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This paper proposes a complex filter excluding inductors with transmission zeros at an arbitrary frequency. Even though the attenuation characteristics of the proposed complex prototype filter and those of the conventional one including inductors are the same, the proposed complex prototype filter includes no inductors. The required elements can be reduced when the proposed prototype complex filter is realized by using Negative Impedance Converters (NIC's). Compared with the required active elements of conventional circuits, those of the proposed one are 50% or less. The experimental result agrees well with the ideal response. The calculation results of the sensitivity characteristics are shown.

In the orthogonal signal processing, wideband complex filters are required for sending and receiving large amounts of information at high speed. In order to reduce the required active elements, a complex filter obtained through the reactance simulation approach using CCII’s has been proposed. In this method, the required CCII’s are reduced by using impedance inverters such that the complex prototype filter includes no inductors. However, the conventional circuit is not suitable for applications which require high-speed data communication because it is difficult to design the wideband complex filter with this method. In this paper, a wideband complex prototype filter suitable for its active realization using CCII’s is proposed. The proposed method overcomes the above problem related to the passband width without increasing the required active elements. Moreover, a technique for compensating the parasitic resistors included in CCII’s is proposed. Experimental result of the compensated circuit agrees well with the ideal response.

In this paper, a first-order complex filter realized by using a voltage follower is proposed. Applying equivalent transformations to a passive complex filter, a complex filter including a series circuit of a resistor and an inductor is obtained. This series circuit can be realized by using a voltage follower, a capacitor and resistors. The resulting circuit includes four resistors, two capacitors and a voltage follower only. The validity of the proposed method is confirmed through computer simulation.