The scattered electromagnetic field from a collection of raindrops is determined by the coherency matrix. To estimate the polarization of the scattered field from radar measurements a dual channel receiver is required. The echo powers in the main and orthogonal channels and the complex correlation between them are proportional to the elements of the coherency matrix. A generalized radar equation is given in matrix form for the bistatic polarization diversity radar and the dependence of radar parameters on various model assumptions, such as drop shape, drop size distribution and canting angle distribution is investigated. Calculated results at 33 GHz show that bistatic measurements with a scattering angle of 90°–100° at horizontal and vertical linear polarizations are especially suited to estimate the parameters of the drop size distribution, the mean canting angle and the canting angle distribution. The effect of rain occurring on the path between the transmitter, the rain target and the receiver is also considered.