This paper presents a newly developed two-layer self-diplexing antenna for mobile satellite communications with mutual coupling suppression between transmitting and receiving antenna. The self-diplexing antenna is composed of circular microstrip and ring patches. Numerical results based on an electromotive force method using boundary admittance are compared with experimental results. The numerical results significantly agree with the experimental results. The experiments show that the total isolation between transmitting and receiving antennas is more than 35 dB.

This paper presents dual bands and dual polarization reflectarrays for 5G millimeter wave applications. The frequency bands of 28GHz and 39GHz are allocated for 5G to realize high speed data transmission. However, these high frequency bands create coverage holes in which no link between base station and receivers is possible. Reflectarray has gained attention for reducing the size and number of coverage holes. This paper proposes a unit cell with swastika and the patch structure to construct the dual bands reflectrray operating at 28GHz and 39GHz by supercell. This paper also presents the detailed design procedure of the dual-bands reflectarray by supercell. The reflectarray is experimentally validated by a bistatic radar cross section measurement system. The experimental results are compared with simulation and reflection angle agreement is observed.

This paper presents a method of synthesizing covariance matrix elements of array input signal for high resolution 2-D Direction-Of-Arrival (DOA) estimation via antenna (sensor) switching. Antenna array generally has the same number of array elements and receiver modules which often leads large receiver hardware cost. Two of the authors have already studied a way of antenna switching to reduce receiver cost, but it can be applied only for periodic incident signals like sinusoid. In this paper, we propose two simple methods of DOA estimation from sparse data by synthesizing covariance matrix elements of array input signal via antenna switching, which can also be applied to DOA estimation of antiperiodic incident signals. Performance of the proposed approach is evaluated in detail through some computer simulation.

Multi-site MIMO (Multiple Input Multiple Output) is a key technology that will enable next generation cellular networks to achieve high throughput in cell edge areas. However, a multi-site single-user MIMO system is subject to performance degradation in terms of cell throughput due to the expense of additional assignments of radio resources to cell edge user equipment. This paper presents a BS-cooperation scheduling scheme for a multi-site single-user MIMO cellular system. The proposed BS-cooperation scheduling scheme aims to maintain cell throughput while improving cell edge user throughput. The proposed scheme employs two policies with respect to the assignment of radio resource to the user equipment with multi-site connection. One is to control the opportunities for radio resource assignment to user equipment with a multi-site connection to avoid the excessive assignment of radio resources and to maintain cell throughput. The other policy governs the decision as to whether the user equipment operates with a multi-site connection or not, making it possible for the multi-site connection to contribute to the improvement in user throughput in the cell edge areas. The simulation results show that the proposed scheme is effective from the perspective of both cell throughput and cell edge user throughput.

This paper introduces a base station antenna system as a future cellular technology. The base station antenna system is the key to achieving high-speed data transmission. It is particularly important to improve the frequency reuse factor as one of the roles of a base station. Furthermore, in order to solve the interference problem due to the same frequency being used by the macro cell and the small cell, the author focuses on beam and null control using an AAS (Active Antenna System) and elucidates their effects through area simulations and field tests. The results showed that AAS can improve the SINR (signal to interference-plus-noise ratio) of the small cell area inside macro cells. The paper shows that cell quality performance can be improved by incorporating the AAS into a cellular base station as its antenna system for beyond 4G radio access technology including the 5G cellular system.

This paper presents a simple 3-D array configuration for high-resolution 2-D Direction-Of-Arrival (DOA) estimation. Planar array structures like Uniform Rectangular Array (URA) or Uniform Circular Array (UCA) often well estimate azimuth angle but cannot well estimate elevation angle because of short antenna aperture in elevation direction. One may put more number of array elements to improve elevation angle estimation accuracy, however it will require very large hardware and software cost. This paper presents a simple 3-D array structure for high-resolution 2-D DOA estimation only by modifying the height of some array elements in a planar array. Based on the analysis of Cramer-Rao Lower Bound (CRLB) formulation and its dependency on the height of array elements, we develop a simple 3-D array structure which improves elevation angle estimation accuracy while preserving azimuth angle estimation accuracy.

This paper presents a newly developed small-sized shaped beam base station antenna in order to reduce inter-sector interference for next generation high speed wireless data communication systems. The developed antenna realizes polarization diversity as a single small-sized antenna without decreasing the 3 dB main beamwidth compared with the conventional antenna by applying a newly designed beam shaping method. Furthermore, side sub-reflectors are newly installed in the radome to reduce the antenna beam gain in the direction toward the edge region neighboring the other sectors of the horizontal antenna pattern. By adopting this type of reflector, the diameter of the radome can be minimized at 0.65 λ, which is slightly longer than that of the conventional antenna. Both a computer simulation and a field measurement test based on an actual cellular network were conducted for the purpose of clarifying the validity of the shaped beam antenna. In the results, the CINR at the service area by the shaped beam antenna was 1 dB and 3.5 dB better than that of the conventional antenna at the median and 10% of CDF, respectively. The developed antenna will be expected to contribute to the enhancement of the quality of cellular radio systems in the future.