How to solve Disciplined convex programming error: Illegal operation: exp( {affine} )

Hello,
I’m trying to solve the problem with cvx in the following:

m=3;n=2;ws=[0 -0.1 -0.4].';
R=[ 1.1757  0.7545 - 0.3659i   0.7469 - 0.1285i;
     0.7545 + 0.3659i  0.9079       0.6923 + 0.2345i;
     0.7469 + 0.1285i   0.6923 - 0.2345i   0.9163 ];

cvx_begin
    variable p(n)
    expressions Az(m,n) Pa(m,m)
    Az=exp(j*ws*p.');
    Pa=Az*(Az'*Az)^(-1)*Az';
    maximize(abs(trace(Pa*R)));
    subject to
    min(p)>=-5;
    max(p)<=25;
cvx_end

It came out an error:Disciplined convex programming error: Illegal operation: exp( {affine} )?
I have read the guide for this kind of Disciplined convex programming error but I’ve no idea how to rewrite the exponential expression for Az. Any help from your guys would be appreciated.
Thanks
Joyce

Your problem is not convex.