New pseudo-orthogonal family of polyphase codes to improve Doppler resilience

Ultrasonic positioning systems presents performance problems when the object to be localized is in movement. The reasons are the degradation suffered by emitted sequences because of Doppler shifts, and the low level of orthogonality of the set of codes when they are being identified in different beacons. In this work, a search of a set of four 256-element polyphase sequences has been carried out, in order to improve the resilience to velocity possessed by other well-known codes, maintaining good orthogonality properties. As result, the obtained set can be used in an ultrasonic Local Positioning System (LPS), where the codes can be detected up to 1.5 m/s.