Optimizing uniformly excited linear arrays through time modulation

Abstract

This letter shows that, by the proper use of time modulation in equispaced linear arrays with uniform excitation distribution, it is possible to maintain the sidelobe zone of the radiated power under certain-previously stipulated-level whereas the undesired harmonics are minimized. In addition to that, the further extension of the technique to nonequispaced arrays permits to obtain broadband response, by simply searching the positions of the elements that reach to the desired power pattern behavior within the required bandwidth.

Synthesis of compromise sum-difference arrays through time-modulation

“…Accordingly, once the number of sub-arrays Q is given, the minimization of (5) It is worth noting that whether, on one hand, the "best compromise" difference pattern at ω 0 can be easily obtained by applying the CP M procedure, on the other hand, SRs are still present because of the commutation between the on and off state of RF switches that controls the time-modulation process. In order to reduce the interferences due to SRs, the optimization of T in uniform arrays [26] or the joint optimization of both T and A [24] has been performed in the literature. However, it should be pointed out [Eq.…”

“…This has been mainly due to the presence of undesired sideband radiations (SRs) which unavoidably affect the performance of time-modulated arrays. In order to minimize the SR power losses, different approaches based on evolutionary optimization algorithms have been proposed [24][25] [26] [27]. Otherwise, it has been demonstrated in [28] that the control of the sideband levels at the harmonic frequencies can be yielded by using suitable switching strategies providing effective pulse sequences.…”

A Study of Am and Fm Signal Reception of Time Modulated Linear Antenna Arrays

“…Alternatively, some optimization algorithms such as the differential evolution (DE) [6,10,11,18], genetic algorithm (GA) [12] and simulated annealing (SA) [9,13] can be used to optimize the time sequences of elements.…”

“…The major problem of the time modulated antenna arrays is that the time modulation generates unwanted harmonics or sidebands at multiples of the time modulation frequency. Many studies on the time modulated antenna arrays were concentrated on minimizing these harmonics [9][10][11][12][13]. However, sidebands do not always be harmful.…”

An Iterative Approach for the Synthesis of Optimized Sparse Time-Modulated Linear Arrays

“…Toward this end, many techniques have been proposed based on differential evolution (DE) [4][5][6][7], simulated annealing (SA) [8], and particle swarm optimizer (P SO) [9][10][11] aimed at minimizing the sideband level (SBL) [4], namely the peak level of the harmonic patterns, or the overall harmonic content [9] or both [11] by suitably defining the timepulse durations. The possibility to modify the periodic waveforms has been also examined in [12][13][14][15] to achieve a better handling of the SRs.…”