Study On The Transmission Properties Of Phononic Crystal Based On Optical Heterodyne System

Propagation of acoustic waves in the phononic crystals has been widespread concernedby many scientific and technical workers.In the range of phononic crystals band gap,the acoustic energy exponential decay rapidly, so the use of phononic crystal canachieve acoustic wave control.Further study shows that the local resonant phononic crystalhave different band gap characteristics significantly.local Resonance of local resonantphononic crystal make the effective mass density change to negative, forming thecharacteristics of low frequency band gap.In this paper, we provide a quantitative guidancefor the phononic crystal design and experiment based on the local resonance.For the phononiccrystal in the application of low frequency noise and vibration reduction has importantsignificance.Optical heterodyne interferometry measurement technology as the leading test method isused in the subject. Phononic crystal which is stimulated by piezoelectric film incentivecrystals produces the surface vibration. Then it is detected by the form of optical signal whichis used with PLL demodulation circuit for signal processing. In the phase lockingdemodulation circuit,first of all, the lock-in amplifier SR844is used to realization ofweak vibration signal detection, then using a self-developed phase lock loop circuit to replacethe SR844, to demodulate the phononic crystal resonance frequency by using two groupsof different methods, to form the test and signal processing system model.This system has successfully realized the measurement of vibration of phononic crystals,it can be stable, overcome the direction fuzzy, noise elimination, It is expected to become themeasurement system of phononic crystals. In the future, the system has important significancefor the design and testing of phononic crystal sheet, Widely used in precision displacementand Angle measurement field.