Ultra-low sidelobes from time-modulated arrays

Abstract

Antenna patterns with ultra-low sidelobes have been obtained for an experimental receiving array designed with timemodulated slot radiators. The technique utilizes on-off RF switches which are programmed in a predetermined sequence to produce the desired pattern.The results of tests on an experimental eight-element slot array designed for sidelobe reduction are presented. Two examples are considered: 1) an initial static pattern with 30-db sidelobes which are reduced to about 40 db by sequential switching and 2) an initial static pattern with 13-db sidelobes which are reduced directly to about 44 db by a m e r e n t sequence of switching. Measured patterns illustrating the sidelobe reduction are included.The applicability of the sidelobe reduction technique to large electronically steerable phased arrays is considered briefly and it is concluded that it is compatible with such systems.

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

“…Over the time-modulated linear array design instances we also compare the performance of MOEA/D-DE with that of two single-objective optimization techniques, namely DEGL (DE with Global and Local Neighborhood) [39] and CLPSO (Comprehensive Learning PSO) [40] that are the state-of-the-art variants of DE and PSO, two metaheuristic algorithms widely used in past for various electromagnetic optimization [2,4,26,[41][42][43][44]. For singleobjective optimization techniques, we use a weighted linear sum of the objective functions given in (5a)-(5c).…”

“…Time-modulated antenna arrays are recently receiving a good deal of attention from researchers due to their efficiency in realizing ultra-low sidelobe levels in the far-field pattern [1][2][3][4][5]. This feature is mainly attributed to the fact that time-modulated antenna arrays incorporate an additional degree of freedom in their design-the time.…”

“…This feature is mainly attributed to the fact that time-modulated antenna arrays incorporate an additional degree of freedom in their design-the time. For an 8-element slotted linear array the time modulation method and the realization of a nearly ultra-low SLL (∼ 39.8 dB) were first achieved by Kummer et al [2]. The general principles for analysis of timemodulated antenna system were first put forward by Bickmore in [5].…”

“…Certain applications demand complete removal of sideband signals and hence they should be suppressed as far as possible to improve the efficiency of array design. In [2], Yang et al proposed a Differential Evolution (DE) based approach for the design of time-modulated linear arrays with effective suppression of sideband radiation patterns. Such designs offer severe challenges to the antenna researchers and as indicated by [6] metaheuristic algorithms can be the best ways to handle them.…”

“…In works like [2,4,10], separate objectives (which are often conflicting) are combined through a weighted linear sum into a single aggregated objective function. The weighted sum method is however, subjective and the solution obtained will depend on the values (more precisely, the relative values) of the weights specified.…”