  Classical gradient-based density topology optimization is adapted for
method-of-moments numerical modeling to design a conductor-based system
attaining the minimal antenna Q-factor evaluated via an energy stored operator.
Standard topology optimization features are discussed, e.g., the interpolation
scheme and density and projection filtering. The performance of the proposed
technique is demonstrated in a few examples in terms of the realized Q-factor
values and necessary computational time to obtain a design. The optimized
designs are compared to the fundamental bound and well-known empirical
structures. The presented framework can provide a completely novel design, as
presented in the second example.
