This paper discusses the dependence of the phase error on the 50 GHz bandwidth oscilloscope's sampling circuitry. We give the definition of the phase error as the difference between the impulse responses of the NTN (nose-to-nose) estimate and the true response of the sampling circuit. We develop a method to predict the NTN phase response arising from the internal sampling circuitry of the oscilloscope. For the default sampling-circuit configuration that we examine, our phase error is approximately 7.03° at 50 GHz. We study the sensitivity of the oscilloscope's phase response to parametric changes in sampling-circuit component values. We develop procedures to quantify the sensitivity of the phase error to each component and to a combination of components that depend on the fractional uncertainty in each of the model parameters as the same value, ±10%. We predict the upper and lower bounds of phase error, that is, we vary all of the circuit parameters simultaneously in such a way as to increase the phase error, and then vary all of the circuit parameters to decrease the phase error. Based on Type B evaluation, this method qualifies the impresses of all parameters of the sampling circuit and gives the value of standard uncertainty, 1.34°. This result is developed at the first time and has important practical uses. It can be used for phase calibration in the 50 GHz bandwidth large signal network analyzers (LSNAs).
在50GHz宽带采样示波器的内部采样电路SPICE仿真模型的基础上,分析了内部采样电路产生相位误差的原因;定义相位误差为NTN(nose-to-nose)校准方法所获得的采样电路冲击响应相位与电路真实冲击响应相位之间的偏差,并给出了相位误差的计算方法,得出在50GHz时仿真的默认采样电路模型的相位误差为7.03°;逐一改变模型的各个参数,研究这些参数与相位误差之间的关系,在各个参数不确定度均为10%的前提下,分别量化分析采样电路每个元件参数的变化对相位误差的影响;在此基础上按照使相位误差增大或减小的趋势同时改变全部元件参数,可获得相位误差的上限和下限.基于B类估计理论,将这些参数的影响加以综合,得出模型相位误差的不确定度为1.34°.这一结论在国际上尚属首次提出,可直接应用到大信号网络分析仪简称LSNAs(large signal network analyzers)的50GHz带宽的相位校准中,具有极高的实用价值.
Closed-form expressions for the spectral regrowth of CDMA signal passing through a nonlinear amplifier with a digitally modulated carrier are derived using the power series and statistical methods of high-order cumulant. The technique yields an analytical expression for the autocorrelation function of the output signal as a function of the statistics of the input signal transformed by a behavioral model of the amplifier. The third-order nonlinearity is expressed in terms of IP3 to include the memory effects of the circuit in-band and out-of-band reactance. The analysis is based on a time-domain model of the signal and the model is used to derive the power spectrum density and other statistical properties of the CDMA signal. Such analytical results are useful in finding optimal operating conditions of the power Amplifier.
