Meaning
Coherent receiver signal processing estimates and corrects rapid phase rotation in ultra high frequency carrier signals. Utilizing sub THz carrier phase tracking permits receiver modems to demodulate complex phase shift keying signals at frequencies above 100 GHz. The scope covers sub terahertz wireless backhaul links and high speed point to point transceivers.
Direct envelope detection systems and low frequency non coherent receivers fall outside this signal processing boundary.
Phase Estimation
Local oscillator phase noise increases severely at sub terahertz frequencies, spreading signal energy across adjacent spectrum. Modern modem architectures apply sub THz carrier phase tracking to estimate phase deviations using pilot symbols embedded in data frames. Digital phase locked loops compute error signals and update local phase estimates every symbol period.
Compensating for fast phase fluctuations preserves signal constellation clarity at high data rates.
Noise Mitigation
Thermal noise and hardware phase jitter degrade carrier recovery loops in sub millimeter wave front ends. Adaptive loop filters adjust bandwidth dynamically to balance noise suppression against tracking speed. Wide loop bandwidths track rapid phase drift but admit more thermal noise into the estimation process.
Optimizing loop parameters requires accurate measurement of phase noise profiles during hardware qualification testing.
Feedback Loop
Phase estimation circuits feed phase corrections directly into digital baseband rotators. High speed sub THz carrier phase tracking prevents symbol errors during transient thermal variations in front end hardware.
