A digital differentiator-based MSK demodulator in a zero-IF receiver for 2.4 GHz Zigbee applications

A new digital differentiator-based demodulator in a zeroIF receiver for 2.4 GHz Zigbee applications is proposed. It receives the In-phase (I) and Quadrature-phase (Q) signals which are oversampled and quantized by a 4-bit ADC @ 8 MHz. Two one-order digital differentiators based on Taylor series, two multipliers and an adder are adopted to calculate the derivative of the signal phase. Then an Integrate-and-Dump Filter (IDF) is applied to obtain the phase difference in the chip time and determine its sign as the transmitted data. No complex carrier synchronization is needed and the demodulator can achieve low power consumption and low cost for its simple architecture. The theoretical analysis of Chip Error Rate (CER) under Additive White Gaussian Noise (AWGN) environment is also presented. The simulation results show that the proposed demodulator achieves Packet Error Rate (PER) of 1% with Carrier Frequency Offset (CFO) of 200 KHz and Signal-Noise Ratio (SNR) of 9.4 dB.