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- Wireless communication based on chirp signals for LoRa IoT DevicesPublication . Fialho, Vitor; Azevedo, FernandoThis paper presents the study of chirp signals for wireless communications between Internet of Thing devices used on low power wide area networks. Up and down chirp concept is introduced as well as the chirp spread spectrum concept. A computationally efficient symbol decoding method is presented based of discrete Fourier transform as an alternative to typical coherent detection. The proposed LoRa simulation model is implemented in MATLAB allowing the communication system evaluation based on bit error rate and packet error rate.
- Local oscillator phase noise model for EVM estimation and optimizationPublication . Fialho, Vitor; Fortes, Fernando; Vieira, ManuelaThis work presents a local oscillator (LO) phase noise model and its experimental validation for carrier to phase noise ratio (CPNR) and error vector magnitude (EVM) evaluation on a radio frequency (RF) transceiver. The proposed LO model is based on a type II charge pump phase locked loop with a combined phase noise source from the voltage controlled oscillator and input reference with a low pass characteristic. The obtained results of CPNR and signal to phase noise ratio are based on numerical simulations and validated with experimental measurements based on a commercial RF transceiver chip. The EVM of the transmitted RF channel is also measured and compared with CPNR.