In this paper we investigate the possibility to generate a multisine signal source, to enhance conversion efficiency in low-power wireless power transfer scenarios. A time modulated array composed by three microstrip patch antennas operating at 868 MHz is chosen. The time modulation is performed by 3 switch diodes, one for each antenna, with properly designed periodic on/off sequences of period equal to 1μs. The multisine behavior of the radiated field is obtained by exploiting the intrinsic generation of sideband harmonics, with 5 frequency bins equally spaced by 1 MHz all directed toward the broadside direction. To obtain this behavior, we design the modulation sequences with a genetic algorithm to produce a broadside radiation at the fundamental and the desired higher harmonics. Realistic antenna radiation patterns for the array structure are simulated with CST Microwave Studio and used as input of the optimization procedure. Preliminary results show the feasibility of the proposed concept.

Wake-up radio is an emerging technology with the ambitious goal of reducing the communication power consumption in smart sensor networks and Internet of Things. This reduction in power consumption will enable a new generation of applications which could achieve a longer lifetime than is achievable today. Wake up radios are required to work with a low power budget and should exhibit low latency coupled with high sensitivity and addressing capabilities. Typically they are combined with existing radio transceiver and power management techniques to reduce the overall communication power while maintaining the same communication performance. This paper presents a dual band (2.4GHz and 868MHz) wake up radio with the above mentioned characteristics. The dual band solution is exploited to increase the flexibility of the wake up radio, allowing interoperability with the two most common frequencies used in Wireless Sensors Networks and Internet of Things. Simulation results present a system able to exploit the two bands with sensitivity as low as -53dBm at 868MHz and -45dBm at 2450MHz. Experimental results on power consumption demonstrate the low power consumption of the proposed solution with only 1.276μW of power consumption in listening mode. The addressing is performed by an ultra low power on board PIC microcontroller with 40nW of power consumption when the wake up radio is in listening mode and only 70 μW when the data are received and parsed.

In this paper, a rigorous procedure for the circuit-level analysis and design of entire systems, developed to provide power wirelessly, is presented. A unified theoretical approach is first introduced, based on a two-port-equivalent circuit representation, to describe the wireless power transfer link when the transmitter and the receiver are either in the near-field or in the far-field region reciprocally. This approach allows one to compute in a straightforward manner the system figure of merit, namely the power transfer efficiency. Specific guidelines for the two configurations are then intensively discussed together with the adopted software tools based on the combination of full-wave analysis and nonlinear harmonic balance techniques. Several practical examples based on this design procedure are presented, demonstrating predicted and experimental behavior of unconventional devices for both near-field and far-field power transfer usage.

This paper demonstrates, for the first time, a circuit-level approach to the analysis of pulse-ultrawideband (UWB) receiver front ends in the presence of interfering communication signals. The procedure is based on a model-order-reduction harmonic-balance technique based on Krylov subspaces. A sophisticated algorithm for performing matrix-vector multiplications has been particularly devised to handle signal spectra including very large numbers of arbitrarily spaced lines with very high numerical efficiency. The resulting simulation tool allows rigorous computation of interference effects on the nonlinear regime of UWB receivers and accurate circuit-level prediction of receiver sensitivity and channel capacitance. Simplifying assumptions typical of system-level approaches are overcome in this way, while keeping computational time at acceptable levels.