In this paper, the main defects of LC-based ΣΔ modulators due to process variations are presented. Resonance frequency shift of LC tank circuit, which was discussed is some publications, is shown to be one among many other possible defects that are discussed in this paper. The effect of each defect on modulator output spectrum is shown and discussed. It is suggested that the information extracted from the output spectrum can be used to calibrate the modulator main blocks.