Pulse coding for a new scanning bistatic acoustic wind profiler.

Abstract

We describe signal coding for a new design of SODAR (atmospheric acoustic RADAR) used for profiling atmospheric turbulence and winds. This bistatic SODAR uses a central vertically pointing transmitter and three synchronized phased‐array scanning receivers spatially distributed on the ground and, at any instant, simultaneously pointing at the same region of the central atmospheric column. There are distinct advantages if continuous transmission can be used, since total signal power and fast profile acquisition are enhanced. However, the weak echoes mean that the receivers will record a combination of transmitted and scattered sound, so the two need to be orthogonal. This suggests a signal coding scheme. However, turbulent scattering acts similarly to an acoustic reflective diffraction grating, and this places severe constraints on signal coding. We therefore explore a sawtooth linear FMCW system, designed to optimize separation of echo and direct signal, while not detuning too much the Bragg diffraction grating relationship. An implementation of this new bistatic system and first results are discussed.