Experimental Evaluation of Joint Clock Recovery and Equalization for Sub-Terahertz Links

This paper proposes and experimentally evaluates a joint clock recovery (CR) and equalization architecture tailored for high-speed sub-terahertz (sub-THz) wireless communication links. Specifically, a Baud-spaced digital receiver architecture is investigated that combines a constant modulus algorithm (CMA) equalizer with a blind timing error detector (TED), enabling robust symbol timing synchronization without decision-directed (DD) feedback or pilot symbols. The proposed TED leverages the CMA filter coefficients to estimate timing errors, which are then used to drive a Farrow interpolator operating at twice the symbol rate. The system is validated experimentally using a 140~GHz wireless testbed with 16-QAM modulation over a 10~GHz bandwidth. Results show that the proposed TED schemes outperform conventional blind TEDs, such as Gardner and blind implementations of Mueller \& M\"uller, in terms of bit error rate (BER), error vector magnitude (EVM), and intersymbol interference (ISI) suppression. These capabilities are especially relevant to next-generation spaceborne communication systems, where wideband sub-THz links are expected to play a key role in enabling ultra-high-data-rate inter-satellite and deep-space communications under challenging synchronization constraints.