Littérature scientifique sur le sujet « SDR Transceiver Calibration »

AbstractContemporary wireless communication transceivers can utilize their multiple antennas to improve positioning abilities. Angle of Arrival (AoA) estimation utilizes shifts in phase between the signal of interest arriving at different receiving antennas. Software Defined Radio (SDR) USRP B210 and GNU Radio implementing the Root Multiple Signal Classification (Root-MUSIC) algorithm are used in this paper. However, this setup requires the consideration of errors caused by hardware and radio environment. The impact of these effects is shown using an analytical model, assessed, mostly by measurements, and relevant solutions are proposed. The hardware distortions are caused mostly by synchronization errors. The intricacies of the most problematic phase synchronization are investigated with the wired setup showing, e.g., changes with frequency or gain. Both synchronizations emitting calibration tone from the same radio front end, resulting in cross-talk, or a separate one are tested. Recommendations enhancing the performance of the system and alleviating hardware imperfections are provided in this paper. The accuracy of AoA estimation is degraded by multipath propagation or radio interference. A signal processing scheme including filtering has been proposed. A set of over-the-air experiments assessed the performance of the system. The presented and publicly available software package, scalable to a higher number of RX antennas, enables straightforward implementation by other researchers.

L'architecture conventionnelle utilisée par toutes les publications précédentes pour le récepteur de balayage de spectre est basée sur le CAN en BB, donc il a une consommation d'énergie élevée, une complexité plus élevée et souffre d'inadéquations de circuits et de non-linéarité. Dans ce travail, nous proposons d'utiliser un récepteur RF basé sur CAN delta-sigma en PB. Les CAN PB DS ajustables précédemment signalés implémentée de manière complexe. Nous présentons une implémentation efficace du CAN PB DS accordable. Un récepteur de détection de spectre, basé sur l'architecture frontale RF à faible consommation d'énergie proposée dans cette thèse, est également proposé. Le récepteur complet proposé ne souffre pas d'un déséquilibre 1/Q. Les résultats de simulation pour montrer l'impact de la non-linéarité du circuit sur les performances sont présentés. Une implémentation de circuit d'un backend numérique du système proposé est présentée. Cette implémentation comprend un mélangeur à conversion descendante efficace, un filtre de décimation, un bloc FFT et un module de détection d'énergie. L'implémentation a été validée à l'aide l'outil SignalTab. Des études, ne présentent que des résultats analytiques ou de simulation, visant à montrer l'impact du déséquilibre 1/Q sur les performances de détection du spectre ont déjà été publiées. Dans ce travail, nous présentons la première mesure matérielle du déséquilibre I/Q sur les performances de détection du spectre. Dans le domaine médical, nous présentons pour la première fois une étude de l'effet de l'exposition aux RF-EMF sur les nouveau-nés via une acquisition simultanée de signaux RF et de paramètres physiologiques
Spectrum sensing applications cover wide variety, such as efficient utilization of frequency spectrum, and in medical applications. The conventional architecture used by all the previous publications for spectrum sensing receiver is based on baseband ADC, hence it has high power consumption, higher complexity, and suffers from circuit mismatches and nonlinearity. In this work, we propose using an RF receiver based on bandpass delta-sigma ADC. It is much more convenient to have a tunable BP ΔΣ ADC to simplify the spectrum sweeping task. The previously reported tunable BP ΔΣ ADC’s are implementing tunability in a complex manner. We present an efficient implementation of tunable BP ΔΣ ADC with fixed ratio between the sampling frequency and center frequency. That fixed ratio further simplifies the implementation of the down conversion mixer and decimation filter which serve as the digital backend of the receiver. A spectrum sensing receiver, based on the power-efficient RF front end architecture proposed in this thesis, is also proposed. The proposed complete receiver does not suffer from I/Q imbalance that highly affect the spectrum sensing performance. Simulation results to show the circuit nonlinearity impact on the performance are presented. A circuit implementation of a digital backend of the proposed system is presented. This implementation comprises an efficient down conversion mixer, decimation filter, custom FFT block, and energy detection module. The implementation was validated on Altera FPGA using the on-chip logic analyzer via the SignalTab tool.Studies to show the impact of I/Q imbalance on spectrum sensing performance were previously published. Nevertheless, those publications presented only either analytical or simulation results. In this work, we present the first hardware measurement of the I/Q imbalance on spectrum sensing performance using a commercial SDR transceiver platform.In the medical field, we also present for the first time a study of the effect of RF-EMF exposure on neonates by performing a simultaneous acquisition of RF signals along with recording the physiological parameters of neonates. Using R-Studio, the stationarity of the signals to be correlated was checked, a transformation was performed on the non-stationary signals. Finally, cross correlation between the acquired RF signal (average of the whole spectrum or in a specific band) and each of the recorded physiological parameters did not show an observable impact of RF-EMF exposure on neonates