Pulse-Shaping Strategy for Time Modulated Arrays—Analysis and Design

Bekele, Ephrem T.; Poli, Lorenzo; Rocca, Paolo; D’Urso, M.; Massa, Andrea

doi:10.1109/tap.2013.2256096

Cited by 86 publications

(38 citation statements)

References 22 publications

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“…However, inherent sideband radiations in TMAA reduces antenna efficiency and directivity [15,16] when the desired pattern is synthesized at the operating frequency only. Accordingly, during the last decade, a number of contributions with different time-modulation approaches based on different optimization tools have been successfully applied to realize different patterns at the operating frequency by suppressing SBLs to sufficiently low values [10][11][12][13][17][18][19][20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Simultaneous Multiple-Harmonic-Patterns in Time-Modulated Linear Antenna Arrays

Mandal¹,

Mahanti²,

Ghatak³

2014

PIER M

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Abstract-In time-modulated antenna arrays (TMAAs), as a result of periodical switch-on and switchoff of the antenna elements, including operating frequency (termed as center frequency) signal, sideband signals are appeared at either sides of the center frequency in integer multiples of the modulation frequency. In this paper, it is shown that without using phase shifters, just by suitably controlling the on-time instants (OTIs) and on-time durations (OTDs) of a time-modulated linear antenna array (TMLAA) elements, simultaneously, along with a pencil beam pattern at the operating frequency, a shaped beam pattern can be obtained at both the first positive and negative harmonics of the timemodulation frequency. The important advantage of such a technique is that realization of multi-beam pattern in conventional antenna array (CAA) system generally requires complex feed network, whereas by using simple radio frequency (RF) switching circuit in the feed network of TMLAA, by virtue of the properties of harmonic radiations, synthesis of a shaped pattern at either (positive or negative) harmonic results in generating the same pattern in its opposite harmonic, and the synthesized patterns at different harmonics can be simultaneously used as independent communication channels. By employing a differential evolution (DE) based optimization method, numerical results for a 16-element TMLAA with uniform excitation show that in conjunction with a pencil beam pattern at the center frequency, a flat-top or a cosec square pattern at first positive and negative sidebands of side-lobe levels (SLL) −20 dB can be synthesized by suppressing the higher sideband level (SBL) to below −10 dB.

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Section: Introductionmentioning

confidence: 99%

Synthesis of Simultaneous Multiple-Harmonic-Patterns in Time-Modulated Linear Antenna Arrays

Mandal¹,

Mahanti²,

Ghatak³

2014

PIER M

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“…Hence, in some application, it is necessary to reduce the sideband power associated with TMAAs. As a consequence, including VAS, [9][10][11][12][13][14] different other time modulation approaches such as pulse shifting, [15,16] binary optimized time sequences (BOTS), [17] sub-sectional optimized time steps (SOTS), [18] sub-division of the element switching sequence combined with the finite bandwidth of the array elements, [19] optimization of the unequal element spacing, [20] exploitation of pattern multiplication for the directive TMAAs [21] and recently, pulse shaping strategy [22] have been incorporated to synthesize the desired low side lobe patterns at the operating frequency by suppressing the maximum sideband level (SBL max ) to significantly low value. In different timemodulation approaches, different optimization tools like simulated annealing (SA), [9,10] differential evolution (DE), [11][12][13]18,20] artificial bee colony (ABC), [14] particle swarm optimization (PSO) [15,16,21,24,25] and genetic algorithm (GA) [17] are successfully employed to realize such optimum patterns in TMAAs.…”

Section: Introductionmentioning

confidence: 99%

Design of a time-modulator to synthesize different patterns in time-modulated antenna arrays

Mandal

Mahanti

Ghatak

2014

Journal of Electromagnetic Waves and Applications

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This paper presents a novel technique to design a time-modulator that can be used as a discrete component to generate different patterns in time-modulated antenna array (TMAA) system. The technique quantizes the modulation period into a number of levels with equal step size between the consecutive levels and rounds off the on-time of the antenna elements to nearest quantization levels to obtain quantized on-times (QOTs) of the corresponding elements. In order to realize the time modulation technique, a representative block diagram of a time-modulator defined as "quantized time-modulator" is presented. It is shown that the effect of quantization errors on the synthesized patterns can be diminished by selecting a suitable number of quantization states by using artificial bee colony (ABC) as a global optimizer. Accordingly, two previously reported examples based on simulated annealing (SA) algorithm, optimized by using continuous search space of on-time are considered, and ABC optimized results using discrete search space of QOT are compared with those obtained by SA. Finally, a fully digitally controlled, low side lobe flat-top pattern with low dynamic range ratio of static amplitude is synthesized by considering discrete search space of QOT.

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“…Recently, a new approach for TMAs design has been proposed where the shapes of the modulating pulses have been taken into account for SR suppression [28]. By knowing that the amplitude weighting coefficients of the pattern at the antenna working frequency of a TMA are equal to the areas of the pulses modulating the static excitations, different pulse shapes have been considered in [28] and close form relationships have been derived to compute the amount of power losses in the SR.…”

Section: Introductionmentioning

confidence: 99%

Pulse shape optimization in time-modulated arrays for sideband radiation suppression

Poli

Bekele

D’Urso³

et al. 2014

The 8th European Conference on Antennas and Propagation (EuCAP 2014)

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In time-modulated arrays, the signal transmitted or received by the array elements is multiplied by means of a train of periodic pulses which allow to obtain an angularly selective radiation pattern at the antenna working frequency. Generally, a set of radio-frequency switches is used for the pulse generation and it is assumed that ideal rectangular waveforms are obtained. In this work, pulse waveforms having noninstantaneous on-off transitions are taken into account and their shapes are optimized by means of a stochastic global algorithm in order to reduce the losses in the sidebands caused by the time modulation process.

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Pulse-Shaping Strategy for Time Modulated Arrays—Analysis and Design

Cited by 86 publications

References 22 publications

Synthesis of Simultaneous Multiple-Harmonic-Patterns in Time-Modulated Linear Antenna Arrays

Synthesis of Simultaneous Multiple-Harmonic-Patterns in Time-Modulated Linear Antenna Arrays

Design of a time-modulator to synthesize different patterns in time-modulated antenna arrays

Pulse shape optimization in time-modulated arrays for sideband radiation suppression

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