一种校准空口误差矢量幅度的辐射信号产生方法

A Method of Radiation Signal Generation for Calibrating Error Vector Magnitude Over⁃the⁃air

新一代通信技术愈发依赖毫米波信号,空口条件下毫米波信号质量的校准成为亟需解决的问题。在此背景下提出了一种用于空口毫米波信号误差矢量幅度(Error Vector Magnitude,EVM)参数校准的W频段宽带矢量调制辐射信号产生方法,可以提供高载频、高传输速率的宽带矢量调制信号,为毫米波接收设备EVM参数的校准提供标准信号。使用倍频加混频的方式,获得符号速率1 GBaud(500 MBaud)的W频段正交相移键控(Quadrature Phase Shift Keying,QPSK)矢量调制信号,通过天线辐射到空间传输。接收天线在远场条件处对信号进行接收,经过下变频后得到载频1 GHz的QPSK接收信号,解调后信号的EVM约为20%@1 GBaud(10%@500 MBaud)。为提高接收信号质量,研究了相应的预失真与信号平均技术,通过结合发射接收信号来估计传输链路误差并进行迭代补偿,将EVM最低降低到5.2%@1 GBaud(2.1%@500 MBaud),大幅度地提高了信号质量,为空口EVM参数校准提供了高质量的辐射信号。

The next⁃generation communication technology more and more relies on millimeter⁃wave signal,so the calibration of millimeter⁃wave signal quality over the air becomes a problem that is urged to solve.In this context,we proposed a W⁃band wideband vector modulated radiated signal generation method for EVM calibration of OTA millimeter⁃wave signal and it can provide standard wideband vector modulated signals with high carrier frequency,high transmission rate for EVM calibration of millimeter⁃wave receivers.By the use of frequency multiplication and frequency mixing,we obtain W⁃band wideband QPSK vector modulated signals with 1 GBaud(500 MBaud)symbol rate,and then transmit it into the space using an antenna.The receiving antenna receive the signal at the far⁃filed condition and by the use of down⁃converter,we finally get the received QPSK signal with 1 GHz carrier.After demodulation the EVM of the signal is about 20%@1 GBaud(10%@500 MBaud).To improve the quality of the received signal,we use proper predistortion technology and signal⁃averaging technology.We estimate the system error combining the transmitted and received signals and then compensate it using iteration method,the EVM drops minimally to 5.2%@1 GBaud(2.1%@500 MBaud)which indicates that the signal quality improves significantly.The predistortion signal can be used as high⁃quality radiated signal for OTA EVM calibration.