MXA N9020A具有窄跨度和宽跨度的互调行为问题

当您扩展跨度并保持RBW和VBW变窄时，我发现MXA频谱分析仪上的互调测量存在问题。
测量MXA互调的正常方法是将频谱分析仪设置为窄范围（1 kHz），RBW和VBW设置为自动（RBW和VBW均显示9.1Hz）。
此外，FFT增益将设置为低。
通过此设置，我可以将系统intermod提高到大约110dBc。
我准备一些演示来显示互调性能，所以我将MXA设置为宽跨度，但是我将RBW和VBW保持在9.1Hz我会假设宽幅度和窄RBW我应该得到与窄跨度相同的互调性能。
我在5MHz范围内获得大约90dBc。
在扩展Span时，看起来在接收器路径中禁用了某些IF滤波器。
我认为这不是正确的行为。
如果保持RBW较低并且扩展跨度，则应该看到的唯一损失是长扫描时间，而不是动态的互调范围。
我想知道是否有任何方法可以强制设置与窄间距相同的设置以获得Intermod足够的动态范围？
我运行的unin上的固件是A.13.12问候。
Im3测量5MHz跨度9_1Hz RBW.png75.2 KB



     以下为原文

  I see an issue with the intermodulation measurement on MXA Spectrum Analyzer when you expand the span and you keep the RBW and VBW narrow.
Normal way to measure intermodulation on MXA is to set Spectrum Analyzer to narrow span (1 kHz)  with RBW and VBW to Auto (it show 9.1Hz for both RBW & VBW). Also the FFT gain will be set to low. With this setting I can get system intermod to around 110dBc.

I prepare some demo to show intermodulation performance, so I set the MXA to wide Span, however I kept the RBW and VBW at 9.1Hz
I will assume that with wide Span and narrow RBW I should get the same Intermodulation performance as narrow span. I am getting around 90dBc with 5MHz span.
It look like some IF filter is disabled in the receiver path as you expand Span. I think that it is not correct behavior.  
If you keep the RBW low and you expand the span the only penalty you should see is long sweep time, not dynamic range of intermodulation.  

I wonder if there is any way to force the same setting as you have on narrow Span to get sufficient dynamic range for Intermod?

The firmware on the unin that I run is A.13.12

Regards.   
附件

• Im3 measurement 1KHz span 9_1Hz RBW.png70.2 KB
• Im3 measurement 5MHz span 9_1Hz RBW.png75.2 KB