Djurhuus, Torsten2; Krozer, Viktor2; Vidkjær, Jens2; Johansen, Tom Keinicke2
1 Electromagnetic Systems, Department of Electrical Engineering, Technical University of Denmark2 Department of Electrical Engineering, Technical University of Denmark
The dynamic equations governing the cross-coupled quadrature harmonic oscillator are derived assuming quasi-sinusoidal operation. This allows for an investigation of the previously reported tradeoff between close-to-carrier phase noise and quadrature precision. The results explain how nonlinearity in the coupling transconductances, in conjunction with a finite amplitude relaxation time and de-tuning of the individual oscillators, cause close-to-carrier AM-to-PM noise conversion. A discussion is presented of how the theoretic results translate into design rules for quadrature oscillator ICs. SPECTRE RF simulations verify the developed theory.
I E E E Transactions on Circuits and Systems Part 1: Regular Papers, 2005, Vol 52, Issue 11, p. 2276-2285