Zenith Radio Corporation

Zenith Electronics Corporation

Kai Hansen

Adrian J DeVries

Michael J Garbacz

A multichannel surface acoustic wave encoder/decoder having a common electrical input is designed so that the insertion losses of the channels differ despite the apparent design constraint of closely matched channel output impedances. The input transducing device or SAW transmitter is divided into individual transducers (or into subtransducers) having different numbers of finger overlaps, thus achieving different acoustic output levels which in turn result in different insertion losses for different channels. The finger spacing of the SAW transmitters can differ between the respective input transducers or subtransducers so as to optimize the center frequency of each channel.

Multichannel surface acoustic wave encoder/decoder

An acoustic surface wave filter is described for receiving one of two electrical signals at either of a pair of input ports and for providing a filtered electrical signal at a common output port. The filter includes a pair of input electro-acoustic transducers on a substrate, each coupled to one of the input ports, for launching surface waves in response to an electrical input signal. Each of the input transducers is associated with a multistrip coupler and an output transducer for converting the surface waves to an electrical output signal. The layout and geometry of the filter components are such that all surface waves are launched in a direction which is oblique to the substrate boundaries to reduce interference due to reflected surface waves. The layout and geometry also result in a relatively small substrate and a simultaneous reduction of insertion loss.

Acoustic surface wave multiplexing filter

In order to avoid spurious responses at the third harmonic of the signal frequency, a surface acoustic wave filter employs a multi-strip track coupler in which the spacing d of the elements is an integral multiple I of the acoustic wavelength .lambda. of the third harmonic. When the condition d=I.lambda. is satisfied, the coupler blocks transmission of the third harmonic from the input transducer track to the output transducer track. This basic principle can also be used to block other frequencies.

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Arlington Heights, IL, United States of America

Kai Hansen