This work describes the design of a reflector for a
PVDF-based ultrasonic transducer (Piezofilm transducer) to
carry out a ultrasonic beacon system, where the covered area be
improved and a 3D indoor positioning be guaranteed. The
proposed Local Positioning System (LPS) for Mobile Robots (MR)
uses simultaneous emissions from ultrasonic beacons. In order to
solve the problem of simultaneous emissions from ultrasonic
beacons, the well-known technique Direct Sequence Code
Multiple Division Access (DS-CDMA) is used. This technique
encodes the ultrasonic signal with a 127-bit Gold code for every
beacon. It implies the emitted signal by every beacon to have a
wide bandwidth. PVDF-based transducers suitably guarantee this
requirement. Their cylindrical or semi-cylindrical shape makes
the emission pattern not suitable when using them as ultrasonic
beacons, often located in the ceiling of an indoor room. To adapt
the emission pattern and to increase the covered area in the
ground, the design process of a conical reflector is described.
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