Unapodization
An unapodized interdigital transducer apparatus, system, and associated methods. The apparatus includes a substrate, a pair of first electrodes oppositely positioned on the substrate, where an aperture is formed between the pair of first electrodes, and a plurality of variable length second electrodes arranged using a predetermined pattern defined by each second electrode in the plurality of second electrodes being coupled to one of the first electrodes in the pair of first electrodes and being configured to extend into the aperture. At least one second electrode in the plurality of second electrodes coupled to one of the first electrodes in the pair of first electrodes has the same length as at least another second electrode in the plurality of second electrodes coupled to another first electrode in the pair of first electrodes. A surface acoustic wave is generated upon application of electrical current to the pair of the first electrodes.
1 . An apparatus, comprising:
a substrate;
a pair of first electrodes oppositely positioned on the substrate, wherein an aperture is formed between the pair of first electrodes;
a plurality of variable length second electrodes arranged using a predetermined pattern defined by each second electrode in the plurality of second electrodes being coupled to one of the first electrodes in the pair of first electrodes and being configured to extend into the aperture, wherein at least one second electrode in the plurality of second electrodes coupled to one of the first electrodes in the pair of first electrodes has the same length as at least another second electrode in the plurality of second electrodes coupled to another first electrode in the pair of first electrodes;
wherein the plurality of second electrodes are arranged in a plurality of groups of second electrodes extending from one of the first pair of electrodes, a first group in the plurality of groups of second electrodes includes a plurality of adjacent second electrodes extending less than halfway across the aperture and having a first length and a second group of the plurality of groups of second electrodes extending at least halfway across the aperture and having a second length different than the first length,
wherein the plurality of second electrodes include a third group of electrodes extending from the another first electrode and extending at least halfway across the aperture and between each of the adjacent electrodes of the first group in the plurality of groups of second electrodes,
wherein a surface acoustic wave is generated upon application of electrical current to the pair of the first electrodes.
2 . The apparatus according to claim 1 , wherein the pair of first electrodes and the plurality of variable length second electrodes form an unapodized interdigital transducer disposed on the substrate.
3 . The apparatus according to claim 1 , wherein the plurality of second electrodes are arranged in a plurality of pairs of second electrodes.
4 . The apparatus according to claim 3 , wherein second electrodes in a pair of second electrodes in the plurality of pairs have same length.
5 . The apparatus according to claim 3 , wherein second electrodes in a pair of second electrodes in the plurality of pairs have different length.
6 . The apparatus according to claim 1 , wherein at least one second electrode in the plurality of second electrodes has a first thickness and at least another second electrode in the plurality of second electrodes has a second thickness, the first thickness being different from the second thickness.
7 . The apparatus according to claim 2 , wherein the interdigital transducer is at least one of an output interdigital transducer and an input interdigital transducer.
8 . The apparatus according to claim 1 , wherein the surface acoustic wave is a uniform surface acoustic wave.
9 . The apparatus according to claim 1 , further comprising a plurality of variable length non-conducting third electrodes, wherein each non-conducting third electrode in the plurality of non-conducting third electrodes is coupled to at least one first electrode in the pair of first electrodes.
10 . The apparatus according to claim 9 , wherein at least one non-conducting third electrode is positioned opposite to at least one second electrode in the plurality of second electrodes.
11 . The apparatus according to claim 1 , wherein the plurality of second electrodes are arranged in one or more groups of second electrodes, at least group in the one or more groups of second electrodes includes at least one second electrode having a different length than a length of at least another second electrode in at least another group in the one or more groups of second electrodes.
12 . The apparatus according to claim 1 , wherein each pair of adjacent second electrodes in the plurality of second electrodes are coupled to the same first electrode in the pair of first electrodes and are positioned a predetermined distance apart.
13 . The apparatus according to claim 1 , wherein the predetermined pattern is dependent on a distribution of an amplitude of the generated surface acoustic wave determined at one or more locations corresponding to positions of one or more second electrodes in the plurality of second electrodes within the aperture.
14 . The apparatus according to claim 13 , wherein the predetermined pattern of the plurality of second electrodes is configured to cause generation of a predetermined acoustic pressure across the aperture.
15 . The apparatus according to claim 14 , wherein the predetermined acoustic pressure is constant.
16 . The apparatus according to claim 14 , wherein the predetermined acoustic pressure is configured to vary at each location corresponding to a position of each second electrode in the plurality of second electrodes within the aperture.
17 . A method, comprising:
providing an unapodized interdigital transducer disposed on a substrate, the unapodized interdigital transducer including
a pair of first electrodes oppositely positioned on the substrate, wherein an aperture is formed between the pair of first electrodes;
a plurality of variable length second electrodes arranged using a predetermined pattern defined by each second electrode in the plurality of second electrodes being coupled to one of the first electrodes in the pair of first electrodes and being configured to extend into the aperture, wherein at least one second electrode in the plurality of second electrodes coupled to one of the first electrodes in the pair of first electrodes has the same length as at least another second electrode in the plurality of second electrodes coupled to another first electrode in the pair of first electrodes;
wherein the plurality of second electrodes are arranged in a plurality of groups of second electrodes extending from one of the first pair of electrodes, a first group in the plurality of groups of second electrodes includes a plurality of adjacent second electrodes extending less than halfway across the aperture and having a first length and a second group of the plurality of groups of second electrodes extending at least halfway across the aperture and having a second length different than the first length,
wherein the plurality of second electrodes include a third group of electrodes extending from the another first electrode and extending at least halfway across the aperture and between each of the adjacent electrodes of the first group in the plurality of groups of second electrodes, and
generating a surface acoustic wave, upon application of electrical current to the pair of the first electrodes.
18 . The method according to claim 17 , wherein the providing includes determining a distribution of an amplitude of the generated surface acoustic wave
determined at one or more locations corresponding to positions of one or more second electrodes in the plurality of second electrodes within the aperture;
generating the predetermined pattern, including selecting a number of second electrodes for positioning within the aperture, determining corresponding lengths of selected electrodes, and determining positions of the selected electrodes.
19 . The apparatus according to claim 1 , further comprising:
a fourth group of electrodes in the plurality of groups of second electrodes includes a plurality of adjacent second electrodes extending substantially the entire width of the aperture from the one of the first pair of electrodes; and
a fifth group of electrodes extending from the another first electrode between each of the adjacent electrodes of the fourth group in the plurality of groups of second electrodes and extending substantially the entire width of the aperture.
20 . The apparatus according to claim 1 , the fourth group of electrodes and the fifth group of electrodes being down stream of the first, second, and third group of electrodes.