Amplitude adaptive asynchronous Sigma-delta modulator

The paper presents an improved version of Asynchronous Sigma-Delta Modulator (ASDM) in order to reduce its power consumption for time-encoding of analog signals. The proposed method is called Amplitude Adaptive ASDM (AA-ASDM) since time-varying envelope of the signal is used in the feedback loop of ASDM to reduce the switching rate of the output trigger. Regardless of this reduction the perfect recovery of the original signal from the obtained time sequence is still possible. The proposed method is particularly advantageous for signals with wide dynamic range and is demonstrated by numerical results on the example of electroencephalography (EEG) signal.