This paper presents a novel adaptive predistortion technique for general cross-coupled microwave/RF filters with improved insertion loss and group-delay equalization. The method enables many potential applications of an almost abandoned technique, and permits a lower Q implementation technology to emulate the performance of a higher Q filter. 10-4-4 filters were built and tested at C- and Ku-band to verify the validity of the new method. The impact to satellite communication channels was also analyzed. Another novel concept of over-predistortion was proposed and evaluated and should lead to significant improvement for applications such as satellite transponder input multiplexers, where insertion loss can be traded off for in-band flatness, mass, volume, and even overall system performance.