We review some of the difficulties previously encountered in defining the phase operator for finite quantum systems. We then propose the Wigner-Weyl quantization of the angle function q> on phase space as the phase operator, and derive a closed expression for its matrix elements with respect to the Hermite functions. We also determine the quantization of e l , which turns out to be a weighted shift operator, its spectrum and that of its adjoint. This is done in the framework of quantization of a certain symbol class of phase space distributions, specialized to those which depend on one variable only. After recalling some results for the position and momentum variables, we apply the scheme to functions of radius or angle. We give necessary and sufficient conditions for operators obtained by quantizing functions of the angle to be elements of ^ + [^(R)] and ^+ [^(R), L 2 (R)], and a sufficient condition for boundedness.We then consider the associated questions of commutation relations and uncertainties for operators in J^+ [5^(R), L 2 (R)], which we define as bilinear forms. As must be the case, the commutator between our phase operator and the number operator exhibits noncanonical terms. Not surprisingly, the Poisson bracket of their phase space symbols also exhibits a noncanonical term. § 1. IntroductionIn one of the first papers on quantum electrodynamics, Dirac [1], in considering the Fourier modes of the field, introduced a polar decomposition of the raising and lowering operators (equation (10) and §10 of [1]). He interpreted the positive self adjoint operator so obtained as the number operator for the mode, and the partial isometry as the exponential of the phase operator. However, a partial isometry which is not unitary cannot be the exponential of an operator, so his interpretation was not quite correct. If one ignores this and proceeds formally, one comes to an operator canonical to the number Communicated by H. Araki, February 24, 1993. 1991 46N50 (secondary)