Cascade configurations for recursive-like adaptive noise cancellation

Two novel recursive-like two-stage adaptive noise cancellers that circumvent the requirement, in prior art one-stage recursive-like cancellers, of incorporating a constraint on filter coefficients, are presented. These novel two-stage cancellers are based on a cascade configuration, rather than the prior art parallel configuration. For applications in which even a small amount of signal distortion is intolerable, a third novel two-stage noise canceller that guarantees distortion-free performance is presented. Finally, a multistage cascade configuration that has the potential for distortion-free, high-performance noise cancellation is presented.