無線MIMO驅動射頻挑戰

　　無線解決方案正在成為移動設備的主要網絡接口，現在正在向消費者和工業應用中的固定設備遷移。這些無線解決方案利用蜂窩電話、無線電話、wi-fi和WiMax頻段。從歷史上講，在這些信道上增加帶寬的方法涉及增加連接所處的基帶頻率。然而，今天傳輸的數據量比使用新的開放頻譜頻率的傳統設計技術要快得多。其結果是，新系統正在從單輸入單輸出（SISO）系統轉向多輸入多輸出（MIMO）和多頻/協議連接選項。MIMO的邏輯和規范被納入新的標準；然而，它們需要單個設計的多個射頻放大器和收發器系統，從而驅動系統的復雜性。

　　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.