Active Envelope Load-Pull for Wideband Multi-tone Stimulus Incorporating Delay Compensation

This paper presents, for the first time, a new active load-pull approach capable of supporting wideband multi-tone modulation based on the active envelope load-pull architecture. The new solution utilizes a digital control unit, implemented on a reconfigurable FPGA platform with high-speed signal processing capability, in the feedback loop to track the time varying amplitude and phase envelope of modulated RF communication signals. This novel approach enables a loop delay compensation scheme to be successfully implemented allowing for synchronization of the transmitted and the reflected signals over wide (>5 MHz) bandwidths. Initial, proof of concept, measurements on this active load-pull system have demonstrated that it can provide constant, frequency independent control of load impedances for signal excitations that are relevant for communication systems.