@conference {746, title = {Estimating bearing angles by encoding ultrasonic transmissions at different frequencies}, booktitle = {2009 IEEE International Instrumentation and Measurement Technology Conference (I2MTC 2009)}, year = {2009}, month = {05/2009}, pages = {1429-1433}, author = {{\'A}lvaro Hern{\'a}ndez and Ana Jimenez and I. G{\'o}mez and J.J. Garcia and Mar{\'\i}a del Carmen P{\'e}rez and E. Garc{\'\i}a and Fernando J. {\'A}lvarez} }