CA2262977C - Elliptic filter and method of making the same - Google Patents
Elliptic filter and method of making the same Download PDFInfo
- Publication number
- CA2262977C CA2262977C CA002262977A CA2262977A CA2262977C CA 2262977 C CA2262977 C CA 2262977C CA 002262977 A CA002262977 A CA 002262977A CA 2262977 A CA2262977 A CA 2262977A CA 2262977 C CA2262977 C CA 2262977C
- Authority
- CA
- Canada
- Prior art keywords
- filter
- baw
- resonator
- resonators
- mode
- 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 - Fee Related
Links
- 238000004519 manufacturing process Methods 0.000 title description 8
- 230000005540 biological transmission Effects 0.000 claims description 17
- 239000003990 capacitor Substances 0.000 claims description 9
- 238000013461 design Methods 0.000 claims description 6
- 230000002238 attenuated effect Effects 0.000 abstract description 4
- 239000000758 substrate Substances 0.000 description 20
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 9
- 238000003780 insertion Methods 0.000 description 6
- 230000037431 insertion Effects 0.000 description 6
- 238000000926 separation method Methods 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 5
- 239000005350 fused silica glass Substances 0.000 description 5
- 239000011787 zinc oxide Substances 0.000 description 5
- 229910052581 Si3N4 Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 4
- 238000004088 simulation Methods 0.000 description 4
- 238000001914 filtration Methods 0.000 description 3
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 230000000873 masking effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052594 sapphire Inorganic materials 0.000 description 2
- 239000010980 sapphire Substances 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- JNDMLEXHDPKVFC-UHFFFAOYSA-N aluminum;oxygen(2-);yttrium(3+) Chemical compound [O-2].[O-2].[O-2].[Al+3].[Y+3] JNDMLEXHDPKVFC-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000001413 cellular effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- PSHMSSXLYVAENJ-UHFFFAOYSA-N dilithium;[oxido(oxoboranyloxy)boranyl]oxy-oxoboranyloxyborinate Chemical compound [Li+].[Li+].O=BOB([O-])OB([O-])OB=O PSHMSSXLYVAENJ-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000001465 metallisation Methods 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
- 229910019901 yttrium aluminum garnet Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezo-electric or electrostrictive material
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02062—Details relating to the vibration mode
- H03H9/02078—Details relating to the vibration mode the vibration mode being overmoded
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H3/04—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezo-electric or electrostrictive material
- H03H9/542—Filters comprising resonators of piezo-electric or electrostrictive material including passive elements
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezo-electric or electrostrictive material
- H03H9/56—Monolithic crystal filters
Abstract
An odd order N-pole, (N-1)/2 zero elliptic filter (300) is provided having ( N- 1)/2 BAW resonators (302 and 304). The first Bulk Acoustic Wave (BAW) resonator (302) operates at a first mode number and a first center frequency and the second BAW resonator (304) operates at a second mode number, and a first centre frequency. Operating BAW resonators (302 and 304) at differing modes allows the unwanted passbands (201) of the first BAW resonators (302) to be attenuated by the stopband of the second BAW resonator (304) and vice ver sa.
Description
W O 98/08303 PCT~US97111392 ELLIPTIC FILTER AND METHOD OF MAKING THE SAME
Field of the Invention The present invention relates generally to broadband filters and, in particular, to broadband elliptic filters made from Overmoded Bulk Acoustic Wave piezoelectric resonators.
Background of the Invention Wideband radio transceivers currently require front-end, broadband filtering. Because of stringent filter specifications of many transceivers (insertion loss, quality factor, size. . ., etc.), expensive front-end filters comprising bulky coaxial resonators in metallic enclosures are 15 typically utilized for broadband filtering. Since next-generation radio transceivers require smaller, less expensive filters, a need exists for a front-end, broadband filter that is less costly and smaller than current filters, yet meets the stringent filter specifications required by many transceivers.
Brief Description of the Drawings FIG. 1 is an over-moded Bulk Acoustic Wave resonator i n 25 accordance with a preferred embodiment of the present invention.
FIG. 2 is a transmission energy versus frequency graph of a Bulk Acoustic Wave resonator operating at mode two.
3 0 FIG. 3 illustrates a broadband filter in accordance with a preferred embodiment of the present invention.
FlGs. 4-6 illustrate attenuation of unwanted passbands i n accordance with a preferred embodiment of the present invention.
WO 98/08303 PCTrUS97/11392 FIG. 7 illustrates a circuit schematic diagram of an elliptic filter in accordance with a preferred embodiment of the present invention.
FlGs. 8 through 10 illustrate a broadband filter on a substrate in 5 accordance with a preferred embodiment of the present invention.
FIG. 11 is a flow chart illustrating manufacture of the filter of FlGs. 8 through 10 in accordance with a preferred embodiment of the present invention.
FlGs. 12 through 18 are specific examples that serve to illustrate the practice of particular embodiments of the present invention.
Detailed Description of the Drawings Stated generally, a broadband elliptic filter is provided having a first Bulk Acoustic Wave (BAW) resonator operating at a first mode 20 number and a first center frequency. A second BAW resonator is provided operating at a second mode number. The first and second BAW
resonators operate at the same center frequency. Operating BAW
resonators at differing modes allows the unwanted passbands of the first BAW resonator to be attenuated by the second BAW resonator. Such an 25 elliptic filter design allows for an N-pole, (N-1)/2 zero elliptic filter having (N-1)/2 BAW resonators, N capacitors, and N transmission lines.
The present invention encompasses a filter having a first BAW
resonator operating at a first mode number and operating at a first center 30 frequency. Additionally, the filter comprises a second BAW resonator operating at a second mode number, and operating at substantially the first center frequency. Such a filter allows for an odd order, N-pole, (N-1)/2 zero filter comprising (N-1)/2 piezoelectric resonators and N
transmission lines.
W 098/08303 PCTrUS97/11392 An alternate embodiment of the present invention encompasses a method of making an odd order, N-pole, (N-1)/2 zero elliptic filter by photolithographically creating on a substrate, a first BAW resonator operating at a first mode number and a first center frequency. A second 5 BAW resonator is photolithographically created on the substrate, the second BAW resonator operates at substantially the first center frequency and at a second mode number.
In order to better illustrate a preferred embodiment of the present 10 invention, it will be beneficial to describe operation of an over-moded BAW resonator. FIG. 1 illustrates a BAW resonator 100 in accordance with a preferred embodiment of the present invention. BAW resonator 100 comprises first electrode 102, first buffer layer 104, piezoelectric film 106, second buffer layer 108, second electrode 1 10, and delay section substrate 112. In a preferred embodiment, electrodes 102 and 110 are Aluminum electrodes, but other highly conductive material (for example, Silver or Gold) may be substituted. Buffer layers 104 and 108 serve to protect piezoelectric film 106 during the manufacturing process, and are preferably Silicon Nitride layers. Additionally, substrate 112 is preferably 20 a Fused Quartz substrate, but other substrates (for example, Lithium Niobate, Dilithium Tetraborate, Yttrium Aluminum Garnet, or Sapphire) can be used as well. As indicated in High-O Microwave Acoustic flesonators and Filters by Kenneth Lakin et al., IEEE Mrr Trans. Dec.
1993, piezoelectric film 106, made from Aluminum Nitride is utilized as a 25 transducer to excite longitudinal waves in substrate 112. In a preferred embodiment of the present invention piezoelectric film 106 is a Zinc Oxide film utilized because of the larger electromechanical coupling coefficient needed in broad band filters.
BAW resonator 100 is capable of achieving very large quality factor (Q) values provided substrate 112 comprises a material with very Iow acoustic loss and mode numbers of more than one are used. ("Mode number" is defined as the ratio of the acoustic half wavelengths of substrate 112 thickness to the acoustic half wavelength of piezoelectric film 106. For example, as described in Lakin et al., a 1.6 Gltz BAW
W O 98/08303 KCTrUS97111392 resonator 100 with piezoelectric film 106 made of Aluminum Nitride and having 650 micrometer thick Sapphire substrate 112, corresponding to an acoustic half wavelength fundamental resonance of 8.648648 MHz, would be operating at 160018.648648=185, or mode 185, and have an 5 unloaded Q of 68,000). Large Q values, however, come at a trade off of decreased filter bandwidlh. In a preferred embodiment of the present invention, a compromise between Q and filter bandwidth is made such that BAW resonator 100 operates at a lower mode number (below 20) in order to obtain the necess~ry bandwidth for front-end, broadband filtering 1 0 requirements.
Elliptic or Cauer filter bandwidth depends on low pass prototype reflection coefficient (p~-ssb~nd ripple), ultimate attenuation required in the stop band, and available resonator shunt to motional capacitance 15 ratio at the working mode. Largest bandwidths are obtained with filters having the lowest stopband attenuation. For a given stopband attenuation the theoretical maximum ripple bandwidth is equal to:
where:
Fo = filter center frequency (Hz), r= resonator (shunt to series) capacitance ratio at the operating mode, 25 and C2~L2 is the smallest product of adjacent, normalized L and C values in standard Cauer low-pass prototype filter tables.
BAW resonator 100 additionally has the property of creati ng 30 unwanted spurious responses that exist at frequencies on either side of the resonator center frequency. This can be seen in FIG. 2, where a transmission energy versus frequency graph of a mode two BAW
resonator 100 is shown. Unwanted spurious responses 201 (referred to as unwanted passbands in a filter context) exist at equal spacing from the 35 center frequency fO on the low and high frequency side of center W 098/08303 PCT~US97/11392 frequency 203 tonly low side unwanted passbands 201 are shown).
Unwanted passbands 201 exist due to the harmonics of substrate 112's fundamental acoustic resonance. Thus for BAW resonator 100 operating at mode number ~, there will be ~ unwanted p~ssb~nds 201. The S approximate frequency locations of unwanted p~ssb~nds 203 are given by the formula:
Fspur(n)=fo +m(fO /(m+1)) for m=1,2,.. ,n (2) 1 0 where FSpur (m) = m th spurious pass band frequency to = filter center frequency n = resonator mode number 1 5 m = spurious number from center frequency.
FIG. 3 illustrates a broadband filter 300 in accordance with a preferred embodiment of the present invention. Filter 300 comprises over-moded BAW resonator 302, overmoded BAW resonator 304 operating at the same center frequency as BAW resonator 302, and coplanar waveguide transmission lines 306-314. In a preferred embodiment of the present invention, filter 300 is an odd order Cauer filter since even ordered filters require the output resonator to be a series LC circuit that cannot be synthesized with the use of BAW resonators like 302 and 304 Although broadband filter 300 is shown as a 5-pole, 2 zero elliptic filter, in alternate embodiments of the present invention, broadband filter 300 can be any odd order N-pole, (N-1)/2 zero elliptic filter with a similar BAW resonator configuration, resulting in an N-pole, (N-1)/2 zero elliptic filter having (N-1)/2 BAW resonators, N capacitors, and N transmission lines. Designing an N-pole, (N-1)/2 zero elliptic filter 300 with (N-1)/2 piezoelectric resonators 302, 304 and N transmission Iines 306-314, halves the number of resonators 302, 304 required to achieve a given filter selectivity, has a lower insertion loss, and allows for the manufacture of a front-end, broadband filter that is less costly and smaller than current comb filters in metallic enclosures. Additionally, W O 98/08303 PCTrUS97/11392 such a filter continues to meet the stringent ~ilter specifications required by many transceivers.
As discussed above, in a preferred embodiment of the present invention, filter 300 is designed with the aid of transmission ~ines 306-314 forming shorted or open stubs to replace the design coils. This is done in order to minimize insertion loss when coils of the required inductance have insufficient Q. Additionally, transmission lines 306-314 are inserted in order to increase the bandwidth obtainable with BAW resonators 302 and 304 alone. As discussed below, filter 300 can meet the insertion loss specification of many cellular wideband filters when manufactured with coils having Q as low as 250 to 300 provided that the resonator's Q is above 3,000 (a Q requirement that can be met only by Overmoded BAW
resonators working at mode numbers between 2 and 6 when using Fused Quartz substrates).
Simulated Zinc Oxide BAW resonators on Fused Quartz substrates at 836.5 MHz, using the K.L.M. model referenced in the paper "New Equivalent Circuits for Elementary Piezoelectric Transducers" written by R. Krimholtz et al. and published in Electronic Letters Vol. 6 No.13,25 ~une 1970, gave the parameters shown in table I below for a BAW
resonator having a shunt capacitance o~ 1 pF.
Mode Cap. ratio Theoretical maxQTypical Lm 0 (ZnO alone) 12.747 1,777 458.432 nH
18.087 2,446 650.501 nH
Field of the Invention The present invention relates generally to broadband filters and, in particular, to broadband elliptic filters made from Overmoded Bulk Acoustic Wave piezoelectric resonators.
Background of the Invention Wideband radio transceivers currently require front-end, broadband filtering. Because of stringent filter specifications of many transceivers (insertion loss, quality factor, size. . ., etc.), expensive front-end filters comprising bulky coaxial resonators in metallic enclosures are 15 typically utilized for broadband filtering. Since next-generation radio transceivers require smaller, less expensive filters, a need exists for a front-end, broadband filter that is less costly and smaller than current filters, yet meets the stringent filter specifications required by many transceivers.
Brief Description of the Drawings FIG. 1 is an over-moded Bulk Acoustic Wave resonator i n 25 accordance with a preferred embodiment of the present invention.
FIG. 2 is a transmission energy versus frequency graph of a Bulk Acoustic Wave resonator operating at mode two.
3 0 FIG. 3 illustrates a broadband filter in accordance with a preferred embodiment of the present invention.
FlGs. 4-6 illustrate attenuation of unwanted passbands i n accordance with a preferred embodiment of the present invention.
WO 98/08303 PCTrUS97/11392 FIG. 7 illustrates a circuit schematic diagram of an elliptic filter in accordance with a preferred embodiment of the present invention.
FlGs. 8 through 10 illustrate a broadband filter on a substrate in 5 accordance with a preferred embodiment of the present invention.
FIG. 11 is a flow chart illustrating manufacture of the filter of FlGs. 8 through 10 in accordance with a preferred embodiment of the present invention.
FlGs. 12 through 18 are specific examples that serve to illustrate the practice of particular embodiments of the present invention.
Detailed Description of the Drawings Stated generally, a broadband elliptic filter is provided having a first Bulk Acoustic Wave (BAW) resonator operating at a first mode 20 number and a first center frequency. A second BAW resonator is provided operating at a second mode number. The first and second BAW
resonators operate at the same center frequency. Operating BAW
resonators at differing modes allows the unwanted passbands of the first BAW resonator to be attenuated by the second BAW resonator. Such an 25 elliptic filter design allows for an N-pole, (N-1)/2 zero elliptic filter having (N-1)/2 BAW resonators, N capacitors, and N transmission lines.
The present invention encompasses a filter having a first BAW
resonator operating at a first mode number and operating at a first center 30 frequency. Additionally, the filter comprises a second BAW resonator operating at a second mode number, and operating at substantially the first center frequency. Such a filter allows for an odd order, N-pole, (N-1)/2 zero filter comprising (N-1)/2 piezoelectric resonators and N
transmission lines.
W 098/08303 PCTrUS97/11392 An alternate embodiment of the present invention encompasses a method of making an odd order, N-pole, (N-1)/2 zero elliptic filter by photolithographically creating on a substrate, a first BAW resonator operating at a first mode number and a first center frequency. A second 5 BAW resonator is photolithographically created on the substrate, the second BAW resonator operates at substantially the first center frequency and at a second mode number.
In order to better illustrate a preferred embodiment of the present 10 invention, it will be beneficial to describe operation of an over-moded BAW resonator. FIG. 1 illustrates a BAW resonator 100 in accordance with a preferred embodiment of the present invention. BAW resonator 100 comprises first electrode 102, first buffer layer 104, piezoelectric film 106, second buffer layer 108, second electrode 1 10, and delay section substrate 112. In a preferred embodiment, electrodes 102 and 110 are Aluminum electrodes, but other highly conductive material (for example, Silver or Gold) may be substituted. Buffer layers 104 and 108 serve to protect piezoelectric film 106 during the manufacturing process, and are preferably Silicon Nitride layers. Additionally, substrate 112 is preferably 20 a Fused Quartz substrate, but other substrates (for example, Lithium Niobate, Dilithium Tetraborate, Yttrium Aluminum Garnet, or Sapphire) can be used as well. As indicated in High-O Microwave Acoustic flesonators and Filters by Kenneth Lakin et al., IEEE Mrr Trans. Dec.
1993, piezoelectric film 106, made from Aluminum Nitride is utilized as a 25 transducer to excite longitudinal waves in substrate 112. In a preferred embodiment of the present invention piezoelectric film 106 is a Zinc Oxide film utilized because of the larger electromechanical coupling coefficient needed in broad band filters.
BAW resonator 100 is capable of achieving very large quality factor (Q) values provided substrate 112 comprises a material with very Iow acoustic loss and mode numbers of more than one are used. ("Mode number" is defined as the ratio of the acoustic half wavelengths of substrate 112 thickness to the acoustic half wavelength of piezoelectric film 106. For example, as described in Lakin et al., a 1.6 Gltz BAW
W O 98/08303 KCTrUS97111392 resonator 100 with piezoelectric film 106 made of Aluminum Nitride and having 650 micrometer thick Sapphire substrate 112, corresponding to an acoustic half wavelength fundamental resonance of 8.648648 MHz, would be operating at 160018.648648=185, or mode 185, and have an 5 unloaded Q of 68,000). Large Q values, however, come at a trade off of decreased filter bandwidlh. In a preferred embodiment of the present invention, a compromise between Q and filter bandwidth is made such that BAW resonator 100 operates at a lower mode number (below 20) in order to obtain the necess~ry bandwidth for front-end, broadband filtering 1 0 requirements.
Elliptic or Cauer filter bandwidth depends on low pass prototype reflection coefficient (p~-ssb~nd ripple), ultimate attenuation required in the stop band, and available resonator shunt to motional capacitance 15 ratio at the working mode. Largest bandwidths are obtained with filters having the lowest stopband attenuation. For a given stopband attenuation the theoretical maximum ripple bandwidth is equal to:
where:
Fo = filter center frequency (Hz), r= resonator (shunt to series) capacitance ratio at the operating mode, 25 and C2~L2 is the smallest product of adjacent, normalized L and C values in standard Cauer low-pass prototype filter tables.
BAW resonator 100 additionally has the property of creati ng 30 unwanted spurious responses that exist at frequencies on either side of the resonator center frequency. This can be seen in FIG. 2, where a transmission energy versus frequency graph of a mode two BAW
resonator 100 is shown. Unwanted spurious responses 201 (referred to as unwanted passbands in a filter context) exist at equal spacing from the 35 center frequency fO on the low and high frequency side of center W 098/08303 PCT~US97/11392 frequency 203 tonly low side unwanted passbands 201 are shown).
Unwanted passbands 201 exist due to the harmonics of substrate 112's fundamental acoustic resonance. Thus for BAW resonator 100 operating at mode number ~, there will be ~ unwanted p~ssb~nds 201. The S approximate frequency locations of unwanted p~ssb~nds 203 are given by the formula:
Fspur(n)=fo +m(fO /(m+1)) for m=1,2,.. ,n (2) 1 0 where FSpur (m) = m th spurious pass band frequency to = filter center frequency n = resonator mode number 1 5 m = spurious number from center frequency.
FIG. 3 illustrates a broadband filter 300 in accordance with a preferred embodiment of the present invention. Filter 300 comprises over-moded BAW resonator 302, overmoded BAW resonator 304 operating at the same center frequency as BAW resonator 302, and coplanar waveguide transmission lines 306-314. In a preferred embodiment of the present invention, filter 300 is an odd order Cauer filter since even ordered filters require the output resonator to be a series LC circuit that cannot be synthesized with the use of BAW resonators like 302 and 304 Although broadband filter 300 is shown as a 5-pole, 2 zero elliptic filter, in alternate embodiments of the present invention, broadband filter 300 can be any odd order N-pole, (N-1)/2 zero elliptic filter with a similar BAW resonator configuration, resulting in an N-pole, (N-1)/2 zero elliptic filter having (N-1)/2 BAW resonators, N capacitors, and N transmission lines. Designing an N-pole, (N-1)/2 zero elliptic filter 300 with (N-1)/2 piezoelectric resonators 302, 304 and N transmission Iines 306-314, halves the number of resonators 302, 304 required to achieve a given filter selectivity, has a lower insertion loss, and allows for the manufacture of a front-end, broadband filter that is less costly and smaller than current comb filters in metallic enclosures. Additionally, W O 98/08303 PCTrUS97/11392 such a filter continues to meet the stringent ~ilter specifications required by many transceivers.
As discussed above, in a preferred embodiment of the present invention, filter 300 is designed with the aid of transmission ~ines 306-314 forming shorted or open stubs to replace the design coils. This is done in order to minimize insertion loss when coils of the required inductance have insufficient Q. Additionally, transmission lines 306-314 are inserted in order to increase the bandwidth obtainable with BAW resonators 302 and 304 alone. As discussed below, filter 300 can meet the insertion loss specification of many cellular wideband filters when manufactured with coils having Q as low as 250 to 300 provided that the resonator's Q is above 3,000 (a Q requirement that can be met only by Overmoded BAW
resonators working at mode numbers between 2 and 6 when using Fused Quartz substrates).
Simulated Zinc Oxide BAW resonators on Fused Quartz substrates at 836.5 MHz, using the K.L.M. model referenced in the paper "New Equivalent Circuits for Elementary Piezoelectric Transducers" written by R. Krimholtz et al. and published in Electronic Letters Vol. 6 No.13,25 ~une 1970, gave the parameters shown in table I below for a BAW
resonator having a shunt capacitance o~ 1 pF.
Mode Cap. ratio Theoretical maxQTypical Lm 0 (ZnO alone) 12.747 1,777 458.432 nH
18.087 2,446 650.501 nH
2 23.428 3,075 842.582 nH
3 28.769 3,669 1.0346 uH
4 34.111 4,230 1.22677 uH
39.452 4,760 1.4189 uH
6 44.795 5,263 1.61101 uH
Table I
25 Overmoded Resonators -Zinc Oxide on Fused Quartz at 836.5 MHz W 098/08303 PCTrUS97/11392 In many transceiver applications, filter 300 requires a minimum capacitance ratio of 44 and unloaded Q of at least 3,000 hence, in a preferred embodiment of the present invention mode 2 through 6 resonators are used.
As illustrated in FIG. 2, when filter 300 is built with resonators 302, 304, each operating at the same mode, secondary p~ssb~nds 201 appear at the approximate frequencies predicted by equation (2).
Because spurious unwanted p~ssb~nds are typically unacceptable if at 1 0 levels less than 2~ dB below the passband insertion loss, in receiver front end applications it is highly desirable to attenuate all the spurious p~ssb~nds 201 at least 25 dB. In order to accomplish this, in a preferred embodiment of the present invention BAW resonator 302 operates at a different mode than BAW resonator 304. Designing filter 300 in such a way will result in the stop band of one resonator attenuating the spurious pass bands of the other.
Although BAW resonators 302 and 304 can be designed any number of modes apart (within the limits indicated above), in a preferred embodiment of the present invention, BAW resonator 302 is designed to - operate at one or two mode below that of BAW resonator 304. The improvement obtained by designing BAW resonator 302 one mode lower than that of BAW resonator 304 is illustrated in FlGs. 4-6. FlGs. 4 and 5 illustrate unwanted passbands 201 for filter 300 designed with BAW
resonator 302 and 304, each operating at mode two and mode three respectively. FIG. 6 illustrates operation of filter 300 with BAW resonator 302 operating at mode two and BAW resonator 304 operating at mode three, with both BAW resonators 302 and 304 operating at the same center frequency. As is evident, designing BAW resonators 302 and 304 with a one mode separation, allows the stop band of one resonator to attenuate the spurious pass bands of the other, resulting in most unwanted passbands 201 being attenuated. In a preferred embodiment of the present invention, the highest two modes are used since the unwanted passbands 201 closest to the p~ssb~nd 203 are higher in level and more difficult to attenuate. In a preferred embodiment of the present . .
W O 98/08303 PCT~US97/11392 invention filter 300 is designed with BAW resonators 302 and 304 operating at modes 2 and 3 or at modes 3 and 4.
In an alternate embodiment of the present invention, unwanted p~-ssb~nds 201 are attenuated by offsetting piezoelectric film 104 thickness between BAW resonator 302 and BAW resonator 304, and compensating the change in center frequency by changing the thickness of electrode 102 accordingly. Such a filter 300 will displace the frequency of unwanted p~ssb~nds 201 of BAW resonator 302 from those of BAW resonator 304 so that the stop band of one resonator attenuates the spurious passb~nds of the other.
FIG. 7 illustrates a circuit schematic diagram of elliptic filter 300 in accordance with a preferred embodiment of the present invention. As disclJssed above, filter 300 is derived from a low pass Cauer C05 10 25 type filter consisting of five parallel LCR and 2 series LCR circuits, all resonant at the same center frequency. In a preferred embodiment of the present invention, the series resonant circuits and two of the shunt capacitors of filter 300 are replaced by the equivalent series LC circuits of BAW resonators 302 and 304, allowing filter 300 to be designed with two piezoelectric resonators. As mentioned above, BAW resonator 302 operates at a different mode than BAW resonator 304, allowing for the stop band of one resonator to attenuate the unwanted passbands of the other. Replacing series resonant circuits and capacitors (CP2 and CP4) of filter 300 with piezoelectric resonators 302, 304 allows for the manufacture of a N-pole, (N-1)/2 zero elliptic front-end, broadband filter 300 comprising only (N-1)/2 piezoelectric resonators. Such a filter 300 is less costly and smaller than current filters, yet meets the stringent filter specifications required by many transceivers.
FlGs. 8 through 10 illustrate broadband filter 800 manufactured on substrate 811 in accordance with a preferred embodiment of the present invention. Filter 800 is a 5 pole, two-zero elliptic filter of the same design as FIG. 5 comprising two overmoded BAW resonators 802 and 804, five short pieces of coplanar waveguide transmission lines 806, and three W 098/08303 PCT~US97/11392 chip capacitors 803. Filter 800 additionally comprises input 801, output 809, air bridges 805, upper ground plane 807, lower ground plane 813, and resonator wells 815. Since coplanar waveguide stubs function as inductances they can be replaced by other types of transmission lines 5 806, such as, but not limited to ribbon inductances, microstrip, suspended microstrip or stripline, provided they have adequate Q (in a preferred embodiment, about 300). Referring to FlGs. 8 and 10, the length (Iss) of the shorted stubs 810, 812, and 814 are calculated with the equation:
~ctan[l/(WOcP(n)zo)]cn=1l2 and 3 w where:
~0 = Filter radian center frequency ( 2-7~-Fo) Cp(n ) = Stub tuning capacitances Cp1, Cp3, Cp5 Zo = Transmission iines 810, 812, and 814 characteristic impedances ~effr = Substrate relative effective permittivity of the transmission lines c= velocity of light, 2.997925 E8 m/sec.
The length (loS) of open stubs 806 are calculated with the equation:
1O5(n)= n=2 and 4 25 where:
cl)O = Filter radian center frequency ( 2-7~-Fo) Cp(n ) = Resonator 802 and 804 shunt capacitances Cp2 and Cp4 Zo = Transmission lines 806 characteristic impedance ~effr= Substrate relative effective permittivity of the transmission line c= velocity of light, 2.997925 E08 m/sec.
. .
The resonators are designed (when possible) to have their shunt capacitance equal to Cp2 and Cp4. When this is not possible, i.e. when the resonator capacitance ratio is too large, small capacitors of Cp2 - Co1 or Cp4 - Co2 values (Co1 and Co2 are the resonator shunt capacitance) 5 are added and used to compensate for tolerances shifting the center frequency.
In a preferred embodiment of the present invention manufacture of filter 800 occurs as described in reference to FIG. 1 1 . At step 1 102, a 1000 micron thick Fused Quartz substrate 811 with pre-etched resonator wells 815, has deposited on both sides, a .1 micron sublayer of chrome, and a 100 micron top layer of copper protected by a 5 micron layer of Gold. Next, at step 1104, both upper and lower sides of substrate 811 are photolithographically processed to expose the desired metalization pattern, and then chemically etched (step 1106) to achieve the desired topography. At step 1 108, Aluminum electrode 110 (preferably .2 microns thick), is deposited on substrate 811 followed by step 1110 where Silicon Nitride buffer layer 108 (preferably .15 microns thick) is deposited onto the Aluminum electrode 110. Next, at step 1 112, piezoelectric film 106 is deposited on the Silicon Nitride buffer layer. In a preferred embodiment of the present invention (for a 836.~ MHz resonator), piezoelectric film 106 comprises a 3.15177 micron thick layer of Zinc Oxide. At step 1 1 14 a Silicon Nitride buffer layer 104 (preferably .15 microns thick) is deposited on piezoelectric film 106, and finally at step 1116, an Aluminum electrode 104 (preferably .2 microns thick) is deposited onto buffer layer completing the build of the resonator. During the deposition of the various layers, which are carried out in a sputtering machine using a masking operation, interconnections are achieved by means of the masking operations while individual layer thickness are controlled by optical and electrical means monitoring the final calibration frequency.
The process steps described above are then repeated for the second BAW resonator 804 or alternatively using masks that build the two resonators at the same time (except for the final calibration which W O 98/08303 PCT~US97/11392 accounts for slight differences in thickness between the resonators during the deposition of the various layers). At step 1117, the remaining components, including chip capacitors 803 and air bridges 805 are applied to filter 800 and the process flow ends at step 1118.
s Examples The following examples serve to give illustrations of the practice of this invention, and are not intended in any way to limit the scope of the invention. All examples are derived from computer simulated circuits made with the use of a MDS (Microwave Design System) Hewlett Packard computer analysis program. The program allows different elliptic band pass filters to ~e derived from the correspondent low pass prototypes by replacing the low pass normalized L and C ' s such as 1 5 those of the tables in the Handbook for Filter Synthesis. by Zverev.
The graph of FIG. 12 shows insertion and return loss of filter 300 having a 25 MHz bandwidth with a parallel LC circuit Q of 300, and a series LC circuit (circuit's that can be replaced by BAW resonators 302 and 304) having a Q of 800 and infinity. Note that even with the series LC circuits Q of infinity, a flat loss of 1.5 dB occurs at midband and about 3 dB at band edges due to the finite Q of the coils. Additionally, dropping the series LC circuit's Q to 800 added only .5 dB at midband and less than .97 dB at the band edges.
A simulation of filter 300 having BAW resonator 302 with no mode separation (both operating at mode 3), one, and two mode separation from BAW resonator 304 is shown in FlGs. 13-15. As is evident, operation at both a one and two mode separation improve the closer unwanted passbands 201 to at least 32 dB, with operation at two mode separation giving the best overall result. For narrow band filters, where higher mode number resonators can be used, the number of mode separation can be more than two, and depends on the bandwidth and the mode at which the higher mode resonator operates. FIG. 16 illustrates a simulation of filter 300 having resonator 302 operating at mode 2 and CA 02262977 1999-02-08.
W O 98/08303 PCT~US97/11392 resonator 304 at mode 4. When the required Q allows the use of mode 1, similar results can be obtained as shown in FIG. 17, where resonator 302 is operating at mode 1 and resonator 304 at mode 4.
S A simulation of filter 300 having a differing electrode thickness between BAW resonators 302 and 304 is illustrated in FIG. 18. In this simulation BAW resonator 302 comprises electrode 102 having a thickness of .10 micrometers and pie~oelectric thickness of 3.2507 micrometers, with BAW resonalor 304 having electrode 102 thickness of .29 micrometers and piezoelectric thickness of 3.05935 micrometers.
Both BAW resonators 302 and 304 operate at the same center frequency.
As is evident, this method is not as effective as is the method of separating modes between BAW resonators 302 and 304, but still reduces the higher frequency unwanted passband 201 to 22 dB and the 1 S lower frequency unwanted passbands 201 to 43 and 71 dB respectively.
The descriptions of the invention, the specific details, and the drawings mentioned above, are not meant to limit the scope of the present invention. For example, a combination of designing BAW
20 resonators with differing modes and changing piezoelectric film 106 thickness can be utilized to attenuate unwanted p~ssb~nds. Additionally, narrowband filters may utilize the present invention by operating BAW
resonators at higher modes. It is the intent of the inventor that various modifications can be made to the present invention without varying from 25 the spirit and scope of the invention, and it is intended that all such modifications come within the scope of the following claims.
What is claimed is:
39.452 4,760 1.4189 uH
6 44.795 5,263 1.61101 uH
Table I
25 Overmoded Resonators -Zinc Oxide on Fused Quartz at 836.5 MHz W 098/08303 PCTrUS97/11392 In many transceiver applications, filter 300 requires a minimum capacitance ratio of 44 and unloaded Q of at least 3,000 hence, in a preferred embodiment of the present invention mode 2 through 6 resonators are used.
As illustrated in FIG. 2, when filter 300 is built with resonators 302, 304, each operating at the same mode, secondary p~ssb~nds 201 appear at the approximate frequencies predicted by equation (2).
Because spurious unwanted p~ssb~nds are typically unacceptable if at 1 0 levels less than 2~ dB below the passband insertion loss, in receiver front end applications it is highly desirable to attenuate all the spurious p~ssb~nds 201 at least 25 dB. In order to accomplish this, in a preferred embodiment of the present invention BAW resonator 302 operates at a different mode than BAW resonator 304. Designing filter 300 in such a way will result in the stop band of one resonator attenuating the spurious pass bands of the other.
Although BAW resonators 302 and 304 can be designed any number of modes apart (within the limits indicated above), in a preferred embodiment of the present invention, BAW resonator 302 is designed to - operate at one or two mode below that of BAW resonator 304. The improvement obtained by designing BAW resonator 302 one mode lower than that of BAW resonator 304 is illustrated in FlGs. 4-6. FlGs. 4 and 5 illustrate unwanted passbands 201 for filter 300 designed with BAW
resonator 302 and 304, each operating at mode two and mode three respectively. FIG. 6 illustrates operation of filter 300 with BAW resonator 302 operating at mode two and BAW resonator 304 operating at mode three, with both BAW resonators 302 and 304 operating at the same center frequency. As is evident, designing BAW resonators 302 and 304 with a one mode separation, allows the stop band of one resonator to attenuate the spurious pass bands of the other, resulting in most unwanted passbands 201 being attenuated. In a preferred embodiment of the present invention, the highest two modes are used since the unwanted passbands 201 closest to the p~ssb~nd 203 are higher in level and more difficult to attenuate. In a preferred embodiment of the present . .
W O 98/08303 PCT~US97/11392 invention filter 300 is designed with BAW resonators 302 and 304 operating at modes 2 and 3 or at modes 3 and 4.
In an alternate embodiment of the present invention, unwanted p~-ssb~nds 201 are attenuated by offsetting piezoelectric film 104 thickness between BAW resonator 302 and BAW resonator 304, and compensating the change in center frequency by changing the thickness of electrode 102 accordingly. Such a filter 300 will displace the frequency of unwanted p~ssb~nds 201 of BAW resonator 302 from those of BAW resonator 304 so that the stop band of one resonator attenuates the spurious passb~nds of the other.
FIG. 7 illustrates a circuit schematic diagram of elliptic filter 300 in accordance with a preferred embodiment of the present invention. As disclJssed above, filter 300 is derived from a low pass Cauer C05 10 25 type filter consisting of five parallel LCR and 2 series LCR circuits, all resonant at the same center frequency. In a preferred embodiment of the present invention, the series resonant circuits and two of the shunt capacitors of filter 300 are replaced by the equivalent series LC circuits of BAW resonators 302 and 304, allowing filter 300 to be designed with two piezoelectric resonators. As mentioned above, BAW resonator 302 operates at a different mode than BAW resonator 304, allowing for the stop band of one resonator to attenuate the unwanted passbands of the other. Replacing series resonant circuits and capacitors (CP2 and CP4) of filter 300 with piezoelectric resonators 302, 304 allows for the manufacture of a N-pole, (N-1)/2 zero elliptic front-end, broadband filter 300 comprising only (N-1)/2 piezoelectric resonators. Such a filter 300 is less costly and smaller than current filters, yet meets the stringent filter specifications required by many transceivers.
FlGs. 8 through 10 illustrate broadband filter 800 manufactured on substrate 811 in accordance with a preferred embodiment of the present invention. Filter 800 is a 5 pole, two-zero elliptic filter of the same design as FIG. 5 comprising two overmoded BAW resonators 802 and 804, five short pieces of coplanar waveguide transmission lines 806, and three W 098/08303 PCT~US97/11392 chip capacitors 803. Filter 800 additionally comprises input 801, output 809, air bridges 805, upper ground plane 807, lower ground plane 813, and resonator wells 815. Since coplanar waveguide stubs function as inductances they can be replaced by other types of transmission lines 5 806, such as, but not limited to ribbon inductances, microstrip, suspended microstrip or stripline, provided they have adequate Q (in a preferred embodiment, about 300). Referring to FlGs. 8 and 10, the length (Iss) of the shorted stubs 810, 812, and 814 are calculated with the equation:
~ctan[l/(WOcP(n)zo)]cn=1l2 and 3 w where:
~0 = Filter radian center frequency ( 2-7~-Fo) Cp(n ) = Stub tuning capacitances Cp1, Cp3, Cp5 Zo = Transmission iines 810, 812, and 814 characteristic impedances ~effr = Substrate relative effective permittivity of the transmission lines c= velocity of light, 2.997925 E8 m/sec.
The length (loS) of open stubs 806 are calculated with the equation:
1O5(n)= n=2 and 4 25 where:
cl)O = Filter radian center frequency ( 2-7~-Fo) Cp(n ) = Resonator 802 and 804 shunt capacitances Cp2 and Cp4 Zo = Transmission lines 806 characteristic impedance ~effr= Substrate relative effective permittivity of the transmission line c= velocity of light, 2.997925 E08 m/sec.
. .
The resonators are designed (when possible) to have their shunt capacitance equal to Cp2 and Cp4. When this is not possible, i.e. when the resonator capacitance ratio is too large, small capacitors of Cp2 - Co1 or Cp4 - Co2 values (Co1 and Co2 are the resonator shunt capacitance) 5 are added and used to compensate for tolerances shifting the center frequency.
In a preferred embodiment of the present invention manufacture of filter 800 occurs as described in reference to FIG. 1 1 . At step 1 102, a 1000 micron thick Fused Quartz substrate 811 with pre-etched resonator wells 815, has deposited on both sides, a .1 micron sublayer of chrome, and a 100 micron top layer of copper protected by a 5 micron layer of Gold. Next, at step 1104, both upper and lower sides of substrate 811 are photolithographically processed to expose the desired metalization pattern, and then chemically etched (step 1106) to achieve the desired topography. At step 1 108, Aluminum electrode 110 (preferably .2 microns thick), is deposited on substrate 811 followed by step 1110 where Silicon Nitride buffer layer 108 (preferably .15 microns thick) is deposited onto the Aluminum electrode 110. Next, at step 1 112, piezoelectric film 106 is deposited on the Silicon Nitride buffer layer. In a preferred embodiment of the present invention (for a 836.~ MHz resonator), piezoelectric film 106 comprises a 3.15177 micron thick layer of Zinc Oxide. At step 1 1 14 a Silicon Nitride buffer layer 104 (preferably .15 microns thick) is deposited on piezoelectric film 106, and finally at step 1116, an Aluminum electrode 104 (preferably .2 microns thick) is deposited onto buffer layer completing the build of the resonator. During the deposition of the various layers, which are carried out in a sputtering machine using a masking operation, interconnections are achieved by means of the masking operations while individual layer thickness are controlled by optical and electrical means monitoring the final calibration frequency.
The process steps described above are then repeated for the second BAW resonator 804 or alternatively using masks that build the two resonators at the same time (except for the final calibration which W O 98/08303 PCT~US97/11392 accounts for slight differences in thickness between the resonators during the deposition of the various layers). At step 1117, the remaining components, including chip capacitors 803 and air bridges 805 are applied to filter 800 and the process flow ends at step 1118.
s Examples The following examples serve to give illustrations of the practice of this invention, and are not intended in any way to limit the scope of the invention. All examples are derived from computer simulated circuits made with the use of a MDS (Microwave Design System) Hewlett Packard computer analysis program. The program allows different elliptic band pass filters to ~e derived from the correspondent low pass prototypes by replacing the low pass normalized L and C ' s such as 1 5 those of the tables in the Handbook for Filter Synthesis. by Zverev.
The graph of FIG. 12 shows insertion and return loss of filter 300 having a 25 MHz bandwidth with a parallel LC circuit Q of 300, and a series LC circuit (circuit's that can be replaced by BAW resonators 302 and 304) having a Q of 800 and infinity. Note that even with the series LC circuits Q of infinity, a flat loss of 1.5 dB occurs at midband and about 3 dB at band edges due to the finite Q of the coils. Additionally, dropping the series LC circuit's Q to 800 added only .5 dB at midband and less than .97 dB at the band edges.
A simulation of filter 300 having BAW resonator 302 with no mode separation (both operating at mode 3), one, and two mode separation from BAW resonator 304 is shown in FlGs. 13-15. As is evident, operation at both a one and two mode separation improve the closer unwanted passbands 201 to at least 32 dB, with operation at two mode separation giving the best overall result. For narrow band filters, where higher mode number resonators can be used, the number of mode separation can be more than two, and depends on the bandwidth and the mode at which the higher mode resonator operates. FIG. 16 illustrates a simulation of filter 300 having resonator 302 operating at mode 2 and CA 02262977 1999-02-08.
W O 98/08303 PCT~US97/11392 resonator 304 at mode 4. When the required Q allows the use of mode 1, similar results can be obtained as shown in FIG. 17, where resonator 302 is operating at mode 1 and resonator 304 at mode 4.
S A simulation of filter 300 having a differing electrode thickness between BAW resonators 302 and 304 is illustrated in FIG. 18. In this simulation BAW resonator 302 comprises electrode 102 having a thickness of .10 micrometers and pie~oelectric thickness of 3.2507 micrometers, with BAW resonalor 304 having electrode 102 thickness of .29 micrometers and piezoelectric thickness of 3.05935 micrometers.
Both BAW resonators 302 and 304 operate at the same center frequency.
As is evident, this method is not as effective as is the method of separating modes between BAW resonators 302 and 304, but still reduces the higher frequency unwanted passband 201 to 22 dB and the 1 S lower frequency unwanted passbands 201 to 43 and 71 dB respectively.
The descriptions of the invention, the specific details, and the drawings mentioned above, are not meant to limit the scope of the present invention. For example, a combination of designing BAW
20 resonators with differing modes and changing piezoelectric film 106 thickness can be utilized to attenuate unwanted p~ssb~nds. Additionally, narrowband filters may utilize the present invention by operating BAW
resonators at higher modes. It is the intent of the inventor that various modifications can be made to the present invention without varying from 25 the spirit and scope of the invention, and it is intended that all such modifications come within the scope of the following claims.
What is claimed is:
Claims (9)
1. A filter comprising:
a first Bulk Acoustic Wave (BAW) resonator operating at a first mode number, and having a first electrode thickness, said BAW resonator operating at a first center frequency; and a second BAW resonator operating at a second mode number differing from the first mode number, and having a second electrode thickness, said BAW resonator operating at substantially the first center frequency.
a first Bulk Acoustic Wave (BAW) resonator operating at a first mode number, and having a first electrode thickness, said BAW resonator operating at a first center frequency; and a second BAW resonator operating at a second mode number differing from the first mode number, and having a second electrode thickness, said BAW resonator operating at substantially the first center frequency.
2. The filter of claim 1 wherein the first electrode thickness is unequal to the second electrode thickness.
3. The filter of claim 1 further comprising a transmission line coupled to the first BAW resonator.
4. The filter of claim 1 further comprising a design coil coupled to the first BAW resonator.
5. The filter of claim 1 further comprising a capacitor coupled to the first BAW resonator.
6. An odd order, N-pole, (N-1)/2 zero filter comprising:
(N-1)/2 [piezoelectric] bulk acoustic wave (BAW) resonators. where N>4 and a mode number of at least two resonators differ; and N components selected from the group consisting of design coils and transmission lines.
(N-1)/2 [piezoelectric] bulk acoustic wave (BAW) resonators. where N>4 and a mode number of at least two resonators differ; and N components selected from the group consisting of design coils and transmission lines.
7. The filter of claim 6 further comprising N capacitors.
8. The filter of claim 6 wherein the piezoelectric resonators are Bulk Acoustic Wave Resonators.
9. The filter of claim 8 wherein a mode number of the first and the second BAW resonators differ.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/701,825 US5760663A (en) | 1996-08-23 | 1996-08-23 | Elliptic baw resonator filter and method of making the same |
| US08/701,825 | 1996-08-23 | ||
| PCT/US1997/011392 WO1998008303A1 (en) | 1996-08-23 | 1997-07-01 | Elliptic filter and method of making the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2262977A1 CA2262977A1 (en) | 1998-02-26 |
| CA2262977C true CA2262977C (en) | 2001-11-06 |
Family
ID=24818833
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002262977A Expired - Fee Related CA2262977C (en) | 1996-08-23 | 1997-07-01 | Elliptic filter and method of making the same |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5760663A (en) |
| EP (1) | EP0922329A4 (en) |
| JP (1) | JP2001523405A (en) |
| KR (1) | KR100321555B1 (en) |
| AU (1) | AU708019B2 (en) |
| CA (1) | CA2262977C (en) |
| WO (1) | WO1998008303A1 (en) |
Families Citing this family (27)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6239536B1 (en) * | 1998-09-08 | 2001-05-29 | Tfr Technologies, Inc. | Encapsulated thin-film resonator and fabrication method |
| US6339276B1 (en) * | 1999-11-01 | 2002-01-15 | Agere Systems Guardian Corp. | Incremental tuning process for electrical resonators based on mechanical motion |
| FI107661B (en) | 1999-11-29 | 2001-09-14 | Nokia Mobile Phones Ltd | A method for adjusting the center frequency of a balanced filter and a plurality of balanced filters |
| US6746577B1 (en) | 1999-12-16 | 2004-06-08 | Agere Systems, Inc. | Method and apparatus for thickness control and reproducibility of dielectric film deposition |
| US6524971B1 (en) | 1999-12-17 | 2003-02-25 | Agere Systems, Inc. | Method of deposition of films |
| DE19962028A1 (en) * | 1999-12-22 | 2001-06-28 | Philips Corp Intellectual Pty | Filter arrangement |
| US6377136B1 (en) | 2000-02-04 | 2002-04-23 | Agere Systems Guardian Corporation | Thin film resonator filter having at least one component with different resonant frequency sets or electrode capacitance |
| US6306313B1 (en) | 2000-02-04 | 2001-10-23 | Agere Systems Guardian Corp. | Selective etching of thin films |
| US6437667B1 (en) | 2000-02-04 | 2002-08-20 | Agere Systems Guardian Corp. | Method of tuning thin film resonator filters by removing or adding piezoelectric material |
| US6323744B1 (en) | 2000-02-04 | 2001-11-27 | Agere Systems Guardian Corp. | Grounding of TFR ladder filters |
| US7296329B1 (en) | 2000-02-04 | 2007-11-20 | Agere Systems Inc. | Method of isolation for acoustic resonator device |
| US6603241B1 (en) | 2000-05-23 | 2003-08-05 | Agere Systems, Inc. | Acoustic mirror materials for acoustic devices |
| US6355498B1 (en) | 2000-08-11 | 2002-03-12 | Agere Systems Guartian Corp. | Thin film resonators fabricated on membranes created by front side releasing |
| US6486751B1 (en) | 2000-09-26 | 2002-11-26 | Agere Systems Inc. | Increased bandwidth thin film resonator having a columnar structure |
| US6674291B1 (en) * | 2000-10-30 | 2004-01-06 | Agere Systems Guardian Corp. | Method and apparatus for determining and/or improving high power reliability in thin film resonator devices, and a thin film resonator device resultant therefrom |
| US6587212B1 (en) | 2000-10-31 | 2003-07-01 | Agere Systems Inc. | Method and apparatus for studying vibrational modes of an electro-acoustic device |
| US6743731B1 (en) | 2000-11-17 | 2004-06-01 | Agere Systems Inc. | Method for making a radio frequency component and component produced thereby |
| US7435613B2 (en) | 2001-02-12 | 2008-10-14 | Agere Systems Inc. | Methods of fabricating a membrane with improved mechanical integrity |
| EP1455448B1 (en) * | 2001-12-14 | 2008-09-24 | Mitsubishi Electric Corporation | Filter circuitry |
| DE10234980B4 (en) * | 2002-07-31 | 2018-01-04 | Snaptrack, Inc. | Resistant to resonant acoustic wave resonator |
| DE10316716A1 (en) * | 2003-04-11 | 2004-10-28 | Epcos Ag | Component with a piezoelectric functional layer |
| GB0308913D0 (en) * | 2003-04-17 | 2003-05-21 | Koninkl Philips Electronics Nv | Method of, and circuit for,broadening the frequency band of frequency dependentloads |
| JP2005136467A (en) * | 2003-10-28 | 2005-05-26 | Tdk Corp | Piezoelectric resonator and electronic component employing same |
| WO2010138838A1 (en) * | 2009-05-28 | 2010-12-02 | Northrop Grumman Systems Corporation | Lateral over-moded bulk acoustic resonators |
| KR101716335B1 (en) * | 2010-12-03 | 2017-03-15 | 삼성전자주식회사 | Low pass filter using bulk acoustic wave resonator |
| CN111587536B (en) * | 2018-01-12 | 2024-01-19 | 株式会社村田制作所 | Elastic wave device, multiplexer, high frequency front-end circuit and communication device |
| DE102018105091A1 (en) * | 2018-03-06 | 2019-09-12 | RF360 Europe GmbH | RF filter, RF filter component and method of making an RF filter |
Family Cites Families (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3609601A (en) * | 1970-01-12 | 1971-09-28 | Collins Radio Co | Monolithic filter having "m" derived characteristics |
| US4052251A (en) * | 1976-03-02 | 1977-10-04 | Rca Corporation | Method of etching sapphire utilizing sulfur hexafluoride |
| US4156214A (en) * | 1977-01-14 | 1979-05-22 | Motorola, Inc. | Multipole resonator |
| US4245193A (en) * | 1978-08-09 | 1981-01-13 | Harris Corporation | High-Q multi-mode resonator controlled source |
| US4785269A (en) * | 1986-05-15 | 1988-11-15 | Westinghouse Electric Corp. | Magnetically tuned high overtone bulk acoustic resonator |
| US5194836A (en) * | 1990-03-26 | 1993-03-16 | Westinghouse Electric Corp. | Thin film, microwave frequency manifolded filter bank |
| US5231327A (en) * | 1990-12-14 | 1993-07-27 | Tfr Technologies, Inc. | Optimized piezoelectric resonator-based networks |
| US5233259A (en) * | 1991-02-19 | 1993-08-03 | Westinghouse Electric Corp. | Lateral field FBAR |
| US5185589A (en) * | 1991-05-17 | 1993-02-09 | Westinghouse Electric Corp. | Microwave film bulk acoustic resonator and manifolded filter bank |
| US5294898A (en) * | 1992-01-29 | 1994-03-15 | Motorola, Inc. | Wide bandwidth bandpass filter comprising parallel connected piezoelectric resonators |
| US5291159A (en) * | 1992-07-20 | 1994-03-01 | Westinghouse Electric Corp. | Acoustic resonator filter with electrically variable center frequency and bandwidth |
| US5382930A (en) * | 1992-12-21 | 1995-01-17 | Trw Inc. | Monolithic multipole filters made of thin film stacked crystal filters |
| US5373268A (en) * | 1993-02-01 | 1994-12-13 | Motorola, Inc. | Thin film resonator having stacked acoustic reflecting impedance matching layers and method |
| US5446306A (en) * | 1993-12-13 | 1995-08-29 | Trw Inc. | Thin film voltage-tuned semiconductor bulk acoustic resonator (SBAR) |
-
1996
- 1996-08-23 US US08/701,825 patent/US5760663A/en not_active Expired - Fee Related
-
1997
- 1997-07-01 KR KR1019997001457A patent/KR100321555B1/en not_active IP Right Cessation
- 1997-07-01 AU AU35866/97A patent/AU708019B2/en not_active Ceased
- 1997-07-01 EP EP97932402A patent/EP0922329A4/en not_active Withdrawn
- 1997-07-01 WO PCT/US1997/011392 patent/WO1998008303A1/en not_active Application Discontinuation
- 1997-07-01 CA CA002262977A patent/CA2262977C/en not_active Expired - Fee Related
- 1997-07-01 JP JP51072598A patent/JP2001523405A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| US5760663A (en) | 1998-06-02 |
| EP0922329A4 (en) | 2004-09-08 |
| AU708019B2 (en) | 1999-07-29 |
| EP0922329A1 (en) | 1999-06-16 |
| JP2001523405A (en) | 2001-11-20 |
| KR100321555B1 (en) | 2002-01-23 |
| KR20000068306A (en) | 2000-11-25 |
| AU3586697A (en) | 1998-03-06 |
| CA2262977A1 (en) | 1998-02-26 |
| WO1998008303A1 (en) | 1998-02-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2262977C (en) | Elliptic filter and method of making the same | |
| DE69838195T2 (en) | Filters with stacked thin-film filter structures and thin-film resonators with bulk acoustic waves | |
| EP1432133B1 (en) | Duplexer and communication apparatus | |
| US7616079B2 (en) | Bulk acoustic wave resonator and circuit comprising same | |
| US5502422A (en) | Filter with an adjustable shunt zero | |
| JP4468185B2 (en) | Cavity filter structure with equal resonant frequency | |
| CN111327288B (en) | Bulk acoustic wave resonator, ultra-narrow band filter, duplexer and multiplexer | |
| KR101238359B1 (en) | Duplexer | |
| JP2018129683A (en) | Filter circuit, multiplexer, and module | |
| JP2006513662A5 (en) | ||
| WO1992017914A1 (en) | Half wave resonator dielectric filter construction having self-shielding top and bottom surfaces | |
| DE102014102521B4 (en) | Tunable RF filter circuit | |
| KR20020029922A (en) | Bulk accoustic wave filter | |
| US7791436B2 (en) | Radio frequency filter having coupled transmission lines and an acoustic impedance element | |
| CN115833783A (en) | Wide-passband film bulk acoustic wave trap structure | |
| US3697903A (en) | Equal-resonator piezoelectric ladder filters | |
| US20040183626A1 (en) | Electronically tunable block filter with tunable transmission zeros | |
| CN113067561A (en) | Band-stop filter and multi-frequency band-stop filter | |
| CN113630102A (en) | Acoustic wave filter | |
| CN215186667U (en) | Band-stop filter and multi-frequency band-stop filter | |
| CN115603690B (en) | N77 frequency band miniaturized filter based on IPD technology | |
| JPH07221504A (en) | Filter circuit and mobile body communication equipment | |
| JP7456797B2 (en) | Filters and multiplexers | |
| WO2022227347A1 (en) | Band-stop filter and multi-frequency band-stop filter | |
| US20230283260A1 (en) | Notch filter and multi-frequency notch filter |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |