Researchers from the Changchun Institute of Optics, Fine Mechanics and Physics , Chinese Academy of Sciences, together with collaborators at Changchun University of Science and Technology, reported a key noise evaluation strategy for space-based interferometry in Symmetry-Basel. The paper introduced a comprehensive noise model and a symmetric differential circuit design, significantly reducing the phase measurement error in gravitational wave detection systems.

Space-based gravitational wave missions, such as Taiji and LISA, operate by measuring changes in distance between satellites with picometer-level precision. This requires the "phasemeter"—the electronic heart of the detector—to resolve phase shifts as small as a few microradians.

However, the analog front-end (AFE) circuitry, which serves as the gateway for converting optical signals into electronic data, is susceptible to inherent electronic noise. Thermal fluctuations, voltage instability, and current noise in this stage can drown out the faint signals from the universe before they are even digitized.To address this bottleneck, the team developed a rigorous theoretical framework to quantify these disturbances.

The researchers established a detailed equivalent noise model to map the complex transfer mechanism of electronic interference. By mathematically decomposing voltage, current, and thermal noise sources (shown in the diagram), the team could predict exactly how these factors convert into fatal phase errors, guiding the design of a quieter circuit.

Guided by this model, the researchers implemented a symmetric differential operational amplifier structure. Unlike traditional transformer-based designs, this architecture offers superior suppression of common-mode interference and better stability at low frequencies. To further purify the signal, the team employed a "pilot tone" technique. By injecting a reference signal of a known frequency, the system can identify and subtract sampling timing jitter—a subtle form of noise introduced during the analog-to-digital conversion process.

The research process validated the effectiveness of this dual approach. Theoretical derivation combined with circuit simulations proved that the additive noise sources could be effectively managed. Subsequent experiments demonstrated that the optimized front-end circuit acts as a "silent" transparent channel, maintaining the integrity of the phase information. The noise floor of the system was found to be well below the stringent requirements for space gravitational wave detection.

Taken together, the study provides a vital engineering foundation for future space observatories. By successfully modeling and suppressing the noise in the critical analog stage, the research ensures that the electronic systems of missions like Taiji will have the extreme sensitivity needed to listen to the ripples of spacetime, opening new windows into the physics of the early universe.