Differential synchronous demodulation for small signal amplitude estimation

A CMOS Magnitude/Phase Measurement Chip for Impedance Spectroscopy

“…Another method for measuring impedance is synchronous sampling [15][16], where sampling of the measured signal at the time when the injected signal peaks and crosses zero allows the calculation of the real and imaginary parts (see Fig. 2).…”

“…Offsets can be eliminated by averaging the samples of both positive and negative half-cycles and multi-frequency realizations can be implemented without the use of band-pass filters [16], similarly to SD. However, the analog implementation of SS [15] can be very challenging especially for high frequencies [15] as it requires very precise sampling timing and, as with SD, synchronization is a major degrading factor for both real and imaginary values.…”

Adaptive cancellations of systematic disturbances in a synchronous amplitude demodulator for sensors and instrumentation applications

“…The filter method [1] is commonly used when the delay introduced by the filtering is tolerable. On the contrary, when such delay becomes detrimental, synchronous techniques are employed [2,3,8,9]. The technique in [2] is faster in settling time when compared to the filter method, which, however, is at the cost of precise clock timing relations.…”

“…Amplitude demodulation finds many practical applications in fields like communication systems [1], sensor instrumentation [2][3][4], signal processing, and system identification. Different approaches [1] are found in literature for demodulation of amplitude modulated (AM) ordinary, single side band (SSB), and double side band (DSB) signals.…”

A Novel Interface for Eddy Current Displacement Sensors

“…In [15], some methods for demodulating an AM-modulated signal are discussed. Demodulating a relatively high-frequency signal with low-power consumption (less than a few milliwatts) is a challenge.…”