HIGH-RESOLUTION PHASE DOPPLER PARTICLE SIZING BASED ON HILBERT TRANSFORM SIGNAL-PROCESSING

A new phase Doppler anemometry (PDA) signal processing method based on a Hilbert transform algorithm is introduced and analysed. By generati ng a 90 degrees phase-shifted burst signal in the time domain, the env elope of the Doppler burst can be determined. In addition, this envelo pe is approximated by a Gaussian exponential function. The difference of the maxima of these Gaussian approximations for two related PDA bur sts gives an estimate of the time difference between these time-shifte d signals. With the introduction of this estimation method, the restri ction to the [0,360 degrees] interval resulting from conventional sign al analysis may be avoided in many cases. To investigate the dependenc e on SNR, burst position, burst frequency and sampling rate, results o f computer simulations are presented. The feasibility of the method is demonstrated briefly by experimental results. Phase differences of mo re than 2000 degrees arising from the measurement of monodisperse drop lets by a conventional PDA setup could be determined.