MXA N9020A的噪声带宽是多少？

我不能肯定地说，但我相信在数字化仪之前IF中使用了不同的模拟滤波器，具体取决于所选的RBW值。
在最窄的RBW滤波器中，形状完全来自DSP滤波器，并且基本上是完美的（例如高斯或平顶），但在最宽的RBW中，部分形状来自硬件滤波器，部分来自DSP滤波器，因此
形状在数值上不是完全高斯的。
我不确定是什么导致了噪音空值。
可能是最宽的滤波器没有那么多的隔离，或者我已经看到（在VNA数字滤波器中）当IF接近ADC采样率时（你的SA的IF BW是多少？）然后附近的噪声
Fs / 2可以折回到测量中。
如果宽IF滤波器在Fs / 2处没有极端隔离可能会导致这种情况，但我再次不是SA的专家。
您可以回复SA的模型，IF BW和FW rev来帮助其他专家回答。



     以下为原文

  I can't say for sure but I believe there are different analog filters used in the IF before the digitizer depending on the RBW value chosen. In the narrowest RBW filters the shape is almoste entirely derived from the DSP filter and is essentially perfect (such as Gaussian or Flattop) but in the widest RBW, part of the shape comes from the hardware filter and part from the DSP filter, and so the shape is not numerically perfectly gaussian.

I'm not sure what is causing the noisy nulls.  Might be that the widest filter doesn't have as much isolation or I've seen (in VNA digital filters) where when the IF gets close to the ADC sample rate (what is the IF BW of your SA?) then the noise near the Fs/2 can be folded back into the measurement.  If the wide IF filter doesn't have extreme isolation at Fs/2 maybe it can cause this, but again I'm not the expert on the SA.  You might post back with model, IF BW, and FW rev of your SA to help other experts answer.

另外，你如何衡量这一点？
你把CW信号放入SA输入端吗？
如果是这样，null的“nosiness”可能确实是由于DSP滤波器旁瓣和硬件滤波器旁瓣的组合，它们可以相位相位和相位不同以引起奇怪的响应。



     以下为原文

  Also, how do you measure this? Do you put a CW signal into the SA input?  If so, the "nosiness" of the null might indeed be due to a combination of the DSP filter sidelobs and the hardware filter sidelobes, that can phase in and out of phase to cause a strange response.