U.S. Philips Corporation

Standard Telephones and Cables Public Limited Company

Standard Telephones & Cables Limited

David E Bower

Douglas F Dwyer

A differential surface acoustic wave (SAW) accelerometer comprises a resilient beam 1 one end of which is clamped in a support 2. Opposite faces of the beam are provided with SAW transducers 3, 4 and 6, 7 which respectively form delay lines driven by oscillator 5. Means are introduced for setting the beam into a low frequency mechanical flexural oscillation. The two outputs are connected in antiphase so that under conditions of no acceleration null points in the output waveform will be equally spaced. During acceleration the time intervals between successive nulls will become unequal.

Surface acoustic wave accelerometer

An accelerometer comprises a quartz beam 1 having on its upper and lower faces surface acoustic wave devices 2, 3 and 2', 3'. The beam is centrally mounted on quartz spacers 4, 5 which have metallized contacts for the lower SAW device. The spacers are carried on a quartz substrate 6 which is supported on a header 7 forming the base of a dual-in-line package. Mass-loading 8 is provided on each end of the beam 1.

A surface acoustic wave filter includes a length-weighted interdigital transducer (T1) on one side of which are bus bar parts (BP1, BP2) which are within the transducer acoustic aperture (A), are inclined at an acute angle to the propagation path (P) and which closely follow the major lobe (L1). These bus bar parts each have a width (W) along the propagation path (P) defined by 2W=n.lambda./2 where n is an odd integer and .lambda. is the wavelength of surface acoustic waves at substantially the maximum amplitude response frequency of the transducer (T1). The components of the surface acoustic waves reflected from the two edges of each inclined bus bar part along the propagation path, that is to say the component reflected waves (SW1) reflected from the edge closest to the overlap envelope and the component reflected waves (SW2) reflected from the edge which forms part of one end of the transducer, are in antiphase at that maximum response frequency and so spurious signals due to the component reflected waves (SW1 and SW2) at that frequency are substantially suppressed.

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London, United Kingdom

David E Bower