Optimum design parameters for ultra-low-power RF transceivers in wireless sensor networks

In wireless sensor networks, the need for ultra-low power consuming nodes is one of the main motivations for research in such field. Because radio sections in sensor nodes contribute to a large extent to the overall power consumption, the focus of this study is on the RF transceiver. The aim is to reduce the average power consumption which depends significantly on the circuit architecture design, operating data rate, and duty cycle. In a symmetric communicating system, due to the tradeoff between transmitting power and receiver sensitivity on one hand, as well as between phase noise tolerance and power dissipation in local oscillators on the other hand, the design and operating parameters of the transceiver need to be determined from the perspective of the average power consumption. Therefore, in our study, as an initial step in system design, the optimum for instantaneous data rate, noise figure, and oscillator power budget are analytically determined. The analysis is carried out, taking into consideration an existing in-channel wideband interference, on two transceiver architectures: RF envelope detection and conventional heterodyne. The transceiver in both architectures employs on-off-keying modulation and duty cycling. The optimums are then calculated numerically based on design constants obtained from a frequently-cited RF envelope transceiver, indicating that an energy efficiency improvement of up to 5 dB can still be achieved.