Simple demodulator for 802.15.4 low-cost receivers

This paper presents a simple demodulator for 802.15.4 (ZigBee) low-cost receivers. Based on a MSK interpretation of the modulation (O-QPSK) specified by the standard, the proposed demodulator is made up of an asynchronous zero crossing detector (AZCD) and of modified matched filters to recover the transmitted data. AZCD topology is simple, low cost and low power since it is mainly built with logic gates. At the output of the detector, a bank of 16 modified matched filters is used to despread and to decode the received symbols. Simulation shows that the demodulator performances (symbol error rate) are good enough to fulfill 802.15.4 requirements. Indeed, the use of the proposed demodulator involves the design of zero-IF receiver with a noise factor (NF) lower than 16.5 dB, which is achievable in a low-cost CMOS process.