Luca Manica

Handling Sideband Radiations in Time-Modulated Arrays Through Particle Swarm Optimization

The minimization of the power losses in time-modulated arrays is addressed by means of a suitable strategy based on particle swarm optimization. By properly modifying the modulation sequence, the method is aimed at reducing the amount of wasted power, analytically computed through a very effective closed-form relationship, while constraining the radiation pattern at the carrier frequency below a fixed sidelobe level. Representative results are reported and compared with previously published solutions to assess the effectiveness of the proposed approach.

ADS-Based Guidelines for Thinned Planar Arrays

We propose an analytical technique based on almost difference sets (ADSs) for thinning planar arrays with well controlled sidelobes. The method allows one to synthesize bidimensional arrangements with peak sidelobe levels (PSLs) predictable and deducible from the knowledge of the array aperture, the filling factor, and the autocorrelation function of the ADS at hand. The numerical validation, concerned with both small and very large apertures, points out that the expected PSL values are significantly below those of random arrays and comparable with those from different sets (DSs) although obtainable in a wider range of configurations.

An Innovative Approach Based on a Tree-Searching Algorithm for the Optimal Matching of Independently Optimum Sum and Difference Excitations

An innovative approach for the optimal matching of independently optimum sum and difference patterns through sub-arrayed monopulse linear arrays is presented. By exploiting the relationship between the independently optimal sum and difference excitations, the set of possible solutions is considerably reduced and the synthesis problem is recast as the search of the best solution in a noncomplete binary tree. Towards this end, a fast resolution algorithm that exploits the presence of elements more suitable to change subarray membership is presented. The results of a set of numerical experiments are reported in order to validate the proposed approach pointing out its effectiveness also in comparison with state-of-the-art optimal matching techniques.

Almost Time-Independent Performance in Time-Modulated Linear Arrays

This letter deals with the optimization of the switch-on instants of the radio-frequency (RF) switches used for the synthesis of time-modulated linear arrays (TMLAs). It is shown that these additional degrees of freedom allow one to increase the stability of the pattern instantaneously radiated by the antenna. Representative results, obtained by means of a particle swarm (PS) optimization, are reported and discussed.

Design of Subarrayed Linear and Planar Array Antennas With SLL Control Based on an Excitation Matching Approach

In this paper, the synthesis of subarrayed antennas with subarrays having different weights and dimensions is considered. The problem is formulated as the definition of the element clustering into spatially contiguous subarrays and the corresponding weights to obtain a pattern with the lowest (i.e., minimum achievable) sidelobe level (SLL). The problem is addressed with an unconstrained approach based on an excitation matching method where the synthesis of subarray weights and sizes is simultaneously carried out. Successively, a hybrid version of such an approach is proposed to directly enforce into the optimization procedure the SLL constraints. A set of representative results concerned with both sum and difference patterns are shown. Furthermore, some comparisons with state-of-the-art hybrid evolutionary-based techniques are reported, as well.

Tolerance Analysis of Antenna Arrays Through Interval Arithmetic

An analytical method based on Interval Analysis (IA) is proposed to predict the impact of the manufacturing tolerances of the excitation amplitudes on the radiated array pattern. By expressing the array factor according to the rules of the Interval Arithmetic, the radiation features of the linear array are described in terms of intervals whose bounds are analytically determined as functions of the nominal value and the tolerances of the array amplitudes. A set of representative numerical experiments dealing with different radiated beams and linear array sizes is reported and discussed to point out the features and potentials of the proposed approach.

A Fast Graph-Searching Algorithm Enabling the Efficient Synthesis of Sub-Arrayed Planar Monopulse Antennas

An innovative approach in its different implementations for the synthesis of compromise sum and difference patterns of monopulse planar arrays is presented. The synthesis method is based on a sub-arraying technique aimed at generating the compromise patterns through an optimal excitation matching procedure. By exploiting some properties of the solution space, the synthesis problem is reformulated as a combinatorial one to allow a considerable saving of computational resources. Thanks to a graph-based representation of the solution space, the use of an efficient path-searching algorithm is enabled to speed up the convergence to the compromise solution. In the numerical validation, a set of representative examples concerned with both pattern matching problems and pattern-feature optimization are reported in order to assess the effectiveness and flexibility of the proposed approach. Comparisons with previously published results and solutions obtained by a hybrid version of the approach customized to deal with the optimization of the sidelobe level (SLL) are reported and discussed, as well.

Analysis of the Pattern Tolerances in Linear Arrays With Arbitrary Amplitude Errors

The analysis of the tolerances on the power pattern of an array of electromagnetic radiators having excitation amplitudes affected by random errors around the nominal values is addressed. Toward this end, an analytic strategy based on interval analysis is exploited to predict the bounds of the variations in the radiated power pattern in correspondence with difference models of the amplitude tolerances. Selected results are presented and discussed in a comparative fashion as well.

An Improved Excitation Matching Method Based on an Ant Colony Optimization for Suboptimal-Free Clustering in Sum-Difference Compromise Synthesis

Dealing with an excitation matching method, this paper presents a global optimization strategy for the optimal clustering in sum-difference compromise linear arrays. Starting from a combinatorial formulation of the problem at hand, the proposed technique is aimed at determining the subarray configuration expressed as the optimal path inside a directed acyclic graph structure modelling the solution space. Towards this end, an ant colony metaheuristic is used to benefit of its hill-climbing properties in dealing with the non-convexity of the sub-arraying as well as in managing graph searches. A selected set of numerical experiments are reported to assess the efficiency and current limitations of the ant-based strategy also in comparison with previous local combinatorial search methods.

An Effective Excitation Matching Method for the Synthesis of Optimal Compromises between Sum and Difference Patterns in Planar Arrays

In this paper, the extension of the Contiguous Partition Method (CPM) from linear to planar arrays is described and assessed. By exploiting some properties of the solution space, the generation of compromise sum-difference patterns is obtained through an optimal excitation matching procedure based on a combinatorial method. The searching of the solution is carried out thanks to an efficient path-searching algorithm aimed at exploring the solution space represented in terms of a graph. A set of representative results are reported for the assessment as well as for comparison purposes. The final version of this article is available at the url of the journal PIERB http://www.jpier.org/PIERB/