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Ultra-wideband transceiver design for low-power: low data-rate applications

Friday, 4 May, 2007 - 17:00
Campus: Brussels Humanities, Sciences & Engineering campus
Julien Ryckaert
phd defence

In sensor network applications, achieving the ultra-low power consumption budget allowed for the radio communication is a major challenge. Therefore, in these applications, the relatively low data rate must be optimally traded for power consumption. However, the energy per bit efficiency in traditional communication systems worsens as the data rate decreases since they are hampered by their inherent baseline power consumption. Impulse-radio ultra-wideband is a novel communication technique that allows a direct scaling of the power consumption with the data rate. This is achieved by duty-cycling the system operations during communication. Thereby, a very high power consumption efficiency can be obtained even at very low data rate.

This work aims at demonstrating the low power capabilities of impulse-radio ultra-wideband (UWB) communication through three design examples realized in CMOS technology. The full-CMOS integration is necessary to satisfy the low-cost requirements of sensor network applications. The first design is a pulse generator featuring PPM modulation that achieves a 40pJ per pulse consumption at 40Mpulses/s. The pulse spectrum is variable both in center frequency, between 3GHz and 5GHz, and bandwidth, between 500MHz and 2GHz, such as to satisfy worldwide
regulatory masks on UWB signal emission. The second design is a full receiver for the reception of the PPM modulated pulses of the pulse generator. The receiver is based on a quadrature analog correlation technique to reduce the sampling rate and hence the total power consumption. It includes a fully-integrated receiver front-end, a quadrature analog correlation section and the ADC. A synchronization algorithm for the receiver has also been implemented on a separate FPGA. The receiver chip consumes 28.8mW for a 20Mpulses/s. Finally, as a standard has recently been defined for low data rate UWB communication, a third design has been realized to demonstrate our concepts to achieve low power on standard-compliant designs. A fully-integrated UWB transmitter has been implemented incorporating a novel frequency synthesis technique optimized for duty-cycled communication. The standard-compliant transmitter achieves an energy consumption between 40pJ and 87pJ per pulse while operating between 3.1GHz and 10GHz.

Innovations at architectural level as well as at circuit level have lead us to designs optimized for low power at low data rate communication. The unique property of system duty-cycling in impulse-radio UWB is exploited in order to achieve a high power consumption efficiency at low data rate. The performance results obtained from the implementations therefore demonstrate the potential of UWB communication, both standard-based and custom-based, for low data rate, low power communication.