Precise mixed signal synchronous detector with spectrally improved binary switching

Synchronous detectors of analogue signals, using binary switching for synchronous rectification of analogue signal, can give high accuracy, but are sensitive to harmonic components of the input signal and also so more sensitive to noise. An example of precise high accuracy synchronous detector with high dynamic reserve is described. Further use of binary periodic sequence to approximate a reference sine- (and cosine-) wave, has been investigated, by using a periodically repeated fragment of a delta-sigma modulated bit-stream. Reasonable parameters for such bit-stream has been found, allowing to improve the spectral purity of the reference signal by an order. Also further possibilities to optimize such bit-streams have been discussed.