Novel high-frequency crystal oscillator cuts jitter and noise

摘要

The inverted Mesa resonator offers a high-performing alternative to SAW-based oscillators and other bulk resonator types, which use a noisy PLL or other such parametric multiplier that also multiplies noise. Oscillators have been developed to demonstrate the effectiveness of this design technique. The fast data rates of today's digital systems continue to demand faster and better clock signals with low jitter and phase noise attributes—not to mention smaller form factors. Crystal oscillators are typically the devices that are providing the originating timing signals for these systems. Oscillators with internal phase-lock loops (PLLs) that generate a high-frequency output from an easily produced low-frequency crystal are often used. However, the degraded phase jitter of this approach is prohibitive for many new applications. Other techniques, such as the use of surface acoustic wave (SAW) devices, have cost, availability and frequency stability issues. We take a look at the design process, trade offs and the resultant benefits of oscillators built with pure analog circuits and no frequency multiplication for providing the clock signals for jitter-intolerant systems. Actual test results of models VF266 and VF261 oscillators are used as an example.