A new theory called Vivaldi nonuniform slot profile antenna (VNSPA) is developed based on the nonuniform transmission lines (NTLs) theory and applied to reduce the size of the predesigned compact ultrawide band (UWB) Vivaldi-tapered slot antenna (VTSA) without affecting its performance in terms of matching and bandwidth. Using this theory, 33% of the taper slot length is reduced, resulting in a novel compact UWB Vivaldi nonuniform slot antenna (VNSA). Furthermore, compactness is achieved by performing parametric studies on VNSA with a final 51.94% size reduction. MATLAB optimization codes, CST simulation, and prototype manufacturing and measurement are used to validate the new theory. The proposed antenna provides a measured S ₁₁ < −10.89 dB through 2.9–13.55 GHz with 2.91% and 5.8% bandwidth and maximum realized gain enhancement, respectively, as compared with VTSA’s results. The effectiveness of VNSPA theory is proven by comparing the simulated and measured findings of VNSA and VTSA.

In this paper, firstly, we point out and correct a common mistake, in the literature, in the formulation of the array factor of an elliptical antenna array (EAA). Secondly, this paper deals with the optimal design of EAAs with low side lobes level using two recently proposed optimisation methods, namely, the Symbiotic Organisms Search (SOS) algorithm and the Antlion Optimisation (ALO) method. Two cases are considered. Firstly, the antennas are assumed to be evenly distributed over the ellipse contour, i.e. their positions are fixed, and the optimisation problem is to search for the current amplitudes ( $I_n$’s) that minimise the maximum side lobe level (SLL). Secondly, the antennas are assumed to be uniformly fed, i.e. I_n’s are assumed to be unity, and the optimisation problem is to search for the elements positions (along the ellipse) that minimise the maximum SLL. In both cases, SOS and ALO are used and their results are compared together. It is found that SOS is statistically better than ALO, though ALO consumes less CPU time to converge to the solution.

A compact Ultra-Wide Band (UWB) Wilkinson power divider with different unequal split ratios of 2:1 and 3:1 using three optimized resistors is analyzed, designed and fabricated in this study. A 31.1% size reduction in each λ/4 uniform transmission line (UTL) of the divider is achieved by applying non-uniform transmission lines (NTLs) theory. The proposed divider is contributed to be suitable as a feeder to currently used wireless communication networks such as cognitive radios (CR), resulting in good impedance matching to its entire ports. In addition, the optimized resistors used provided good isolation between the output ports. The simulation is carried out in this study uses High Frequency Structure Simulator (HFSS) software. The simulation results are compared with the hardware measurements to validate the results. It was observed that there was approximately 5% of the difference between simulated and hardware measurements which is within the acceptable limit.

In this paper, firstly, a common mistake in the formulation of the array factor of concentric elliptical antenna array (CEAA) is pointed out and corrected. Secondly, several CEAAs are optimally designed to have the smallest side lobe level (SLL). This is accomplished using four optimization algorithms; Antlion Optimization algorithm (ALO), Grasshopper Optimization Algorithm (GOA), Symbiotic Organisms Search (SOS) and a newly proposed hybrid algorithm based on ALO and GOA. Two cases for CEAA synthesis are presented. The goal in the first case is to find the optimal values for the current amplitudes ( $I_n$’s) to minimize the side lobe level, assuming that the antennas’ positions are fixed along the ellipses. In the second case, the current amplitudes ( $I_n$’s) are assumed to be unity, and the optimization problem is to find the optimal values for the elements positions along the ellipses. The results of the proposed optimization algorithms are compared to uniform antenna array results.

In this paper, compact Ultra-Wide Band (UWB) 1:2:1 unequal split modified Bagley Power Divider (BPD) using Non-Uniform Transmission Lines (NTLs) theory is designed and tested. Based on this theory, 42.44% and 31.1% size reductions are obtained in the lower and upper λ/4 Uniform Transmission Lines (UTLs) in the first and second sections of the proposed divider. To evaluate the effect of the divider’s compactness on its performance, it is compared with UWB 1:2:1 unequal split BPD using Tapered Transmission Lines (TTLs). Both dividers show good results where the measured return loss is appeared to be S₁₁ < −10.6 dB and < −13.4 dB for NTL and TTL BPDs, respectively. However, the insertion losses S₁₂ = S₁₄ and S₁₃ are around −6 ± 1.5 dB and – 3 ± 1.3 dB, respectively for both dividers. In this study, simulations are carried out using High-Frequency Structure Simulator (HFSS) software. The evaluation of the proposed divider is obtained from the simulation and hardware measurements results.