Substrate Noise Characterization

Substrate noise is a major problem that plagues mixed-signal circuits. Parasitic interactions from switching digital circuits propagate via the shared substrate to sensitive analog circuits adversely affecting performance. A chip was designed to characterize substrate noise generated by digital circuits as well as to study the effect of substrate noise on the performance of a standard component of the RF front-end, the voltage controlled oscillator (VCO). The chip was fabricated in a 0.18 µm CMOS mixed-signal process.