FSK zero-crossing demodulator for 802.15.4 low-cost receivers

This paper presents an asynchronous binary-FSK demodulator (AZCD) for 802.15.4 (ZigBee) low-cost receivers. Based on the zero-crossing demodulator (ZCD) principle, the proposed demodulator architecture is asynchronous, e.g operating without symbol synchronization. Compared to the Zero Intermediate Frequency Zero-Crossing Demodulator (ZIFZCD) technique, the AZCD performances, in terms of BER as a function of E_b/N₀, are degraded of about 3.5 dB but its complexity is much lower since no recovery timing device is needed and AZCD is mainly built with logic gates. Moreover, AZCD performances (BER) are good enough to fulfil 802.15.4 requirements. Indeed, the use of AZCD involves the design of zero-IF receiver with a noise factor (NF) of about 10 dB, which is achievable in a low-cost CMOS process.