Modulated Measurements and Time-Local Signal Level Control

Power control directly on modulated signals with varying envelopes for network analysis and other measurements may be needed when pre-amplifier or other network drift is noticeable and the DUT is operating somewhat nonlinearly or not in thermal equilibrium. More importantly, this control (or leveling) may need to focus on certain portions of the envelope (e.g., maximum overshoot point at the beginning of a frame). Detection planes, detection methods and leveling loop structure are all important considerations and affect bandwidth, latency, control range and practical power accuracy. Direct digitizing detection at an IF can offer bandwidth and control range advantages but care is needed on latency control. Several hundred MHz to several GHz bandwidths with~100 dB detection range and ms-scale latencies are achievable through mm-wave carrier frequencies with sub-dB inaccuracies even for time scales of the order of nanoseconds.