Federico Viani

Directions-of-Arrival Estimation Through Bayesian Compressive Sensing Strategies

The estimation of the directions of arrival (DoAs) of narrow-band signals impinging on a linear antenna array is addressed within the Bayesian compressive sensing (BCS) framework. Unlike several state-of-the-art approaches, the voltages at the output of the receiving sensors are directly used to determine the DoAs of the signals thus avoiding the computation of the correlation matrix. Towards this end, the estimation problem is properly formulated to enforce the sparsity of the solution in the linear relationships between output voltages (i.e., the problem data) and the unknown DoAs. Customized implementations exploiting the measurements collected at a unique time instant (single-snapshot) and multiple time instants (multiple-snapshots) are presented and discussed. The effectiveness of the proposed approaches is assessed through an extensive numerical analysis addressing different scenarios, signal configurations, and noise conditions. Comparisons with state-of-the-art methods are reported, as well.

Optimization of a Spline-Shaped UWB Antenna by PSO

This letter presents the design of a planar antenna for ultrawideband (UWB) applications with a bandwidth of 5.5 GHz over 3.7 to 9.2 GHz and return loss values lower than -10 dB. The antenna geometry is described in terms of a spline-based representation whose control parameters, together with other geometrical descriptive quantities, are determined through a suitable particle swarm optimizer (PSO) in order to fit the UWB requirements. Representative results of both numerical and experimental validations are reported in order to assess the performance of the prototype as well as to give some preliminary indications on the reliability and effectiveness of the whole synthesis approach

Wireless Architectures for Heterogeneous Sensing in Smart Home Applications: Concepts and Real Implementation

Application of wireless technologies in the smart home is dealt with by pointing out advantages and limitations of available approaches for the solution of heterogeneous and coexisting problems related to the distributed monitoring of the home and the inhabitants. Some hot challenges facing the exploitation of noninvasive wireless devices for user behavior monitoring are then addressed and the application fields of smart power management and elderly people monitoring are chosen as representative cases where the estimation of user activities improves the potential of location-aware services in the smart home. The problem of user localization is considered with great care to minimize the invasiveness of the monitoring system. Wireless architectures are reviewed and discussed as flexible and transparent tools toward the paradigm of a totally automatic/autonomic environment. With respect to available state-of-the-art solutions, our proposed architecture is based also on existing wireless devices and exploits, in an opportunistic way, the characteristics of wireless signals to estimate the presence, the movements, and the behaviors of inhabitants, reducing the system complexity and costs. Selected and representative examples from real implementations are presented to give some insight on state-of-the-art solutions also envisaging possible future trends.

A Miniaturized UWB Antenna for Wireless Dongle Devices

In this letter, a planar ultra wideband (UWB) antenna suitable for the integration in wireless universal serial bus (USB) dongles is described. The antenna has a bandwidth equal to 2 GHz from 3 GHz up to 5 GHz with return loss values below -10 dB in the whole frequency range. To comply with UWB system needs, the antenna presents good distortionless properties when employed in a TX/RX system. Moreover, thanks to its simple shape and miniaturized geometry, the proposed prototype can be easily integrated and printed on dongle PCBs. In order to assess the reliability and efficiency of the antenna, a selected set of results from the experimental validation are shown and compared with the outcomes of the numerical simulations carried out during the synthesis process.

MT – BCS-Based Microwave Imaging Approach Through Minimum-Norm Current Expansion

An innovative three-step technique based on the multi-task Bayesian compressive sensing (MT - BCS) strategy is introduced to image 2D-sparse dielectric profiles. The proposed approach reformulates the contrast source mathematical description of the inversion problem into two fictitious real-valued ones jointly solved through a fast Relevance Vector Machine by taking into account the inter-relationships between the real and the imaginary parts of the unknown equivalent currents. Selected results from a numerical validation are presented and discussed to comparatively assess the accuracy, the robustness, and the computational efficiency of the proposed implementation.

A PSO-Driven Spline-Based Shaping Approach for Ultrawideband (UWB) Antenna Synthesis

Synthesis of ultrawideband (UWB) antennas by means of a particle swarm optimizer (PSO)-driven spline-based shaping approach is described. In order to devise a reliable and effective solution, such a topic is analyzed according to different perspectives: 1) representation of the antenna shape with a simple and efficient description; 2) definition of a suitable description of the UWB Tx/Rx system; 3) formulation of the synthesis problem in terms of an optimization one; 4) integration of the modelling of the UWB system into a computationally efficient minimization procedure. As a result, an innovative synthesis technique based on the PSO-based iterative evolution of suitable shape descriptors is carefully detailed. To assess the effectiveness of the proposed method, a set of representative numerical simulations are performed and the results are compared with the measurements from experimental prototypes built according to the design specifications coming from the optimization procedure. To focus on the main advantages and features of the proposed approach, comparisons with the results obtained with a standard parametric approach are reported, as well.

Compressive Sensing Pattern Matching Techniques for Synthesizing Planar Sparse Arrays

In this paper, the design of sparse planar arrays is yielded through a set of innovative and efficient pattern matching algorithms within the Bayesian Compressive Sensing (BCS) framework. Towards this end, the 2D sparse synthesis problem is formulated in a probabilistic fashion and the single-task (ST) and the multi-task (MT) BCS solutions are derived. The results from a numerical validation concerned with different aperture size and target patterns prove that the proposed implementations enable an element saving ranging from 25% up to 87%, while achieving a reliable beam control.

A Monopolar Quad-Band Antenna Based on a Hilbert Self-Affine Prefractal Geometry

In this letter, the design of a quad-band antenna is presented. The antenna has a planar geometry printed on a dielectric substrate orthogonal to a reference ground plane and its geometrical parameters are optimized starting from a Hilbert-like prefractal reference shape. The reliability of the synthesized antenna is assessed by means of a set of experimental tests to verify its compliance with the project constraints.

An Innovative Multiresolution Approach for DOA Estimation Based on a Support Vector Classification

The knowledge of the directions of arrival (DOAs) of the signals impinging on an antenna receiver enables the use of adaptive control algorithm suitable for limiting the effects of interferences and increasing the gain towards the desired signals in order to improve the performances of wireless communication systems. In this paper, an innovative multi-resolution approach for the real-time DOA estimation of multiple signals impinging on a planar array is presented. The method is based on a support vector classifier and it exploits a multi-scaling procedure to enhance the angular resolution of the detection process in the regions of incidence of the incoming waves. The data acquired from the array sensors are iteratively processed with a support vector machine (SVM) customized to the problem at hand. The final result is the definition of a map of the probability that a signal impinges on the antenna from a fixed angular direction. Selected numerical results, concerned with both single and multiple signals, are provided to assess potentialities and current limitations of the proposed approach.

A DVBH/GSM/UMTS Planar Antenna for Multimode Wireless Devices

In this letter, the prototype of a planar antenna working in three different frequency bands and suitable to be integrated in multimode wireless devices is described. The antenna is fed by a single RF port without any matching circuit, and it operates in a DVBH channel and at GSM and UMTS frequency bands. Its dimension is of 0.15 lambda at the lower frequency band. The effectiveness and feasibility of the proposed antenna is assessed by means of both simulations and measurements.