Patent EP0140618A2 successfully refreshed from Google Patents.
EP0140618A2
Expired / Lapsed
EP
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Acoustic transducer
Assignee: Qinetiq Ltd
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Filing: 1984-10-11
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Granted: —
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Expires: 2004-10-11
Abstract
Abstract An acoustic transducer (10) is arranged as a ladder having uprights and rungs consisting of contact pads (11, 12) and interdigital fingers (14, 15) respectively. The transducer (10) has inter-rung spaces (17) occupied by arrays (18) of reflector strips (20). Each reflector strip (20) is offset by λ/8 from a respective position distant ½nλ from a transducer finger centre, λ being the transducer finger centre and n an integer. The λ/8 offset reflector strips (20) provide constructive interference between transducer output waves travelling in one direction. This provides a transducer with undirectional properties which can be manufactured in one metal deposition process. Unwanted reflections at fingers (14, 15) may be reduced by additional blooming reflector banks (105, 106) or by repositioning reflector strips to provide both unidirectional and blooming properties. Other options include variation in spatial periodicity, overlap, length, width and/or number of reflector strips and/or transducer fingers.
Inventors
- 👤 Meirion Francis Lewis
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 16:19
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/46; H03H9/64; H03H9/6423; H03H9/643; H03H9/02; H03H9/02535; H03H9/02637; H03H9/02685; H03H9/0274; H03H9/125; H03H9/145; H03H9/14502; H03H9/14505
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
62 words
An acoustic transducer characterised in that it is arranged on a piezoelectric substrate as a ladder (11,12,16) having rungs (16) comprising interdigital fingers (14,15) and it includes one or more reflector strips (20) arranged in inter-rung positions (17) appropriate to enhance acoustic wave generation in one direction and to reduce acoustic wave generation in the opposite direction in a given frequency band.
Claim 2
Dependent Claim
62 words
An acoustic transducer characterised in that it is arranged on a piezoelectric substrate as a ladder (11,12,16) having rungs (16) comprising interdigital fingers (14,15) and it includes one or more reflector strips (20) arranged in inter-rung positions (17) appropriate to enhance acoustic wave generation in one direction and to reduce acoustic wave generation in the opposite direction in a given frequency band.
Claim 3
Dependent Claim
30 words
An acoustic transducer according to Claim 1 characterised in that the said one or more reflector strips are provided by one or more arrays (18) of parallel reflector strips (20).
Claim 4
Dependent Claim
47 words
An acoustic transducer according to Claim 2 characterised in that each reflector strip (20) is offset by substantially X/8 from a respective location distant nλ/2 from a transducer finger centre (31,32), where X is a wavelength corresponding to the transducer centre frequency and n is an integer.
Claim 5
Dependent Claim
23 words
An acoustic transducer according to Claim 3 characterised in that it includes one or more reflector strip arrays (19) arranged in non-inter-rung locations.
Claim 6
Dependent Claim
26 words
An acoustic transducer according to any preceding claim characterised in that the transducer finger length and/or reflector strip length are/is weighted to obtain desired transducer characteristics.
Claim 7
Dependent Claim
34 words
An acoustic transducer according to any preceding claim characterised in that it is arranged adjacent a second such transducer, the transducers (10) being disposed to emit acoustic waves towards or away from one another.
Claim 8
Dependent Claim
24 words
An acoustic transducer according to any preceding claim characterised in that acoustic absorbing means is arranged on the substrate to absorb unwanted acoustic waves.
Claim 9
Dependent Claim
21 words
An acoustic transducer according to Claim 1 characterised in that it is arranged to be spatially aperiodic or of varying periodicity.
Claim 10
Dependent Claim
15 words
An acoustic transducer according to Claim 1 characterised in that it has weighted finger overlap.
Claim 11
Dependent Claim
22 words
An acoustic transducer according to Claim 9 characterised in that it has finger overlap varying in accordance with a sampled Fourier transform.
Claim 12
Dependent Claim
26 words
An acoustic transducer according to Claim 10 characterised in that it has reflector strips located at one or more positions (73) corresponding to zero finger overlap.
Claim 13
Dependent Claim
29 words
An acoustic transducer according to Claim 2 characterised in that it has first reflector strips (104) arranged for unidirectional transducer properties and second reflector strips (107) arranged for blooming.
Claim 14
Dependent Claim
61 words
An acoustic transducer according to Claim 2 characterised in that it has reflector strips positioned both for unidirectional transducer properties and for blooming, the reflector strips being offset by from spatial periodicity with transducer finger centres, where M is the number of fingers per transducer rung, N is the number of reflector strips per array and N is greater than M.
Claim 15
Dependent Claim
24 words
An acoustic transducer according to Claim 12 or 13 characterised in that is has transducer fingers (108,110) and reflector strips (104,107) X/4 in width.
Claim 16
Dependent Claim
20 words
An acoustic transducer according to Claim 2 characterised in that reflector strip length and/or width varies over the reflector array.
Claim 17
Dependent Claim
25 words
An acoustic transducer according to Claim 2 characterised in that it includes a plurality of reflector arrays with differing numbers of reflector strips per array.
Claim 18
Dependent Claim
17 words
An acoustic transducer according to Claim 2 characterised in that the reflector array has varying spatial periodicity.
Claim 19
Dependent Claim
22 words
An acoustic transducer according to Claim 2 characterised in that the transducer fingers vary in length and/or width and/or number per rung.
Claim 20
Dependent Claim
17 words
An acoustic transducer according to Claim 2 characterised in that it has varying transducer finger spatial periodicity.
Claim 21
Dependent Claim
22 words
An acoustic transducer characterised in that it is in accordance with any combination of two or more of Claims 15 to 20.
References Cited (Backward Citations)
No citation records indexed.
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