Tilt angle and side‐lobe level control of microwave array antennas

Abstract

This article describes a new strategy for controlling the tilt angle and side‐lobe level of linear array antennas by using a genetic algorithm. A very simple fitness function for controlling the performance of the array was constructed and is suggested. Simulations show excellent results for directing the main lobe and side‐lobe levels. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 12–14, 2002; DOI 10.1002/mop.10215

Genetic Algorithm with Maximum-Minimum Crossover (GA-MMC) Applied in Optimization of Radiation Pattern Control of Phased-Array Radars for Rocket Tracking Systems

“…Moreover, as the GA-MMC is generic and allows adaptation to any type of element, isotropic radiators were chosen, for they reduce calculations during tests, and can be easily extended to other types of elements, such as dipoles or microstrip antennas [7]. They also allow a comparison with other studies [20,22]. …”

“…For a linear array with variation only in tilt angle, θ, the normalized expression of U , in dB, is given in Equation (2). The parameter used to quantify the level of sidelobes is the Relative Side Lobe Level (RSLL), calculated as the ratio between the amplitudes of the main lobe, A M , and the greater sidelobe, A S , according to (3) [20]. $U_{dB}\left(\theta \right)=20·\text{log}\left(\frac{AF}{\text{max}\left(AF\right)}\right)$ $\mathit{\text{RSLL}}=\mathit{200}·\text{log}\left(\frac{A_M}{A_S}\right)$…”

“…Populations tend to have fixed size, and values of 30–100 individuals usually resolve most problems [20,22,53]. Knowing that, GA-MMC uses a population of 100 individuals, randomly generated to increase genetic diversity.…”

“…GA-MMC was then tested in two applications. In the first one, the objectives are to control the tilt angle of the main lobe and to maximize the RSLL, with the objective function given by Equation (5), in which A M is the main lobe amplitude, A S is the greater sidelobe amplitude, θ C is the calculated tilt angle, θ 0 is the desired tilt angle and K M is the main lobe adjustment factor [20]. The values A M and A S are obtained from AF in Equation (4), considering θ 0 varying from 0 rad (0°) until π rad (180°) with resolution, Δθ, equal to 0.01 rad (0,573°), in a total of 315 scanning angles.…”

“…They manipulate the numerous restrictions imposed on projects in several areas, with a fairly generic method. So, the GAs are quite useful in optimizing the design of PAs, which is a nonlinear problem of multiple objectives, in which conventional deterministic methods are vulnerable to a local optimum [ 13 , 16 , 20 , 21 – 23 ]. Thus, the GA can calculate the optimal values of excitation signals of the array elements, which will be used to control the radiation pattern in several applications, such as directing the main beam, determining the width and the number of beams, increasing gain and scanning speed, reducing sidelobes, rejecting interfering signals or improving the coverage area of the radiated signal.…”