Toshiteru Hayashi

Compact Built-In Handset MIMO Antenna Using L-Shaped Folded Monopole Antennas

A compact built-in handset antenna for multiple-input multiple-output (MIMO) system at 2GHz, comprising two elements array of newly proposed L-shaped folded monopole antenna (LFMA), is evaluated under the multipath radio wave propagation environments. By analyzing the fundamental characteristics, mean effective gain (MEG), correlation, and channel capacity, the significant enhancement in the capability, as a handset MIMO antenna under practical use conditions, was confirmed. The performances were also compared to those of an array antenna comprising two planar inversed-F antenna (PIFA) elements in order to verify the effectiveness of the proposed antenna. The results show that the equivalent or improved performances can be realized, by using the proposed LFMA array with a compact size, taking only the volume of 44% of a PIFA array. The LFMA array provides almost the same bandwidth and enhanced isolation compared with a PIFA array, and the sufficiently low correlation and acceptable effective gain are obtained under the multipath radio wave propagation environments. In addition, a greater channel capacity than a PIFA array is achieved especially when the proposed LFMA array is inclined for the display-viewing mode, and moreover, an almost doubled increase in the channel capacity is obtained by using MIMO transmission compared with single-input single-output (SISO). This study also show that the MEG has much effects on the channel capacity, rather than the correlations, for the proposed antenna.

Outdoor Urban Propagation Experiment of a Handset MIMO Antenna with a Human Phantom Located in a Browsing Stance

Outdoor radio propagation experiments are presented at 2.4 GHz, using a handset MIMO antenna with two monopoles and two planar inverted-F antennas (PIFAs), adjacent to a human phantom in browsing stance. The propagation test was performed in an urban area of a city, which resulted in non line-of-sight (NLOS) situations. In our investigation, the 4-by-4 MIMO and SISO channel capacities for the reception signals were evaluated. These measurements show that the handset MIMO antenna, close to the human operator, is capable of MIMO reception.

Small array antenna for 2x2 MIMO terminal using folded loop antenna

Recently, MIMO technologies for mobile phones have been investigated to achieve high-speed data communication. It is preferable to have a smaller and more efficient antenna system for the MIMO terminal. Although built-in antennas are more convenient, coupling between antennas and the human body is larger than with extended antennas. So far, for the built-in elements, we have proposed a folded loop antenna (FLA) with balanced feed and a parallel plane antenna (PPA) with unbalanced feed. Because of the smaller human effects, these antennas may work effectively as MIMO antenna arrays. In this paper, 3 types of 2times2 MIMO antenna are investigated to show the effectiveness of the built-in antenna array for the terminal in a multi-pass wave environment. The channel capacity is employed to estimate the antenna performance.

Experimental investigation of a dual-band handset MIMO antenna using a spatial fading emulator

There have been a significant number of investigations into handset MIMO antennas applicable for cellular mobile radios [1], [2]. Some measurement apparatuses have been proposed for evaluating MIMOs or diversity arrays for a handset terminal [3], [4]. A spatial fading emulator consists of a number of transmitting antennas in order to reproduce a multipath fading channel in the spatial domain [4]. However, there has been little study of the effectiveness of the emulator in an actual cellular environment. This paper presents the experimental investigation of a dual-band handset MIMO antenna using a spatial fading emulator in a street microcell environment to compare with experimental data of a radio propagation test. Four handset arrays, which included two monopole antennas with dual-band operation, were used for the test, thus permitting the evaluation of 2-by-2 MIMO characteristics. The propagation test was conducted in a central downtown area of Aalborg city in Denmark. Comparison between the measured results obtained by the emulator and the propagation confirmed the effectiveness of the emulator.

Optimum L/C-based practical matching for the maximum wideband channel capacity of a compact MIMO array

The use of a MIMO array in a small handset often affects system performance due to mutual coupling between the elements. This has motivated many researchers to conduct extensive studies on the effects of mutual coupling, and to optimize the impedance matching conditions to increase the channel capacity [1]. However, there has been little study on enhancing channel capacity using a practical impedance matching circuit that can be used in a MIMO array installed in a commercial handset. In addition, in studying the matching circuit, we must consider the wideband characteristics since the plan for future cellular systems is that they are to be allocated a very wide frequency band, such as the LTE-advanced system. This paper studies the impact of a matching circuit of a dipole array constructed from practical L/C-based circuit components on channel capacity over a wide frequency band.

Multi-resonance characteristic of the L-shaped Folded Monopole Antenna using parasitic elements

The latest trend in handset unit used in the cellular phone is to reduce the size and the weight. Antennas used for such handsets must also follow downsizing of the handset unit and yet keep the antenna performance unchanged or even improved. Furthermore, built-in antennas for handset are becoming normal. There is the Folded Monopole Antenna which is half-space than The Folded Dipole Antenna (FDA) has already been being studied for downsizing [1][2][3][4]. This antenna bended into L-shape is called the L-shaped Folded Monopole Antenna (LFMA). In this paper, multi resonance of the LFMA using a parasitic element is investigated.

Cellular MIMO system performance versus base station element spacing

Outdoor MIMO propagation tests were carried out in an urban area in the Danish city of Aalborg in order to investigate some parameters that affect cellular MIMO base-station antennas. We experimentally examined the 2-by-2 MIMO channel responses of base-station arrays with differently-spaced antennas. From these trials, a clear dependence was found between antenna spacing and fading correlation, going from about 0.6 to about 0.1 when the spacing is increased from 1 to 6 wavelengths. However, due to the overall low correlation, the corresponding MIMO capacity gain over SISO capacity only increases from about 1.78 to about 1.87, and thus only a small extra capacity obtained.