Realization and testing of a non-coherent FSK receiver for biotelemetry applications
DEI Ph.D. Student
aula Alpha - Edificio 24, via Golgi 40
28 Luglio 2011
Multi-channel neural recordings are widely used in many neurophysiology laboratories to study the brain functionality in neuroscience experiments with freely-behaving animals. In this framework, systems able to transmit wirelessly the acquired huge amount of data are preferred over wired devices to reduce motion artifacts and to allow freedom of animal movements. The realization of such systems is not straightforward since power consumption is limited in few mW for maintaining a reasonable battery life. A multi-channel neural recording system-on-chip with wireless telemetry has been developed; the system is able to acquire neural signals from 64-channel electrode array, to perform AD conversion of the incoming signal and transmit the data at relatively short distance. Wireless transmission is implemented through binary Frequency Shift Keying (FSK) modulation in order to reduce the transmitter complexity and power consumption. The aim of this work is the realization of an off-the-shelf receiver able to acquire the transmitted signal and perform demodulation of the incoming data. Two different architectures for the receiver have been realized and tested: the first receiver is based on the down-conversion of the signal to an intermediate frequency (IF conversion) and consists in a RF section and in a wideband Phase Locked Loop for frequency discrimination and data demodulation. The demodulated signal is converted into a digital data stream and elaborated by an FPGA module, which is in charge of the decoding and decompression of the signal. This demodulating scheme can be simplified by omitting the PLL and performing frequency discrimination with a fast Fourier transform algorithm. IF demodulation receiver showed a poor performance in terms of sensitivity and transmission range, and thus a solution based on direct conversion has been developed. Direct conversion receiver (DCR) allowed to obtain a better sensitivity and to improve the transmission range. On bench measurements have been performed and the receiver has been employed in "in-vivo" neuroscience experiments.
This activity has been be carried out in collaboration with Italian Institute of Technology (IIT, Genova) and UniversitÓ degli Studi (Ferrara) under the supervision of Prof. Luciano Fadiga.
Area di ricerca:
Microelettronica e tecnologie emergenti