Design of Time-Modulated Linear Arrays With a Multi-Objective Optimization Approach

Abstract

Abstract-This article proposes a Multi-objective Optimization (MO) framework for the design of time-modulated linear antenna arrays with ultra low maximum Side Lobe Level (SLL), maximum Side Band Level (SBL) and main lobe Beam Width between the First Nulls (BWFN). In contrast to the existing optimization-based methods that attempt to minimize a weighted sum of SLL, SBL, and BWFN, we treat these as three distinct objectives that are to be achieved simultaneously and use one of the best known MultiObjective Evolutionary Algorithms (MOEAs) of current interest called MOEA/D-DE (Decomposition based MOEA with Differential Evolution operator) to determine the best compromise among these three objectives. Unlike the single-objective approaches, the MO approach provides greater flexibility in the design by yielding a set of equivalent final solutions from which the user can choose one that attains a suitable trade-off margin as per requirements. We compared time-modulated antenna structures with other methods for linear array synthesis such as the excitation method and the phase-position synthesis method on the basis of the approximated Pareto Fronts

Multi-Objective Evolutionary Optimization of Aperiodic Symmetrical Linear Arrays

“…For comparison, the Dolph-Chebyshev front is also reported (solid line). It is apparent that the introduction of the third objective helps the MOGA procedure to converge towards fronts with a better spread [27]. In fact, the fronts are calculated over a wider range of SLLs.…”

“…Other numerical optimization strategies have also been proposed, based on the synthesis of a density-tapered distribution of uniformly excited elements [7], [12], or of a combined amplitude-density tapered distribution of non-uniformly excited elements [11], approximating a properly chosen continuous source. Stochastic global optimization techniques based on meta-heuristics, such as evolutionary algorithms (GAs, differential evolution), have been successfully applied to the antenna array design problem showing a high flexibility [3], [15]- [27]. In [28], a comparison is presented between different population-based optimization methods applied to the design of scannable circular antenna arrays: genetic algorithms, particle-swarm optimization and the differential evolution method are considered.…”

Rf Directional Modulation Technique Using a Switched Antenna Array for Physical Layer Secure Communication Applications

“…Our work in this paper is different from the aforementioned works in the following aspects: i) The antenna switching scheme is controlled by a spreading sequence for the purpose of forming a RF directional modulation signal with LPI and LPD, unlike paper [25][26][27][28] for radiation pattern synthesis; ii) Fundamental frequency component and all harmonic components are used to form a RF directional modulation signal different from radiation pattern synthesis only using fundamental frequency component in paper [25][26][27][28] and direction finding application using fundamental frequency component and harmonic components in paper [35]; iii) RF directional modulation signal is associated with the spreading sequence and the direction of the receiver, unlike traditional spread-spectrum signal only depended on the spreading sequence. This advantage ensures that eavesdroppers can not demodulate the RF directional modulation signal even if eavesdroppers know the information about spreading sequence.…”

“…Paper [28][29][30] consider that these harmonic components are harmful for the pattern synthesis, which need to minimize its power levels and filter by a low-pass filter. However, we utilize these harmonic components to form the RF directional modulation signal for secure communication applications.…”

“…In the late 1950s, "Time" as a design parameter is first proposed to suppress the sidelobes of the linear array in [24]. Researches on TMLA have followed this work for the purpose of achieving lower sidelobe level [25][26][27][28]. TMLA is widely applied to airborne pulsed Doppler radar system [29], direction of arrivals (DOAs) system [30] and digital beamforming (DBF) system [31].…”