[en] The ECH system on TCV has recently been upgraded to a total of 4.5 MW of installed power. In order to extend the density range of ECH heated plasmas up to electron densities of 1.2 x 10²⁰ m^-3, three 0.5 MW gyrotrons at a frequency of 118 GHz have been added to the existing 3 MW 2. harmonic system operating at a frequency of 82.7 GHz. The launcher consists of one mirror placed at the top of the vessel, which collects the power of the 3 microwave sources, and can be steered radially and poloidally to ensure maximum flexibility. The choice of the top-launch scheme results as a compromise between heating of high density plasmas and the maximization of single-pass absorption in ohmically heated target plasmas. In this launching configuration, the high sensitivity of single-pass absorption on launching geometry has been experimentally demonstrated. A comparison between the experimental results and the linear ray-tracing/absorption code TORAY-GA shows a good agreement for densities up to 6.0 x 10¹⁹ m^-3. (authors)