Non-Ideal Switching-Based Design of Directional Time-Modulated Linear Antenna Arrays for Beam Steering in Arbitrary, Multiple and User-Defined Directions Using Cultural Algorithms

This paper proposes a trapezoidal pulse-based ON-OFF switching approach for the optimum beamforming performance in a time-modulated linear antenna array (TMLAA). The Fourier series property is used to adjust the transient behaviour trapezoidal switching function (τn1) and constant slope (τn2) of the trapezoidal pulse to obtain the highest steering main beam of the fundamental and harmonic components of the radiation pattern. Also, the sidelobe level (SLL) and sideband level (SBL) are simultaneously lowered. Despite the fact that harmonic beams are typically thought of as an interfering radiated pattern in time-modulated antenna arrays, the shifted harmonic frequency can also be useful in a variety of contexts. The beam steering of the harmonic is made possible by the optimal adjustment of the switch time instant τn1 and τn2 of the trapezoidal pulse signal without any optimization of the excitation amplitude weights. The optimal switching ON and OFF duration is evaluated by utilizing an evolutionary algorithm called Cultural Algorithm (CA). The antenna radiation characteristics are changed by using a series of Radio Frequency (RF) switches to modulate the static excitations using a trapezoidal pulse sequence to alter the time-modulation. Toward this approach, unique cost functions are designed and simulated for the simultaneous reduction of SLL, SBL and harmonic beam steering in TMLAA. The proposed cost function-based CA algorithm is able to get beam steering as arbitrary beam steering, multi-beam steering and beam steering in a user-defined direction.