Obtaining wide steered nulls in linear array patterns by optimizing the locations of two edge elements

Mohammed, Jafar Ramadhan

doi:10.1016/j.aeue.2019.02.004

Cited by 16 publications

(22 citation statements)

References 26 publications

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“…Each wide null at the desired direction is generated by forming two adjacent nulls with a small spacing equal to u = 0.02 around the interfering directions. The effectiveness of the simplified null steering array [26] compared to the fully nonuniform spaced array has been illustrated by the design of 30 elements linear array with the main beam directed toward the broadside. The smoothing, elite sample selection and population parameters of the optimization algorithm are chosen to be 0.7, 0.1, and 100, respectively [26].…”

Section: The Resultsmentioning

confidence: 99%

“…As we have shown in the previous section, the practical implementation of the feeding network in the electronically null steering methods is a real challenging issue, especially when dealing with large arrays. To solve this problem, many researchers, for example, see [22][23][24][25][26], proposed to mechanically control the spacing between the array elements instead of electronically controlling the amplitude and/ or phase excitations to achieve the required null steering. However, in practice, these fully nonuniform spaced arrays have also some disadvantages and difficulties to build.…”

Section: Mechanical Null Steering Methodsmentioning

confidence: 99%

“…The far-field radiation pattern of an array consisting of N isotropic mechanically movable elements that are arranged in nonuniform locations x n according to the second structure (see Figure 16), can be written by [26] AF u ðÞ¼2 ∑ N=2 n¼1 a n cos kx n u ðÞ (8) where N is assumed an even number, and a n is the electronic weighting of the array elements which is chosen to be constant or uniform in this method. In order to introduce the required nulls and at the same time reducing the sidelobe level in the array pattern of (8), the following cost function is used [26] CostFunction ¼ 10 log 10 max AF u ðÞ jj 2 þ ∑ I i¼1 AF u i upperbound &u i lowerbound (9) where λ=Nd ≤ u ≤ 1, and i ¼ 1, 2, …I. Note that λ=Nd represents the angular location of the first null in the array pattern and I represents the total number of the steered nulls.…”

Section: Fully Nonuniform Spaced Arraymentioning

confidence: 99%

“…Redesigning the array in a very short time interval is really a challenging problem. One effective and simple solution to this important problem is addressed and proposed in [26].…”

Section: Fully Nonuniform Spaced Arraymentioning

confidence: 99%

“…On the other hand, the mechanical null steering methods that are based on the controlling of the separation distance between the array elements were considered as an alternative and competitive solution to the electronic counterpart [23][24][25]. In [26], the author proved that the mechanical null steering made better patterns when compared with the electronic counterpart [20], by mechanically controlling the positions of the extreme elements while leaving all the electronic excitations including the edge elements constant.…”

Section: Introductionmentioning

confidence: 99%

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Sidelobe Nulling by Optimizing Selected Elements in the Linear and Planar Arrays

Mohammed¹,

Sayidmarie²

2019

Array Pattern Optimization

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Currently, there are significant interests in the antenna arrays that are composed of a large number of elements controlled by an appropriate optimizer for the next generation of wireless communication systems, where the massive multiple-inputs multiple-outputs (MIMO) systems are expected to play a major role in such systems. On the other hand, the interfering signals which are expected to rise dramatically in these applications due to the crowded spectrum represent a real challenging issue that limits and causes great degradation in their performances. To achieve an optimum performance, these antenna arrays should be optimized and designed to have maximum gain, narrow beam width, and very low sidelobes or deep nulls. Toward achieving this goal, the overall array performance can be either electronically controlling the design parameters, such as amplitude and/or phase excitations of the individual elements, or mechanically controlling the element positions. This chapter discusses techniques proposed for sidelobe nulling by optimizing the excitations and positions of selected elements in the linear and planar arrays.

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Section: The Resultsmentioning

confidence: 99%

Section: Mechanical Null Steering Methodsmentioning

confidence: 99%

Section: Fully Nonuniform Spaced Arraymentioning

confidence: 99%

“…Redesigning the array in a very short time interval is really a challenging problem. One effective and simple solution to this important problem is addressed and proposed in [26].…”

Section: Fully Nonuniform Spaced Arraymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sidelobe Nulling by Optimizing Selected Elements in the Linear and Planar Arrays

Mohammed¹,

Sayidmarie²

2019

Array Pattern Optimization

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A novel linear and planar multiband fractal‐shaped antenna arrays with low sidelobes

Mohammed

2024

Int J Communication

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SummaryFractal antenna arrays are usually used to tune multiband frequencies. However, these types of iteratively constructed antennas are associated with undesirable high sidelobe levels and low directivities. In this paper, an optimization procedure based on the genetic algorithm is used to find the optimal weights of the array elements such that the corresponding array patterns have low sidelobe levels and good directivity. Moreover, the fractal nature in the proposed arrays is maintained regardless of the optimized weights. Thus, the proposed fractal‐shaped array maintains its capability in performing multiband frequency operation. These good radiation features make the proposed fractal‐shaped array more appropriate for the current and future wireless communication applications. Simulation results confirm the superiority of the presented linear and planar fractal‐shaped array structures with compared to the conventional fractal cantor linear array and the standard Sierpinski carpet planar array. For the proposed fractal cantor linear array, the sidelobe level has been reduced to more than −20 dB at different operating frequencies, and the directivity has been improved by more than 8 dB, while the modified Sierpinski carpet planar array has achieved −30 dB depressions in the sidelobe level and 6 dB improvement in the directivity.

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Closed‐loop controlled microwave beamformer

Fabiani

Oliveira

Vieira

et al. 2021

Int J RF Mic Comp-Aid Eng

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This article presents the design and tests of a closed‐loop controlled microwave beamformer for phased arrays. The proposed circuit owns an internal reference signal used to automatically set predefined amplitudes and phases of the beamformer branches. This signal is applied to the branches through directional couplers with high directivity and propagates in them similar to the actual signals coming from the antenna array. As a consequence of this architecture, we found that the impedance mismatch between the antennas and the beamformer as well as the mutual coupling in the array is taken into account during calibration, resulting in a more accurate adjustment of amplitudes and phases. In this work, the influence of the mutual coupling between the antennas and the directivity of the couplers on the beamforming calibration uncertainty is also analyzed. From the derived uncertainties, the corresponding pattern degradation is evaluated by performing Monte Carlo simulations. It is shown that using couplers with low directivity together with tightly coupled arrays can produce undesirable main lobe squints of up to 4.5°, main lobe level deviations of up to 4.2 dB, and side lobe level variations of up to 24 dB. On the other hand, the use of high directivity couplers can mitigate these problems. Lastly, the validation of the designed circuit is conducted in two stages: bench tests and measurements in an anechoic chamber with an array of six printed monopoles operating at 2.2 GHz. Amplitude and phase calibration errors less than 0.5 dB and 3°, respectively, were observed in the bench tests.

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Obtaining wide steered nulls in linear array patterns by optimizing the locations of two edge elements

Cited by 16 publications

References 26 publications

Sidelobe Nulling by Optimizing Selected Elements in the Linear and Planar Arrays

Sidelobe Nulling by Optimizing Selected Elements in the Linear and Planar Arrays

A novel linear and planar multiband fractal‐shaped antenna arrays with low sidelobes

Closed‐loop controlled microwave beamformer

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