Beyond PLL: Measuring Your Resonator With 10x Higher Accuracy

Are you measuring or developing resonators and running into drift, instability, or unexplained frequency shifts? PLL-based methods are widely used, but they’re also highly sensitive to parasitic phase errors coming from cables, wiring, and setup variations. In this episode of The Measurement Minute, Tim sits down with Jim Phillips (Zurich Instruments USA) to explore how Pound–Drever–Hall (PDH) sensing provides a 10× improvement in resonator frequency stability compared to traditional PLL measurements. Jim walks through: • 01:55 Why PLLs react to spurious phase shifts that don’t come from the resonator • 02:28 What this means for achieving true center-frequency accuracy • 03:31 How PDH cancels these parasitic effects using triple-tone detection • 04:14 Real results from PDH vs PLL experiments in the lab Whether you work with SAW devices, microwave resonators, optical cavities, or cryogenic setups with unavoidable cabling, this episode shows how PDH can help reveal the real behavior of your device free from cable related drift. If you have any questions, write us in the comments below! _________________ Follow the latest from Zurich Instruments: Website: https://www.zhinst.com/ LinkedIn:   / zurich-instruments-ag