where f is complex vector,K0_hat,K2_plus_hat are positive semi-definite,lambda,p1,c are constant.

My code:

1 cvx_begin quiet

2 ~~~~ variable f( M^2 ) complex

3 ~~~~ variables x

4 ~~~~ minimize( square_pos( norm( K0_hat * f + k0_hat ) ) + lambda * x );

5 ~~~~ subject to

6 ~~~~~~~~ square_pos( norm( f ) ) <= P1;

7 ~~~~~~~~ square_pos( norm( K2_plus_hat * f + k2_hat ) ) <= c + x;

8 ~~~~~~~~ x >= 0;

9 cvx_end

There is a error at line 7

??? Error using ==> cvx.plus at 83

Disciplined convex programming error:

Illegal operation: {complex affine} + {invalid}

The question；

How to amend this error?