This paper proposes two effective numerical methods to solve the optimal pr
oblem of contrast enhancement for the coherent and incoherent cases, respec
tively, For the coherent case, the objective function of the optimal proble
m is transformed into a bilinear form. Then a numerical method is presented
by using the idea of the Sequential Unconstrained Minimization Technique (
SUMT). For the incoherent case, a cross-iterative method is proposed for so
lving the optimal problem of contrast enhancement, based on the formula of
the optimal contrast polarization state in the matched-polarized channel. B
oth the proposed methods are convergent and straightforward for programming
. In addition, the proposed methods can he used for the bistatic radar case
because in this paper, it is unnecessary to restrict the symmetry of the s
cattering matrix and the Kennaugh matrix, For showing the effectiveness of
the proposed methods, we give three examples, The results of the calculatio
n are completely identical with other papers', showing the validity of the
proposed methods. In these three examples, if the receiving polarization st
ate is independent of the transmitting's, the power ratios mag be much larg
er than those in the cases of the co-polarized, the cross-polarized, and th
e matched-polarized channels, showing the importance of the considered mode
ls, In addition, the computation costs are estimated by these illustrative
examples? illustrating that the proposed methods are very effective.