Improvement In Sidelobe Level Research Articles

Improving the Sidelobe Level, Return Loss and Bandwidth of Notch-Loaded TM30 Mode Patch via Fractal-Slot

This paper presents a method for sidelobe level (SLL) reduction, return loss improvement, and bandwidth enhancement in notch-loaded TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode rectangular patch antennas. In this method, a fractal-slot is introduced in the center of notch-loaded patch to remove the unwanted out-of-phase current regions. It is shown that a combination of the fractal-slot and notch loading technique can achieve significant improvement in SLL, return loss, and bandwidth of notch-loaded TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode without compromising gain or symmetry of radiation patterns. Moreover, the method also gives an additional degree of freedom to improve the impedance matching without changing the feed location. A prototype of the antenna is fabricated to verify the proposed method. The proposed antenna shows a measured gain of 13 dBi with a low SLL of −16 dB. Furthermore, it shows symmetrical patterns in both planes with cross-polarization (X-pol) levels of less than 35 dB. An under-sampled <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> array of the proposed antenna is also presented by utilizing its low SLL property to simplify the complexity of feed networks in high gain array antennas. The array offers the same directivity and SLL as that of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times 8$ </tex-math></inline-formula> array of fundamental mode rectangular patch elements in the same area.

An optimal mutually coupled concentric circular antenna array synthesis using ant lion optimization

This paper presents an accurate design approach for concentric circular antenna array (CCAA) synthesis to improve the far-field radiation characteristics using a meta-heuristic optimization technique called ant lion optimization (ALO). The far-field radiation pattern is improved with lower side lobe level (SLL) which is essential for the reduction of interference in the entire side lobe regions. The ALO algorithm is a recently proposed evolutionary technique which is applied to determine the optimal sets of current excitation weights and to find the optimal inter-element spacing between the array elements in the 3-ring structure of the CCAA design. In this context, the design examples of two 3-ring CCAAs, one having the set of (4, 6, 8) elements and the other having the set of (8, 10, 12) elements, with and without the centre element, are presented by optimizing the array parameters. The results obtained by using the ALO algorithm–based approach show considerable improvement of SLL with respect to that of the uniform array pattern and those of the methods reported in the recent literature.

Improving side lobe level of X-band microstrip Rotman lens utilizing nonuniform distribution of output ports

A new microstrip Rotman lens with enhanced side lobe level (SLL) is proposed for X-band applications. A proper nonuniform distribution of the initial width of output ports is considered to improve the SLL. The benefit of SLL improvement is not based on using additional attenuators or amplifiers at the output ports. Moreover, an analytical background is presented to investigate the resulting SLL of the proposed structure. The advantage of SLL enhancement is obtained at all noncorner scan angles considering 10 GHz operating frequency. As the middle input port is excited, more than 3 dB of SLL enhancement is achieved at 10 GHz. The proposed structure provides even more accurate scan angles than those of the conventional Rotman lens. The designed structure is simulated using full-wave HFSS 15 software. The comparison between simulated results and measurements of the fabricated proposed Rotman lens shows good agreement.

Moth flame optimization based design of linear and circular antenna array for side lobe reduction

AbstractThis paper presents an accurate approach to design a symmetrical linear antenna array (LAA) and a non‐uniformly excited single ring circular antenna array (CAA) to improve the far‐field radiation characteristics. The far‐field radiation pattern is improved with lower side lobe level (SLL) which is essential for the reduction of interference in the entire side lobe regions. A recently proposed meta‐heuristic based optimization algorithm called moth flame optimization (MFO) is applied to determine the optimal sets of current excitation weights and the inter‐element spacing among the array elements to reduce the SLL. In this context, 10‐element and 16‐element LAA and 8‐element, 10‐element, and 12‐element CAA design examples are presented by optimizing the array parameters. The simulation results obtained by using MFO algorithm based approach yield a considerable improvement in SLL and some marked improvement of half power beam width with respect to the uniform array pattern and those of the recently reported literature.

A Heuristic Approach to Design Linear and Circular Antenna Array for Side Lobe Reduction

This paper presents a heuristic approach-based design of a symmetric linear antenna array (LAA) and a non-uniformly excited single-ring circular antenna array (CAA) to improve the far-field radiation characteristics. The far-field radiation pattern improves with lower side lobe level (SLL) which is essential for the reduction in interference in the entire side lobe regions. A recently proposed evolutionary algorithm called social spider algorithm (SSA) is applied to determine the optimum sets of current excitation weights and the inter-element spacing among the array elements to reduce the SLL. In this context, 10-element and 16-element LAA and 8-element, 10-element and 12-element CAA design examples are presented by optimizing the array parameters. The simulation results obtained by using SSA-based approach confirm a considerable improvement in SLL and some restricted improvement in half-power beam width with respect to the uniform array pattern and those of the recently reported literature.

Concentric circular antenna array synthesis for side lobe suppression using moth flame optimization

This paper presents an accurate approach for Concentric Circular Antenna Array (CCAA) synthesis to improve the far-field radiation characteristics of the antenna using a meta-heuristic optimization technique called Moth Flame Optimization (MFO). The far-field radiation pattern improves with lower Side Lobe Level (SLL) which is essential for the reduction of interference in the entire side lobe regions. MFO algorithm is a recently proposed evolutionary algorithm which is applied to determine the optimum sets of current excitation weights and to find the optimal inter-element spacing between the array elements in the 3-rings structure of CCAA design. In this context, the design examples of two 3-ring CCAAs, one having the set of 4, 6, 8 elements and the other having the set of 8, 10, 12 elements, with and without centre element, are presented by optimizing the array parameters. The results obtained by using MFO algorithm based approach show a considerable improvement of SLL with respect to that of the uniform array pattern and those of the approaches reported in the recent literature.

Radiation Performance Characteristic Optimization of Time-Modulated Circular Antenna Arrays

ABSTRACTIn this paper, memetic flower pollination algorithm (MFPA) is proposed for solving the optimal synthesis of time-modulated half symmetric circular antenna array (TMHSCAA) and time-modulated asymmetric circular antenna array (TMASCAA) by controlling the switching time sequence and the excitation phase of each element time intervals and phases. Current excitation and inter-element spacing of each element are kept uniform. A unique cost function has been formulated for both the case studies. Several low-side lobe patterns synthesized from TMHSCAA and TMASCAA have been compared with those of the conventional circular array. A 20- and 36-element TMHSCAA and TMASCAA have been taken as examples. Furthermore, a novel six-ring time-modulated concentric hexagonal antenna array (TMCHAA) design has been considered to check superiority of the MFPA. The cost function has been designed for the concurrent improvement of side lobe level (SLL) and directivity in the new geometry of TMCHAA by an appropriate fine-tuning of the switching time succession and the inter-element separation of the hexagonal ring. Numerical results show that TMHSCAA, TMASCAA, and TMCHAA can be successfully used for the synthesis of low SLLs even if the amplitude excitations and inter-element spacing are uniform. Statistical analysis is also carried out to ensure that the results are significant in terms of the statistics. The results show that MFPA can exhibit a better performance than the other algorithms like real-coded genetic algorithm, particle swarm optimization, and differential evolution for the antenna array synthesis examples.

Improvement in side-lobe performance of prime focal reflector antenna

This paper presents a simple and elegant solution to improve the degradation of side lobe level (SLL) caused by strut and feed system blockage in prime focal reflector antenna system. This is accomplished by numerical optimization of reflecting wedges, which may be integrated with conventional rectangular cross-sectional struts. Design, optimization and analysis of metallic sheet feed cover have been carried out to reduce diffraction caused by the feed system. Quadrilateral meshing is used to analyze non-standard scatterers. Comprehensive analysis results showing frequency response of SLL of antenna system have been discussed, for different antenna component assemblies. A novel method has been implemented to understand the effect of wedged struts and feed cover for SLL improvement. Experimental data have also been presented to validate the simulated antenna parameters. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1304–1311, 2016

60-GHz LTCC Patch Antenna Array With an Integrated EBG Structure for Gain Enhancement

This letter presents a 60-GHz $2 \times 2$ low temperature co-fired ceramic (LTCC) aperture-coupled patch antenna array with an integrated Sievenpiper electromagnetic band-gap (EBG) structure used to suppress TM-mode surface waves. The merit of this EBG structure is to yield a predicted 4-dB enhancement in broadside directivity and gain, and an 8-dB improvement in sidelobe level. The novelty of this antenna lies in the combination of a relatively new LTCC material system (DuPont Greentape 9K7) along with laser ablation processing for fine line and fine slot definition ( $50-\mu\hbox{m}$ gaps with $+ / - 6 \mu\hbox{m} $ tolerance) allowing the first successful integration of a Sievenpiper EBG structure with a millimeter-wave LTCC patch array. A measured broadside gain/directivity of 11.5/14 dBi at 60 GHz is achieved with an aperture footprint of only $350 \times 410\hbox{mil}^2$ ( $1.78\lambda \times 2.08\lambda$ ) including the EBG structure. This thin (27 mil) LTCC array is well suited for chip-scale package applications.

Hybrid GSADE algorithm for optimization of far-field radiation pattern of circular arrays

In this paper, a design problem of non-uniform single-ring circular antenna arrays (CAA) and concentric circular antenna array (CCAA) for maximum side lobe level (SLL) by a hybridized method based on gravitational search algorithm with differential evolution (GSADE) is dealt with. The algorithm is used to determine an optimal set of current excitation weights and antenna inter-element spacing for CAA and an optimal set of current excitation weights for CCAA that provide a radiation pattern with maximum reduction of SLL. The same algorithm has been applied successively on CAAs of 8, 10, and 12 elements and two 3-ring CCAA, one having the set of 4, 6, and 8 elements and the other having 8, 10, and 12 elements with and without center element. Experimental results show a considerable improvement of SLL and some restricted improvement of first null beamwidth (FNBW) and 3-dB beamwidth as well with respect to the corresponding uniform cases and those of some recent literature reported in this paper.

Circular and Concentric Circular Antenna Array Synthesis Using Cat Swarm Optimization

ABSTRACTThis paper proposes an algorithm called cat swarm optimization (CSO) for the optimal design of non-uniform single-ring circular antenna array (CAA) and non-uniform three-ring concentric circular antenna array (CCAA). The algorithm is used to determine an optimum set of current excitation weights and antenna inter-element separations for CAA of 8, 10 and 12 elements and optimal current excitation weights for CCAA, respectively, which provide radiation pattern with maximum reduction of side lobe level (SLL). Two 3-ring CCAAs, one having the set of 4-, 6-, 8-, elements and the other having 8-, 10-, 12- elements, with and without centre element are considered. Simulation results show a considerable improvement of SLL and some restricted improvement of 3-dB beamwidth with respect to the corresponding uniform cases of both the types of antenna array and the corresponding results of some recent literature reported in this paper.

Bow‐tie antenna using high‐impedance ground plane

AbstractThis presents a high‐impedance ground plane (HIGP) structure for bow–tie antenna in order to improve its radiation performances. The HIGP is a kind of electromagnetic bandgap (EBG) structure to decrease surface waves and to bring an improvement of side lobe level, and reduce the mutual coupling between the two antennas. As compared to proposed antenna without HIGP, the measurement results show a fairly good antenna gain and a 5–10 dB reduction in the back lobes. Several properties of the proposed antenna for WLAN operation such as impedance bandwidth, radiation pattern, and measured gain have been investigated in detail, numerically and experimentally. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2928–2931, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23807

Array shape estimation and tracking using active sonar reverberation

This paper concerns the problem of array shape estimation and tracking for towed active sonar arrays, using received reverberation returns from a single transmitted CW pulse. Uniform linear arrays (ULAs) deviate from their nominal geometry while being towed due to ship maneuvers as well as ocean currents. In such scenarios, conventional beamforming performed under the assumption of a ULA can sometimes lead to unacceptably high spatial sidelobes. The reverberation leaking through the sidelobes can potentially mask weak targets in Doppler, especially when the target Doppler is close to that of the mainlobe reverberation and the reverberation-to-target ratio (RTR) is very high. Although heading sensors located along the array can be used to provide shape estimates, they may not be sufficiently available or accurate to provide the required sidelobe levels. We propose an array shape calibration algorithm using multipath reverberation returns from each ping as a distributed source of opportunity. More specifically, a maximum likelihood (ML) array shape calibration algorithm is developed, which exploits a deterministic relationship between the reverberation spatial and Doppler frequencies causing it to be low rank in the space-time vector space formed across a single coherent processing interval (CPI). In this application, a sequence of overlapped CPI length snapshots of duration less than the CW pulse is used. The ML estimates obtained for each snapshot are tracked using a Kalman filter with a state equation corresponding to the water pulley model for array dynamics. Simulations performed using real heading sensor data in conjunction with simulated reverberation suggest that 8-10 dB improvement in sidelobe level may be possible using the proposed array shape tracking algorithm versus an algorithm that uses only the available heading information.