NEP estimation. As a function of the channel frequency: (a) LEKID frequency shift for illuminations with black-body sources at 300 K and 0 K; and (b) LEKID relative frequency shift for an illumination with the millimetre-wave source. Normalisation is with respect to state-of-the art NIKA pixels (see text for more details), (c) LEKID noise spectral density at 10 Hz. (d) NEP estimated with the black-body source illumination (bb) or with the millimetre-wave source (mm).