Methods of Weyl representation of the phase space and canonical transformations. I

The structure of the kernel of a canonical transformation and a differential equation for the symbol of the intertwining operator are found. The symbol of a general linear canonical transformation is constructed in terms of a Cayley transformation of the symplectic transformation of the phase space. Its singularities and applications to group theory are studied. The Green's functions and spectral projectors of arbitrary quadratic systems are constructed using the classification methods of classical mechanics.