Log constraint in cvx

i was wondering how to change such constraint so cvx can accept it; “a” is the only variable, others are constant.

thanks in advance

The LHS changes between convex and concave at some a value, depending on the constant values. So in general, I believe this is a non-convex constraint.

If you have more detailed information on all the constant values and can prove convexity of the constraint, please do so.