Assess whether digital crosstalk limits science performance

Determine whether the measured digital channel crosstalk in the Gen2 KID readout limits the science performance of the science-grade 850 GHz KID arrays, and establish whether software enforcement of a minimum one-grid-step separation between tones’ bin-center offsets is necessary.

Background

The Gen2 receiver can exhibit increased crosstalk when neighboring probe tones have identical nonzero offsets from their FFT-bin centers. In measurements, separating these offsets by one 488.28 Hz frequency-grid step reduces the worst-case crosstalk increase, although the residual crosstalk remains above the zero-tone reference.

The science-grade 850 GHz KID arrays were still undergoing fabrication and characterization when the measurements were reported. Consequently, the paper does not resolve whether the observed crosstalk is consequential for scientific observations or whether the proposed software-only mitigation must be applied.