在高斯信道下,幅度受限系统的最佳发送功率选择会直接影响系统性能:信号功率太低会被噪声淹没,功率太高会进入非线性畸变范围,产生信号失真.针对这个问题,通过分析幅度受限系统的信号噪声畸变比(signal to noise-and-distortion rate,SN...在高斯信道下,幅度受限系统的最佳发送功率选择会直接影响系统性能:信号功率太低会被噪声淹没,功率太高会进入非线性畸变范围,产生信号失真.针对这个问题,通过分析幅度受限系统的信号噪声畸变比(signal to noise-and-distortion rate,SNDR),提出了一种最优信号功率的选择方法.仿真结果表明,采用基于最大SNDR准则的信号功率选择能够获得最好的系统性能.展开更多
为提高高速连续时间带通型Delta-Sigma模数转换电路的信号转换精度,分析内部谐振电路的有限Q值对转换电路整体SNDR(信号噪声+失真比)的影响,提出加入数字滤波电路的方法以改善模数转换电路的NTF(噪声传递函数)的方案,使电路SNDR提高15 ...为提高高速连续时间带通型Delta-Sigma模数转换电路的信号转换精度,分析内部谐振电路的有限Q值对转换电路整体SNDR(信号噪声+失真比)的影响,提出加入数字滤波电路的方法以改善模数转换电路的NTF(噪声传递函数)的方案,使电路SNDR提高15 d B以上.Matlab建模及SPICE仿真证明了该方案的有效性.展开更多
In a visible light communication （VLC） system, the light emitting diode （LED） is nonlinear for large signals, which limits the trans- mission power or equivalently the coverage of the VLC system. When the input si...In a visible light communication （VLC） system, the light emitting diode （LED） is nonlinear for large signals, which limits the trans- mission power or equivalently the coverage of the VLC system. When the input signal amplitude is large, the nonlinear distortion creates harmonic and intermodulation distortion, which degrades the transmission error vector magnitude （EVM）. To evaluate the impact of nonlinearity on system performance, the signal to noise and distortion ratio （SNDR） is applied, defined as the linear signal power over the thermal noise plus the front end nonlinear distortion. At a given noise level, the optimal system performance can be achieved by maximizing the SNDR, which results in high transmission rate or long transmission range for the VLC system. In this paper, we provide theoretical analysis on the optimization of SNDR with a nonlinear Hammerstein model of LED. Simulation results and lab experiments validate the theoretical analysis.展开更多
设计了一个在信号带宽200kHz下,动态范围超过90dB的5阶单环单比特Σ-Δ调制器,该调制器能够很好的应用于中低频GSM接收机中。为了降低电路的复杂程度,提高系统抗噪性,该调制器采用了具有前反馈和负反馈分支的Σ-Δ结构。Matlab仿真结果...设计了一个在信号带宽200kHz下,动态范围超过90dB的5阶单环单比特Σ-Δ调制器,该调制器能够很好的应用于中低频GSM接收机中。为了降低电路的复杂程度,提高系统抗噪性,该调制器采用了具有前反馈和负反馈分支的Σ-Δ结构。Matlab仿真结果显示,在1.8V工作电压、0.18μ m CMOS工艺条件下,采样频率为21M Hz,SNDR为93.9dB,功耗为9.5mW,该系统具有较高实用价值。展开更多
文摘在高斯信道下,幅度受限系统的最佳发送功率选择会直接影响系统性能:信号功率太低会被噪声淹没,功率太高会进入非线性畸变范围,产生信号失真.针对这个问题,通过分析幅度受限系统的信号噪声畸变比(signal to noise-and-distortion rate,SNDR),提出了一种最优信号功率的选择方法.仿真结果表明,采用基于最大SNDR准则的信号功率选择能够获得最好的系统性能.
文摘为提高高速连续时间带通型Delta-Sigma模数转换电路的信号转换精度,分析内部谐振电路的有限Q值对转换电路整体SNDR(信号噪声+失真比)的影响,提出加入数字滤波电路的方法以改善模数转换电路的NTF(噪声传递函数)的方案,使电路SNDR提高15 d B以上.Matlab建模及SPICE仿真证明了该方案的有效性.
基金supported in part by the National Key Science and Technology“863”Project under Grant No.SS2015AA011303the Science and Technology Commission Foundation of Shanghai under Gant No.14511100200
文摘In a visible light communication （VLC） system, the light emitting diode （LED） is nonlinear for large signals, which limits the trans- mission power or equivalently the coverage of the VLC system. When the input signal amplitude is large, the nonlinear distortion creates harmonic and intermodulation distortion, which degrades the transmission error vector magnitude （EVM）. To evaluate the impact of nonlinearity on system performance, the signal to noise and distortion ratio （SNDR） is applied, defined as the linear signal power over the thermal noise plus the front end nonlinear distortion. At a given noise level, the optimal system performance can be achieved by maximizing the SNDR, which results in high transmission rate or long transmission range for the VLC system. In this paper, we provide theoretical analysis on the optimization of SNDR with a nonlinear Hammerstein model of LED. Simulation results and lab experiments validate the theoretical analysis.
文摘设计了一个在信号带宽200kHz下,动态范围超过90dB的5阶单环单比特Σ-Δ调制器,该调制器能够很好的应用于中低频GSM接收机中。为了降低电路的复杂程度,提高系统抗噪性,该调制器采用了具有前反馈和负反馈分支的Σ-Δ结构。Matlab仿真结果显示,在1.8V工作电压、0.18μ m CMOS工艺条件下,采样频率为21M Hz,SNDR为93.9dB,功耗为9.5mW,该系统具有较高实用价值。
