I am a beginner in CVX and I have read the reference guide and the DCP ruleset, but I cannot find any useful information. Could anyone help me with this problem?

In my objective function, there is an expression of v’*R_A*v*v’*R_B*v, where R_A and R_B are both Hermitian matrices. So this part should be a biquadratic function of the variable v and it should be convex, but it seems that CVX cannot accept it and it shows:

Disciplined convex programming error:

Cannot perform the operation: {convex} .* {convex}

Can anyone offer me some hints to deal with this problem? Thanks in advance.