Switched-current wave group delay equalisers

To improve the elliptic filter step response, group delay equalisers are often cascaded with the filters. The paper describes the design of switched-current (SI) group delay equalisers using the wave synthesis technique. This design is based on a new all-pass circuit, where the poles are generated using wave structures. Simulation results are included demonstrating that the 3rd-order SI group delay equaliser can reduce the amount of overshoot in the 100kHz elliptic low-pass filter step response by ≥50%. This is as a result of reducing the filter group delay variation from 2.29 μs to 0.32 μs when the group delay equaliser is employed.