Acoustic interferometer

About: Acoustic interferometer is a research topic. Over the lifetime, 1493 publications have been published within this topic receiving 19355 citations.

Coda wave interferometry

Abstract: An interferometer is an instrument that is sensitive to the interference of two or more waves (optic…

Acoustic Surface Wave Filters

Abstract: Acoustic surface waves offer several advantages in the construction of delay lines and filters in the UHF range. In these devices the frequency response is determined by the finger spacing and overlap of the interdigital comb structures used as input and output transducers. Models are developed to describe these devices, and the predictions of these theories are compared with several experimental filters, including band-pass filters and dispersive delay lines.

Measurement of Humidity Using Surface Acoustic Waves

Abstract: Th i s paper d e s c r i b e s a t e c h n i q u e f o r measuri n g humid i ty wi th h igh s e n s i t i v i t y and wide dynamic range us ing s u r f a c e a c o u s t i c waves. A d e l a y l i n e s t a b i l i z e d SAW o s c i l l a t o r i s used , t h e d e l a y l i n e be ing coa ted wi th a t h i n f i l m o f a s u i t a b l e hygroscop ic m a t e r i a l . S o r p t i o n o f m o i s t u r e produces r a p i d changes i n t h e e l e c t r i c a l and mechanica l p r o p e r t i e s o f t h e f i l m . T h i s r e s u l t s i n a change i n t h e v e l o c i t y of t h e s u r f a c e acoust i c wave and hence i n t h e f r equency o f t h e SAW o s c i l l a t o r . With poly imide used a s t h e hygros c o p i c m a t e r i a l , t h e f r equency o f a 75 MHz o s c i l l a t o r f a b r i c a t e d on a 128" Y-X LiNbOj s u b s t r a t e i s found t o va ry by more than 150 kHz as t h e r e l a t i v e humid i ty i s v a r i e d f r o m n e a r 0% RH t o 100% RH. The c a l c u l a t e d d e t e c t i o n l i m i t (assuming o s c i l l a t o r sho r t t e rm s t a b i l i t y o f 1 p a r t i n 10') i s less than 1 .5 pp"v o f humid i ty , o r a co r re spond ing dew p o i n t of -72°C. S imul t aneous humid i ty and t empera tu re s e n s i n g h a s been demons t r a t e d u s i n g a d u a l d e l a y l i n e approach .

Frequency Trimming of SAW Resonators

Abstract: Surface acoustic wave devices with precisely set frequencies are produced by laser trimming metallization strips on the device while monitoring the device frequency and/or phase shift. The trimming strips may be metallizations added during device manufacture or after device manufacture, or they may include selected ones of the reflecting gratings.