| Interest in indoor wireless communications has been increasing. In addition to high through-put WLAN systems such as 802.11a/b/g/n, attention is also being focused on lower rate, short distance systems such as Bluetooth and Zigbee. These low rate radios are being proposed for a variety of applications including automation/security, smart toys, remote sensing/control, asset tracking, and as a replacement for computer peripheral wires. While not demanding aggressive throughput, these radios do require low cost, power efficient operation and optionally the ability to perform ranging. Unfortunately, currently reported radios are up to an order of magnitude away from these power and cost targets or do not support ranging. However, a recent ruling from the FCC has opened up nearly 8GHz of unlicensed spectrum (from dc to 960MHz and from 3.1GHz to 10.6 GHz) for ultra-wideband (UWB) deployment. One attractive method of UWB signaling that seems suited to a low power, highly integrated implementation communicates with short pulses, on the order of a nanosecond, that spread energy over at least 500MHz of bandwidth. Termed "impulse-UWB," the baseband nature of this signaling promises low cost and low power consumption through design simplicity, pulsed (or "duty-cycled") operation, and a "mostly-digital" implementation. The benefits of this approach are balanced by the risk of jamming from in-band interference, of stricter sampling and gain constraints, and of increased digital complexity. This dissertation presents the system exploration, specification, design, and demonstration of a low power, highly integrated, flexible, baseband, impulse ultra-wideband transceiver front-end. Comprising a 1-bit, 1.92Gsample/s ADC, 50O input matched gain stage with 0dB to 42dB of variable gain, programmable control logic, a sub-1PPM trimmable 60 MHz third-harmonic oscillator, and pulse transmitter, this front-end was implemented in a standard digital 0.13/mum CMOS process in 2.52 mm2 of active area. Aggressively designed at the circuit level for low power, the front-end gain and sampling are also duty-cycled between pulses to further reduce power consumption, yielding 4mW (RX) and 2mW (TX) at 30Mpulse/s, and 0.6 mW (RX) and 0.4mW (TX) at 1Mpulse/s. Communication rates on the order of 1Mbps are supported over short distances and ranging is possible through time-of-flight measurements. |
