COVARIANT TIME-FREQUENCY DISTRIBUTIONS BASED ON CONJUGATE OPERATORS

We propose classes of quadratic time-frequency distributions that reta in the inner structure of Cohen's class. Each of these classes is base d on a pair of ''conjugate'' unitary operators producing time-frequenc y displacements. The classes satisfy covariance and marginal propertie s corresponding to these operators. For each class, we define a ''cent ral member'' generalizing the Wigner distribution and the Q-distributi on, and we specify a transformation by which the class can be derived from Cohen's class.