Adaptive multibeam phased array design for a Spacelab experiment

The parametric tradeoff analyses and design for an Adaptive Multibeam Phased Array (AMPA) for a Spacelab experiment are described. This AMPA Experiment System was designed with particular emphasis to maximize channel capacity and minimize implementation and cost impacts for future austere maritime and aeronautical users, operating with a low gain hemispherical coverage antenna element, low effective radiated power, and low antenna gain-to-system noise temperature ratio

Characteristics of different focusing antennas in the near field region

Focusing antennas are of interest in many application including microwave wireless power transmission, remote (non-contact) sensing, and medical applications. Different kinds of antennas such as array antennas, reflector antennas and Fresnel zone plate (FZP) antennas have been used for these applications. Here, first, a new scheme in designing focused array antennas with desired sidelobe levels (SLLs) in the near field region is presented. The performance of the large focused array antennas is predicted based on the knowledge of the mutual admittances of a smaller array. The effects of various focal distances on the near field pattern of these antennas are investigated. Then, electric field pattern characteristics of the focused Fresnel zone plate lens antennas in the near-field region are presented. The FZP antenna fed by a circular horn is implemented and the effects of various focal lengths on the near field pattern of this antenna are examined. It is shown that the maximum field intensity occurs closer to the antenna aperture than to the focal point and this displacement increases as the focal point moves away from the antenna aperture. The focusing properties of ultra-wideband (UWB) array antennas are also presented. Large current radiator (LCR) antennas are modeled by replacing the antenna with a set of infinitesimal dipoles producing the same near field of the antenna. LCR antenna arrays are used to provide high concentration of microwave power into a small region. It is shown that the defocusing effect occurs in pulse radiating antennas as well. Invasive weed optimization (IWO), a new optimization algorithm, is also employed to optimize the pulsed array antenna. In the attempt of optimizing the focused arrays, a new scenario for designing thinned array antennas using this optimization method is introduced. It is shown that by using this method, the number of elements in the array can be optimized, which yields a more efficient pattern with less number of elements. By applying this new optimization method to UWB arrays, the peak power delivered to a localized region can be increased

Adaptive multibeam antennas for spacelab. Phase A: Feasibility study

The feasibility was studied of using adaptive multibeam multi-frequency antennas on the spacelab, and to define the experiment configuration and program plan needed for a demonstration to prove the concept. Three applications missions were selected, and requirements were defined for an L band communications experiment, an L band radiometer experiment, and a Ku band communications experiment. Reflector, passive lens, and phased array antenna systems were considered, and the Adaptive Multibeam Phased Array (AMPA) was chosen. Array configuration and beamforming network tradeoffs resulted in a single 3m x 3m L band array with 576 elements for high radiometer beam efficiency. Separate 0.4m x 0.4 m arrays are used to transmit and receive at Ku band with either 576 elements or thinned apertures. Each array has two independently steerable 5 deg beams, which are adaptively controlled

Phased array-fed antenna configuration study

The scope of this contract entails a configuration study for a phased array fed transmit antenna operating in the frequency band of 17.7 to 20.2 GHz. This initial contract provides a basis for understanding the design limitations and advantages of advanced phased array and cluster feeds (both utilizing intergral MMIC modules) illuminating folded reflector optics (both near field and focused types). Design parametric analyses are performed utilizing as constraints the objective secondary performance requirements of the Advanced Communications Technology Satellite (Table 1.0). The output of the study provides design information which serves as a data base for future active phased array fed antenna studies such as detailed designs required to support the development of a ground tested breadboard. In general, this study is significant because it provides the antenna community with an understanding of the basic principles which govern near field phased scanned feed effects on secondary reflector system performance. Although several articles have been written on analysis procedures and results for these systems, the authors of this report have observed phenomenon of near field antenna systems not previously documented. Because the physical justification for the exhibited performance is provided herein, the findings of this study add a new dimension to the available knowledge of the subject matter

Subsurface sounders

Airborne or spaceborne electromagnetic systems used to detect subsurface features are discussed. Data are given as a function of resistivity of ground material, magnetic permeability of free space, and angular frequency. It was noted that resistivities vary with the water content and temperature

Planar Thinned Arrays: Optimization and Subarray Based Adaptive Processing

A new approach is presented for the optimized design of a planar thinned array; the proposed strategy works with single antenna elements or with small sets of different subarray types, properly located on a planar surface. The optimization approach is based on the maximization of an objective function accounting for side lobe level and considering a fixed number of active elements/subarrays. The proposed technique is suitable for different shapes of the desired output array, allowing the achievement of the desired directivity properties on the corresponding antenna pattern. The use of subarrays with a limited number of different shapes is relevant for industrial production, which would benefit from reduced design and manufacturing costs. The resulting modularity allows scalable antenna designs for different applications. Moreover, subarrays can be arranged in a set of subapertures, each connected to an independent receiving channel. Therefore, adaptive processing techniques could be applied to cope with and mitigate clutter echoes and external electromagnetic interferences. The performance of adaptive techniques with subapertures taken from the optimized thinned array is evaluated against assigned clutter and jamming scenarios and compared to the performance achievable considering a subarray based filled array with the same number of active elements

Thinning of concentric two-ring circular array antenna using fire fly algorithm

AbstractThe paper describes the application of novel meta-heuristics of the fire fly algorithm for reduction of the maximum Side Lobe Level (SLL) with specific First Null Beam Width (FNBW) of thinned two-ring Uniform Concentric Circular Arrays (UCCA) of isotropic elements. The effect of thinning is analyzed in the four subsequent examples using uniform and non-uniform excitations for different FNBW. Optimization is carried out without and with prefixing the value of the percentage of thinning. The UCCA containing 35 and 70 elements in the two successive concentric rings is optimized using FFA. The example using non-uniform excitation is proved more efficient to reduce SLL for same FNBW. Simulation results show the SLL performance improves as we chose the FNBW wider in the designing problem. Fixing the percentage of thinning at a higher value increases the power efficiency of the feeding network with little compromise on the design specifications. The non-uniformly excited thinned concentric array is again optimized using two more state-of-the-art algorithms, namely, Particle Swarm Optimization (PSO) and Differential Evolution (DE) to compare the effectiveness of each algorithm in a statistically meaningful way. Design results using fire fly algorithm shows better performances compared to PSO and DE provided the same number of function evaluation has been considered for all the algorithms

Linear Array Thinning with Cavity backed U-slot Patch Antenna using Genetic Algorithm

In this paper, a thinned linear array with Cavity backed U-slot Patch has been investigated using the Genetic Algorithm to minimize peak sidelobe level and the number of antenna elements. One of the essential steps in the Genetic Algorithm method is a crossover, which uses the Paired Top Ten and Combined Top Five rules applied to the Cavity backed U-slot Patch antenna. The peak sidelobe level value is -18.63 dB with a array filling of 63.33% at the broadside angle using Combined Top Five rules. In Paired Top Ten, the peak sidelobe level value is -19.48 dB with a array filling of 70%. The two methods are still better as compared to a dense array. This study is essential in the development of radar technologies since it needs a low sidelobe level