117 are similar to the capacitor element 107 in the Figure 5 embodiment.Because of the provision of the capacitor element 113, it has been observed that the frequency characteristic of the Figure 6 embodiment is superior to that of the Figure 5 embodiment.
As readily understood from the foregoing description, the number of capacitor elements distributed along the axial direction of the feed-through capacitor may be determined as desired, although the more capacitor elements, the better the frequency characteristic. The kind, geometry, the structure, and the like of the respective capacitor elements are properly determined so as to meet the requirements. The point is that the frequency characteristic of the respective capacitor elements are selected such that any adverse affect upon the frequency/impedance characteristic of the respective capacitor elements is compensated through parallel connection of the respective capacitor elements in the feed-through capacitor.Preferably. however, capacitor elements adapted to be effective for a lower frequency region are disposed at the input and output ends of the feed-through capacitor while the capacitor elements adapted to be effective for a higher frequency region are disposed in the vicinity of the center of the feed-through capacitor. In order to reduce a loss and a reactance component at the contact between the inner electrode layers of the respective capacitor elements and the feed-through conductor, the inner electrode layers of the respective capacitor elements are adapted to be in electrical contact with the feed-through conductor over a large area. The same applies to the outer electrode layers of the respective capacitor elements. For the same reasons, the inner and outer electrode layers of the respective capacitor elements are preferably formed to be contiguous to each other.It is pointed out that the structure for fixing the feed-through capacitor to a conductor plate such as a chassis is not limited to the embodiment shown but may be modified to a different structure.
Figure 7 is a sectional view of a further embodiment of the present invention. It is pointed out that the Figure 7 feed-through capacitor is somewhat different from the feed-through capacitors shown in Figures 5 and 6 but rather similar to the feed-through capacitor shown in Figures 1 to 3 in the internal layered structure. It is further pointed out that the Figure 7 feed-through capacitor is of the same internal layered structure as that shown in Figures 1 to 3, except for the following differences. Therefore, similar portions in the Figure 7 capacitor have been denoted by the same reference characters as used in Figures 1 to 3.
Referring to Figure 7, a characteristic feature of the feed-through capacitor shown is that the dielectric layer 21 is made of portions of dielectric constants different in the axial direction of the capacitor, as compared with the capacitor shown in Figures 1 to 3 where a dielectric material of uniform dielectric constant distribution was employed throughout the axial direction of the capacitor. According to one example, the dielectric material of the upper half portion as viewed in Figure 7 will be made of a ceramic material of a higher dielectric constant, while the lower half portion of dielectric material as viewed in Figure 7 may be made of a ceramic material of a lower dielectric constant.Since the Figure 7 capacitor is so structured, the capacitance values of the respective capacitance elements in the upper half portion are relatively large while the capacitance values of the respective capacitor elements in the lower half portion are relatively small, in spite of the fact that the configuration and the area of the opposing electrode plates are selected to be the same, with the result that a non-uniform capacitance distribution is achieved in a feed-through capacitor. As a result, a frequency characteristic having a wide flat portion is achieved.
Figure 14 is a graph showing such a frequency characteristic achieved by the Figure 7 embodiment, wherein the abscissa indicates the frequency and the ordinate indicates the attenuation value. In the graph. the curves shown by the dotted lines each show a frequency characteristic of a respective portion of a different capacitance distribution, while the solid line shows the overall frequency characteristic of the Figure 7 embodiment. Thus, it would be appreciated that if the feed-through capacitor is utilized as a filter, an applicable frequency range as a filter can be broadened.
In the Figure 7 embodiment. if and when the dielectric constant of the ceramic material constituting the dielectric material 21 for the respective capacitor elements is different from element to element then the frequency charcteristic of the respective capacitor elements can be more broadly distributed and thus the overall frequency characteristic of the feed-though capacitor can also be broadened.
Figure 15 shows such a frequency characteristic as achieved by the Figure 7 embodiment by causing the dielectric constant of the dielectric material 21 to vary from element to element in a fine manner. wherein the curves indicated by the dotted lines each show the frequency characteristic of a respective capacitor element while the curve of the solid line shows the overall frequency characteristic of such an embodiment of the Figure 7 structure.
It is understood that according to such an embodiment a broader frequency characteristic is attained as compared with the embodiment discussed with reference to Figure 14.
In the above described embodiments, a frequency characteristic having a flat peak portion was attained. If desired, however, a frequency characteristic having two peaks with an interval therebetween can be also attained. as shown in Figure 16, by properly selecting the distribution of the dielectric constant of the dielectric layer 21.
Figure 8 is a sectional view of a further embodiment of the present invention. The Figure 8 embodiment is similar to the Figure 7 embodiment, except for the following modifications. More specifically, in accordance with the Figure 8 embodiment, the non-uniform distribution of the capacitane values of the respective capacitor elements in the axial direction is achieved by varying the distances between the adjacent electrode plates 22 and 23. It would be appreciated that various types of frequency characteristics as discussed in conjunction with Figures 14 through 16 can be achieved by employing the
Figure 8 embodiment.
Figure 9 is a sectional view of still another embodiment of the present invention. The embodiment shown comprises a capacitor portion 2 having a pincushion capacitance distribution. More specifically. the capacitor portion 2 is shaped such that the diameter of the capacitor portion increases with the distance from the grounding plate 3, whereby the capacitance value of the respective capacitance elements increases with the distance of the capacitance element from the grounding plate 3. Accordingly, the external electrode 25 is configured in a pincushion shape in the sectional view. Accordingly, an annular conductor ring 5 having a triangular section, as shown in Figure 9 is provided between the external electrode 25 and the grounding conductor 3.
According to the embodiment shown, the opposing areas of the adjacent inner electrode plates 22 and 23 increase with distance from the grounding conductor 3. On the other hand, the inductance value of the inductance component of each corresponding capacitor element increases with the distance of the capacitor element from the grounding conductor 3. As a result, a feed-through capacitor in which there is a variation from a combination of a small capacitance value and a small inductance value to a combination of a large capacitance value and a large inductance value in the axial direction is provided. It would be appreciated that with such a feed-through capacitor the frequency characteristic as shown in
Figure 15 discussed previously is achieved.
Figure 10 is a sectional view of a still further embodiment of the present invention. The embodiment shown comprises a capacitor portion 2 wherein a small diameter portion in the middle position is sandwiched by two large diameter portions disposed coaxially to be contiguous with the middle small diameter portion, whereby the capacitance value of the respective capacitance elements in the small diameter portion is accordingly small while the capacitance value of the respective capacitance elements in the large diameter portions is accordingly large. The recessed portion of the outer electrode 25 corresponding to the small diameter portion is filled with an annular conductor 5, which is coupled to the grounding conductor 3.
According to the embodiment shown, the area of the opposing adjacent electrode plates 22 and 23 is large and accordingly the capacitance value of the respective capacitor elements is large in the large diameter portions, which are located relatively far from the grounding conductor 3, with the result of a large inductance value of the inductance component for these capacitor elements in the large diameter portions, while the area of the opposing adjacent electrode plates 22 and 23 is small and the capacitance value of the respective capacitor elements is accordingly small in the small diameter portion, which is located near the position of the grounding conductor 3, with the result of a small inductance value of the inductance component with respect to these inductor elements, As a result, the frequency characteristics as shown in Figures 14 and 16 discussed previously are attained, depending on selection of diameters in the large and small diameter portions.
Figure 11 is a sectional view of a still further embodiment of the present invention. The
Figure 11 embodiment can be considered as a modification of the Figure 10 embodiment, wherein the large diameter portion at one side of the capacitor portion is removed. In comparison with the Figure 10 embodiment, the Figure 11 embodiment is further structured as if the conductor 5 is dispensed with. Accordingly, the grounding conductor 3 is directly joined to the outer electrode 25. According to the embodiment shown, substantially the same frequency characteristics as discussed with reference to Figure 10 can be attained.
Figure 12 is a sectional view of a still further embodiment of the present invention. The
Figure 12 embodiment can be considered as a modification of the Figure 9 embodiment, wherein one conical portion constituting the capacitor portion 2 is omitted. The grounding conductor 3 is directly joined to the outer electrode 25.
According to the Figure 12 embodiment, a frequency characteristic totally different from those discussed in the foregoing can be attained depending on the selection of the capacitance distribution of the respective capacitance elements. More specifically. as best seen in Figure 12, the embodiment shown has a capacitance distribution of a decreasing tendency in a direction away from the position of the grounding conductor 3.Therefore, in the embodiment shown, the distribution of inductance, as determined between the grounding conductor 3 and a position on the feed-through conductor, which increases in a direction away from the position of the grounding conductor 3, is combined with a capacitance distribution of a decreasing tendency in a direction away from the position of the grounding conductor 3, with the result that the product of the inductance value and the capacitance value of each capacitor element can be made substantially constant throughout the length of the feed-through conductor, unlike in the earlier embodiments wherein this product varied along the length of the conductor.As a result, a frequency characteristic of a relatively high attenuation value with respect to a relatively narrow frequency region can be attained, particularly when the embodiment is employed in a higher frequency region.
Such a frequency characteristic is shown by the solid curve in Figure 17. wherein the characteristic curve shown by the dotted line indicates that of an example such as the embodiment shown in Figures 1 to 3 where the above described consideration has not been employed. In comparison of these two characteristics, it would be appreciated that the
Figure 12 embodiment is most suited for applications where a frequency characteristic having a relatively high attenuation value in a relatively narrow frequency region is required.
In the embodiment shown in Figure 12, in order to attain a capacitance distribution of a decreasing tendency in a direction away from the position of the grounding conductor, the geometry of the capacitance portion was made small as the distance of the capacitor element from the grounding conductor increased. In such an embodiment it is possible for not only the capacitance values of the capacitance elements to decrease with distance from the grounding conductor, but also the inductance values corresponding to the respective capacitance elements can decrease. More specifically, in general an inherent inductance value of a coaxial conductor may be expressed by the following equation: R2
L = 2 loge R1 x 10-7 [H/m] where L is an inherent inductance value, R1 is an outer diameter of a central conductor and
R2 is an outer diameter of an outer conductor. As apparent from the above described equation, when the outer diameter R2 of the outer conductor is made small in accordance with a capacitance distribution of a decreasing tendency, an inherent inductance value L for the corresponding capacitance element is accordingly decreased. This tendency can override the above-mentioned tendency of the inductance to increase with distance from the grounding point, with the result that the resonance frequency increases with this distance. Thus substantially the same frequency characteristics as those discussed with reference to the Figure 9 embodiment can be attained.
Figure 13 is a sectional view of a still further embodiment of the present invention adapted for achieving substantially the same frequency characteristics as discussed with reference to Figure 12. The Figure 13 embodiment is similar to the Figure 12 embodiment, except for the following modifications. More specifically, in the Figure 13 embodiment, the grounding conductor 3 is positioned in the middle of the capacitor portion 2 and the capacitance distribution has been selected to have a decreasing tendency in both directions away from the position of the grounding conductor 3. It would be appreciated that substantially the same frequency characteristics as discussed in conjunction with the Figure 12 embodiment can be achieved.
As a further modification of the present invention, the capacitance distribution may be selected to have a stepwise changing tendency rather than a continuous gradual changing tendency as discussed in conjunction with the foregoing description. By way of a further modification of the present invention, the capacitor portion may be of a polygonal shape rather than a circular shape as discussed in the foregoing description.
By way of a further modification of the present invention, in order to achieve a capacitance distribution of a decreasing tendency in a direction away from the grounding conductor, the dielectric constant of the dielectric material may be decreased in a direction away from the position of the grounding conductor. To that end, a plurality of dielectric layers of different materials having dielectric constants of decreasing values may be layered in turn for each capacitor element. Alternatively, the distances between the opposing adjacent electrode plates 22 and 23 may be gradually decreased in a direction away from the position of the grounding conductor. In such a case, the capacitor portion 2 need not be tapered in a direction away from the position of the grounding conductor.
As described previously, Figures 14 to 17 show frequency response curves illustrating some resonance frequency characteristics which can be attained by the various embodiments of the present invention. The frequency characteristic shown in Figure 14 can be attained by the embodiments shown in Figures 5, 7, 8, 10 and 11. The resonance frequency characteristic shown in Figure 15 can be attained by the embodiment shown in Figure 6, a modification of the Figure 7 embodiment. a modification of the Figure 8 embodiment, and the embodiments shown in Figures 9, 12 and 13. The resonance frequency characteristic shown in Figure 16 can be attained by the embodiments shown in Figures 5, 6, 7, 8, 9, 10 and 11.The resonance frequency characteristic shown in Figure 17 can be attained by a modification of the Figure 7 embodiment, a modification of the Figure 8 embodiment, and the embodiments shown in Figures 12 and 13.
Although embodiments of the present invention have been described and illustrated in detail. it is to be clearly understood that these are by way of illustration and example only and should not be taken by way of limitation, the scope of the present invention being limited by the terms of the appended claims.
WHAT WE CLAIM IS:
1. A feed-through capacitor having an inner electrode comprising a feed-through conductor and an outer electrode comprising an outer conductor disposed around a length of the feed-through conductor, wherein there is. between said electrodes, a capacitance which is non-uniformly distributed along the length of the feed-through conductor, the distribution being such that the overall shape of the frequency response curve of the capacitor is substantially different from that of a feed-through capacitor of equivalent value with a uniform distribution.
2. A feed-through capacitor in accordance with any preceding claim, which further comprises a grounding point determined on said outer conductor.
3. A feed-through capacitor in accordance with claim 2, wherein the distribution of capacitance is such that the product of the capacitance value at a position along the feed-through conductor and the inductance value determined between said grounding point and said position varies throughout the length of said feed-through conductor.
4. A feed-through capacitor in accordance with claim 3, in which the said product increases with the distance of said position from said grounding point.
5. A feed-through capacitor in accordance with claim 2, wherein the distribution of capacitance is such that the product of the capacitance value at a position along the feed-through conductor and the inductance value determined between said grounding point and said position is substantially constant throughout the length of the feed-through
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (22)
1. A feed-through capacitor having an inner electrode comprising a feed-through conductor and an outer electrode comprising an outer conductor disposed around a length of the feed-through conductor, wherein there is. between said electrodes, a capacitance which is non-uniformly distributed along the length of the feed-through conductor, the distribution being such that the overall shape of the frequency response curve of the capacitor is substantially different from that of a feed-through capacitor of equivalent value with a uniform distribution.
2. A feed-through capacitor in accordance with any preceding claim, which further comprises a grounding point determined on said outer conductor.
3. A feed-through capacitor in accordance with claim 2, wherein the distribution of capacitance is such that the product of the capacitance value at a position along the feed-through conductor and the inductance value determined between said grounding point and said position varies throughout the length of said feed-through conductor.
4. A feed-through capacitor in accordance with claim 3, in which the said product increases with the distance of said position from said grounding point.
5. A feed-through capacitor in accordance with claim 2, wherein the distribution of capacitance is such that the product of the capacitance value at a position along the feed-through conductor and the inductance value determined between said grounding point and said position is substantially constant throughout the length of the feed-through
conductor.
6. A feed-through capacitor in accordance with any one of claims 2 to 5, wherein the distribution of capacitance along the length of said feed-through conductor is symmetrical on both sides of said grounding point.
7. A feed-through capacitor in accordance with any preceding claim, wherein the non-uniform distribution of capacitance is provided by a non-uniform distribution, along the length of said feed-through conductor, of the dielectric constant of dielectric material between the inner and outer electrodes.
8. A feed-through capacitor in accordance with any one of claims 1 to 6, wherein the non-uniform distribution of capacitance is provided by a non-uniform distribution, along the length of said feed-through conductor. of the distance between said inner and outer electrodes.
9. A feed-through capacitor in accordance with any one of claims 1 to 6, wherein the non-uniform distribution of capacitance is provided by a non-uniform distribution, along the length of said feed-through conductor, of opposing areas of said inner and outer electrodes.
10. A feed-through capacitor in accordance with any one of claims 1 to 6, having a plurality of inner electrode plates coupled to said feed-through conductor and disposed along the length of said feed-through conductor, each plate extending in the direction orthogonal to said feed-through conductor, and a plurality of outer electrode plates coupled to said outer conductor and disposed along the length of said feed-through conductor so as to be interdigitated with said plurality of inner electrode plates with a space therebetween, each outer electrode plate extending in the direction orthogonal to said feed-through conductor, dielectric material being disposed between said plurality of inner electrode plates and said plurality of outer electrode plates.
11. A feed-through capacitor in accordance with claim 10, wherein the non-uniform distribution of capacitance is provided by a non-uniform distribution, along the length of said feed-through conductor, of the dielectric constant of said dielectric material between said plurality of inner electrode plates and said plurality of outer electrode plates.
12. A feed-through capacitor in accordance with claim 10, wherein the non-uniform distribution of capacitance is provided by a variation, along the length of said feed-through conductor, in the distances between adjacent inner and outer electrode plates.
13. A feed-through capacitor in accordance with claim 10, wherein the non-uniform distribution of capacitance is provided by a variation, along the length of said feed-through conductor, in the opposing areas of adjacent inner and outer electrode plates.
14. A feed-through capacitor substantially as herein described with reference to Figure 5 of the accompanying drawings.
15. A feed-through capacitor substantially as herein described with reference to Figure 6 of the accompanying drawings.
16. A feed-through capacitor substantially as herein described with reference to
Figure 7 of the accompanying drawings.
17. A feed-through capacitor substantially as herein described with reference to Figure 8 of the accompanying drawings.
18. A feed-through capacitor substantially as herein described with reference to Figure 9 of the accompanying drawings.
19. A feed-through capacitor substantially as herein described with reference to Figure 10 of the accompanying drawings.
20. A feed-through capacitor substantially as herein described with reference to Figure 11 of the accompanying drawings.
21. A feed-through capacitor substantially as herein described with reference to Figure 12 of the accompanying drawings.
22. -A feed-through capacitor substantially as herein described with reference to Figure 13 of the accompanying drawings.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1977043807U JPS5758755Y2 (en) | 1977-04-07 | 1977-04-07 | |
| JP8399477U JPS5847700Y2 (en) | 1977-06-24 | 1977-06-24 | Multilayer feedthrough capacitor |
| JP1977162507U JPS584185Y2 (en) | 1977-12-02 | 1977-12-02 | Multilayer feedthrough capacitor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1601857A true GB1601857A (en) | 1981-11-04 |
Family
ID=27291678
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1355978A Expired GB1601857A (en) | 1977-04-07 | 1978-04-06 | Feed-through capacitor |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE2815118C2 (en) |
| FR (1) | FR2386895A1 (en) |
| GB (1) | GB1601857A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4424551B1 (en) | 1982-01-25 | 1991-06-11 | Highly-reliable feed through/filter capacitor and method for making same | |
| AU3299995A (en) * | 1994-10-04 | 1996-04-18 | Medtronic, Inc. | Protective feedthrough |
| US5870272A (en) * | 1997-05-06 | 1999-02-09 | Medtronic Inc. | Capacitive filter feedthrough for implantable medical device |
| WO2019090298A1 (en) | 2017-11-06 | 2019-05-09 | Avx Corporation | Emi feedthrough filter terminal assembly containing a laminated insulative seal |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB722747A (en) * | 1951-06-28 | 1955-01-26 | Siemens Ag | Improvements in or relating to electric condensers |
| US2756375A (en) * | 1952-02-06 | 1956-07-24 | Sprague Electric Co | Feed-through capacitors |
| DE1020119B (en) * | 1956-10-18 | 1957-11-28 | Rohde & Schwarz | Feed-through capacitor |
| US3007121A (en) * | 1959-02-05 | 1961-10-31 | Allen Bradley Co | Deresonated capacitor |
| US3320557A (en) * | 1963-04-02 | 1967-05-16 | Globe Union Inc | Feed-through capacitor |
| US3238429A (en) * | 1964-04-10 | 1966-03-01 | Ncr Co | Dual by-pass capacitor unit |
| US3617830A (en) * | 1970-04-30 | 1971-11-02 | Phase Industries | Miniature feed-through wide band bypass capacitor assembly |
| DE2454582A1 (en) * | 1974-11-18 | 1976-05-26 | Siemens Ag | DEVICE FOR PREVENTING LEAKAGE OF RF ENERGY FROM BREAKINGS PLACED IN WALLS OF HIGH FREQUENCY TREATMENT DEVICES |
-
1978
- 1978-04-06 GB GB1355978A patent/GB1601857A/en not_active Expired
- 1978-04-07 FR FR7810452A patent/FR2386895A1/en active Granted
- 1978-04-07 DE DE19782815118 patent/DE2815118C2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2815118C2 (en) | 1985-02-21 |
| DE2815118A1 (en) | 1978-10-19 |
| FR2386895A1 (en) | 1978-11-03 |
| FR2386895B1 (en) | 1983-06-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PE20 | Patent expired after termination of 20 years |
Effective date: 19980405 |