Predistorted Distributed Active Filters

This paper outlines a novel and systematic method for designing active microwave filters in Microwave Integrated Circuits (MICs) technology. The technique is based on predistortion of the filter transfer function by appropriate loss or gain factor, enabling the designer to realize all his filter specifications without resorting to circuit optimization and tuning (tweaking). The strength of this technique has been demonstrated in terms of computation time and memory requirement, and in comparison with the well established EM-Simulator software by Sonnet. A 3rd order passive coupled-line band-pass microstrip filter has been designed and fabricated in-house using this technique, while a negative resistance chip, which was fabricated using GEC-Marconi F20 process, is coupled to the passive filter to compensate for the passband insertion loss. This will realize the desired active MIC filter. The simulated and measured results are in good agreement and validate our proposed method.