The design of low power ultra-wideband RF CMOS wireless systems for sensor networks

The wireless market is continuing its rapid development towards higher bandwidth, lower power, and lower cost. Recently, wireless sensor networks (WSN) have emerged and captivated the interest of many researchers and the industry. A promising wireless communication technology for wireless sensor networks is the ultra-wideband (UWB) technology. The architecture and circuit designs of UWB wireless communication systems can be very different from traditional narrowband systems.;The design of two low power CMOS ultra-wideband (UWB) pulse-based transmitters is also reported in this thesis. The goal is to propose simple, low power, and tunable topologies for full-band and sub-band UWB transmitters. The first transmitter utilizes a gated ring oscillator, an NMOS switch, and a passive pulse shaping filter to generate a 3.1–10.6 GHz full-band UWB signal. The second transmitter multiplies a carrier and a triangular signal to up-convert and to generate a low side-band UWB signal for sub-band applications. We propose the use of two NMOS switches in series to perform this multiplication while consuming minimum power. Control voltages incorporated in both designs are used to adjust the shapes of the pulses to compensate for mismatch and process variations. Both the full-band and sub-band transmitters, fabricated in a 0.18 μm CMOS process, generate Federal Communications Commission (FCC) compliant UWB signals with a supply voltage of 1.8 V and power consumptions of 237.4 and 254.9 μW, respectively.;In the design of the RF building blocks, numerous RF passive components are often utilized. When carefully modeled and co-designed, these passive RF components can improve the efficiency, reliability, and performance of the systems. The design methodology of the passive components (e.g. on-chip inductors and bonding wire transformers) are described. The impact of the geometrical structure of these passive RF components on their performance is carefully examined.;The design of a dual-source power scavenging and management system for ultra low power wireless applications is also presented. Power scavenging is achieved by harvesting energy both from solar (primary) and RF power (secondary) sources. Depending on the available energy, the system can supply 1–2 mW of power to a wireless device, with up to a 50% duty cycle. A radio-triggering based technique is used to control the activation and shutting down of the complete wireless system, and thus eliminates energy wasting wake-up periods. The system provides a regulated output voltage of 1.5 V, with a total power consumption of less than 8.0 μW in the sleep mode, and 48 μW in the operating mode.;This thesis focuses on the design of UWB radio frequency (RF) front-end transceivers, power scavenging and power management systems for low power wireless sensor networks. A sub-miliWatt ultra-wideband CMOS common gate (CG) low-noise amplifier (LNA) is demonstrated in this work. To achieve good gain, wideband input impedance matching, and low power consumption, the proposed LNA exploits the combination of RF transformers, current reuse, and back-gate coupling techniques to boost the transconductance of the gain transistors. To realize a compact low cost design with no discrete components, the LNA utilizes special high quality bonding wire transformers on an IC package. The LNA prototype, fabricated in a 0.18 μm CMOS process, consumes 698.5 μW from a 1.5 V supply.