Additional circuits for current-mode frequency discriminators

The concept of current-mode frequency discriminators based on the Butterworth lowpass approximation and realized by cascading network sections was introduced in a previous paper. However, these circuits were limited to odd order because of the effects of parasitic capacitance which restricted the usefulness of even order realizations at higher frequencies. Odd order realizations needed only two types of current-mode circuits, and compensation could be employed for the parasitic capacitances. In this paper, additional circuits are devised so that the previous results can be extended to realizations of even order current-mode frequency discriminators based on the Butterworth approximation and to odd order approximations using the inverse Chebyshev approximation. As with the odd order realizations given previously, only two types of current-mode circuits are needed in the realization of a particular frequency discriminator, and parasitic capacitances can be taken into account. The circuits are simulated using non-ideal models for the current conveyors, and the results are compared with laboratory data. The effects of parasitic elements and departures of circuit characteristics from ideal are discussed.