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AssigneeNortel Networks Limited
InventorsChun-Yun Jian, Steve A. Beaudin, Conrad F. Gratton
Estimating the term…
A spatial harmonic transducer of a SAW device is made directional for SAWs at a spatial harmonic signal frequency of the transducer by a reflector for reflecting SAWs at that frequency. The transducer comprises repeated groups of consecutive electrodes having a predetermined polarity sequence, positioned to operate coherently for SAWs at the signal frequency. The reflector comprises reflector electrodes for producing constructive and destructive interference in opposite SAW directions, with electrode widths and spacings of at least a quarter wavelength at the signal frequency. A SAW device with two such spatial harmonic SPUDTs using different polarity sequences can provide desirable characteristics for filters and delay lines at frequencies of about 2 GHz.
A SAW (surface wave) device comprising an inter-digital transducer on a substrate of piezoelectric material, the transducer comprising a plurality of groups of electrodes, the electrodes of each group having a predetermined polarity sequence, the groups being arranged along a length of the transducer to operate coherently for SAWs at a signal frequency of the transducer, the signal frequency having a spatial harmonic relationship to a frequency corresponding to a pitch of said electrodes, wherein the transducer further comprises at least one reflector for reflecting SAWs at the signal frequency, the reflector being positioned relative to said groups of electrodes to provide constructive interference of SAWs at the signal frequency in one direction along the length of the transducer and to provide destructive interference of SAWs at the signal frequency in an opposite direction.
A SAW (surface wave) device interdigital transducer comprising a plurality of groups each of q consecutive electrodes having a predetermined polarity sequence, each group having a length rλ0 along the transducer, for transducing SAWs with a wavelength λ0 at a frequency f0, where q is a positive integer greater than 2 and r is a positive integer less than q and not equal to q/2, the groups being arranged along the length of the transducer to operate coherently for SAWs at the frequency f0, the transducer further comprising at least one reflector for reflecting SAWs at the frequency f0, the reflector being positioned relative to said groups to provide constructive interference of SAWs at the frequency f0 in one direction along the length of the transducer and to provide destructive interference of SAWs at the frequency f0 in an opposite direction, the reflector comprising one or more reflector electrodes, each reflector electrode and each space between reflector electrodes having a width of at least about λ0/4.
A SAW device comprising a spatial harmonic transducer having a preferential direction for propagation of SAWs at a spatial harmonic signal frequency of the transducer, the transducer comprising a plurality of groups of electrodes having a predetermined polarity sequence for transducing SAWs at said frequency, and at least one reflector for reflecting SAWs at said frequency, the reflector being positioned relative to said groups of electrodes to provide relative constructive interference of SAWs at said frequency in one direction along the length of the transducer and to provide relative destructive interference of SAWs at said frequency in an opposite direction, the reflector comprising one or more reflector electrodes, each reflector electrode and each space between reflector electrodes having a width of at least about one quarter of a SAW wavelength at said frequency.
Dependencies are inferred from the claim text.