Special analog multipliers in voltage-controlled oscillator and phase-locked loop-based FM demodulator for measurement and processing of sensed low-frequency signals

•A special voltage-controlled oscillator (VCO) is proposed for PLL-based frequency demodulator.•Issues with large values of capacities, due to AC coupling, at the processing of very low frequency signals in on-chip systems aresignificantly suppressed.•The proposed concept allows feasible measurement of AC coupled slowly varying signals (e.g. from biosensors) incommunication subsystems integrated on chip.