High-Accuracy Wideband Frequency Measurement With Dual Optical Combs Using Solution Space Partitioning Method

Noncooperative electromagnetic radiation source sensing faces challenges such as wide bandwidth and an unknown number of sources, which hinder various applications like electromagnetic compatibility, radar detection, and passive positioning. Traditional sweep reception methods, based on antennas and superheterodyne receivers, struggle to meet real-time requirements. Optical undersampling sensing technologies enable rapid reception in ultrawideband. Frequency measurement in these systems, however, requires triple-comb or higher-dimensional information, introducing complexity and instability. The dual-comb-based frequency measurement method is further complicated by dead zones due to its underdetermined nature. In this article, we demonstrate, for the first time, the boundedness and reachability of the solution to the dual-comb ultrawideband frequency measurement problem. We propose a boundary determination method that ensures error-free solutions. Simulation and experimental results demonstrate that our method achieves 98% accuracy for a single source with seven octave bandwidths and over 90% accuracy for the coexistence of two-five sources. This method can achieve accurate measurement with only a 5 dB signal-to-noise ratio (SNR) and exhibits high robustness. Our work clearly defines the theoretical limits of frequency measurement for dual-comb undersampling systems, significantly enhancing both test accuracy and engineering practicability. This method can be widely applied to frequency measurement and signal estimation in RF and optical systems, paving new high-speed, accurate and robust pathways in microwave photonics metrology and ultrawideband signal processing.