N9030A PXA绝对振幅高2 dB

Hi -The PXA在加电时以及在时间/温度的基础上执行自动对齐。
您是否注意到此例程失败（可能是左下方状态栏中显示“立即对齐所有必需”消息）？确保您没有关闭对齐！
按* System，Alignments *，顶部软键应显示* Auto Align Normal *（不OFF）。
除非你真的想要对齐关闭，在这种情况下你有责任将它们重新打开一段时间，这样仪器可以正确对齐。仪器可以通过对准，但仍然有绝对振幅问题。我假设你
测量了你的信号源并知道确切的输出功率吗？当你说你检查幅度偏移时，我假设你做的事情就像按*输入/输出，外部增益*前置放大器增益并设置为0 dBm。看看PXA
内部50 MHz校准器信号，以确定此信号是否也读得太高。
按，*输入/输出，RF校准器*，50 MHz，* FREQ *，输入50 MHz并按* Span *并输入1 MHz。
按*峰值搜索*。
信号测量应非常接近-25 dBm。
您可以尝试上述相同的步骤，但这次选择4.8 GHz校准器（假设您的PXA具有比3.6 GHz更高的频率范围）。设置中心频率以匹配校准器4.8 GHz，此信号应测量接近-28 dBm
。
该仪器具有“高频带”信号路径，从3.6 GHz开始，与“低频带”路径分开。
因此，如果4.8 GHz校准器信号显示OK幅度，而50 GHz校准器信号不显示，我们将问题缩小到低频段。
如果两个校准器都显示出不良振幅，则两个路径的问题都很常见。
最后，仪器需要修理，但您可能已经对仪器有了更多了解。没有办法“调整”仪器增益。
一切都由DAC控制，“调整”通过测量完成，并创建校准文件，仪器用它来补偿增益或损失。
你可以取下盖子并转动锅的日子已经一去不复返了。注意 -



     以下为原文

  Hi -

The PXA performs an auto align at power up, and also on a time/temperature basis. Do you notice this routine failing (probably the Align Now All required message appears in the lower left status bar)?

Assure you do not have the alignments turned off!   Press *System, Alignments*, and the top softkey should show *Auto Align Normal* (not OFF). Unless you really want the alignments OFF, in which case you are responsible for turning them back on once in awhile so the instrument can align properly.

The instrument may be able to pass the alignments, but still have the Absolute Amplitude issue.

I assume you have measured your signal sources and know the exact output power?

When you said you checked for amplitude offset, I assume you did something like press *Input/Output, External Gain* preamp gain and it was set to 0 dBm.

Look at the PXA internal 50 MHz calibrator signal to determine if this signal also reads too high. Press, *Input/Output, RF Calibrator*, 50 MHz,
*FREQ*, enter 50 MHz and Press *Span* and enter 1 MHz.  Press *Peak Search*. The signal should measure  very close to -25 dBm.

You might try the same procedure above, but this time select the 4.8 GHz calibrator (assumes your PXA has a higher freq range than 3.6 GHz).
Set the center frequency to match the calibrator 4.8 GHz  and this signal should measure close to -28 dBm. The instrument has a “High Band” signal path that begins at 3.6 GHz that is separate from the “lowband” path. So if the 4.8 GHz calibrator signal shows OK amplitude, and the 50 GHz calibrator signal is not, we have narrowed the problem to the low band. If both calibrators  show bad amplitude, the problem is common to both paths.
In the end, the instrument requires repair, but you may have learned a bit more about the instrument.

There is no  way to “tweak” the instrument gain. Everything is DAC controlled and “adjustments” are done by measurement, and creating  calibration files, which the instrument uses to compensate for gain or loss. Gone are the days you could remove the lid and turn a pot.

Regards -

根据您的描述，这听起来可能是50 MHz内部校准器电路幅度错误的情况。
本机具有3.6 GHz频率选项（503）并且无任何错误地运行Align Now All并显示为Alignment Complete。
我查看了内部50 MHz校准器信号，它显示的标记读数为-25.00 dBm +/- 0.01 dB。
因此，如果对齐过程与此幅度水平对齐，那就是问题出现的地方。
就我的测试信号而言，我对频谱分析仪校准的主要参考是Fluke 9640A-LPN精密射频源，这可能是频谱分析仪校准的最新技术。
这也与HP 3335A Level Generator和更简单的HP 8657B进行了比较。
所有这些都显示PXA高达1.5 - 2 dB的PXA。
正如您所说，最终这是一个修复问题，因为它必须回到安捷伦服务中心才能正确使用。
谢谢。



     以下为原文

  From what you describe, this sounds like it MAY be a case of the 50 MHz internal calibrator circuit amplitude being wrong. This unit has the 3.6 GHz frequency option (503) and runs the Align Now All without any errors and shows as Alignment Complete. 

I looked at the internal 50 MHz calibrator signal and it shows a marker reading of -25.00 dBm +/- 0.01 dB. So if the alignment process aligns to this amplitude level, that's where the issue is arising.

As far as my test signal(s), my main reference for spectrum analyzer calibration is a Fluke 9640A-LPN Precision RF Source, which is probably the state-of-the-art for spectrum analyzer calibration. This was also compared with an HP 3335A Level Generator and a simpler HP 8657B. All show the PXA as being 1.5 - 2 dB high - way off for the PXA.

And as you say, in the end it's a repair issue since it will have to go back to the Agilent Service Center to be put right.

Thanks.