EP0693794A1 - Ceramic microwave filter - Google Patents
Ceramic microwave filter Download PDFInfo
- Publication number
- EP0693794A1 EP0693794A1 EP95110347A EP95110347A EP0693794A1 EP 0693794 A1 EP0693794 A1 EP 0693794A1 EP 95110347 A EP95110347 A EP 95110347A EP 95110347 A EP95110347 A EP 95110347A EP 0693794 A1 EP0693794 A1 EP 0693794A1
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- European Patent Office
- Prior art keywords
- resonators
- coaxial resonators
- frequency
- filter
- coaxial
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
Definitions
- the present invention relates to a microwave ceramic filter according to the preamble of patent claim 1.
- microwave ceramic filters are used to select useful frequencies lying in a predetermined pass frequency band, i. H. to pass and block frequencies lying outside this pass frequency band as completely as possible.
- microwave ceramic filters are constructed as follows: through holes are provided at predetermined intervals in a body made of dielectric ceramic material, for example with a cuboid shape. Electrically conductive layers are applied to the inner peripheral surfaces of these through holes, while the ceramic body is metallized on all sides apart from at least one end face on which the through holes emerge on one side. Each region of the ceramic body containing a through hole forms a coaxial resonator. These coaxial resonators are coupled to one another in a suitable manner to complete the filter. This can be done, for example, by providing a coupling hole in the ceramic body between two through holes. Ceramic bodies of this type are known, for example, from US Pat. No. 4,464,640.
- a microwave ceramic filter known from DE-OS 42 32 054
- the selection has been increased in that at least one coaxial resonator forming a bandstop is connected in series to the filter defining the pass frequency band with a plurality of ceramic resonators coupled to one another.
- a damping peak outside the pass frequency band is realized outside the pass frequency band at a specific point at which there is an interference frequency, as a result of which the interference frequency is sufficiently attenuated.
- the present invention has for its object to provide a microwave ceramic filter of the type in question with even higher selection and less temperature dependence.
- an embodiment of a microwave ceramic filter according to the invention is formed by two coaxial resonators 1 and 2, which have a cuboid shape and each contain a through hole 3 and 4, respectively. Electrically conductive layers are applied to the inner circumferential surfaces of these through holes, while the ceramic body is metallized on all sides apart from at least one end face on which the through hole emerges on one side.
- These coaxial resonators are coupled to one another in a suitable manner to complete the filter.
- an insulating insert 5 is provided between the coaxial resonators 1 and 2, which can engage in the through holes 3 and 4, for example, via lugs (not shown).
- a bracket 6 can be provided for the mechanically stable connection of the coaxial resonators 1 and 2, the z. B. is soldered, so that the additional advantage for the user arises that the filter is present as a one-piece element for assembly.
- a series connection of a microwave resonator of the type in question forms a bandstop.
- This case is shown schematically in FIG. 2, in which a microwave resonator 1 lies in series between inputs 10 and 11 and outputs 12 and 13.
- FIG. 3 The characteristic of such a resonator operated as a bandstopper is shown in FIG. 3, in which an output variable of the microwave resonator operated as a bandstopper, about a signal amplitude A is shown as a function of frequency f.
- the bandstop can be seen to have a high attenuation peak at the resonance frequency f r , ie it works in this case as a bandstop.
- a plurality of such resonators operated as a bandstop filter are connected in series, compared to known filters, for example according to DE-OS 42 32 054, there is an increased additional selection or attenuation in a predetermined frequency range.
- Such a damping characteristic for an embodiment with two coaxial resonators connected in series is shown in FIG. 4, in which the amplitude A is also plotted against the frequency f.
- coaxial resonators are connected in series as a bandstop filter and have resonance frequencies that deviate from the predetermined frequency at which there is high attenuation outside the pass frequency band, this results in a wider attenuation curve with two bumps typical of the embodiment with two resonators.
- the deviation of the resonance frequencies of the coaxial resonators from the frequency in which the attenuation range is to be can be, for example, + - or -5 MHz, whereby of these frequency deviations a deviation range of + 5- and -3MHz or + 3- and -5MHz can be possible.
- a temperature drift of the resonance frequency of the individual resonators is additionally reduced or the manufacturing tolerance for setting the resonator frequencies can be reduced.
- the invention is not limited to the series connection of two individual resonators according to the embodiment according to FIG. 2. Depending on the application, several individual resonators can also be used.
- the individual resonators can in principle be produced with connections in the form of solder lugs or with integrated HF connections, as is described, for example, in DE-OS 42 29 165.
- the ceramic bodies 1 and 2 forming the resonators according to FIG. 1 can be metallized, apart from their end faces at which the through holes 3, 5 emerge.
- ⁇ means the wavelength corresponding to the resonance frequencies of the resonators.
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Abstract
Description
Die vorliegende Erfindung betrifft einen Mikrowellen-Keramikfilter nach dem Oberbegriff des Patentanspruchs 1.The present invention relates to a microwave ceramic filter according to the preamble of patent claim 1.
Derartige Mikrowellen-Keramikfilter dienen dazu, in einem vorgegebenen Durchlaßfrequenzband liegende Nutzfrequenzen zu selektieren, d. h. durchzulassen und außerhalb dieses Durchlaßfrequenzbandes liegende Frequenzen möglichst vollständig zu sperren. Derartige Mikrowellen-Keramikfilter sind im Prinzip folgendermaßen aufgebaut: In einem Körper aus dielektrischem keramischem Material, beispielsweise mit Quaderform, sind in vorgegebenen Intervallen Durchgangslöcher vorgesehen. Auf den Innenumfangsflächen dieser Durchgangslöcher sind elektrisch leitende Schichten aufgebracht, wahrend der Keramikkörper abgesehen von mindestens einer Stirnfläche, an der die Durchgangslöcher an einer Seite austreten, allseitig metallisiert sind. Jeder ein Durchgangsloch enthaltender Bereich des Keramikkörpers bildet dabei einen Koaxial-Resonator. Diese Koaxial-Resonatoren sind zur Vervollständigung des Filters in geeigneter Weise miteinander gekoppelt. Dies kann beispielsweise dadurch erfolgen, daß zwischen jeweils zwei Durchgangslöchern ein Koppelloch im Keramikkörper vorgesehen ist. Derartige Keramikkörper sind beispielsweise aus der US-PS 4,464,640 bekannt.Such microwave ceramic filters are used to select useful frequencies lying in a predetermined pass frequency band, i. H. to pass and block frequencies lying outside this pass frequency band as completely as possible. In principle, such microwave ceramic filters are constructed as follows: through holes are provided at predetermined intervals in a body made of dielectric ceramic material, for example with a cuboid shape. Electrically conductive layers are applied to the inner peripheral surfaces of these through holes, while the ceramic body is metallized on all sides apart from at least one end face on which the through holes emerge on one side. Each region of the ceramic body containing a through hole forms a coaxial resonator. These coaxial resonators are coupled to one another in a suitable manner to complete the filter. This can be done, for example, by providing a coupling hole in the ceramic body between two through holes. Ceramic bodies of this type are known, for example, from US Pat. No. 4,464,640.
Je hoher die obengenannte Frequenzselektion sein soll, desto größer muß die Anzahl der vorstehend erläuterten zu verkoppelnden Koaxial-Resonatoren sein. Mit zunehmender Anzahl von Koaxial-Resonatoren steigt jedoch die Einfügungsdämpfung und damit die dissipative Verlustdämpfung des Filters. Dies kann im ungünstigsten Fall dazu fuhren, daß die Verlustdämpfung zu groß ist und die verbleibende Durchgangsleistung nach der Filterung für nachfolgende Funktionen, beispielsweise Abstrahlung oder Signalverarbeitung, nicht mehr ausreicht.The higher the above-mentioned frequency selection is to be, the greater the number of coaxial resonators to be coupled explained above must be. With increasing number of coaxial resonators, however, the insertion loss and thus the dissipative loss loss of the filter increases. In the worst case, this can lead to the loss loss being too great and the remaining throughput after Filtering for subsequent functions, such as radiation or signal processing, is no longer sufficient.
Sucht man eine hohe Selektion durch Erhöhung der Anzahl von zu verkoppelnden Resonatoren zu realisieren, so kann das vorgenannte Problem der zu großen Einfügungsdämpfung nur durch eine aufwendige und damit teure Verstärkung des gefilterten Nutzsignals gelöst werden.If you are looking for a high selection by increasing the number of resonators to be coupled, the aforementioned problem of excessive insertion loss can only be solved by a complex and therefore expensive amplification of the filtered useful signal.
Bei einem aus der DE-OS 42 32 054 bekannten Mikrowellen-Keramikfilter ist die Selektion dadurch erhöht worden, das dem das Durchlaßfrequenzband definierenden Filter mit einer Vielzahl von miteinander verkoppelten Keramik-Resonatoren mindestens ein eine Bandsperre bildender Koaxial-Resonator in Reihe geschaltet ist. Dadurch wird außerhalb des Durchlaßfrequenzbandes an einer bestimmten Stelle, an der eine Störfrequenz liegt, eine Dämpfungsspitze außerhalb des Durchlaßfrequenzbandes realisiert, wodurch die Störfrequenz ausreichend gedämpft wird.In a microwave ceramic filter known from DE-OS 42 32 054, the selection has been increased in that at least one coaxial resonator forming a bandstop is connected in series to the filter defining the pass frequency band with a plurality of ceramic resonators coupled to one another. As a result, a damping peak outside the pass frequency band is realized outside the pass frequency band at a specific point at which there is an interference frequency, as a result of which the interference frequency is sufficiently attenuated.
Der vorliegenden Erfindung liegt die Aufgabe zugrunde, ein Mikrowellen-Keramikfilter der in Rede stehenden Art mit noch höherer Selektion und geringerer Temperaturabhängigkeit anzugeben.The present invention has for its object to provide a microwave ceramic filter of the type in question with even higher selection and less temperature dependence.
Diese Aufgabe wird bei einem Mikrowellen-Keramikfilter der eingangs genannten Art erfindungsgemäß durch die Merkmale des kennzeichnenden Teils des Patentanspruchs 1 gelöst.This object is achieved according to the invention in a microwave ceramic filter of the type mentioned at the outset by the features of the characterizing part of patent claim 1.
Weiterbildungen der Erfindung sind Gegenstand von Unteransprüchen.Developments of the invention are the subject of dependent claims.
Die Erfindung wird im folgenden anhand eines Ausführungsbeispiels gemäß den Figuren der Zeichnung naher erläutert. Es zeigt:
- Figur 1
- eine schematische perspektivische Darstellung eines erfindungsgemäß ausgebildeten Mikrowellen-Keramikfilters;
- Figur 2
- ein schematisches Schaltbild eines als Bandsperre betriebenen Keramik-Resonator;
Figur 3- eine Charakteristik des als Bandsperre betriebenen Keramik-Resonators nach Figur 2; und
- Figur 4
- eine Filtercharakteristik des Filters nach Figur 1.
- Figure 1
- is a schematic perspective view of a microwave ceramic filter designed according to the invention;
- Figure 2
- a schematic diagram of a ceramic resonator operated as a bandstop;
- Figure 3
- a characteristic of the ceramic resonator operated as a bandstop according to Figure 2; and
- Figure 4
- a filter characteristic of the filter of Figure 1.
Gemäß Figur 1 wird eine Ausführungsform eines erfindungsgemäß Mikrowellen-Keramikfilters durch zwei Koaxial-Resonatoren 1 und 2 gebildet, die Quaderform besitzen und jeweils ein Durchgangsloch 3 bzw. 4 enthalten. Auf den Innenumfangsflächen dieser Durchgangslöcher sind elektrisch leitende Schichten aufgebracht, während der Keramikkörper abgesehen von mindestens einer Stirnfläche, an der das Durchgangsloch an einer Seite austritt, allseitig metallisiert ist. Diese Koaxial-Resonatoren werden zur Vervollständigung des Filters in geeigneter Weise miteinander gekoppelt. Bei der dargestellten Ausführungsform ist zwischen den Koaxial-Resonatoren 1 und 2 ein isolierender Einsatz 5 vorgesehen, der beispielsweise über (nicht dargestellte) Ansätze in die Durchgangslöcher 3 und 4 eingreifen kann. Weiterhin kann zur mechanisch stabilen Verbindung der Koaxial-Resonatoren 1 und 2 ein Bügel 6 vorgesehen sein, der z. B. angelötet ist, so daß der zusätzliche Vorteil für den Anwender entsteht, daß das Filter insgesamt als einstückiges Element für eine Bestückung vorliegt.According to FIG. 1, an embodiment of a microwave ceramic filter according to the invention is formed by two coaxial resonators 1 and 2, which have a cuboid shape and each contain a through
In an sich bekannter Weise bildet eine Serienschaltung eines Mikrowellen-Resonators der in Rede stehenden Art eine Bandsperre. Dieser Fall ist schematisch in Figur 2 dargestellt, in der ein Mikrowellen-Resonator 1 in Reihe zwischen Eingängen 10 und 11 und Ausgängen 12 und 13 liegt.In a manner known per se, a series connection of a microwave resonator of the type in question forms a bandstop. This case is shown schematically in FIG. 2, in which a microwave resonator 1 lies in series between inputs 10 and 11 and
Die Charakteristik eines derartigen als Bandsperre betriebenen Resonators ist in Figur 3 dargestellt, in der einen Ausgangsgröße des als Bandsperre betriebenen Mikrowellen-Resonators, etwa eine Signalamplitude A als Funktion der Frequenz f dargestellt ist. Ersichtlich besitzt die Bandsperre bei der Resonanzfrequenz fr eine hohe Dämpfungsspitze, d. h. sie arbeitet in diesem Fall als Bandsperre.The characteristic of such a resonator operated as a bandstopper is shown in FIG. 3, in which an output variable of the microwave resonator operated as a bandstopper, about a signal amplitude A is shown as a function of frequency f. The bandstop can be seen to have a high attenuation peak at the resonance frequency f r , ie it works in this case as a bandstop.
Werden erfindungsgemäß mehrere derartige als Bandsperre betriebene Resonatoren in Reihe geschaltet, so ergibt sich gegenüber bekannten Filtern etwa nach der obengenannten DE-OS 42 32 054 eine erhöhte zusätzlich Selektion bzw. Dämpfung in einem vorgegebenen Frequenzbereich. Eine solche Dämpfungscharakteristik für eine Ausführungsform mit zwei in Reihe geschalteten Koaxial-Resonatoren ist in Figur 4 dargestellt, in der ebenfalls die Amplitude A über der Frequenz f aufgetragen ist.If, according to the invention, a plurality of such resonators operated as a bandstop filter are connected in series, compared to known filters, for example according to DE-OS 42 32 054, there is an increased additional selection or attenuation in a predetermined frequency range. Such a damping characteristic for an embodiment with two coaxial resonators connected in series is shown in FIG. 4, in which the amplitude A is also plotted against the frequency f.
Werden Koaxial-Resonatoren wie ausgeführt als Bandsperre und in Reihe geschaltet und besitzen von der vorgegebenen Frequenz, bei der außerhalb des Durchlaßfrequenzbandes eine hohe Dämpfung vorhanden ist, abweichende Resonanzfrequenzen, so ergibt sich ein breiterer Dämpfungsverlauf mit zwei für die Ausführungsform mit zwei Resonatoren typischen Höckern. Im Anwendungsbereich für Mobilfunk- und Schnurlos-Telefonsysteme, die im Höchstfrequenzbereich von 400MHz bis 2GHz arbeiten, kann die Abweichung der Resonanzfrequenzen der Koaxial-Resonatoren von der Frequenz, in welcher der Dämpfungsbereich liegen soll, beispielsweise +- bzw. -5MHz betragen, wobei von diesen Frequenzabweichungen noch einmal ein Abweichungsbereich von +5- und -3MHz bzw. +3- und -5MHz möglich sein.If coaxial resonators are connected in series as a bandstop filter and have resonance frequencies that deviate from the predetermined frequency at which there is high attenuation outside the pass frequency band, this results in a wider attenuation curve with two bumps typical of the embodiment with two resonators. In the area of application for mobile and cordless telephone systems, which operate in the maximum frequency range from 400 MHz to 2 GHz, the deviation of the resonance frequencies of the coaxial resonators from the frequency in which the attenuation range is to be can be, for example, + - or -5 MHz, whereby of these frequency deviations a deviation range of + 5- and -3MHz or + 3- and -5MHz can be possible.
Zusätzlich zu der erhöhten zusätzlichen Selektion wird auch ein Temperaturdriften der Resonanzfrequenz der Einzelresonatoren zusätzlich vermindert oder es kann die Fertigungstoleranz zum Einstellen der Resonatorfrequenzen verringert werden.In addition to the increased additional selection, a temperature drift of the resonance frequency of the individual resonators is additionally reduced or the manufacturing tolerance for setting the resonator frequencies can be reduced.
Die Erfindung ist nicht auf die Reihenschaltung von zwei Einzelresonatoren gemäß der Ausführungsform nach Figur 2 beschränkt. Es können auch je nach Anwendungsfall mehrere Einzelresonatoren Verwendung finden.The invention is not limited to the series connection of two individual resonators according to the embodiment according to FIG. 2. Depending on the application, several individual resonators can also be used.
Die Einzelresonatoren können grundsätzlich mit Anschlüssen in Form von Lötfahnen oder mit integrierten HF-Anschlüssen hergestellt werden, wie dies beispielsweise in der DE-OS 42 29 165 beschrieben ist.The individual resonators can in principle be produced with connections in the form of solder lugs or with integrated HF connections, as is described, for example, in DE-OS 42 29 165.
Sollen die Koaxial-Resonatoren als λ/2-Resonatoren ausgebildet sein, so können die die Resonatoren bildenden Keramikkörper 1 und 2 nach Figur 1 abgesehen von ihren Stirnflächen, an denen die Durchgangslöcher 3, 5 austreten, metallisiert sein.If the coaxial resonators are to be designed as λ / 2 resonators, the ceramic bodies 1 and 2 forming the resonators according to FIG. 1 can be metallized, apart from their end faces at which the through
Sollen die Resonatoren als λ/4-Resonatoren ausgebildet sein, so ist lediglich eine der Stirnflächen metallisiert. λ bedeutet dabei die der Resonanzfrequenzen der Resonatoren entsprechende Wellenlänge.If the resonators are to be designed as λ / 4 resonators, only one of the end faces is metallized. λ means the wavelength corresponding to the resonance frequencies of the resonators.
Claims (4)
dadurch gekennzeichnet,
daß die Koaxial-Resonatoren (1, 2) als Bandsperre und in Reihe geschaltet sind und von der vorgegebenen Frequenz abweichende Resonanzfrequenzen besitzen.Microwave ceramic filter with a predetermined pass frequency band and with a region of high attenuation around a predetermined frequency outside the pass frequency band using at least two coaxial resonators (1, 2),
characterized,
that the coaxial resonators (1, 2) are connected as a bandstop and in series and have different resonance frequencies from the predetermined frequency.
dadurch gekennzeichnet,
daß für den Fall zweier Koaxial-Resonatoren (1, 2) die Resonanzfrequenz des einen nach oben und die des anderen nach unten von der vorgegebenen Frequenz abweicht.Microwave ceramic filter according to claim 1,
characterized,
that in the case of two coaxial resonators (1, 2) the resonance frequency of one deviates upwards and that of the other downwards from the predetermined frequency.
dadurch gekennzeichnet,
daß die Koaxial-Resonatoren (1, 2) dadurch als λ/2-Resonatoren ausgebildet sind, daß die Außenfläche eines den Resonator bildenden Keramikkörpers abgesehen von Stirnflächen, an denen ein Durchgangsloch (3, 4) austritt, metallisiert ist, wobei λ die Wellenlänge bei der Filtermittenfrequenz bedeutet.Microwave ceramic filter according to claim 1 and / or 2,
characterized,
that the coaxial resonators (1, 2) are designed as λ / 2 resonators in that the outer surface of a ceramic body forming the resonator is metallized, apart from end faces at which a through hole (3, 4) emerges, where λ is the wavelength means at the filter center frequency.
dadurch gekennzeichnet,
daß die Koaxial-Resonatoren (1, 2) dadurch als λ/4-Resonatoren ausgebildet sind, daß die Außenfläche eines den Resonator bildenden Keramikkörpers abgesehen von einer Stirnfläche, an der ein Durchgangsloch (3, 4) austritt, metallisiert ist, wobei λ die Wellenlänge bei der Filtermittenfrequenz bedeutet.Microwave ceramic filter according to claim 1 and / or 2,
characterized,
that the coaxial resonators (1, 2) are designed as λ / 4 resonators in that the outer surface of a ceramic body forming the resonator is metallized apart from an end face at which a through hole (3, 4) emerges, where λ is the Wavelength at the filter center frequency means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19944425707 DE4425707C2 (en) | 1994-07-20 | 1994-07-20 | Microwave ceramic filter |
| DE4425707 | 1994-07-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP0693794A1 true EP0693794A1 (en) | 1996-01-24 |
Family
ID=6523697
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP95110347A Ceased EP0693794A1 (en) | 1994-07-20 | 1995-07-03 | Ceramic microwave filter |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0693794A1 (en) |
| DE (1) | DE4425707C2 (en) |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2630490A (en) * | 1946-01-03 | 1953-03-03 | Paul I Richards | Coaxial transmission line filter |
| JPS57199302A (en) * | 1981-06-02 | 1982-12-07 | Murata Mfg Co Ltd | Manufacture for dielectric coaxial tem resonator |
| US4464640A (en) | 1981-10-02 | 1984-08-07 | Murata Manufacturing Co., Ltd. | Distribution constant type filter |
| US4636759A (en) * | 1984-03-30 | 1987-01-13 | Murata Manufacturing Co., Ltd. | Electrical trap construction |
| US4862122A (en) * | 1988-12-14 | 1989-08-29 | Alcatel Na, Inc | Dielectric notch filter |
| JPH0617702A (en) * | 1992-03-09 | 1994-01-25 | Goetze Ag | Cylinder head gasket for internal combustion engine |
| DE4229165A1 (en) | 1992-09-01 | 1994-03-10 | Siemens Matsushita Components | Ceramic coaxial resonator |
| DE4232054A1 (en) | 1992-09-24 | 1994-03-31 | Siemens Matsushita Components | Microwave ceramic filter - incorporates throughput frequency band-defining filter and series-connected coaxial resonator as band stop |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2413009A1 (en) * | 1974-03-18 | 1975-03-27 | Perthen Gmbh Messgeraete Und A | Filtering compensation of fundamental wave - is for irregular measurable variables caused by measurement process |
-
1994
- 1994-07-20 DE DE19944425707 patent/DE4425707C2/en not_active Expired - Fee Related
-
1995
- 1995-07-03 EP EP95110347A patent/EP0693794A1/en not_active Ceased
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2630490A (en) * | 1946-01-03 | 1953-03-03 | Paul I Richards | Coaxial transmission line filter |
| JPS57199302A (en) * | 1981-06-02 | 1982-12-07 | Murata Mfg Co Ltd | Manufacture for dielectric coaxial tem resonator |
| US4464640A (en) | 1981-10-02 | 1984-08-07 | Murata Manufacturing Co., Ltd. | Distribution constant type filter |
| US4636759A (en) * | 1984-03-30 | 1987-01-13 | Murata Manufacturing Co., Ltd. | Electrical trap construction |
| US4862122A (en) * | 1988-12-14 | 1989-08-29 | Alcatel Na, Inc | Dielectric notch filter |
| JPH0617702A (en) * | 1992-03-09 | 1994-01-25 | Goetze Ag | Cylinder head gasket for internal combustion engine |
| DE4229165A1 (en) | 1992-09-01 | 1994-03-10 | Siemens Matsushita Components | Ceramic coaxial resonator |
| DE4232054A1 (en) | 1992-09-24 | 1994-03-31 | Siemens Matsushita Components | Microwave ceramic filter - incorporates throughput frequency band-defining filter and series-connected coaxial resonator as band stop |
Non-Patent Citations (2)
| Title |
|---|
| PATENT ABSTRACTS OF JAPAN vol. 10, no. 145 (E - 407)<2202> 28 May 1986 (1986-05-28) * |
| PATENT ABSTRACTS OF JAPAN vol. 7, no. 49 (E - 161)<1194> 25 February 1983 (1983-02-25) * |
Also Published As
| Publication number | Publication date |
|---|---|
| DE4425707C2 (en) | 1996-12-19 |
| DE4425707A1 (en) | 1996-02-01 |
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| 18R | Application refused |
Effective date: 19990314 |