CA1050127A - Low insertion loss waveguide filter - Google Patents
Low insertion loss waveguide filterInfo
- Publication number
- CA1050127A CA1050127A CA250,162A CA250162A CA1050127A CA 1050127 A CA1050127 A CA 1050127A CA 250162 A CA250162 A CA 250162A CA 1050127 A CA1050127 A CA 1050127A
- Authority
- CA
- Canada
- Prior art keywords
- cavities
- filter
- cavity
- cylindrical
- square
- 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.)
- Expired
Links
Classifications
-
- 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
- H01P1/207—Hollow waveguide filters
- H01P1/208—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure
- H01P1/2082—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure with multimode resonators
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Abstract
ABSTRACT OF THE DISCLOSURE:
A low insertion loss waveguide bandpass filter, having a high unloaded Q factor, is achieved using cascaded cavities of a length which is n times the half guide wavelength, and being the third index of a TE mode microwave to be transmitted and at least larger than one. Volume optimization for high Q performance is obtained by cascading cylindrical or square cavities of the same cross-sectional area whereas two different techniques are used to eliminate spurious responses in the stop-band. In the first technique, exclusively square or cylindrical cavities of different cross-sectional areas are cascaded whereas the second technique is based upon an alternate arrangement of square and cylindrical cavities. Also, even order filters as well as odd order filters having high Q performances are realized.
A low insertion loss waveguide bandpass filter, having a high unloaded Q factor, is achieved using cascaded cavities of a length which is n times the half guide wavelength, and being the third index of a TE mode microwave to be transmitted and at least larger than one. Volume optimization for high Q performance is obtained by cascading cylindrical or square cavities of the same cross-sectional area whereas two different techniques are used to eliminate spurious responses in the stop-band. In the first technique, exclusively square or cylindrical cavities of different cross-sectional areas are cascaded whereas the second technique is based upon an alternate arrangement of square and cylindrical cavities. Also, even order filters as well as odd order filters having high Q performances are realized.
Description
i~O50~27 The present invention relates in general to waveguide bandpass filters for Transverse Electric (TE) waves and concerns in particular a low-loss waveguide band-pass filter having a~high unloaded Q factor, the latter being a quality factor which deter~
mines, and is inversely proportional to, the mid-band insertion loss of a speclfic filter design.
Known rectangular waveguide band-pass filters use s~nchro-nously tuned rectangular cavities in cascade. These filters arecons~
tructed out of a straight waveguide section in which the cavities are formed through the use of inductive posts or irises. A more recent development of waveguide type microwave filters i5 the dual mode filter. Such filters employ square or cylindrical resonators operating in TElol and TElll modes respectively. The length of each cavity is equal to half guide'wave'length at the filter centre fre-quency, and its unloaded Q is approximately equal to the Q of the rectangular waveguide filters. For those types of filters the un-loaded Q decreases with increasing frequency.
The advantages and the construction details of the dual mode filter are described, for example, in Canadian Patent No.
896,116 issued on March 21, 1972, to Blachier et al. It is much lighter than the conventional filters and also its mechanical struc-ture permits to achieve elliptic filter functions.
The types of filter described above can, with care, be realized to exhibit unloaded ~'s of 10,000 at 4 GHz and 5,000 at 12 GHz. This means that the mid-band insertion loss of a filter at 12 GHz, with the same percentage bandwidth and other passband cha-racteristics as one at 4 GHz, will be twice larger. In modern com-munication systems, the realization of filters with higher unloaded Q's, particularly at frequencies above 10 GHz, would be advantageous.
In satellite systems, a second advantage would accrue i~ the volume, and hence the weight of such filters could be minimized.
A prime o~ject of the present invention resides in a 105~27 waveguide bandpass filter which exhibits significantly higher un-loaded Q's than conventional ones, and which therefore promotes a substantially low mid-band insertion loss therein.
In accordance with the present invention, the low-loss bandpass waveguide filter comprises M waveguide resonant cavities provided with intercoupling means, M being an integer, and wherein each cavity has a physical length of "n" times the haLf guide wave-length, where "n" is the third mode index of a TE mode microwave to be transmitted and is larger than one.
Preferred emb~diments of the present invention ~ill be hereinafter described with reference to the accompanying drawings, wherein Figures lA and lB show views, in perspective, of TElo and T~ dual mode bandpass microwave filters in accordance with the lln present invention, which filters are respectively constituted of square and cylindrical cavities of the same cross-sectional area;
Figures lC and lD are cross-sectional views taken along line C-C and line D-D, respectively, of figures lA and lB;
Figures 2A and 2B respectively show square and cylindrical filters provided with cavities of different cross-sectional areas, following another embodiment of the present invention;
Figure 3 depicts a bandpass filter having cascaded cylin-drical and squa~ cavities of cross-sectional areas in accordance with a further embodiment of the present invention.
Figures 4A and 4B illustrate a bandpass filter wherein a single rectangular cavity is cascaded with other square or cylindri-cal cavities, respectively, according to a further embodiment of the present invention.
Figures lA and lB illustrate, in perspective, high Q, low insertion loss, dual mode filters provided with M cascaded cavities each bein~ of a length "1", M ~einq an inte~er.The ilter of figure lA
is a TElon filter macle up of cavities Sl ..Sm of square cross-~ )5C~127 sectional area whereas the ilter of figure lB is a TE ~ filter madeup of cylindrical cavitiesC~ . The cavities composina each filter have the ~ame cross-sectional area and ~ach cavit.v is n ~ g long, where ~ g is the guide wavelength at the centre frequency of the filter. Also, the height or diameter of each cavity is carefully selected from known mode lattice charts for optimum ~ and spurious response elimination. - ~
The reSonance modes TE10 and TElln' where n ls the third mGde index and larger than 1, have been selected in order to accomplish effectivély a reduction in both the insertion loss and the volume of the filter. In the embodiments of figures lA and lB, each increase in the index "n" corresponds to an additional increase of.half a guide wavelength in the length of the cavity.
According to the present invention, by choosing n larger than 1, in connection with the length of each cavity, the unloaded Q of the filter thereby obtained for the TE modes is approximately 60% lar-ger than that of conventional filters, wherein n _ 1. Therefore, with the illustrated filters, unloaded Q optimization in the filter is achieved through a volume optimization of each cavity, which volume is proportional to the length thereof.
Turning again to figures lA and lB, two adjacent cavities of the filters are separated by an intercoupling reElective plate 1 or ~ provided with a slot or iris 1' or 2', and both filters are limited by input ports 3 and 5 and output por~s 4 and 6, res-pectively.
Three tuning screws per cavity are used, these screws being disposed along a predetermined cross-sectional plane in a given cavity. The frequency tuning screws Tl and T2 are 90 apart and are in line with the two orthogonal E field components of the cavity, as better seen from figures lC and lD. The coupling screw .
C can be located at any multiples of 45 with respect to Tl and T2. The length location Ls of the screws is a function of the 5~7 mode index "n" and is equal to Ls = (2K~- 1) Lj where K is any integer ranging from 1 to n. The choices of Ls = Lj/2 for n odd, and Ls close to Lj/2 for n even are preferable, Lj being the length of the cavity.
Two dual mode filters of the type shown in Fig~ lA and lB
were realized in the 11.7-12.2 GHz communications band. Both filters were four-section elliptic function type. The square waveguide type was operated in TE103 mode and i~s side was of 0.860 inch.
The cylindrical waveguide type was operating in TE112 mode and its diameter D was of 1.275 inches. Both filters have a bandwidth of 80 MHz centred on 12 GHz and a measured unloaded Q of 8000. The intercavity coupling was obtained via inductive irises, and the ..
in-band spurious signals at a level of 35 dB below that of the use-ful signal transmitted in the passband.
Figures 2A and 2B show further arrangements of the bandpass of the present invention, wherein the various cascaded cavities Si...S or C ...C ,composing each filter are of different cross-sectional areas for improved elimination of spurious waves. Bv doing so, the spurious of any one cavity do not coincide with the spurious o~ the other cavities, and are therefore attenuated. The attenuation level of the spurious passbands is dependent on the number of filter sections, the communication band, and the numher of non-identical ~ilter cavities.
The filters of Figures 2A and 2B are constructed out of square or cylindrical cavities with gradually or successively increa-sing and/or decreasing cross-sectional areas. Such cavities may be cascaded having the cavity with the minimum or maximum cross-sec-tional area at the centre of the filter and repeated pairs of square or cylindrical cavities in such a way that its symmetry is maintained.
In the arrangements of Figures 2A and 2B, by eliminating the spurious responses the cavity volume can be optimized for higher ~5~1~,7 values of unloaded Q's. The location of the tuning screws (not shown) is the same as in the filters of Fig. 1, but the cavity length is equal to n 2 gc, where ~ gc is the cavity guide wave-length and n ls the mode index.
One square four-section elliptic function prototype fil-ter using cavities of heights 0.860 inch and 0.900 inch,and one filter havin~ cylindrical cavities at diam~ters of 1.275 inches and 1.225 inches were both experimented in the 11.7-12.2 G~z communica-tions band. ~oth filters had a bandwidth of 80 M~z and a measured unloaded Q of 8300. The in-band spurious ~ere at a level of 50 dB
below that of the transmitted signal in the passband.
In most communication systems, we are usually concerned with having a 500 MHz band free of any spurious responses. The above-described technique in accordance with the present invention satisfies this requirement. But, if spurious have also to be eliminated at frequencies outside of that band, then the filter may be constructed out of mixed square and cylindrical cavities S' and C', as shown in Fi~. 3. That illustrated arran~ement is even more powerful hecause the behaviour of the two types of cavities is entirely different. ~ combination of both techni~ues ~i.e., a cascade of s~uare and cylindrical cavities with different cross sections), along with modes of different index "n" will give excellent spurious eliminationand unloaded Q performance. The dimensions o the cavities can be calculated using known square or cylindrical mode lattice charts, the frequency location o each spurious can also be evaluated.
In Fig. 3, the square and cylindrical cavities of diffe-rent cross sections are cascaded, in conformity with the methods described in Figs. 2A and 2B above. Such cavity arrangements pro-vide a ilter near its optimum Q at the frequency of interest and,at the same time, eliminate the spurious passbands. In this case, mixed mode cavities can also be employed (i.e., TE103 and TE
mines, and is inversely proportional to, the mid-band insertion loss of a speclfic filter design.
Known rectangular waveguide band-pass filters use s~nchro-nously tuned rectangular cavities in cascade. These filters arecons~
tructed out of a straight waveguide section in which the cavities are formed through the use of inductive posts or irises. A more recent development of waveguide type microwave filters i5 the dual mode filter. Such filters employ square or cylindrical resonators operating in TElol and TElll modes respectively. The length of each cavity is equal to half guide'wave'length at the filter centre fre-quency, and its unloaded Q is approximately equal to the Q of the rectangular waveguide filters. For those types of filters the un-loaded Q decreases with increasing frequency.
The advantages and the construction details of the dual mode filter are described, for example, in Canadian Patent No.
896,116 issued on March 21, 1972, to Blachier et al. It is much lighter than the conventional filters and also its mechanical struc-ture permits to achieve elliptic filter functions.
The types of filter described above can, with care, be realized to exhibit unloaded ~'s of 10,000 at 4 GHz and 5,000 at 12 GHz. This means that the mid-band insertion loss of a filter at 12 GHz, with the same percentage bandwidth and other passband cha-racteristics as one at 4 GHz, will be twice larger. In modern com-munication systems, the realization of filters with higher unloaded Q's, particularly at frequencies above 10 GHz, would be advantageous.
In satellite systems, a second advantage would accrue i~ the volume, and hence the weight of such filters could be minimized.
A prime o~ject of the present invention resides in a 105~27 waveguide bandpass filter which exhibits significantly higher un-loaded Q's than conventional ones, and which therefore promotes a substantially low mid-band insertion loss therein.
In accordance with the present invention, the low-loss bandpass waveguide filter comprises M waveguide resonant cavities provided with intercoupling means, M being an integer, and wherein each cavity has a physical length of "n" times the haLf guide wave-length, where "n" is the third mode index of a TE mode microwave to be transmitted and is larger than one.
Preferred emb~diments of the present invention ~ill be hereinafter described with reference to the accompanying drawings, wherein Figures lA and lB show views, in perspective, of TElo and T~ dual mode bandpass microwave filters in accordance with the lln present invention, which filters are respectively constituted of square and cylindrical cavities of the same cross-sectional area;
Figures lC and lD are cross-sectional views taken along line C-C and line D-D, respectively, of figures lA and lB;
Figures 2A and 2B respectively show square and cylindrical filters provided with cavities of different cross-sectional areas, following another embodiment of the present invention;
Figure 3 depicts a bandpass filter having cascaded cylin-drical and squa~ cavities of cross-sectional areas in accordance with a further embodiment of the present invention.
Figures 4A and 4B illustrate a bandpass filter wherein a single rectangular cavity is cascaded with other square or cylindri-cal cavities, respectively, according to a further embodiment of the present invention.
Figures lA and lB illustrate, in perspective, high Q, low insertion loss, dual mode filters provided with M cascaded cavities each bein~ of a length "1", M ~einq an inte~er.The ilter of figure lA
is a TElon filter macle up of cavities Sl ..Sm of square cross-~ )5C~127 sectional area whereas the ilter of figure lB is a TE ~ filter madeup of cylindrical cavitiesC~ . The cavities composina each filter have the ~ame cross-sectional area and ~ach cavit.v is n ~ g long, where ~ g is the guide wavelength at the centre frequency of the filter. Also, the height or diameter of each cavity is carefully selected from known mode lattice charts for optimum ~ and spurious response elimination. - ~
The reSonance modes TE10 and TElln' where n ls the third mGde index and larger than 1, have been selected in order to accomplish effectivély a reduction in both the insertion loss and the volume of the filter. In the embodiments of figures lA and lB, each increase in the index "n" corresponds to an additional increase of.half a guide wavelength in the length of the cavity.
According to the present invention, by choosing n larger than 1, in connection with the length of each cavity, the unloaded Q of the filter thereby obtained for the TE modes is approximately 60% lar-ger than that of conventional filters, wherein n _ 1. Therefore, with the illustrated filters, unloaded Q optimization in the filter is achieved through a volume optimization of each cavity, which volume is proportional to the length thereof.
Turning again to figures lA and lB, two adjacent cavities of the filters are separated by an intercoupling reElective plate 1 or ~ provided with a slot or iris 1' or 2', and both filters are limited by input ports 3 and 5 and output por~s 4 and 6, res-pectively.
Three tuning screws per cavity are used, these screws being disposed along a predetermined cross-sectional plane in a given cavity. The frequency tuning screws Tl and T2 are 90 apart and are in line with the two orthogonal E field components of the cavity, as better seen from figures lC and lD. The coupling screw .
C can be located at any multiples of 45 with respect to Tl and T2. The length location Ls of the screws is a function of the 5~7 mode index "n" and is equal to Ls = (2K~- 1) Lj where K is any integer ranging from 1 to n. The choices of Ls = Lj/2 for n odd, and Ls close to Lj/2 for n even are preferable, Lj being the length of the cavity.
Two dual mode filters of the type shown in Fig~ lA and lB
were realized in the 11.7-12.2 GHz communications band. Both filters were four-section elliptic function type. The square waveguide type was operated in TE103 mode and i~s side was of 0.860 inch.
The cylindrical waveguide type was operating in TE112 mode and its diameter D was of 1.275 inches. Both filters have a bandwidth of 80 MHz centred on 12 GHz and a measured unloaded Q of 8000. The intercavity coupling was obtained via inductive irises, and the ..
in-band spurious signals at a level of 35 dB below that of the use-ful signal transmitted in the passband.
Figures 2A and 2B show further arrangements of the bandpass of the present invention, wherein the various cascaded cavities Si...S or C ...C ,composing each filter are of different cross-sectional areas for improved elimination of spurious waves. Bv doing so, the spurious of any one cavity do not coincide with the spurious o~ the other cavities, and are therefore attenuated. The attenuation level of the spurious passbands is dependent on the number of filter sections, the communication band, and the numher of non-identical ~ilter cavities.
The filters of Figures 2A and 2B are constructed out of square or cylindrical cavities with gradually or successively increa-sing and/or decreasing cross-sectional areas. Such cavities may be cascaded having the cavity with the minimum or maximum cross-sec-tional area at the centre of the filter and repeated pairs of square or cylindrical cavities in such a way that its symmetry is maintained.
In the arrangements of Figures 2A and 2B, by eliminating the spurious responses the cavity volume can be optimized for higher ~5~1~,7 values of unloaded Q's. The location of the tuning screws (not shown) is the same as in the filters of Fig. 1, but the cavity length is equal to n 2 gc, where ~ gc is the cavity guide wave-length and n ls the mode index.
One square four-section elliptic function prototype fil-ter using cavities of heights 0.860 inch and 0.900 inch,and one filter havin~ cylindrical cavities at diam~ters of 1.275 inches and 1.225 inches were both experimented in the 11.7-12.2 G~z communica-tions band. ~oth filters had a bandwidth of 80 M~z and a measured unloaded Q of 8300. The in-band spurious ~ere at a level of 50 dB
below that of the transmitted signal in the passband.
In most communication systems, we are usually concerned with having a 500 MHz band free of any spurious responses. The above-described technique in accordance with the present invention satisfies this requirement. But, if spurious have also to be eliminated at frequencies outside of that band, then the filter may be constructed out of mixed square and cylindrical cavities S' and C', as shown in Fi~. 3. That illustrated arran~ement is even more powerful hecause the behaviour of the two types of cavities is entirely different. ~ combination of both techni~ues ~i.e., a cascade of s~uare and cylindrical cavities with different cross sections), along with modes of different index "n" will give excellent spurious eliminationand unloaded Q performance. The dimensions o the cavities can be calculated using known square or cylindrical mode lattice charts, the frequency location o each spurious can also be evaluated.
In Fig. 3, the square and cylindrical cavities of diffe-rent cross sections are cascaded, in conformity with the methods described in Figs. 2A and 2B above. Such cavity arrangements pro-vide a ilter near its optimum Q at the frequency of interest and,at the same time, eliminate the spurious passbands. In this case, mixed mode cavities can also be employed (i.e., TE103 and TE
2'7 or TE103 and TE113). The construction de-tails of Figs. lA and ls as well as 2A and 2B remain valid in such fil~er embodiments.
In the above-described bandpass filters, the filter order "N" is also of importance in the selection of filter cavities.
Where "N" is even, the filter can be carried out by using N/2 dual mode physical cavities. For "N" odd, the filter is made up of (N-1)/2 cavities operating in dual mode, and an additional cavity operating in single mode. The symmetry of the filter may be pre-served by placing the single mode cavity at the centre of the filter.
Using the above technique, every filter order can be carried out with the restriction that a gO rotation exists between input-output ports for some "N" values (i.e., N = 6, 7, 10, 11, etc.).
-If port rotation is undesirable, then additional single mode cavi-ties are used to bring the input and output ports in line.
~ igures 4A and 4B show the interconnection of a single mode cavity R in odd ord~,r filters and filters of n~n-rotated input-output ports. A rectangular aavity with a suitably chosen height-~o-width ratio is cascaded between square or cylindrical cavities.
In this case, only one frequency tuning screw ~not shown) is re~ui-red. Cavities of different cross sections, cylindrical or ~qu~re,or both ~an also be used.
A five-section Chebychev function filter incorporating two square cavities of height 0.860 inch operating in dual mode and a single mode centre rectangular cavity having a height of 0.900 inch and a width of 0.800 inch was experimented in the 11.7-12.2 GHz communication band. The filter's unloaded Q was 8000 and its in-band spurious responses at a level of 45 dB below that of the trans-mitted signal in the passband. A further attenuation of the spurious passbands may be achieved when using filter cavities of the type discussed in Figs. 2A, 2B and 3. Bandpass filters having maximally flat or Chebychev or quasi-elliptic responses can be realized using the configurations of Figs. 4A and 4B.
i~ 27 It is to be understood that modifications may be drawn to the above-described, preferred embodiments c the present inven-tion without departing from the ambit thereof which is solely limi-ted by the scope of claims which follow.
. . ,
In the above-described bandpass filters, the filter order "N" is also of importance in the selection of filter cavities.
Where "N" is even, the filter can be carried out by using N/2 dual mode physical cavities. For "N" odd, the filter is made up of (N-1)/2 cavities operating in dual mode, and an additional cavity operating in single mode. The symmetry of the filter may be pre-served by placing the single mode cavity at the centre of the filter.
Using the above technique, every filter order can be carried out with the restriction that a gO rotation exists between input-output ports for some "N" values (i.e., N = 6, 7, 10, 11, etc.).
-If port rotation is undesirable, then additional single mode cavi-ties are used to bring the input and output ports in line.
~ igures 4A and 4B show the interconnection of a single mode cavity R in odd ord~,r filters and filters of n~n-rotated input-output ports. A rectangular aavity with a suitably chosen height-~o-width ratio is cascaded between square or cylindrical cavities.
In this case, only one frequency tuning screw ~not shown) is re~ui-red. Cavities of different cross sections, cylindrical or ~qu~re,or both ~an also be used.
A five-section Chebychev function filter incorporating two square cavities of height 0.860 inch operating in dual mode and a single mode centre rectangular cavity having a height of 0.900 inch and a width of 0.800 inch was experimented in the 11.7-12.2 GHz communication band. The filter's unloaded Q was 8000 and its in-band spurious responses at a level of 45 dB below that of the trans-mitted signal in the passband. A further attenuation of the spurious passbands may be achieved when using filter cavities of the type discussed in Figs. 2A, 2B and 3. Bandpass filters having maximally flat or Chebychev or quasi-elliptic responses can be realized using the configurations of Figs. 4A and 4B.
i~ 27 It is to be understood that modifications may be drawn to the above-described, preferred embodiments c the present inven-tion without departing from the ambit thereof which is solely limi-ted by the scope of claims which follow.
. . ,
Claims (9)
1. A low insertion loss waveguide band pass filter, comprising M waveguide resonant cavities provided with inter-coupling means, M being an integer, each of said cavities having a physical length equal to "n" times the half guide wavelength, where "n" corresponds to the third mode index of a TE mode microwave, to be transmitted and is at least larger than one.
2. A filter as claimed in claim 1, wherein said filter is a dual mode filter and said cavities are of a same cross-sectional area, each cavity having a length equal to n times the half guide wavelength at the centre frequency of the filter.
3. A filter as claimed in claim 1, wherein at least one of said cavities is of a different cross-sectional area than the other cavities, each cavity being of a length equating n times the half-guide wavelength thereof.
4. A filter as claimed in claims 2 or 3, wherein all of said cavities have a square cross-sectional area.
5. A filter as claimed in claim 2 or 3, wherein all said cavities are cylindrical.
6. A filter as claimed in claims 2 or 3, wherein at least one of said cavities has a square cross-sectional area and the remaining cavities are cylindrical.
7. A filter as claimed in claims 1, 2 or 3, further characterized in that said filter is of order N, N being an even integer, and that the number M of cavities is equal to ?.
8. A filter as claimed in claims 1, 2 or 3, further characterized in that said filter is of order M, N being an odd integer, and that the number M of cavities is equal to cavities operating in dual mode plus at least one single mode cavity.
9. A filter as claimed in claims 1, 2 or 3, wherein said filter further comprises a rectangular cross-sectional cavity mounted in cascade with said M cavities.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA250,162A CA1050127A (en) | 1976-04-13 | 1976-04-13 | Low insertion loss waveguide filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA250,162A CA1050127A (en) | 1976-04-13 | 1976-04-13 | Low insertion loss waveguide filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1050127A true CA1050127A (en) | 1979-03-06 |
Family
ID=4105703
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA250,162A Expired CA1050127A (en) | 1976-04-13 | 1976-04-13 | Low insertion loss waveguide filter |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1050127A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2452801A1 (en) * | 1979-03-29 | 1980-10-24 | Cit Alcatel | MICROWAVE FILTER |
| US4652843A (en) * | 1984-05-28 | 1987-03-24 | Com Dev Ltd. | Planar dual-mode cavity filters including dielectric resonators |
| FR2616972A1 (en) * | 1987-06-22 | 1988-12-23 | Enertec | Frequency-tunable band-pass filter with yttrium iron garnet bead with wide tuning band |
| US5821837A (en) * | 1996-01-30 | 1998-10-13 | Cselt- Centro Studi E Laboratori Telecomunicazioni S.P.A. | Multi-mode cavity for waveguide filters |
| US5894250A (en) * | 1997-03-20 | 1999-04-13 | Adc Solitra, Inc. | Cavity resonator filter structure having improved cavity arrangement |
| US6538535B2 (en) * | 2000-06-05 | 2003-03-25 | Agence Spatiale Europeenne | Dual-mode microwave filter |
-
1976
- 1976-04-13 CA CA250,162A patent/CA1050127A/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2452801A1 (en) * | 1979-03-29 | 1980-10-24 | Cit Alcatel | MICROWAVE FILTER |
| US4652843A (en) * | 1984-05-28 | 1987-03-24 | Com Dev Ltd. | Planar dual-mode cavity filters including dielectric resonators |
| FR2616972A1 (en) * | 1987-06-22 | 1988-12-23 | Enertec | Frequency-tunable band-pass filter with yttrium iron garnet bead with wide tuning band |
| US5821837A (en) * | 1996-01-30 | 1998-10-13 | Cselt- Centro Studi E Laboratori Telecomunicazioni S.P.A. | Multi-mode cavity for waveguide filters |
| US5894250A (en) * | 1997-03-20 | 1999-04-13 | Adc Solitra, Inc. | Cavity resonator filter structure having improved cavity arrangement |
| US6538535B2 (en) * | 2000-06-05 | 2003-03-25 | Agence Spatiale Europeenne | Dual-mode microwave filter |
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