On-chip Electromagnetic Interactions in CMOS Cascode LNAs

Target of this work is to explain the significance of electromagnetic effects due to on-chip spiral inductors and passive interconnects on the circuit behavior. Starting from the design aspects of spiral inductors in a cascode CMOS LNA, the influence of their on-chip coupling on the reverse isolation performance of the amplifier will be presented. The importance of the careful consideration of on-chip spiral inductor shielding and substrate coupling effects are detailed and justified by comparison with the measured S-parameter results. Finally, it will be shown that by considering all the on-chip spirals and critical passives through electromagnetic analysis it is possible to estimate very precisely the measured isolation, gain and matching characteristics of a cascode CMOS low noise amplifier around 6 GHz frequency of operation.