Northern Telecom Limited

John Choo Saw

Mark S Suthers

Thomas P Cameron

Yufeng Xu

Ji-Dong Dai

John Jackson Nisbet

Samuel Alfred Tiller

Harry Leib

Paul Alan Kennard

Conrad F Gratton

Zhuo-Hui Chen

A longitudinally coupled double mode surface wave resonator comprises two reflectors, two lateral IDTs (inter-digital transducers), and a centre IDT arranged on a surface of a piezoelectric substrate, for coupling surface waves longitudinally between the IDTs. The two lateral IDTs operate with opposite signal phases by virtue of opposite connections, opposite polarities, or oppositely phased spacings from the centre IDT. Alternatively, or in addition, the centre IDT is divided into two oppositely phased halves. A filter comprising one or more resonators can replace both a filter and a balun in a radio frequency circuit.

Longitudinally coupled double mode surface wave resonators

A cascaded surface wave device filter comprises two 2-pole surface wave device filters connected in cascade. The 2-pole filters each provide a balun function between balanced and unbalanced signal connections, and have either their unbalanced or their balanced signal connections interconnected in the cascade to reduce electromagnetic feedthrough and improve spurious mode suppression. The 2-pole filters are conveniently longitudinally coupled double mode surface wave resonators which are described, or transversely coupled double mode surface wave resonators. Higher order filters can be provided by connecting further 2-pole filters in the cascade. The cascaded filter is particularly useful for filtering at radio and intermediate frequencies in cellular radio equipment.

Cascaded surface wave device filters providing balanced and unbalanced

A double mode surface wave resonator comprises two IDTs (inter-digital transducers), arranged side by side between reflection gratings, on a surface of a piezoelectric substrate to provide for coupling of surface waves therebetween, each IDT having interleaved electrodes extending from a common rail between the two IDTs and from a respective outer rail of the IDT. One or each of the IDTs and its outer rail is divided into two halves for providing a differential signal connection to the resonator. The electrodes of the IDTs can be arranged in spatial synchronism with adjacent fingers of the reflection gratings to reduce spurious longitudinal modes.

Double mode surface wave resonators

A SAW (surface acoustic wave) device tapped delay line comprises a continuous pattern of bifurcated inter-digital fingers having a constant pitch of .lambda./2 and forming a first IDT (inter-digital transducer), a plurality of second IDTs, substantially identical to one another and arranged with a predetermined pitch P for consecutively receiving a SAW propagated from the first IDT with respective propagation delays, and grounded dummy fingers in regions between adjacent IDTs. The first IDT is apodized in accordance with a Hermitian response to provide it with a pass band centered at a first frequency, and .lambda. is the wavelength of a SAW at a second frequency different from the first frequency and within the pass band. P is an integral multiple of .lambda./2, so that there is a constant finger periodicity throughout the SAW device whereby reflections between the second IDTs are avoided. The SAW device tapped delay line is used in an adaptive time delay equalizer of a high capacity microwave radio communications system, with the first frequency equal to the receiver intermediate frequency and the second frequency being an integral multiple of half the symbol rate of the system.

Saw device tapped delay lines

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Kanata, Canada

John Choo Saw