This paper, which is mostly tutorial in nature, deals with the design of CMOS microelectromechanical systems MEMS using standard microelectronic computer-aided design tools. The proposed case study is an on-chip spectrum analyzer with an electronic mixer and a mechanical filter. Based on both analytical modeling and characterization, the filter is described using an analog hardware description language. System level simulations are then performed using a recently released simulation tool that offer new possibilities regarding the analysis of multidomain, multifrequency designs. Presented results include periodic steady state determination, small-signal analysis and noise investigation. The simulations demonstrate the ability of the proposed system to identify the harmonics of a 50-Hz square-wave signal, owing to the selectivity of the mechanical filter.