Wave transmission lines and networks – Coupling networks – Delay lines including elastic surface wave propagation means
Patent
1991-01-10
1992-06-16
LaRoche, Eugene R.
Wave transmission lines and networks
Coupling networks
Delay lines including elastic surface wave propagation means
333196, 310313C, H03H 900
Patent
active
051227673
ABSTRACT:
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.
REFERENCES:
patent: 3968461 (1976-07-01), Mitchell
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M. Suthers et al., "SAW Nyquist Filters for Digital Radio", Proceedings of the IEEE 1987 Ultrasonics Symposium.
M. Suthers et al., "SAW Bandpass Filter Design Using Hermitian Function Techniques", IEEE Transactions on Sonics and Ultrasonics, vol. SU-27, No. 2, Mar. 1980.
Cameron Thomas P.
Kennard Paul A.
Saw John C. B.
Suthers Mark S.
Haley R. John
LaRoche Eugene R.
Northern Telecom Limited
Zarabian A.
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