This presentation highlights two portions of a larger research program to study combustion instabilities (CIs) in liquid rocket engines (LRE). The first topic is the development of a real-time active acoustic impedance boundary control system, focusing on the required wave separation algorithm. The second topic is an update of the processing techniques for high-speed, simultaneous diagnostic data by the simultaneous dynamic decomposition (SDD). The goal of this processing technique is to use sub-scale experimental testing to elucidate the CI driving mechanisms in full-scale LREs.