Semester Thesis

A UWB front-end based on off-the-shelf components

Recently, ultra-wideband (UWB) wireless sensor and body area networks (BAN) gained much interest due to a multitude of attractive applications. In a BAN, several nodes are placed directly on the human body or very close to it. Since BAN nodes get their power from rechargeable batteries or by energy harvesting, it is inevitable that they are extremely energy efficient.

Recently, we presented an energy detection based ultra-low power UWB system design with an overall estimated current consumption of about 0:45 mA [1]. Low duty cycle operation together with a high peak data rate are the key to achieve a medium data rate system with very low current consumption. Using binary pulse position modulation (PPM), data is transmitted at different time-shifts according to the different bit values. Having a delay spread of tau_rms=10 ns,the minimal PPM frame duration without inter-symbol interference (ISI) is restricted to 20 ns [2], implying a peak data rate of 50 Mbps. Requiring an average data rate of 500 kbps, a duty cycle of 1% can be realized. With respect to streaming applications, the maximum allowed latency time is set to 1 ms. Therefore, a burst of 500 bits and 10 šs duration is sent every millisecond. Besides the low duty cycle operation also the usage of low complexity resonant circuits in the analog part, which requires a moderate relative bandwidth, is important to achieve low power consumption. Hence, the frequency range from 3.5 to 4 GHz has been chosen for the design. The theoretical feasibility of the presented design respecting FCC power limits together with transmission of only one pulse per bit has been shown by means of computer simulation and over the air. For the over-the-air demonstration an arbitrary waveform generator and a sampling oscilloscope are used as transmitter and receiver, respectively. The receive signal is fed into a control PC where the analog front-end is implemented in Matlab.

In this work, the functional blocks of the analog front-end shall be replaced by off-the-shelf components (COTS). Based on the specifications from [1], suited components shall be identified and its specifications verified by measurements. Finally, a performance comparison between the Matlab- and the COTS-based analog front-end realization shall be done.

[1] F. Troesch, C. Steiner, T. Zasowski, T. Burger, and A. Wittneben. Hardware Aware Optimization of an Ultra Low Power UWB Communication System. 2007 IEEE International Conference on Ultra-Wideband, ICUWB 2007, Singapore, Sept. 2007.

[2] T. Zasowski, F. Troesch, and A. Wittneben. Partial Channel State Information and Intersymbol Interference in Low Complexity UWB PPM detection. IEEE International Conference on Ultra-Wideband, ICUWB 2006, Waltham, Massachusetts, USA, Sept. 2006.

Subject area Ultra Wideband, Body Area Networks, System Demonstrator
Type of work 90% Measurements and System Integration, 10% Theory
Students Christoph Roth
Supervisor Dr. Thomas Zasowski, Dr. Heinrich Luecken
Professor Prof. Dr. Armin Wittneben