Abstract
Low-noise gigahertz (GHz) frequency sources are essential for applications in signal processing, sensing, and telecommunications. Surface acoustic wave (SAW) resonator-based oscillators offer compact form factors and low-phase noise due to their short mechanical wavelengths and high-quality (Q) factors. However, their small footprint makes them vulnerable to environmental variation, resulting in their poor long-term frequency stability. Injection locking is widely used to suppress frequency drift of lasers and oscillators by synchronizing to an ultra-stable reference. Here, injection locking of a 1-GHz SAW phononic-crystal oscillator is demonstrated, achieving 40-dB phase noise reduction at low offset frequencies and unperturbed low noise at large offset frequencies. Compared to a free-running SAW oscillator, which typically exhibits frequency drifts of several hundred hertz over minutes, the injection-locked oscillator reduces the frequency deviation to below 0.35 Hz. The locking range and oscillator dynamics is also investigated in the injection pulling region. The demonstrated injection-locked SAW oscillator could find applications in high-performance portable telecommunications and sensing systems.
| Original language | English |
|---|---|
| Article number | e202500605 |
| Journal | Physica Status Solidi (A) Applications and Materials Science |
| Volume | 223 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 2026 |
Funding
The authors thank Prof. Honghu Liu for fruitful discussions on the mathematics of injection‐locking dynamics. Device fabrication and SEMs were conducted as part of user projects (CNMS2024‐B‐02643, CNMS2025‐A‐02944) at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. This work was performed in part at Oak Ridge National Laboratory, operated by UT‐Battelle for the U.S. Department of Energy under contract no. DE‐AC05‐00OR22725, funding was in part provided by ORNL's Laboratory Directed Research and Development Program. This work was supported in part by the Defense Advanced Research Projects Agency (DARPA) OPTIM program under contract HR00112320031. This work was sponsored in part by the Air Force Office of Scientific Research (AFOSR) and was accomplished under grant number W911NF‐23‐1‐0235. The views and conclusions contained in this document are those of the authors and do not necessarily reflect the position or the policy of the Government. No official endorsement should be inferred. Approved for public release; distribution is unlimited.
Keywords
- injection locking
- phononic crystals
- surface-acoustic wave oscillator