The Key Technologies Of RF Transceivers For Wireless Sensor Networks

With the rapid development of the technologies in the field of wireless sensor net-works, the requirements for system on chip are becoming more and more urgent, and theradio-frequency part is the bottleneck to design a node chip. This dissertation investi-gates the key technologies of radio-frequency transceivers for wireless sensor networks,and the following works are completed and taped out:To meet the requirements on low cost, flexibility, low power, and easy developmentof transceivers for wireless sensor networks, we design a system architecture, and makean assignment of the specifications.To meet the requirements on low cost, flexibility, and image rejection of transceiversfor wireless sensor networks, we propose a low-noise large-dynamic-range radio-frequency receiving front end with image rejection, and give the design flow of active-RCcomplex filters. Meanwhile, we propose an implementation method of digital-controlledcapacitor arrays that can be used for the tuning of active-RC circuits. In addition, we pro-pose a method for low-cost generation of local oscillation, which is composed of a1.72GHz～1.74GHz phase-locked loop and a÷4divider. Then, the desired430MHz～435MHz output signals can be obtained, and the low-intermediate-frequency receiver can besupplied with both in-phase and quadrature-phase local oscillating signals. After that webuild a model for the÷4divider, and design a low-spur, low-noise and low-power÷4divider based on the model, and then the adjacent channel selectivity of the receiver canbe improved.To meet the requirements on low cost and low power of transceivers for wirelesssensor networks, we propose a10.6mW phase-locked loop frequency synthesizer with18～25μs settling time. Bond wires are adopted as the inductors of the voltage-controlledoscillator, and then the power consumption, the die area and the phase noise are all de-creased. Therefore, the adjacent channel selectivity can be improved. A scheme of fastautomatic frequency calibration is proposed to calibrate the frequency deviations inducedby the bond-wire inductors, and a resistor based electro-static discharge protection circuitis proposed to enlarge the calibration range. Additionally, a dynamic-bandwidth schemeis also proposed to meet the requirements of time-division half-duplex wireless sensor networks, and an analytical model is built to forecast the noise distribution under difer-ent bandwidths of a phase-locked loop. Furthermore, we build a design-for-testabilityscheme for the frequency synthesizer with gauss frequency shift keying, and propose amulti-stage power-scaling technology for the prescaler to further reduce the power con-sumption of the frequency synthesizer.To meet the requirements on low power and flexibility of transceivers for wirelesssensor networks, we propose an all-analog intermediate-frequency circuit with5dB min-imum input signal-to-noise ratio,5.9mW power, and a55.4dB dynamic range. The lim-iting amplifier and received signal strength indicator is composed of folded amplifiers,folded subtractors, and current subtractor based rectifiers, and then the process deviationscan be depressed efectively. Taking into account the nonlinearity and static current ofthe rectifiers, we propose an accurate approximation model of the received signal strengthindicator’s transfer function, and provide a design flow of received signal strength indica-tors assisted by the proposed model. In addition, we proposed an active-RC demodulationscheme for gauss frequency shift keying, and the scheme has the advantages of low powerand a large dynamic range.