“…[22,26], has found important applications in Signal Processing and related problems in Numerical Analysis, see for example [8,42] and references therein. More recently, time-frequency methods have been applied to the study of the partial differential equations, in particular constant coefficient wave, Klein-Gordon, parabolic and Schrödinger equations [2,3,12,21,31,32,33,36,45,46], let us also refer to the survey [41] and the monograph [47]. The analysis of variable coefficient Schrödinger type equations was carried out in [4,9,10,13,14,15,16,19,43], see also [17,18] in the analytic category.…”