A Low-Power and Highly Linear Merged Low Noise Amplifier-Mixer for Wireless Sensor Network Applications

In the literature, a number of merged low noise amplifier and mixer (LNAM) have been reported for Zigbee based low-power wireless sensor network (WSN). However, they suffer from the requirement of larger silicon area and degradation in the linearity due to second-order effects. In this paper, a number of techniques are proposed for overcoming these limitations and to increase the gain and reduce the noise figure. In this paper, the low noise amplifier (LNA) with capacitive feedback and -matching input, capacitive cross-coupling (CCC) at cascode nodes, MOSFETs operating in moderate inversion-region (MIR), cross coupled RC-feedback between the outputs of differential cascode LNA and the cascode nodes in opposite arm (LNA-CFB) is proposed and it is merged with folded double balanced mixer (LNAM-CFB) using complementary current-reuse technique. The proposed LNAM-CFB achieves higher linearity, higher gain and lower silicon area. For the purpose of comparison, the proposed LNAM-CFB is designed in UMC 0.18-μm MMRF CMOS process with the supply voltage of 0.8-V and studied through post-layout simulation at 2.4 GHz frequency. From this study, it is found that the conversion gain (CG) of LNAM-CFB is higher by 3.02 dB, noise figure (NF) of LNAM-CFB is lower by 0.08 dB, and linearity (IIP3) of LNAM-CFB is higher by 15.6 dBm compared to those reported in the literature. The proposed LNAM-CFB has better input reflection coefficient (S11) of – 44.62 dB and output reflection coefficient (S22) of – 12.23 dB at 2.44 GHz, lower power dissipation of 733 μW and lower silicon area of approximately 41.66%.