A metal-only reflectarray (MOR) antenna for 77 [GHz] was analyzed with the equivalent surface current sources. The equivalent current sources can be used to produce the incident fields radiated from a feed. When a feed is an openended rectangular waveguide (OERW), the calculated antenna gains for the equivalent current sources, point source, and CST Microwave Studio (MWS) are 31.8, 30.0, and 31.6 [dBi], respectively. The simulated results of the equivalent current sources and CST MWS are in good agreement with each other in terms of the antenna gain.Index Terms-metal-only reflectarray, equivalent current source, surface equivalence principle, feed modeling. I. IntroductionA reflectarray antenna [1]-[6] is a viable candidate for the millimeter-wave applications. The reflectarray antenna has several advantages in the design of millimeter-wave high gain antennas. For instance, we can design the various radiation patterns by controlling the physical dimensions of each element in the reflectarray. Recently, a metalonly reflectarray (MOR) antenna [3], [4] was proposed for the millimeter-wave bands. Since a MOR antenna is only made of metal, the MOR does not have any dielectric loss. In addition, the MOR antenna has much less loss in the millimeter-wave due to the spatial feeding by a feed. However, the MOR antenna is bulky and heavy for the lower frequency bands below the millimeter-wave. In order to design better antenna gain, we need to model a feed, a reflectarray, or scatterers as precise as possible. To this end, the design procedures based on the near-field measurements were proposed in [5], [6].In this Work, we will use the surface equivalence principle to model the incident fields radiated from a feed. In view of the surface equivalence principle and the vector potential formulations, the surface current densities on feed apertures can be transformed into the electric and magnetic fields at any positions. Thus, the incident fields from a feed to the MOR antenna can be easily computed with the equivalent surface current sources to model the arbitrary feeds. Although modern commercial software tools can calculate a reflectary excited by arbitray feeds at the same time, the computational procedures based on the equivalent surface current sources enable us to design

A metal-only reflectarray (MOR) antenna was proposed for the millimeter-wave applications. The MOR antenna has low-profile, ease of fabrication, and high gain characteristics. In this paper, we use three kinds of metaheuristics which are genetic algorithms (GA), particle swarm optimization (PSO) and differential evolution (DE) to design a high gain MOR antenna. To improve the performance, we insert a local search scheme into metaheuristics. Local search optimizations for the 77GHz MOR antenna with 2.2cm diameter were performed by applying the GA, PSO, and DE. Simulated results show that the GA, PSO, and DE with a local search have better performance to improve the antenna gain and aperture efficiency of a MOR antenna.

In this paper, we introduce a second version of modified binary particle swarm optimization using a concept of genotype-phenotype in genetic algorithms. Particle swarm optimization uses an information of difference between a position of the best solution and one's own position in the process of searching optimum. To obtain this difference of positions, the first version of modified binary particle swarm optimization uses a phenotype but the proposed second version uses a genotype. We can represent the solution space in large search space by using a genotype which provides continuous whole space as search space compared to a phenotype which provides only binary information. Experimental results in 10 De Jong benchmark function show that the second version outperforms the first version in six functions which has a broad search space and many local optima.■ keyword :|Binary Particle Swarm Optimization|Genotype-phenotype|