Efficient numerical analysis and design of reflectarray antennas

Erçil, Erdinç
The accurate numerical analysis of electrically large reflectarray antennas has been a challenging task since their advent because it becomes impractical to employ the generalized numerical electromagnetic tools for their numerical analysis. Therefore the classical approach is to resort to approximate methods. However, approximate methods trade off accuracy against memory and speed. In this thesis study; an approximate analysis technique is established such that it is more accurate than the present approximate analysis techniques and more efficient than the full wave analysis schemes in terms of memory requirement and speed. The technique relies on using characteristic modes as macro basis functions and reusing the dominant characteristic mode of the resonant element for all elements in the reflectarray. This utilization leads to obtaining a reduced matrix system where the number of unknowns is drastically decreased. As far as the far field is concerned, accurate results even with a single characteristic mode are achieved. The accuracy is attained owing to preservation of mutual coupling information via the original MoM impedance matrix. The solution is further accelerated by tabulating the entries of the reduced matrix as a function of interacting patch sizes and their relative displacements. It is observed that for sufficiently separated patches, the reduced matrix entry is almost a separable function of the two dimensional displacement between patches and patch sizes associated with the matrix entry. Tabulation is efficiently performed by exploiting this fact. Achieved acceleration is sufficient to use this analysis method in the design of reflectarrays. For a 1000 element array, the tabulation process takes 28 min on a platform with 3.3 GHz CPU clock speed. With the lookup table at hand, the solution time, which is important for the design iterations, is 0.38 seconds. The speed provided by the method makes it possible to employ gradient based optimization algorithms such as Steepest Descent or Conjugate Gradient Method, both of which are successfully applied to two design problems in the scope of the study.


Theoretical investigation and design of wideband dielectric resonator antennas
Yüksel, Yılmaz Çağrı; Alatan, Lale; Department of Electrical and Electronics Engineering (2015)
The aim of this thesis is to utilize Dielectric Resonator Antennas (DRA) as array elements due to their advantages over other conventional antenna elements such as dipoles and microstrip patches. Depending on both the excitation mechanisms and the antenna shape, a Dielectric Resonator Antenna (DRA) provides its designer multiple independent degrees of freedom. In this thesis three antenna shapes, namely hemispherical, cylindrical and rectangular DRAs, are investigated. The cylindrical and the rectangular sh...
Modified neural multiple source tracking algorithm in the presence of mutual coupling
Caylar, Selcuk; Leblebicioğlu, Mehmet Kemal; Dural, Guelbin (2007-06-15)
In smart antenna systems, mutual coupling between elements can significantly degrade the processing algorithms [1]. In this paper mutual coupling effects on Modified Neural Multiple Source Tracking Algorithm (MN-MUST) has been studied. MN-MUST algorithm applied to the Uniform Circular Array (UCA) geometry for the first time. The validity of MN-MUST algorithm in the presence of mutual coupling has been proved for both Uniform Linear Array (ULA) and UCA. Simulation results of MN-MUST algorithm are provided fo...
Rigorous optimizations of three dimensional antenna arrays using full wave simulations
Onol, Can; Gokce, Ozer; Boyacı, Huseyın; Ergül, Özgür Salih (null; 2015-07-09)
We present optimizations of three-dimensional antenna arrays using heuristic techniques coupled with the multilevel fast multipole algorithm (MLFMA). Without resorting to any periodicity and infinity assumptions, antenna arrays are modeled with surface integral equations and simulated via MLFMA, which also enables the analysis of arrays with non-identical elements. Genetic algorithms and particle swarm optimization methods are employed on the complex data produced by MLFMA in phasor domain to find optimal s...
Wideband omnidirectional and sector coverage antenna arrays for base stations
Alatan, Lale (2018-01-01)
By using parallel strip line fed printed dipole antennas as array elements, an omnidirectional antenna array and a wide angle sector coverage array operating in octave band are designed. A maximum deviation of ±1.25 dB from the omnidirectional pattern is achieved for the omnidirectional array, and the average gain of the antenna was measured as being 5 dB in the 1.35–2.7GHz band. For the sector coverage array, a special reflector design is utilized to maintain a half power beam width of around 115◦ with a s...
Efficient MOM analysis of printed structures by utilizing characteristic modes
Çetin, Metehan; Alatan, Lale; Department of Electrical and Electronics Engineering (2016)
In recent years, the theory of characteristic modes has been widely used for antenna design purposes. This theory provides physical insight about scattering and radiating properties of conducting bodies. In this thesis work, a MATLAB code is developed for analyzing printed structures by using characteristic mode theory. Characteristic modes of printed structures can be calculated by using the Method of Moments (MoM) matrix corresponding to the structure. To generate the MoM matrix, the electric field integr...
Citation Formats
E. Erçil, “Efficient numerical analysis and design of reflectarray antennas,” Ph.D. - Doctoral Program, Middle East Technical University, 2015.