Inductorless variable equalizers

This paper shows that by mapping the range of the variable element in the classical Bode variable equalizer from
0 \leq R \leq \infty
to
- R_0 \leq R \leq R_0
, one arrives at a different formulation of the equalizer transfer function.[ Canadian and U.S. Patent Applications pending.] This transfer function suggests new forms of variable equalizer network structures. The advantage of these structures is that they require only a single shaping immittance for realization, thus enabling simulation of coaxial cable losses in terms of
RC
or
\overline{RC}
networks alone. This is important in hybrid IC realizations. Furthermore, active realizations provide basic building blocks for direct cascading of multiple sections. An experimental RC variable equalizer has been designed for
\pm
10 dB continuously variable magnitude range and the measured responses are shown to be in excellent agreement with those evaluated from the computer-simulated model.