無線MIMO驅(qū)動射頻挑戰(zhàn)

　　無線解決方案正在成為移動設(shè)備的主要網(wǎng)絡(luò)接口，現(xiàn)在正在向消費者和工業(yè)應(yīng)用中的固定設(shè)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?shù)臄?shù)據(jù)量比使用新的開放頻譜頻率的傳統(tǒng)設(shè)計技術(shù)要快得多。其結(jié)果是，新系統(tǒng)正在從單輸入單輸出（SISO）系統(tǒng)轉(zhuǎn)向多輸入多輸出（MIMO）和多頻/協(xié)議連接選項。MIMO的邏輯和規(guī)范被納入新的標(biāo)準(zhǔn)；然而，它們需要單個設(shè)計的多個射頻放大器和收發(fā)器系統(tǒng)，從而驅(qū)動系統(tǒng)的復(fù)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.