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Several novel configurations based on leaf structures are proposed for generating radiating elements. The next leaf architectures (found in nature) are assessed and studied: Phyllanthus poumensis Phyllanthaceae, Desfontainea spinosa Desfontaineaceae, Rubus mesogaeus Rosaceae, Adenia heterophylla Passifloraceae, Leepierceia preartocarpoides Proteales and Tetracera rotundifolia Dilleniaceae. Each leaf architecture generates a radiating element by processing the image of plant leaf. The contributions of this proposal are: Six new antenna designs are provided with interesting characteristics in electromagnetic radiation and frequency performance, and a comparative study is made between the performance of the proposed designs and the existing work found in the literature. Simulation and experimental results are provided to evaluate and discuss each leaf antenna. An analysis in detail is provided considering parameters such as reflection coefficient, VSWR, antenna gain, current distribution and radiation pattern. The prototype and the experimental results (of each leaf architecture) are assessed considering the impact on the design of radiating elements and some wireless technology applications. [ABSTRACT FROM AUTHOR]

Plant diversity includes over 300,000 species, and leaf structure is one of the main targets of selection, being highly variable in shape and size. On the other hand, the optimization of antenna design has no unique solution to satisfy the current range of applications. We analyzed the foliar geometries of 100 plant species and applied them as a biomimetic design template for microstrip patch antenna systems. From this set, a subset of seven species were further analyzed, including species from tropical and temperate forests across the phylogeny of the Angiosperms. Foliar geometry per species was processed by image processing analyses, and the resultant geometries were used in simulations of the reflection coefficients and the radiation patterns via finite differences methods. A value below −10 dB is set for the reflection coefficient to determine the operation frequencies of all antenna elements. All species showed between 3 and 15 operational frequencies, and four species had operational frequencies that included the 2.4 and 5 GHz bands. The reflection coefficients and the radiation patterns in most of the designs were equal or superior to those of conventional antennas, with several species showing multiband effects and omnidirectional radiation. We demonstrate that plant structures can be used as a biomimetic tool in designing microstrip antenna for a wide range of applications. [ABSTRACT FROM AUTHOR]

This paper presents the application of CORPS (coherently radiating periodic structures) for feeding CRA (concentric rings array) with a reduced number of phase shifters. The proposed design technique for the structure of concentric rings provides a better scanning capability with respect to other existing configurations. This design technique utilizes 2 × 3 or 4 × 7 CORPS networks depending on the configuration or the number of antenna elements in the phased array system. These CORPS networks are set strategically in the feeding network to provide several advantages with respect to others in the scanning capability and the reduction of the number of phase shifters of the array system. The contribution of this paper is the full antenna system design of phased CRA for analyzing scanning and the reduction of phase shifters. The proposed phased array reduces the number of phase shifter devices in CRA for a scanning range of ±25° in the elevation plane. Differential evolution (DE) was applied to optimize the amplitudes of the proposed system. Several design cases were analyzed using full-wave simulation results to verify the phased array model and to take mutual coupling into account. Full-wave simulation results provide radiation patterns with low SLL in all scanning directions. The proposed phased array was validated by experimental measurements of the full antenna system prototype. [ABSTRACT FROM AUTHOR]

This research presents the design of time-modulated antenna arrays with UWB performance. The antenna arrays consider a linear topology with eight UWB disk-notch patch antennas. The technological problem is to find out the optimum antenna positions and/or time sequences to reduce the side lobes and the sidebands in all of the UWB frequency ranges. The design process is formulated as a bacterial foraging optimization. The results show that the uniform array generates a better SLL performance whereas the non-uniform array obtains a wider bandwidth. The uniform array obtains an SLL < −20 dB from 3.37 GHz to 4.8 GHz and the non-uniform array generates an SLL < −7 dB from 2.97 GHz to 5.26 GHz. The sideband levels are very similar for both cases with a value of around −17 dB. [ABSTRACT FROM AUTHOR]

This work is concerned with the methodology for improvement of the radiation pattern performance and eliminating the effect of unwanted interference of symmetric time modulated linear antenna array (STMLAA) in the predefined direction. This is achieved using evolutionary technique called Novel Particle Swarm Optimization with Wavelet Mutation (NPSOWM) for various application specific optimization like SLL only reduction, dual broad null and multiple broad null optimization. The optimized results obtained by using NPSOWM are validated by CST-MWS by captivating practical elements of dipole antenna and its array configuration. The numerical results show the effect of the particular (practical) antenna on the array. Various examples have taken for this purpose. A set of 16-element antenna array have designed for SLL only reduction. 16-, 32-, and 64-element STMLAA for incorporating the dual broad nulls in the angular range from 400 to 700 over the elevation plane. A set of 24-, 30-, and 32-element antenna array have occupied for multiple broad nulls. The strength of the adopted algorithm is tested for different number of array antenna configuration, which establish the efficacy of the optimization technique NPSOWM adopted for achieving the interference cancellation in the predefined direction and performance improvement of the antenna array such as simultaneous improvements of broad nulls (BNs), sidelobe level (SLL), sideband level (SBL), and the directivity. From the simulated results it is clear that NPSOWM can perform better than that of un-optimized linear antenna array with respect to BNs, SLL, and SBLs and Directivity. [ABSTRACT FROM AUTHOR]

A novel design of timed Vivaldi antenna arrays for steerable energy patterns is presented in this work. Three geometries are studied and designed in order to obtain an optimum energy pattern with low side lobe level (SLL) during beam steering: equally antenna array, unequally antenna array, and concentric ring array. The antenna elements are fed with the fifth derivative Gaussian pulse. The design process is carried out by the well-known sequential quadratic programming. Three design examples with 16 antenna elements are studied by considering different distribution of antenna positions. The mutual coupling phenomenon is considered by full wave simulations of Vivaldi antenna elements in the design examples. The results show a good performance of the steerable energy pattern with low SLL with ultra wideband operation. [ABSTRACT FROM PUBLISHER]