Low Sidelobe Level Research Articles

The optimal synthesis of thinned concentric circular antenna arrays using slime mold algorithm

ABSTRACT In this paper, thinned concentric circular antenna arrays (CCAAs) with low sidelobe levels and fixed half-power beamwidths are synthesized by using the Slime Mold Algorithm (SMA). SMA is a novel stochastic optimization method inspired by the oscillation mode of the slime mold in nature. Entering the literature as a new optimization technique, SMA is based on a matchless mathematical model that finds the most suitable way to find food in the search space thanks to the negative and positive oscillations of the slime mold. SMA is also used to obtain thinned CCAAs having different ring numbers. It is seen that the results obtained by SMA are very good. Besides, the flexibility of SMA in different values of parameters is a promising feature for the other antenna array synthesis problems. The results obtained by SMA are compared with several meta-heuristic algorithms in the literature. SMA shows a better performance in synthesizing CCAAs than the other compared algorithms.

Tunable metasurfaces using phase change materials and transparent graphene heaters

Tunable metasurfaces enable us to dynamically control light at subwavelength scales. Here, using phase change materials and transparent graphene heaters, a new structure is proposed to develop tunable metasurfaces which support first-order Mie-type resonance in the near-IR regime. In the proposed structure, by adjusting the bias voltages applied to transparent graphene heaters, the crystallization levels of the phase change materials are controlled, which in turn modifies the response of the metasurface. The proposed metasurface is able to modulate the phase of the reflected wave in the range of 0° to -270° at the telecommunication wavelength of λ = 1.55 µm. A comprehensive Joule heating analysis is performed to investigate the thermal characterizations of the proposed structure. The results of this analysis show that there is a suitable thermal isolation between adjacent unit cells, making individual control on unit cells possible. The potential ability of the proposed metasurface as a beam steering device is also demonstrated. By using the proposed unit cells, a beam-steering device is designed and numerically studied. This study shows that the device can reflect a light normally incident on it in the range of ±65° with reasonably low sidelobe levels. The proposed structure can be used in developing low-cost integrated LiDARs.

Generation of difference pattern from a linear microstrip patch array for the monopulse radar application

This paper presents a new technique to generate difference pattern from a circularly polarized (CP) microstrip array antenna for monopulse radar application. The individual truncated corner radiators of the array are left-handed CP (LHCP). The difference pattern is generated by placing together the left and right side proposed single elements in opposite direction to each other along the y-axis with an inter-element spacing of 3λ/4. In order to achieve a stable radiation pattern with low sidelobe level over a resonating band, a uniform feed network is designed for the array. Finally, the proposed single element and the 4 × 1 array are designed, fabricated, and measured. The left-polarized element of the array structure, resonates at 5.90 GHz with good circular polarization properties. The array prototype resonates at 5.904 GHz with 3.60% impedance bandwidth. The array gives null depth greater than −30 dB at θ = 0∘ in different ϕ cuts. The proposed left-CP array has a gain of 9.48 dBic and a radiation efficiency of 77.50%. Moreover, the measured results matched well with the simulated results, which proves the effectiveness of the proposed approach for practical application.

Coupled‐line proximity‐coupled microstrip linear array antenna for millimetre‐wave applications

A novel low-cost, millimetre-wave antenna has been presented in this communication. The proposed antenna is a proximity-coupled linear array with coupled feedlines to achieve wideband characteristics. Good agreement between simulated and measured results is achieved and proves that the proposed antenna structure is capable of attaining over twice the bandwidth with the coupled lines than that attained with a single microstrip feedline while achieving lower sidelobe levels. The antenna has a gain of about 15.0 dBi with an half-power beam width of 12° ± 2° over a frequency range of 27.25–29.25 GHz. It also exhibits an impedance bandwidth of 19.6% from 24.48 to 29.8 GHz.

Shaped Elevation Beam Design for Airborne Conformal Array Detection

When airborne early warning radar performs beam scanning, there are often various requirements for the shape of the beam and sidelobe levels. In this letter, the design of elevation beamforming for airborne conformal radar and the beam shape required for its detection are analyzed. The optimization introduces an amplitude control variable into the modified Bernstein polynomial to obtain lower sidelobe levels of arrays, which is useful for early warning radar detection. Particle swarm optimization is used to optimize the modified Bernstein polynomial parameters with the amplitude control variable and phase. The results demonstrate that the excitation amplitude optimized by this method and phase optimized randomly can achieve the beam shape required for airborne conformal array detection. Furthermore, modified Bernstein polynomials defined with five and six parameters are compared. The introduction of an amplitude control variable produces lower sidelobes, and the optimized amplitude distribution is smoother, making it easier to feed the array.

Pattern Synthesis of Linear Antenna Array Using Improved Differential Evolution Algorithm with SPS Framework

In this paper, an improved differential evolution (DE) algorithm with the successful-parent-selecting (SPS) framework, named SPS-JADE, is applied to the pattern synthesis of linear antenna arrays. Here, the pattern synthesis of the linear antenna arrays is viewed as an optimization problem with excitation amplitudes being the optimization variables and attaining sidelobe suppression and null depth being the optimization objectives. For this optimization problem, an improved DE algorithm named JADE is introduced, and the SPS framework is used to solve the stagnation problem of the DE algorithm, which further improves the DE algorithm’s performance. Finally, the combined SPS-JADE algorithm is verified in simulation experiments of the pattern synthesis of an antenna array, and the results are compared with those obtained by other state-of-the-art random optimization algorithms. The results demonstrate that the proposed SPS-JADE algorithm is superior to other algorithms in the pattern synthesis performance with a lower sidelobe level and a more satisfactory null depth under the constraint of beamwidth requirement.

A TM 03 mode reduced side lobe high‐gain printed antenna array in K band for UDN and IoT applications in 5G

A single layer simple feed reduced side lobe gain-enhanced microstrip antenna array using higher-order modes is analyzed and designed in this work. The relationship between the relative magnitude of equivalent magnetic currents and directivity are studied. Modal analysis for rectangular patch is considered for broadside and non-broadside radiation. Comparative investigations on antenna radiation and impedance characteristics for fundamental and higher-order modes are presented. It is observed that an array can be designed to operate in TM03 mode for enhanced gain with broadside radiation. Parametric optimization is carried out to attain low side lobe level. The proposed theory is validated by designing and fabricating a single layer single feed 2 × 2 microstrip patch array in the K band operating in TM03 mode. The simulated and measured realized gain of the fabricated TM03 mode array is 16.1 and 15.5 dBi, respectively, at 22 GHz with consistent broadside radiation pattern and linear polarization.

New correlated MIMO radar covariance matrix design with low side lobe levels and much lower complexity

In this paper, a new correlated covariance matrix for Multi-Input Multi-Output (MIMO) radar is proposed, which has lower SideLobe Levels (SLLs) compared to the new covariance matrix designs and the well-known multi-antenna radar designs including phased-array, MIMO radar and phased-MIMO radar schemes. It is shown that Binary Phased-Shift Keying (BPSK) waveforms that have constant envelope can be used in a closed-form to realize the proposed covariance matrix. Therefore, there is no need to deploy different types of radio amplifiers in the transmitter which will reduce the cost, considerably. The proposed design allows the same transmit power from each antenna in contrast to the phased-MIMO radar. Moreover, the proposed covariance matrix is full-rank and has the same capability as MIMO radar to identify more targets, simultaneously. Performance of the proposed transmit covariance matrix including receive beampattern and output Signal-to-Interference plus Noise Ratio (SINR) is simulated, which validates analytical results.

Design and analysis of dual-polarized reflectarray with low sidelobe level for wireless communication applications

Design and analysis of dual-polarized reflectarray with low sidelobe level for wireless communication applications

Deterministic Synthesis Approach for Linear Sparse Array Antennas

This article discusses a deterministic technique for the synthesis of isophoric (equally fed) linear sparse array antennas (LSAAs) consisting of nonuniform (aperiodic) placement of the radiating elements on the array aperture. This article derives nonequal interelements spacing in LSAA for demonstrating low sidelobe level (SLL) with equally fed elements. The deterministic approach is called as Array Dilation Technique (ADT). It stretches the array in analogy to an elastic membrane and henceforth, creating an aperiodicity in the array. This technique does not require any model taper and simply takes a uniformly fed array with uniform interelement spacing as the initial array subjected to the application of ADT. The technique demonstrates achieving comparatively lower SLL for optimal thinning levels in comparison to the prior published literature. The numerical case studies presented are compared with the previous literature demonstrating the effectiveness and the outperformance of the newly proposed technique.

Unequally spaced resonant slotted‐waveguide antenna array with low side lobe level based on an open‐ended substrate integrated waveguide resonator

AbstractIn this article, an unequally spaced resonant slotted‐waveguide antenna array with low side lobe level (SLL) is presented. In the conventional resonant arrays with longitudinal slots on the waveguide broad wall, slots must be separated one half guided wavelength (λg/2) from each other and be on opposite sides of the center line to have an in‐phase excitation. The open‐ended substrate integrated waveguide (SIW) resonator can support a resonance mode with the infinite wavelength. Hence using this kind of resonator, distances between slots in the resonant array are free parameters and can be optimized to achieve a low SLL. Based on the mentioned resonator, a 10‐element resonant slotted‐waveguide antenna array at 10 GHz with 10° beam‐width is designed and simulated. The distances between slots are determined by using genetic algorithm (GA). This antenna has been fabricated and measured. The measurement results show that the SLL of the presented antenna is 16 dB.

Wideband linear microstrip array antenna with high efficiency and low side lobe level

In this letter, the design and fabrication of the linear microstrip array antenna by series fed are presented. The array antenna consists of 16 reflector slot-strip-foam-inverted patch (RSSFIP) antennas. The gain and efficiency of the linear array antenna is 16.6 dBi and 61% at 10 GHz, respectively. The antenna has a bandwidth (BW) of 45% from 8.1 to 12.8 GHz (S11 < −10 dB) and side lobe level (SLL) of −25.6 dB across the BW of 19.2% from 9.4 to 10.4 GHz. These are achieved by using a microstrip series fed with defected ground structure (DGS) to feed the patch array antenna. Good agreement is achieved between measurement and simulation results.

Circular Antenna Array Synthesis Using Multiverse Optimizer

Antenna array synthesis is one of the most popular topics in the electromagnetic field. Since achieving a desired antenna radiation pattern is a mathematical problem, in the literature, there are various optimization algorithms applied to the synthesis process of different kinds of antenna arrays. In this study, Multiverse Optimizer (MVO) and modified MVO (MMVO) are used to perform circular antenna array (CAA) synthesis. During the exploration, exploitation, and local search phases of calculation, MVO uses three concepts in cosmology; white hole, black hole, and wormhole. Convergence capability of this nature-inspired algorithm is employed for finding optimum amplitude and position values of CAA elements in order to achieve an array pattern with low maximum sidelobe level (MSL) and minimum circumference. The performance of MVO and MMVO was tested on five design examples of pattern synthesis, and the obtained results were compared with ten different algorithms. The simulation results show that MVO and MMVO provide low MSLs with small circumferences.

Enhanced bandwidth, low sidelobe resonant cavity antenna using tapered complementary FSS layers

A novel resonant cavity antenna (RCA) with low sidelobe levels over an enhanced bandwidth is presented. Radiation bandwidth of the antenna is increased by using a pair of complementary FSS layers, giving a positive reflection phase over a wide frequency range, as the proposed PRS. Low sidelobes are achieved by lowering the reflection amplitude of the PRS along its length while keeping reflection phase almost the same throughout the operating band. The performance of the proposed PRS is validated by creating a circular aperture RCA and measuring its radiation characteristics. The cavity is excited by an aperture coupled patch antenna having a broad impedance bandwidth. Prototype RCA gives a peak realized gain of 16.1 dBi and a 3-dB gain bandwidth of 8.6% ranging from 14.5 to 15.8 GHz. Measured sidelobe levels are reduced, respectively, to less than −17 dB and −23 dB in the E- and H-plane of the prototype antenna.

A New Linear Printed Vivaldi Antenna Array with Low Side Lobe Level and High Gain for the Band 3.5 GHz

This paper proposes a new design of low sidelobe level (SLL) and high gain linear printed Vivaldi antenna array. The array composes of two parts, which are a linear Vivaldi antenna array and a back reflector. The array consists of 10 single Vivaldi antennas and a series-fed network, those are based on Roger RO4003C substrate (ε = 3.55) with the dimension of 140 x 450 x 1.524 mm3. A new Bat algorithm with the amplitude-only control technique has been applied to optimize the output coefficients of the series-fed network for gaining a low SLL. The simulation results indicate that the proposed antenna provides a low SLL of -29.2 dB in E-plane with a high gain of 16.5 dBi at the frequency of 3500 MHz. A prototype of the proposed antenna array has been fabricated. The measured data has a good agreement with the simulated data.

2D/3D Shaped Radiation Patterns of Sunflower and Conformal Antenna Arrays Using Phase Synthesis

2D and 3D beam synthesis from different antenna array arrangements are investigated in this paper. Planar sunflower, conformal cylinderical and spherical helical array arrangements are studied. The particle swarm optimization (PSO) technique is used to predict the phase distribution on the array elements. The beam synthesis is achieved by comparing the array factor with a predetermined mask with both upper and lower limits according to the intented application requirements. Different 2D and 3D masks are used in beam synthesis as pencil, flat-top, and cosecant single beam are predicted. The planar sunflower antenna array is investigated due to its high gain, low side-lobe level (SLL) below − 20 dB and its compact size. The phase distribution of sunflower array is estimated using PSO to radiate dual-beams in different planes. Dual-beam with pencil, flat-top, and cosecant beams are obtained with different half-power beam widths. 3D conformal antenna arrays of cylindrical and spherical helical arrangements are studied. Each 3D conformal array consists of four arms shifted in position by 90° orintation angle. Each arm is designed to radiate single beam in a specific direction. Four-beams are considered to radiate in the directions of θ1,2,3,4 = 30°, and ϕ1 = 0°, ϕ2 = 90°, ϕ3 = 180°, and ϕ4 = 270° with SLL optimized below − 17 dB. The array arrangements analysis is based on the array theory formulation, through the implemention of the estimiated equation using a home programmed MATLAB code.

Synthesizing Beam-Scannable Thinned Massive Antenna Array Utilizing Modified Iterative FFT for Millimeter-Wave Communication

In this letter, a modified iterative fast Fourier transform (MI-FFT) technique is presented to synthesize thinned massive array for 5G millimeter-wave (mm-wave) communications. The periodicity of a scannable array factor for a uniformly spaced planar array is discussed and employed to reduce the complexity of array factor computation. A gradual array thinning strategy is introduced to prevent the iterative procedure from being trapped into an endless loop so that a better solution with lower sidelobe level (SLL) can be found. The beamwidth control is also added in the MI-FFT to control the pattern beamwidth. A thinned 128-element planar array with parasitic patch covered microstrip antenna elements is designed with the frequency band from 25.2 to 31.6 GHz. The 128-element positions are optimally selected from a prescribed larger layout by the proposed method, and consequently the obtained thinned array has a much lower SLL and narrower beamwidth than a conventional fully occupied 128-element array.

Frequency Diverse Array with Cubic Sinusoidal Frequency Offset

Frequency diversity array radar (FDA) has range-angle dependent beampattern, providing enormous potential for the application of this new type of radar. However, the beampattern of conventional FDA (CFDA) has two problems: range-angle coupling and range periodicity, limiting the application of FDA. How to solve the problems is the premise of realizing beam accurate control and target accurate positioning. In this paper, we propose a new FDA transmitter structure with cubic sinusoidal frequency offset (Cubic sin-FDA). Simulation results show that this FDA beampattern eliminates coupling and forms a spot-shaped beampattern. Compared with the existing nonlinear frequency offset FDA beampattern, this method has a narrower half power bandwidth and lower side lobe level.

Compact High-Gain Si-Imprinted THz Antenna for Ultrahigh Speed Wireless Communications

A low-profile and high-gain Gaussian beam antenna (GBA) operating at 1 THz is demonstrated for the first time. Imprint and dry etching technologies in silicon are employed. A complementary antenna feed based on the magnetoelectric dipole is proposed for enhancing the radiation characteristics of the antenna. The microfabrication technologies are compatible with the Si-based integrated circuit manufacturing process. The terahertz (THz) antenna is realized with over 20 dBi in antenna gain. With high-precision fabrication technologies, a highly efficient THz GBA with smooth morphology and much lower profile than conventional horn and lens antennas is developed. Moreover, the antenna has the characteristic of low sidelobe levels which is advantageous in many wireless applications.

New design of a linear double‐sided printed dipole array based on bat algorithm for interference suppression in the first sidelobe direction

This study proposes a design of a double-sided printed dipole (DSPD) antenna array with a low first sidelobe level (FSLL) for interference suppression. The proposed array consists of ten DSPD antennas based on the Rogers RO4003C substrate (ɛr = 3.55). The FSLL has been compressed by imposing a single null at the centre of the first sidelobe. The excitation power distribution of the array has been calculated by using the bat algorithm with the amplitude-only control technique and has been implemented by a series-fed network. A back reflector, which is based on an FR4 substrate (ɛr = 4.4), has been used to improve the maximum gain. The simulation results show that the FSLL can be reduced with a null deep level (NDL) of −40 dB in the E-plane at the frequency of 3.5 GHz, while the maximum gain of the array is around 17.7 dBi, and the bandwidth is 600 MHz (3.3–3.9 GHz) with −10 dB of S 11. A prototype of the proposed DSPD antenna array has been fabricated and measured. A good agreement can be achieved between simulation and measurement results.