Surface wave devices with low passband ripple
OwnerChun-Yun Jian, Steve A. Beaudin +1inventors
InventorsChun-Yun Jian, Steve A. Beaudin, Somsack Sychaleun
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Abstract
Very low passband ripple is provided in a wide bandwidth high frequency SAW FIR filter using slanted finger IDTs by one or more of three techniques: cancelling regenerated SAWs at parallel-connected input IDTs of two SAW filters which are similar except for a quarter-wavelength difference in spacing of the input and output IDTs, this difference varying with wavelength across the IDT aperture; shaping edges of shield electrodes to provide quarter-wavelength differences in, and hence cancellation of, SAWs reflected at the edges, the differences varying with wavelength across the IDT aperture; and making pairs of slanted shield electrodes symmetrical to compensate for refraction of SAWS by the shield electrodes.
Claims4
A SAW (surface wave) device comprising:
- a first input IDT (inter-digital transducer) and a first output IDT forming a first SAW filter, at least one of the IDTs of the first SAW filter having a slanted finger geometry for SAWs at a plurality of different wavelengths over an aperture of the IDT;
- and
- a second SAW filter comprising a second input IDT and a second output IDT;
- wherein the second SAW filter is similar to the first SAW filter except that it provides a 180 degree phase change, relative to the first SAW filter, for SAWs regenerated at the output IDT and returned to the input IDT, said 180 degree phase change being provided respectively for said plurality of different wavelengths;
- the second input IDT being connected in parallel with the first input IDT so that said regenerated SAWs substantially cancel one another at the input IDTs for said plurality of wavelengths over said aperture.
Dependencies are inferred from the claim text.