Development of Adaptive Array Antenna for Mobile Handsets

随着高速通信网络的发展，人们对高速无线通信系统也提出了更高的要求。然而，由于频率资源的限制，高速无线系统难以实现。为了克服这一困难，需要在手机上应用自适应阵列天线系统。本研究分析了手机天线间的相互耦合，并开发了天线间相互耦合的补偿技术。本文还研究了手机自适应阵列天线对干扰信号抑制的局限性。针对手机天线间互耦的补偿问题，提出了一种通过计算和存储天线间互耦数据来获取天线阵列元方向图的方法。用单极子天线和倒平面f形天线组成的阵列天线进行了到达方向估计的数值仿真和实验，验证了该方法的有效性。干扰抑制性能限制的研究利用本研究组研制的用于2.45 GHz四元自适应阵列天线的W-CDMA接收机，对干扰抑制性能进行了评价。用四元单极子阵列天线进行视距和非视距传播实验表明，在视距情况下，四分之一波长的阵列间距足以抑制干扰。另一方面，当传播路径为非站线时，阵列间距应大于半个波长。本文还对具有频域均衡器的2元阵列天线接收机的干扰抑制性能进行了实验研究。

With the recent development of high-speed communications network, high-speed wireless communication system is also desired. However, it is difficult to obtain high-speed wireless system because of the limitation of frequency resources. In order to overcome this difficulty, application of adaptive array antenna system to mobile handsets is required. In the present research, mutual coupling among antennas mounted on a mobile handset has been analyzed and compensation technique of the mutual coupling has been developed. Limitation of the suppression of interference signal in the case of adaptive array antenna for mobile handsets has been also investigated.1. Compensation of mutual coupling among antennas mounted on mobile handset For the compensation of mutual coupling, a method, in which the data of mutual coupling are calculated and stored to obtain the array element pattern, has been developed. Numerical simulation of DOA (direction of arrival) estimation using array antennas composed of a monopole antenna and an inverted planar F-shaped antenna and experiments are performed confirming the validity of the proposed method.2. Investigation of limitation of interference suppression performance Performance of interference suppression is evaluated by using a W-CDMA receiver for 4 element adaptive array antenna at 2.45 GHz, which was developed by the present investigators. Experiment using 4 element monopole array antenna for line-of-sight and non-line-of-site propagation paths shows that a quarter wavelength array spacing is enough to suppress the interference for the case of line-of-sight. On the other hand, the array spacing should be longer than a half wavelength when the propagation path is non-line-of-site. Experimental investigation of the performance of interference suppression for a receiver having frequency domain equalizer for 2 element array antenna has been also performed.