Design of a direct conversion ultra low power ZigBee receiver RF front-end for wireless sensor networks

This paper describes an ultra low power receiver RF front-end to be utilized for wireless sensor network (WSN) applications. The design of the LV cell (LNA and VCO) that is proposed in this paper is suitable for direct conversion architecture, while the conventional LMV cell (LNA, Mixer, and VCO) is used only in low-IF architectures, due to the prohibitive high flicker noise. A passive mixer is utilized instead of an active mixer and a capacitor is added to block the DC current flowing into the mixer. So, flicker noise corner frequency is reduced to 13.8 kHz. The proposed design can be used more easily compared to conventional LMV cell in a low voltage technology, because of the stacking of only two blocks (LNA and VCO), while three blocks of LNA, mixer, and VCO are stacked in the conventional LMV cell. The proposed receiver RF front-end consumes 1 mW in 0.18 μm CMOS technology with a 1.2 V supply source. NF and IIP3 are 4.7 dB and −7 dBm, respectively.