关于混合器级别与SA内部失真的关系

嗨，大家好，我想问一下SA的设置，关于Max Mixer Lvl，对于SA内部失真，它与混音器级别密切相关。
我的问题是（1）如何设置Max Mixer Lvl？
应该设置为较大的值吗？
对于我的型号PSA E4440A，最大。
是-10dBm。
我可以这样理解，如果进入SA的主信号为20dBm，SA输入衰减器应至少大于30dB，以确保混频器的信号电平不超过-10dBm？
（2）如何最大。
混合器Lvl设置会影响测量结果吗？
较低的Max Mixer Lvl会导致更大的默认SA输入衰减器值吗？
（3）对于每个SA模型，都有信号到失真曲线。
x轴为“混频器功率”，y轴为“失真dBc”。
以下理解是否正确？
主信号f0以10dBm的功率电平输入SA，SA输入衰减器为40dB。
混频器功率为-30dBm。
参考信号失真二阶曲线，找出X = -30dBm处的Y值为-60dBc。
我可以得出系统内部二阶为10dBm-60dB = -50dBm的结论吗？
任何具有优于50dBm的二阶失真性能的DUT都无法通过此设置进行测量。
除非SA输入衰减器增加，否则我将非常感谢您的帮助和评论！
你的，伊柳



     以下为原文

  Hi, everyone,

I would like to ask about the setting of the SA, about Max Mixer Lvl,  
For the SA internal distortion, it is closely related to the mixer level.

My questions are
(1) How should the Max Mixer Lvl be set? Should it be set to a large value?
For my model PSA E4440A,  max. is -10dBm.  
Can I understand it like this, if the main signal into the SA is 20dBm, SA
input attenuator should be at least greater than 30dB, to make sure that the signal
level at mixer is no more than -10dBm?

(2) How the Max. Mixer Lvl setting would affect the measurement results?
Would a lower Max Mixer Lvl results in bigger default SA input attenuator value?

(3) For each SA model, there is the signal-to-distortion curve. With the x axis be "power at mixer"
y axis be "distortion dBc."
Is the following understanding correct?
Main signal f0 input to SA at power level of 10dBm, SA input attenuator is 40dB.
Power at mixer is -30dBm.  
Refer to the signal-to-distortion second order curve and find out the Y value at X= -30dBm is -60dBc.  
Can I come to the conclusion that the system internal 2nd order is 10dBm-60dB=-50dBm? Any DUT with
its 2nd order distortion performance better than 50dBm can NOT be measured via this setup. Unless, say,
SA input attenuator is increased

Your help and comments would be greatly appreciated!

Yours,
Yiliu