无线MIMO驱动射频挑战

　　无线MIMO驱动射频挑战

　　无线解决方案正在成为移动设备的主要网络接口，现在正在向消费者和工业应用中的固定设备迁移。这些无线解决方案利用蜂窝电话、无线电话、wi-fi和WiMax频段。从历史上讲，在这些信道上增加带宽的方法涉及增加连接所处的基带频率。然而，今天传输的数据量比使用新的开放频谱频率的传统设计技术要快得多。其结果是，新系统正在从单输入单输出（SISO）系统转向多输入多输出（MIMO）和多频/协议连接选项。MIMO的逻辑和规范被纳入新的标准；然而，它们需要单个设计的多个射频放大器和收发器系统，从而驱动系统的复杂性。

　　What is MIMO？

　　RF communication employs a set of receivers and transmitters to send data from point to point. In clear spectrum areas， RF communication has been dominated by SISO systems that consist of a set of antennas and RF circuits.

　　With rising data rates and signal congestion， multiple antenna configurations that include more than one receiver and transmitter are being utilized. These MIMO configurations improve communication performance by spreading the total transmit power of the antennas in order to achieve an array gain that increases the spectral efficiency and/or a diversity gain that improves the reliability of the connection. Spectral efficiency is the measure of the number of bits per second per hertz of bandwidth; diversity gain is measured by the fading characteristics of the wireless signal and reflects the change in attenuation of the signal through the carrier medium and obstacles such as walls. Figure 1 shows the various antenna and transmitter/receiver combinations that range from SISO to MIMO.