Low-Power Quadrature Receivers for ZigBee (IEEE 802.15.4) Applications

Abstract

Two very compact and low power quadrature re- ceivers for ZigBee applications are presented. Area and power savings are obtained through both current reuse and oscillator tank sharing between the I and Q paths. Since this choice can cause I and Q amplitude/phase mismatches, the conversion gain is analyzed and a technique to minimize these errors is imple- mented. Moreover, since using a single tank makes quadrature generation at the local oscillator level costly and power-hungry, two alternative quadrature generation techniques in the RF path are proposed, together with the corresponding input matching strategies. Two 90 nm CMOS receiver prototypes that implement the above strategies were designed and integrated. The measurements resulted in a power consumption of 3.6 mW and an active die area of 0.23 mm /50when the LNA is separated from the self-oscillating mixer and high quality factor bond-wire inductors are used in the LC tank. The active area increases to 0.35 mm /50when the LNA is stacked with the self-oscillating-mixer and an integrated inductor is used. Both prototypes have area and power consumption below state of the art receivers with similar level of performance. The receiver prototypes are based on a low-IF architecture and include also a base band variable gain complex filter for channel selection and image rejection.