Invalid quadratic form: not a scalar

Hi every one,
I have the below

    variable A_tilda(2,m);
   minimize (trace(A_tilda'*DD*A_tilda*G)-2*trace(D*A_tilda*PP));
    subject to 
        bb*phi <= 1;
        A_tilda * phi >= 0;

where m=10, DD is (22), G is (1010), D is (32), PP is (103), bb is (110) and phi is (101).
I tried to run it but i have error message and this message is

{Error using * (line 109)
Disciplined convex programming error:
Invalid quadratic form: not a scalar.}
and that line (i.e. line 109) is the minimization line within the cvx.
Can anyone help me with this issue.