Northern Telecom Limited

Blair K MacLaurin

Richard W Streater

Mark S Suthers

Grantley O Este

William D Westwood

David R Baraff

Nur M Serinken

Carla J Miner

Robert J Boynton

A SAW device includes aligned IDTs (inter-digital transducers) with a continuous pattern of fingers between their front edges. Each IDT may be symmetrical about its center, and includes front and back edge reflection suppressing regions of fingers of successively decreasing length, which serve to suppress surface acoustic wave reflections at the respective edges. Optional shield regions between the two front edge suppressing regions, and between the back edge suppressing regions and acoustic absorbers, include fingers of successively increasing length complementary to and adjacent the fingers of successively decreasing length of the reflection suppressing regions. The IDTs may be apodized or unapodized, and each IDT may include dummy fingers between its active region and each reflection suppressing region.

SAW device with continuous finger pattern

Each IDT (inter-digital transducer) of a SAW (surface acoustic wave) device is formed on a thin resistive doped silicon film having the same pattern as the IDT, which improves adhesion of the IDT to the substrate. The silicon film also constitutes electroacoustic absorbers between the IDTs and edges of the substrate, and can have a linearly tapered edge adjacent to each IDT to suppress reflections at the absorber boundary. The SAW device is formed by sputtering silicon onto the substrate, subsequently forming the IDTs, and then etching the silicon from areas where it is not wanted.

Saw devices including resistive films

Each IDT (inter-digital transducer) of a SAW (surface acoustic wave) device has a linearly tapered back edge formed by reflection-suppressing fingers of successively decreasing length spaced apart with a pitch of lambda/4 behind the active region of the IDT, where lambda is the wavelength of a SAW to be propagated, whereby SAW reflections at the back edge of the IDT are substantially eliminated. A thin resistive doped silicon film between the back edge of each IDT and the adjacent edge of the substrate absorbs waves propagated via this back edge. The film underlies the IDTs to provide improved adhesion to the substrate.

Saw devices with reflection-suppressing fingers

A matrix multiplexed field effect display has switch devices at matrix crosspoints to provide a turn-on threshold for the field effect material. The switch devices are thin film metal-insulator-metal (MIM) switches. The display is operated at low current so that the MIM switches, which may be deposited on glass, do not degrade rapidly in use.

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Nepean, Canada

Blair K MacLaurin