A measurement method for instantaneous frequency estimation is presented in this paper. The method is based on the use of the chirplet transform, a linear time-frequency representation (TFR) allowing additional modifications of each cell on the time-frequency plane with respect to other TFRs. In particular, a modified version of this transform is proposed here; a bending effect can be further imposed on the cells. Thanks both to this feature and a suitable measurement procedure, properly set up by the authors, the method assures a satisfying accuracy in reconstructing the instantaneous frequency trajectory of monocomponent signals as well as a good resolving capability in the analysis of multicomponent signals whose instantaneous frequency trajectories are strongly nonlinear and very close to one another. Theoretical details concerning the chirplet transform and its modified version are first given. Then, the proposed measurement procedure for choosing the optimal values of the parameters of the transform according to the local features of the analyzed signal is described. At the end, the results of several experimental tests conducted both on monocomponent and multicomponent signals are presented; advantages over other solutions are also highlighted.

A digital signal-processing method for phase noise measurement is presented. By properly over-sampling the input signal and adopting an optimized quadrature demodulation scheme, the method grants acceptable performance in analyzing sinusoidal carriers, the frequencies of which range from fractions of hertz up to hundreds of megahertz. Moreover, the method shows itself a valid alternative both to analog measurement systems, especially for the evaluation of close-to-the-carrier phase noise and time interval analyzers, particularly for carrier frequencies greater than a few units of megahertz. At first, the fundamental stages of the proposed method are described in detail. Its theoretical performance is then derived and compared to that offered by other measurement solutions already available on the market. Finally, the results of experiments carried out on actual signal sources are presented.

An innovative digital-signal-processing method, which is aimed at detecting and evaluating I/Q impairments in radio-frequency digital transmitters, is presented and validated. It takes advantage of a suitable clustering procedure that is capable of matching each symbol in the distorted I/Q diagram to its ideal position, even though concurrent and severe impairments disturb the standard functioning of the transmitter under test. Right identification of impairments, along with accurate evaluation of their amount, is then achieved through the application of original and straightforward measurement algorithms to the recovered symbols. The results of a number of experiments, which are conducted on quadrature-amplitude-modulation signals affected by the known I/Q impairments, show the superior performance of the proposed method over measurement techniques suggested by the European Telecommunications Standards Institute and alternative solutions already presented in literature. Further experiments conducted in the presence of interfering tones or phase jitter give evidence of the method's reliability also in critical measurement conditions.

Wireless sensor networks are today more and more widespread. Along with the installation of more and more networks, a number of new standard documents has also been produced to update the regulation concerning data communication between sensors and data collectors. Differently, less attention has been paid to the different modes of powering the local sensors. At present, the energy required for local sensors functioning is essentially battery provided, despite the battery supply is often recognized as a critical aspect of remote sensing. In fact, the periodical battery replacement is sometimes non-strategic and troublesome, especially for those sensors which have to be installed in difficult to reach sites, or are integrated into medical implantable devices. In the above mentioned circumstances, battery-less sensors appear to be attractive, both from a pragmatic point of view, because of the strategic role they can play in critical scenarios, and from an innovation-oriented point of view, because of the novelty that wireless power transmission can add to a new ground-breaking remote sensors technology. Wireless power transmission technologies are capable of supporting battery-less sensor functioning. In this paper, first the main issues related to alternative remote devices powering solutions are plainly discussed, then, a resonant-based induction power transmission system for supplying a sensor network is also presented.