Abstract: A reflective grating (36) for a SAW filter (10) or resonator. The reflective grating (36) is formed by selectively dithering grating grid lines (38) with respect to a uniform spaced grid of M number of grid lines (38) per each N wavelength (?) of the grating (36) (N?/M), where ? is the wavelength of the center of the frequency band of interest, M and N are integers and M>N. M and N are selected so that the grating (36) does not have a net reflection when all of the grid lines (38) are uniformly spaced. By controlling the dithering pattern of the grid line in each sampling period of N?, any desired net distributed reflectivity from the grating can be implemented in both magnitude and phase.

Abstract: A reflective grating (36) for a SAW filter (10) or resonator. The reflective grating (36) is formed by selectively dithering grating grid lines (38) with respect to a uniform spaced grid of M number of grid lines (38) per each N wavelength (&lgr;) of the grating (36) (N&lgr;/M), where &lgr; is the wavelength of the center of the frequency band of interest, M and N are integers and M>N. M and N are selected so that the grating (36) does not have a net reflection when all of the grid lines (38) are uniformly spaced. By controlling the dithering pattern of the grid line in each sampling period of N&lgr;, any desired net distributed reflectivity from the grating can be implemented in both magnitude and phase.

Abstract: A dual track SAW reflector filter (150) including a first track (152) and a second track (154). The first track and the second track (152, 154) include an input transducer (156, 164), an output transducer (158, 166), first reflectors (160, 168) and second reflectors (162, 170). The reflectivity function of the first reflectors (160, 168) and the second reflectors (162, 170) are equal in magnitude and opposite in phase. The input transducers (156,164) have the same polarity and the output transducers (158, 166) have opposite polarities. Surface acoustic waves produced by the input transducers (156, 164) and received directly by the output transducers (158, 166) are in phase and cancel at the output transducers (158, 166). Surface acoustic waves reflected by the reflectors (160, 162, 168 and 170) are in phase and add at the output transducers (158, 166).

Abstract: A cascaded SAW filter system includes first and second SAW filters (12a, 12b) each including an input transducer (36, 36′) and an output transducer (37, 37′) on a piezoelectric substrate (38, 38′). Group delay and pass band ripples associated with a time spur at TD′ away from the main signal of the second filter (12b) cancel the group delay and pass band ripples associated with a time spur at TD away from the main signal of the first filter (12a) because: 1) the input and output transducers (36′, 37′) of the second filter (12a) are offset from those of the first filter (12a); 2) the center frequency (f0′) of the second filter (12b) is offset from the center frequency (f0) of the first filter (12a); 3) the perturbation region (P1) of the first filter (12a) is different from the perturbation region (P2) of the second filter (12b) or 3) a combination of 1), 2) and/or 3. The associated time spur echo of the cascaded response will also be canceled.

Abstract: A cascaded SAW filter system includes first and second SAW filters (12a, 12b) each including an input transducer (36, 36′) and an output transducer (37, 37′) on a piezoelectric substrate (38, 38′). Group delay and pass band ripples associated with a time spur at TD′ away from the main signal of the second filter (12b) cancel the group delay and pass band ripples associated with a time spur at TD away from the main signal of the first filter (12a) because: 1) the input and output transducers (36′, 37′) of the second filter (12a) are offset from those of the first filter (12a); 2) the center frequency (f0′) of the second filter (12b) is offset from the center frequency (f0) of the first filter (12a); 3) the perturbation region (P1) of the first filter (12a) is different from the perturbation region (P2) of the second filter (12b) or 3) a combination of 1), 2) and/or 3. The associated time spur echo of the cascaded response will also be canceled.

Abstract: The invention relates to a new family of surface acoustic wave single-phase unidirectional transducers (SPUDTs) by using M uniform width, uniformly spaced, single-level interdigitated electrodes lying on a uniform grid of a piezoelectric substrate where unidirectionality is achieved by selectively etching reflective structures into the substrate either in the spaces located between adjacent electrodes or under selected electrodes of the transducer. A SAW filter, resonator or delay line can also be formed by fabricating two such transducers on a single substrate, each having surface acoustic waves radiating towards the other.

Abstract: The invention relates to a new family of surface acoustic wave single-phase unidirectional transducers (SPUDTs) by using M uniform width, uniformly spaced, single-level interdigitated electrodes lying on a uniform grid of a piezoelectric substrate where unidirectionality is achieved by selectively etching reflective structures into the substrate either in the spaces located between adjacent electrodes or under selected electrodes of the transducer. A SAW filter, resonator or delay line can also be formed by fabricating two such transducers on a single substrate, each having surface acoustic waves radiating towards the other.