Delay Tracking of Spread-Spectrum Signals for Indoor Optical Ranging

Sensors

David Salido-Monzú¹  Ernesto Martín-Gorostiza¹  José Luis Lázaro-Galilea¹  Eduardo Martos-Naya² 

[1] Department of Electronics, University of Alcalá, Madrid 28871, Spain; E-Mails:;Communication Engineering Department, University of Málaga, Campus de Teatinos, Málaga 29010, Spain; E-Mail:

关键词: optical ranging;    spread-spectrum;    delay-locked loop;    multipath mitigation;    indoor positioning;   

DOI  :  10.3390/s141223176

来源: mdpi

【 摘 要 】

Delay tracking of spread-spectrum signals is widely used for ranging in radio frequency based navigation. Its use in non-coherent optical ranging, however, has not been extensively studied since optical channels are less subject to narrowband interference situations where these techniques become more useful. In this work, an early-late delay-locked loop adapted to indoor optical ranging is presented and analyzed. The specific constraints of free-space infrared channels in this context substantially differ from those typically considered in radio frequency applications. The tracking stage is part of an infrared differential range measuring system with application to mobile target indoor localization. Spread-spectrum signals are used in this context to provide accurate ranging while reducing the effect of multipath interferences. The performance of the stage regarding noise and dynamic errors is analyzed and validated, providing expressions that allow an adequate selection of the design parameters depending on the expected input signal characteristics. The behavior of the stage in a general multipath scenario is also addressed to estimate the multipath error bounds. The results, evaluated under realistic conditions corresponding to an 870 nm link with 25 MHz chip-rate, built with low-cost up-to-date devices, show that an overall error below 6% of a chip time can be achieved.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.