Ichiro Oshima

Omnidirectional composite right/left-handed leaky-wave antenna with downtilted beam

In this study, we propose a novel leaky-wave omnidirectional antenna using a coplanar-strip-type composite right/left-handed (CRLH) line for application to a base station antenna used for a mobile communication system. Further, we realize an extremely slender omnidirectional antenna by adopting a polarization composite method. We also design a prototype antenna in the 3.5 GHz band and show the results of measurement obtained using this prototype antenna.

Equivalent circuit analysis for double layer patch type AMC in consideration of mutual coupling between layers

This paper describes the equivalent circuit analysis of a double layer AMC (Artificial Magnetic Conductor) in consideration of mutual coupling between layers. The AMC with double layer patch type FSS (Frequency Selective Surface) is focused. This paper treats two type double layer structures. The one is stacked structure, and the other is alternated structure. It was shown that the calculated results by using the equivalent circuit well agreed with the results of the FDTD analysis. In addition, it was clarified that the stacked and alternated structures cause the common mode and the differential mode coupling, respectively. Moreover, it was shown that the miniaturization of the AMC is designed by setting the distance between the layers of double layer FSS as thin as possible.

Equivalent circuit analysis for AMC with double layer patch type FSS

This paper describes the possibility of the miniaturized AMC (Artificial Magnetic Conductor) by the equivalent circuit analysis. The AMC with double layer patch type FSS (Frequency selective surface) is focused as the structure of AMC. It is clarified by the theoretical results that the operation frequency of the FSS becomes the half by using double layer patch type FSS. It is also shown that unit cell size of an AMC is miniaturized by the half.

Design of a parallel plate slot array antenna fed by a rectangular coaxial line

We propose a parallel plate slot array antenna fed by a rectangular coaxial line, which can dispense with perfect electrical contact between the bottom plate of the parallel plate and the rectangular coaxial line. We adopt hard walls at the both side walls of the parallel plate in order to maintain a quasi-transverse electromagnetic (TEM) wave. We design the antenna in the 5GHz band. The calculated bandwidth for VSWR less than 1.5 is 3.0%, and the antenna efficiency is 70.6% at 4.89 GHz.

Equivalent circuit analysis for alternated double layer patch type FSS with dielectric substrate

This paper describes the filtering characteristics of the alternated double layer patch type FSS (Frequency Selective Surface) in which a patch type FSS is arranged alternately at the surface and the back of a dielectric substrate. The equivalent circuit and the empirical equation of the coupling coefficient including dielectric substrate effect are proposed. It is also shown that the approximate equation is valid when the thickness of the dielectric substrate t/p less than 0.5.

Fundamental propagation characteristics in a 4(m)×2(m)×2(m)-sized reverberation chamber for MIMO-OTA measurements

Recently, the application of MIMO technologies is becoming more widespread and growing. With this increasing in usage, MIMO antennas are also need to be precisely analyzed, using antenna measurement system. Here, creating a multipath-rich propagation environment is needed to evaluate the performance of a MIMO communication device assuming the operation in the real environment. Of the proposed measurement systems, OTA (Over-the-Air) measurement systems are an essential part of the certification test of MIMO devices. At present, there are two types of MIMO-OTA schemes. One is a field emulator (FE-type), which is created by setting the virtual scattering antennas in a radio anechoic chamber. The other one is a radio echoic chamber, named “Reverberation Chamber”, surrounded by 6-plate metallic walls. In this paper, we focus our analysis on the latter scheme, reverberation chamber (RC) type of MIMO-OTA.