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Sensors 2011, 11(11), 10326-10342;

Measuring Time-of-Flight in an Ultrasonic LPS System Using Generalized Cross-Correlation

Department of Electronics, Polytechnic School, University of Alcalá, Ctra. Madrid-Barcelona Km. 33,600, Alcalá de Henares, Madrid 28805, Spain
Department of Electronic Engineering, National University of Patagonia San Juan Bosco, Ciudad Universitaria, Ruta Provincial n° 1 s/n, km. 4, Comodoro Rivadavia (Chubut) 9000, Argentina
Author to whom correspondence should be addressed.
Received: 14 August 2011 / Revised: 28 September 2011 / Accepted: 24 October 2011 / Published: 31 October 2011
(This article belongs to the Special Issue Sensorial Systems Applied to Intelligent Spaces)
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In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic Local Positioning System (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (Direct-Sequence Code Division Multiple Access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the Generalized Cross-Correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the Time Differences of Arrival (TDOA) between a reference beacon and the others. View Full-Text
Keywords: generalized cross-correlation; ultrasonic LPS; phase transform; Kasami codes generalized cross-correlation; ultrasonic LPS; phase transform; Kasami codes

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This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Villladangos, J.M.; Ureña, J.; García, J.J.; Mazo, M.; Hernández, Á.; Jiménez, A.; Ruíz, D.; Marziani, C.D. Measuring Time-of-Flight in an Ultrasonic LPS System Using Generalized Cross-Correlation. Sensors 2011, 11, 10326-10342.

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