Doppler-tolerant receiver for an ultrasonic LPS based on Kasami sequences

Abstract

This paper presents the design of a novel receiver for a broadband ultrasonic Local Positioning System (LPS). As in other devices based on matched filtering of the transmitted encoded signals, this receiver features high robustness to noise and multiple access capability. Unlike previous solutions, the proposed receiver is capable of detecting beacons emissions despite being installed in a fast moving device, and it also provides estimation of its velocity. The system has been implemented in an FPGA-based architecture. An experimental analysis of performance has been carried out. Firstly using a set of test signals synthetically generated to simulate different positions and velocities of the receiver. Secondly, a set of real signals obtained with a prototype have been used. The simulated results show the capability of the system to detect the encoded signals emitted by the LPS infrastructure when the device is moving at velocities of up to 3m/s under low SNR conditions. The real results confirm the improved system capability, but also make evident the negative influence that phenomena such as the transducers response and multipath propagation can have on system performance.