  We introduce a new class of unitary transformations based on the su(1,1) Lie
algebra that generalizes, for certain particular representations of its
generators, well-known squeezing transformations in quantum optics. To
illustrate our results, we focus on the two-mode bosonic representation and
show how the parametric amplifier model can be modified in order to generate
such a generalized squeezing operator. Furthermore, we obtain a general
expression for the bipartite Wigner function which allows us to identify two
distinct sources of entanglement, here labelled by dynamical and kinematical
entanglement. We also establish a quantitative estimate of entanglement for
bipartite systems through some basic definitions of entropy functionals in
continuous phase-space representations.
