Electron Cyclotron Resonance Ion Sources (ECRIS) are compact plasma-based machines able to feed particle accelerators with high intensity beams of multi-charged ions. ECRIS plasmas are density-limited, since they are sustained by E.M. wave propagation up to a cut-off density value. In the past, the only way to improve ECRIS performance was to increase the microwave frequency and the magnetic field strength to satisfy the ECR condition. A different plasma heating mechanism is being applied at INFN-LNS. It is based on Electron Bernstein Waves (EBW), i.e., electrostatic waves which do not suffer any density cut-off. Highlights concerning preliminary signatures of EBW formation and subsequent absorption are given here.