Inductor-Based Tuning in $LC$ -Quadrature Oscillators: A Comparative Study

This brief analyzes three different mechanisms for injecting a tuning current into the tank of inductively tuned LC-quadrature oscillators. It is shown that, by controlling how the tuning current is injected into the tank, either by magnetic coupling, direct coupling, or the newly proposed partial coupling, a tradeoff exists between tuning range, phase noise, and power consumption. This leads to a very flexible design methodology where the coupling mechanism can be selected based on system-level requirements, which may change from one design to the next.