Designing SAW resonators and DRO oscillators using nonlinear CAD tools

In recent years, these types of high stability oscillators have been empirically designed. The key quality factors one seeks are both short- and long-term stability. When using CAD tools, the analysis of such oscillators has been done looking for the negative resistance approach indicating that there is potential for oscillation. Under large signal conditions, however, the semiconductor parameters change and the loading by the transistor imposes changes on the circuit, specifically the resonator, and therefore, the linearized assumptions will fail. By taking advantage of a) precise design modeling for time domain nonlinear equivalent circuits and its noise contribution, b) using the noise correlation matrix as a vehicle to put the noise sources together, and c) by using the modulation matrix calculation for close-in phase noise and the conversion matrix calculation for far-out noise, we gain accurate insight into the phase noise. By combining all of these techniques and applying optimization techniques, we can take circuits of arbitrary topologies at microwave frequencies which exhibit high Q and optimize them for performance. This method eliminates the time consuming trial and error approach and provides accurate results as will be demonstrated using simulation and published measured results.