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US 5,670,920 AGranted
Multi-track SAW filter with reflectors and reversed polarity IDT connections
AssigneeAdvanced SAW Products SA
InventorDavid P. Morgan
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AssigneeAdvanced SAW Products SA
InventorDavid P. Morgan
Estimating the term…
A SAW filter comprising at least one group of N tracks, where N is an integer greater than 2, and including at least one input interdigitated transducer (IDT) spaced apart from at least one output IDT and a reflector disposed substantially collinear with and adjacent the input and output IDTs. The respective tracks are adapted to have different effective electro-acoustic lengths such that SAWs launched from respective input IDTs undergo at least one reflection at corresponding output IDTs and at least one reflection from the respective input IDTs prior to generating coherent signals from respective output IDTs. The different effective electro-acoustic lengths may be substantially provided by there being different physical separation between input and output IDTs of respective tracks, or by IDTs of respective tracks having different polarity connections of electrodes or different amounts of material disposed in respective tracks between the input and output IDTs.
A SAW filter comprising a group of N tracks, where N is an integer greater than or equal to two, including an input interdigitated transducer (IDT) spaced apart from an output IDT and a reflector disposed substantially collinear with and adjacent the input and output IDTs, wherein respective tracks are selected to have different effective electro-acoustic lengths such that surface acoustic waves launched into respective tracks from the input IDT undergo at least one reflection at a reflector corresponding to the output IDT prior to forming a substantially coherent signal at the output IDT, wherein the output IDT comprises N respective output IDTs electrically coupled together and corresponding to said respective tracks, and wherein the electrode connections of at least one of the respective IDTs are reversed with respect to the polarity of the electrode connections of the IDTs of other ones of the tracks.
A SAW filter comprising a group of N tracks, where N is an integer greater than or equal to two, including an input interdigitated transducer (IDT) spaced apart from an output IDT and a reflector disposed substantially collinear with and adjacent the input and output IDTs, wherein respective tracks are selected to have different effective electro-acoustic lengths such that surface acoustic raves launched into respective tracks from the input IDT undergo at least one reflection at a reflector corresponding to the output IDT prior to forming a substantially coherent signal at the output IDT, wherein the input IDT comprises N respective input IDTs electrically coupled together and corresponding to said respective tracks, and wherein electrode connections of at least one of the respective input or respective output IDTs are reversed with respect to the polarity of electrode connections of the IDTs of other tracks.
A SAW filter comprising a group of N tracks, where N is an integer greater than or equal to two, including an input interdigitated transducer (IDT) space apart from an output IDT and a reflector disposed substantially collinear with and adjacent the input and output IDTs, wherein respective tracks are selectable to have different effective electro-acoustic lengths such that surface acoustic waves launched into respective tracks from the input IDT undergo at least one reflection at a reflector corresponding to the output IDT prior to forming a substantially coherent signal at the output IDT, wherein the input IDTs are symmetrically disposed relative to the output IDTs about a center of the tracks, wherein the IDTs in a second one of the tracks are offset .alpha. inwards relative to the IDTs of a first one of the tracks where .alpha. is an acoustic wavelength of j/2N for j=1,2, . . . 2N-1, and wherein the reflector of the second track is displaced .beta./2 outward from the center of the tracks relative to the reflector of the first track where .beta. is an acoustic wavelength of i/N for i=1,2 . . . 2N-1.
A SAW filter comprising a group of N tracks, where N is an integer greater than or equal to two, including an input interdigitated transducer (IDT) spaced apart from an output IDT and a reflector disposed substantially collinear with and adjacent the input and output IDTs, wherein respective tracks are selectable to have different effective electro-acoustic lengths such that surface acoustic waves launched into respective tracks from the input IDT undergo at least one reflection at a reflector corresponding to the output IDT prior to forming a substantially coherent signal at the output IDT, wherein N is an even number, wherein the input IDTs are asymmetrically disposed relative to output IDTs with a first set of the IDTs in different tracks being in line, wherein a second set of IDTs and corresponding reflectors opposite the first set are displaced relative to each other from track to track by .alpha. and .beta./2 respectively, wherein .alpha. is an acoustic wavelengths of 2.pi.r/N with r an odd multiple of N/2 and .beta./2 is an acoustic wavelength of 2.pi.s/N with s an integer that is not a multiple of N, and wherein spacing in at least one of the tracks complies with the following equations:
A SAW filter comprising a group of N tracks, where N is an integer greater than or equal to two, including an input interdigitated transducer (IDT) spaced apart from an output IDT and a reflector disposed substantially collinear with and adjacent the input and output IDTs, wherein respective tracks are selectable to have different effective electro-acoustic lengths such that surface acoustic waves launched into respective tracks from the input IDT undergo at least one reflection at a reflector corresponding to the output IDT prior to forming a substantially coherent signal at the output IDT, wherein N is an odd number, wherein one of the IDTs and its corresponding reflector in one of the tracks are respectively offset from one of the IDTs and its corresponding reflector in another track by .alpha. and .beta./2, where .alpha. is an acoustic wavelength of 2.pi.r/N and .beta./2 is an acoustic wavelength of 2.pi.s/N with s as an integer which is not a multiple of N, and r can be obtained from the equation:
Dependencies are inferred from the claim text.