Dynamic overload recover mechanism for sigma delta modulators

An example of a non-linear filtering technique has been presented as a means of stabilising higher order sigma delta modulators in which a limiter is employed to prevent the output of higher order filter stages from dominating at the input to the quantizer. Recovery of the lower order filter stages is thus enabled. An output from the lower order stages is derived with properties which enable the subsequent recovery of the higher order filters. Switching noise from the limiter is shaped out of the passband by the modulation process, and may thus be operated frequently with negligible degradation to the output. This enables greater noise suppression than is possible with overload detect/reset schemes, and the dynamic range of the modulator is extended before catastrophic failure occurs