PSA E4446A虚假图像

使用E4446A频谱分析仪，我看到由大输入信号引起的虚假图像。
我没有故意使用确切的数字，但它们很接近。
输入为+14 dBm，内部为0 dB。
Fin是2.5 GHz Span是300MHz到1 GHz，我相信RWB是1MHz。
观测到的杂散结果显着高于0.5 ghz的噪声基底。
我知道Fin的混音器电平高于应有的水平但是（s / b -10dBm max）但我认为预选器可以防止从高电平输入移开时的杂散..在这种情况下非常多。
我后来用校准的sig gen注入了我自己的信号并获得了相同的结果。
我知道这是一个虚假的神器，因为增加10分贝的注意力使它完全消失......超过10分贝。
那么..我做错了吗？
我是否必须手动调整YTF或在每次扫描时自动调整？
编辑：timbo于2012年5月16日下午2:10更正..最初有0 dB衰减编辑：Timbo于2012年5月16日下午2:11



     以下为原文

  Using  an E4446A spectrum analyzer I was seeing spurious images caused by an large input signal.
I'm not using exact numbers intentionally, but they are close.

Input was +14 dBm with 0 dB atten internal.
Fin was 2.5 GHz
Span was 300MHz to 1 GHz and I believe the RWB was at 1MHz.
The observed spurious result was significantly above the noise floor at aprox 0.5 Ghz.  

I know the mixer level at Fin was higher than it should be but (s/b -10dBm max) but I thought the preselector would prevent spurs when moved off the high level input.. in this case quite alot.

I later injected my own signal with a calibrated sig gen and obtained the same result. I know it was a spurious artifact because adding 10 dB atten caused it to vanish completely..by much more than 10 dB.

So.. am I doing something wrong? Should I have to manually adjust the YTF or does it auto adjust at each sweep?

Edited by: Timbo on May 16, 2012 2:10 PM Correction.. intially had 0 dB attenuation

Edited by: Timbo on May 16, 2012 2:11 PM