First-order adjustable transfer sections for synthesis suitable for special purposes in constant phase block approximation

The main aim of this work is to investigate electronically adjustable properties of discussed simple transfer sections i.e. all-pass and bilinear filters and their practical verification. Signal-flow graph (SFG) approach was used for better understanding of circuit design and its principle. Simultaneous and separated control of the zero and pole frequencies is available, thus this circuit is favorable for design of both classical and special applications such as constant phase elements/blocks and fractional-order synthesis. Interesting example of operation in two-port block (so-called half integrator) with approximation of constant phase character (shift) is given. Our intentions are supported by PSpice simulation results prepared with active elements modeled on CMOS transistor level in low-voltage TSMC LO EPI 0.18 μm process and also by experimental laboratory tests employing commercially available active elements.