Performance of Multi-band Multi-antenna for Mobile Terminal Employing Folded Inverted-L Antennas

The rapid growth in mobile communication systems leads to a great demand for Multi-Input Multi-Output (MIMO) and multi-band systems to enhance the data rate and the capacity of the radio network [1]-[4], thus both multi-antenna and multi-band technologies must be employed for mobile terminals. In regard to the link budget, the performance of antennas is a vital element since the performance will not only affect the quality and the coverage of the mobile network but also the capacity of the entire networks. Hence, clarification of the performance of multi-band and multiantennas mounted on actual mobile terminals is currently urgently needed. This is especially true in practical usage situations and since the size and style of mobile terminals have changed significantly over the last several years. This paper presents the available performance of multi-band and multi-antennas designed for 4x4 MIMO and triple-band operation covering the 800 MHz, 1.7 GHz, and 2 GHz bands, when the antennas are mounted on an actual mobile terminal. We first propose a multi-band folded inverted-L antenna in this study. Then we investigate the influence of mutual coupling, implementation losses and multi-antenna performance when employing the multi-band folded inverted-L antennas. The investigation is based on the measurement in an anechoic chamber. The developed measurement facility that employs the multi-channel antenna pattern measurement system enables us to acquire the amplitude and phase patterns of multi-antennas at high speed. The rest of this paper is organized as follows. Section 2 describes the proposed antenna configurations and Section 3 presents the measured results for the antenna characteristics. The simulated Maximum Ratio Combining (MRC) beamforming gain and the MIMO channel capacity based on the measured radiation patterns are discussed in Section 4 and the concluding remarks are given in Section 5.