A complex coefficient filter obtained by directly exchanging several reactance elements included in a real coefficient BPF for imaginary valued resistors is described. By using the proposed method, we obtain four varieties of complex coefficient filters. The stability problem is examined.

In this paper, a new frequency transformation for complex analog filter design which is suitable for integration is discussed. Arbitrary specified passband and stopband edges are easily transformed into those of the normalized LPF by solving simultaneous equations with four unknowns. Different from previous methods, the proposed transformation provides better performance in active realization of complex filters.

Complex filters are used to synthesize real filters in digital signal processing, but few in analog one. In this paper, we propose a leapfrog synthesis of complex analog filters. By shifting frequency response of an LCR network along the ω-axis, we have a complex filter with imaginary resistances, which is called an "LCRRi filter." The complex resonator is then used to simulate series- or parallel-arms of the LCRRi filter. We analyze nonideal properties of the complex resonator due to finite gain-bandwidth product of operational amplifiers and propose a compensation method to put a pole on correct location. Experimental results show good performance of the proposed method.