A high performance FSK demodulator for zero-IF receiver in the 863–870-MHz band application: Wireless sensor

A co-simulation result of a Zero crossing BFSK demodulator with a frequency-hopped spread-spectrum receiver for wireless sensor applications in the 863-870-MHz ISM band is presented. The structure is suitable for Zigbee (IEEE 802.15.4) receiver. The zero crossing demodulator uses a digital one-shot circuit as a differentiator and a pulse width equalization circuit. The proposed demodulator is able to maintain good performance under process variation. The receiver simulations show -7 dBm IIP3, -15 dB return loss (S11), and 10 dB NF. The BER results show that the proposed Zero crossing BFSK demodulator has better performance over the Correlating BFSK detector and the Arctangent-differentiated BFSK demodulator. The analog receiver with the Zero crossing BFSK demodulator achieves a sensitivity of -115 dBm witch is in good agreement with specifications. To achieve a BER of 10^-3 as specified in zigbee standard the proposed system needs only 10 dB input signal_to_noise ratio.