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This paper presents an optimal radome design using particle swarm optimization (PSO) which has recently drawn considerable attention in a wide range of applications. The frequency characteristics of the transmission coefficient for the radome are adopted as the objective function, and the radome wall thickness and radome shape are optimized. Furthermore, in order to enhance the reliability of the original PSO, we introduce a concept analogous to 'mutation' in genetic algorithms. Numerical experiments reveal that the mutation operation is capable of considerably enhancing the stability and the reliability of the PSO. We also confirm that the PSO is successfully applied to the problem of a practical radome design, and the transmission coefficient attained by the PSO is above the targeted value of −1 dB for the entire frequency bandwidth and for all evaluated beam scan angles.

This paper reports plasma antenna characteristics investigated theoretically and experimentally, on the basis of the plasma parameters: gaseous collisionality and electron density. The antenna structure is a basic quarter-wavelength monopole antenna in the UHF band. The dependence of the antenna gain on the plasma parameters is obtained by analytical equations from plasma and antenna theory, and by numerical simulations. In the plasma antenna, the ratio of the electron elastic collision frequency to the total number of electrons at the plasma cross section determines the antenna’s internal loss and the electrical equivalent antenna length, whereas the ratio of the radio wave frequency to the total number of electrons at the plasma cross section determines the antenna’s resonant frequency. These results are confirmed by experimental results of the antenna’s impedance and radiation patterns.

In this study, we investigate the performance of the variants of the induced dimension reduction (IDR) in large-scale electromagnetic scattering problems. We also focus on the tolerance to the so-call spurious convergence and convergence property of the IDR variant methods. Comparative numerical experiments, using IDR(s), Bi-IDR(s), and GIDR(s, L), reveal that GIDR(s, L) with L F 2 or 4 and an s value of around 15 shows the best performance with respect to the balance between the convergence property and the tolerance to the spurious convergence for problems with several levels of geometry complexity.