Approximate Synthesis of a Higher-Order Passive Complex Coefficient Filter Using Autotransformers

Abstract

In this paper, a new method for synthesizing a higher-order passive complex filter using autotransformers is proposed. The proposed filter can be synthesized approximately by transforming the conventional one. Since the proposed transformation replaces all transformers with autotransformers, the proposed filter has no floating windings. As examples, both first-order and third-order complex filters are synthesized. The validity of the proposed method was confirmed through computer simulation and experiment. Due to approximate synthesis, the transfer function of the real output is different from that of the imaginary output. However, both of them have roughly the same response near the passband. Experimental results show good agreement with the theoretical value. It means that the proposed method is valid for the practical application.