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The digital multistage-noise-shaping (MASH) 61 modulators used in fractional frequency synthesizers are prone to spur tone generation in their output spectrum. In this paper, the state of the art on spur-tone-magnitude reduction is used to demonstrate that an-bit MASH architecture dithered by a simple-bit linear feedback shift register (LFSR) can be as effective as more sophisticated topologies if the dither signal is properly added. A comparison between the existent digital 61 modulators used in fractional synthesizers is presented to demonstrate that the MASH architecture has the best tradeoff between complexity and quantization noise shaping, but they present spur tones. The objective of this paper was to significantly decrease the area of the circuit used to reduce the spur tone magnitude for these MASH topologies. The analysis is validated with a theoretical study of the paths where the dither signal can be added. Experimental results of a digital-bit MASH 1-1-1 61 modulator with the proposed way to add the LFSR dither are presented to make a hardware comparison.

International audienceEvent-triggered control is a resource-aware sampling strategy that updates the control value only when a certain condition is satis ed, which denotes event instants. Such a technique allows to reduce the control computational cost and communications. In this paper, a quaternion-based feedback is developed for event-triggered attitude stabilization of a quadrotor mini-helicopter. The feedback is derived from the universal formula for eventtriggered stabilization of general nonlinear systems a ne in the control. The proposed feedback ensures the asymptotic stability to the desired attitude. Real-time experiments are carried out in order to show the convergence of the quadrotor states to the desired attitude as well as the robustness with respect to external disturbances. Results show that the proposed control can reduce by 80 % the communications of the embedded system without sacri cing performance of the whole system. To the best of the authors' knowledge, this is the rst time that a nonlinear event-triggered controller is experimentally applied to the attitude stabilization of an unmanned aircraft system

This article presents the design and implementation of an event-triggered control approach, applied to the leader-following consensus and formation of a group of autonomous micro-aircraft with capabilities of vertical take-off and landing (VTOL-UAVs). The control strategy is based on an inner–outer loop control approach. The inner control law stabilizes the attitude and position of one agent, whereas the outer control follows a virtual leader to achieve position consensus cooperatively through an event-triggered policy. The communication topology uses undirected and connected graphs. With such an event-triggered control, the closed-loop trajectories converge to a compact sphere, centered in the origin of the error space. Furthermore, the minimal inter-sampling time is proven to be below bounded avoiding the Zeno behavior. The formation problem addresses the group of agents to fly in a given shape configuration. The simulation and experimental results highlight the performance of the proposed control strategy.

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