Weighted SAW reflector grating using dithered acoustic reflectors
AssigneeNorthrop Grumman Corporation
InventorDavid S. Yip
Life of this patent
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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 (λ) of the grating (36) (Nλ/M), where λ 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 Nλ, any desired net distributed reflectivity from the grating can be implemented in both magnitude and phase.
Claims30
A reflector for reflecting acoustic waves, said reflector comprising:
- a substrate;
- and
- a reflective grating disposed on the substrate, said grating including patterned grid lines oriented in a parallel configuration and defining gaps therebetween, wherein the grid lines are oriented relative to a uniform or periodic spacing arrangement defined by a certain grid line width and gap width, and wherein a predetermined number of the grid lines are dithered relative to the uniform spacing to provide a reflectivity function that sets the magnitude and phase of the reflected waves relative to a frequency band of interest.
A reflector for reflecting acoustic waves, said reflector comprising:
- a piezoelectric substrate;
- and
- a reflective grating structure disposed on the substrate, said grating structure including a series of grid lines defining gaps therebetween, wherein the grid lines are oriented relative to a uniform or periodic spacing arrangement defined by a certain grid line width and gap width, and wherein a predetermined number of the grid lines are dithered relative to the uniform spacing to provide a reflectivity function that sets the magnitude and phase of the reflected wave relative to a frequency band of interest, and wherein a certain number of the grid lines define a predetermined and repeated sampling period, said sampling period being defined by M number of grid lines per N wavelengths (Nλ/M), where λ is the wavelength of the center of the frequency band of interest, M and N are integers and M>N, and wherein the uniform spacing arrangement provides no net reflectivity.
A SAW filter for filtering a signal, said filtering comprising:
- a piezoelectric substrate;
- at least one input transducer, said input transducer generating surface acoustic waves propagating on the piezoelectric substrate in response to the signal;
- at least one reflective grating for reflecting the acoustic waves from the at least one input transducer, said grating including patterned grid lines oriented in a parallel configuration and defining gaps therebetween, wherein the grid lines are oriented relative to a uniform or periodic spacing arrangement defined by a certain grid line width and gap width, and wherein a predetermined number of the grid lines are dithered relative to the uniform spacing to provide a reflectivity function that sets the magnitude and phase of the reflected waves relative to a frequency band of interest;
- and
- at least one output transducer, said output transducer responsive to the reflected acoustic waves from the reflective grating, said at least one output transducer converting the acoustic waves into electrical energy.
Dependencies are inferred from the claim text.