Realization of Low-frequency Amplitude Modulator and Demodulator with FPAAs

This paper presents a low-frequency amplitude modulator and demodulator based on Field Programmable Analogue Array (FPAA) devices. For creating the FPAA circuits, amplitude modulation and synchronous demodulation methods known from designing analogue RF transmission systems have been adapted. The proposed system allows redesigning the analogue conditioning stage thanks to the use of a FPAA device, which may be adapted to the requirements of the signal shape and the electrical parameters. For a sinusoidal carrier signal the amplitude modulation (AM) is performed with multiplier, while for a square-wave carrier signal, switch is employed instead of multiplier. In the synchronous demodulation the modulated carrier sinusoidal signal is multiplied by an unmodulated carrier signal with the same frequency and phase. For a square-wave carrier signal in the demodulation process the multiplier is replaced with switch, controlled by square-wave signal. The functional elements of the structures are realized by employing available configurable analogue modules (CAMs) of the FPAAs AN231E04 and AN220E04 from Anadigm. The FPAA circuits can operate with single supply voltage of +3,3V and +5V, respectively. The simulation and experimental results show good agreement with the theoretical predictions.