Northern Telecom Limited

Grantley O Este

Mark S Suthers

Richard W Streater

Blair K MacLaurin

Herman W Willemsen

Bruce C Beggs

A SAW (surface acoustic wave) device includes a substrate having thereon at least one apodized IDT (inter-digital transducer). The axis of the apodization pattern is inclined towards a driven conductive rail of the IDT at the ends of the pattern, whereby the driven end fingers have a low capacitive coupling to a ground plane on which the substrate is supported. The capacitive coupling to the ground plane may also be reduced by supporting the substrate on the ground plane via an insulating support, whereby an air gap or the insulating support decreases the capacitance between the IDT and the ground plane.

Saw device with apodized IDT

A grating is positioned on a surface acoustic wave device on a first axis in-line with the delay line for substantially reducing the amount of energy reflected on that axis to the transmitter and receiver. The grating site on the first axis at a position between the delay line and one of the edges of the device. The grating is comprised of a parallel series of grating members each oriented so as to extend at a first angle relative to the first axis, the grating members being generally longitudinally bisected by that axis. An optimum value for the first angle is provided by a theoretical analysis, and experimental results are presented. On the experimental device, the grating is defined by a series of parallel grooves formed in the surface of the device; however, the grating may also be defined by a series of metallic strips mounted on the surface of the device.

Surface acoustic wave scattering grating

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

An interdigitated transducer (IDT) has parallel electrodes extending inwardly from one voltage rail and parallel electrodes extending inwardly from another voltage rail. The respective electrodes are interleaved to give a region of overlap or apodization within which the SAW is generated or received, the width of the apodized area varying along the length of the IDT. To prevent performance degradation in the event of an open circuit in a non-overlap region, the electrodes associated with a particular voltage rail are additionally linked by a thin conductor positioned near the boundaries between the apodized or overlap region and each of the non-overlap regions.

Surface acoustic wave devices

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 surface acoustic wave (SAW) device has an input interdigitated transducer (IDT) and an output IDT. One of the transducers is formed as two loops which are interconnected so that unwanted magnetic feedthrough voltages induced in or by such current loops cancel, while currents producing or produced by the SAW add.

Magnetic feedthrough cancelling surface acoustic wave device

A device for accurately positioning an optical system element uses an array of electromagnets to alter fluid pressure distribution in a mass of ferromagnetic fluid. The pressure redistribution causes movement of an optical system element positioned adjacent to the ferromagnetic fluid. The invention is concerned with particular arrangements of fluid and energizing electromagnets to ensure combined rectilinear and angular movement of the optical system elements. The device has neither the complexity nor the delicacy of known structures used for moving optical system elements.

Positioning device for optical system element

Surface relief analyzing equipment comprises a turntable and an audio frequency pick-up including a stylus. A substrate bearing the surface relief is rotated on the turntable at a fixed frequency and and analogue electrical signal produced at a pick-up transducer is passed through an a-d converter. Digital data is processed to produce an input to a display for registering a pictorial representation of the surface relief.

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Stittsville, Canada

Grantley O Este