Effect of Aperture Jitter

Set the first switch to the down position. The Variable Delay block delays the signal sample-by-sample by the amount on itstdinput. The Noise Source block generates a uniform random variable, which is low-pass filtered by the Shape the jitter noise spectrum block before it arrives at thetd输入变量延迟。使用形状均匀的噪声分布来表示抖动。请注意，在此模型中，ADC的时钟是在理想的零级保持块中指定的，并且等于1/fs，其中FS是模型初始化回调中定义的MATLAB®变量，并等于1.024GHz。

set_param（[模型'/Aperture Jitter'],'sw','0'）；

As expected, the spectrum degrades because of the presence of the jitter.

sim(model);

Effect of Nonlinearity

Set the second switch to the up position. This enables the ADC nonlinearity. A scaled hyperbolic tangent function provides nonlinearity. Its scale factor,alpha,确定s the amount of nonlinearity the tanh applies to the signal. By default,alphais0.01.

set_param（[模型'/Non Linearity'],'sw','1'）；

由于非线性的产生，因此由于非线性而降低了频谱。

sim(model);

Effect of Quantization and Saturation

Set the third switch to the up position enabling the ADC quantization and hard saturation.

set_param（[模型'/Quantization and Saturation'],'sw','1'）；

The spectrum degrades because of the quantization effects. The noise floor raises as seen in the spectrum.

sim(model);

ADC交流测量

使用混合信号阻滞™中的ADC AC测量块来测量ADC的噪声性能，并计算有效数量（ENOB）。

Use single sinusoidal tone as input to the ADC to measure other metrics.

bdclose（模型）;模型='msadcimpairments_ac'; open_system(model);

Ftest = 33/round(2*pi*2^8)*Fs; set_param([model'/Sine Wave'],'Frequency','2*pi*ftest'）；scopecfg = get_param（[模型'/Spectrum Scope'],'ScopeConfiguration'）；scopecfg.DistortionMeasurements.Algorithm ='Harmonic'; scopecfg.FFTLength ='512'; scopecfg.WindowLength ='512'; sim(model);

The Aperture Jitter Measurement block from Mixed-Signal Blockset™ measures the average jitter introduced on the signal to be approximately equal to1ps.

Additionally, use the spectrum analyzer to measure:

Increase the factoralphato increase the nonlinearity of the ADC and make the effects of nonlinearity more evident on top of the noise floor. This is just for demonstration purposes.

alpha = 0.8;

Use a two tone test signal as input to the ADC for the intermodulation measurements.

set_param（[模型'/Sine Wave'],'Frequency','2*pi*[50E6 75E6]'）；

To enable distortion measurements in the spectrum analyzer, click onDistortion Measurementas in the figure below and selectIntermodulationasDistortiontype.

scopecfg.DistortionMeasurements.Algorithm ='Intermodulation'; scopecfg.FFTLength ='4096'; scopecfg.WindowLength ='4096'; sim(model);

The scope allows for the measurement of the third order products adjacent to the input signals, and determines the output referred third order intercept point.