PSA E4440A PRESEL CENTER命令是什么

此外，我们一直在研究将所有PSA转换为PXA。
我将保留此订单，直到我们获得有关此主题的更明确的信息。
这是否也会影响PXA读数？



     以下为原文

  In addition, we've been investigating converting all of our PSAs to PXAs.  I'm going to hold this order until we get more definitive information on this subject.  Does this also affect PXA readings?

还注意到我们根据固件版本得到不同的读数......版本越晚（直到A.11.20），我们看到的差别就越小。
早期版本（A.11.10）提供了更多不同的阅读。



     以下为原文

  Also noticed that we get different readings depending on the firmware version...the later the version (as late as A.11.20) we see less of a difference.  An earlier version (A.11.10) gives a much more different reading.

嗨 - 如果在进行测量之前应用了预选中心，则可以保证PSA和X系列在预选频段内的频率规格。
预选器确实具有迟滞并且确实存在一些漂移，尤其是在宽范围内进行调谐时。
分析仪使用预选器对中校准。
为了使预选器居中，分析仪上下调整预选器，并查看信号下降指定量（约5 dB）的位置。
然后将预选器调到中点。
预选器的通带中有一些纹波，因此如果预选器没有居中，则会有一些幅度差异。
X系列对其对准进行了改进，通常可以减少对预选器对中的需求。
X系列具有内置噪声源，用于预选中心。
PSA需要使用外部CW源。
此外，只要运行完整的内部对准，X系列就会对预选器进行双频校准。
另外，X系列有一个“Characterize preselector”对齐，可以在System - > Alignment菜单下完成，以进一步校准预选器的默认调整。
因此，对于PSA，如果发现预选器的默认调谐超过YTF带宽的一半，则建议发送仪器进行校准并请求服务中心运行预选器的TME软件调整以改善默认值
YTF调整。
YTF的带宽在3 GHz时约为30 MHz，在26.5 GHz时增加到60 MHz。
毫米波PSA的26.5 GHz以上，YTF带宽约为300 MHz。
问候 -



     以下为原文

  Hi -

The specifications for PSA and X-Series for frequencies in the preselected bands are guaranteed if Preselector Centering is applied before making a measurement.  The preselector does have hysteresis and does have some drift, especially when tuning it over a wide range.  The analyzers are calibrated with preselector centering applied.  To center the preselector, the analyzer tunes the preselector up and down and looks to see where the signal drops by specified amount (about 5 dB).  The preselector is then tuned to the mid point.  There is some ripple in the pass band of the preselector, so if the preselector has not been centered, there will be some amplitude difference.  The X-Series has improvements to its alignments that generally reduce the need for preselector centering.  The X-Series has a built in noise source that it uses to preselector center.  The PSA required an external CW source be used.  Also, the X-Series does a two frequency calibration of the preselector whenever the full internal alignments are run.  Additonally, the X-Series has a “Characterize preselector” alignment that can be done under the System -> Alignment menu to further calibrate the preselector’s default tuning.  Consequently, for the PSA, if the preselector’s default tuning is found to be further than half the YTF’s bandwidth, then it is recommended to send in the instrument for calibration and request the service center TME software adjustment for the preselector be run to improve the default YTF tuning.  The YTF’s bandwidth starts at about 30 MHz at 3 GHz and increases to 60 MHz at 26.5 GHz.  Above 26.5 GHz for the mm-wave PSAs, the YTF bandwidth is about 300 MHz.

Regards -

如果预测器中心在测量扫描过程中仅在一个频率上执行，而在频率扫描中测量的每个频率，是否有任何关于测量误差的信息？
随着时间的推移呢？
我们每天进行数千次测量，如果我们需要将预选器置于3GHz以上的所有测量值的中心，我们将受到严重阻碍。



     以下为原文

  Is there any information on how much error would be in a measurement if the preselector centering is performed at only one single frequency during a measurement sweep over frequency vs every frequency being measured in a frequency sweep? What about over time? We are performing thousands of measurements a day and would be severely hampered if we are required to center the preselector for all measurements above 3GHz.

嗨 - 对于我们的许多客户来说，在每次测量之前将预选器对中是不切实际的。
但是，我们的规格基于预选器对中应用。
有一些方法可以减少不居中的额外错误。
首先，限制扫描的频率范围以减少YTF滞后的影响是有利的。
对于PSA，一种策略是首先通过转到感兴趣的每个频率并使预选器居中并记录每个频率的距离来自己表征预选器。
然后，当您运行测试并调整分析仪的中心频率时，只需将预选器偏移设置为运行特征化过程时的偏移量。
对于X系列，如果只是在系统菜单下运行Characterize预选器调整，则默认的预选器调整将非常好。
在非预选器对中和预选器对中之间，您可能只看到幅度的十分之几dB差异。
实际上，一旦运行了特征并运行了内部对齐，使用X系列，您应该能够在没有预选器居中的情况下实现高频段的幅度规格。
然而，当没有预选器居中时，我的规格没有任何确定的幅度差异。
第10页的应用笔记1443有图表来说明PSA的预选器迟滞。
问候 -



     以下为原文

  Hi -

For many of our customers it is impractical to center the preselector before each measurement; however, our specifications are based on preselector centering applied.  There are ways to mitigate the additional errors from not centering.  Firstly, it is advantageous to limit the frequency range that you sweep over to reduce the effect of YTF hysteresis.  For PSA one strategy is to first characterize the preselector yourself by going to each frequency of interest and centering the preselector and recording how far off it was at each frequency.  Then, when you run your test and tune the analyzer’s center frequency, simply set the preselector offset to what it was when you ran you characterization procedure.  For X-Series, if you simply run the Characterize preselector adjustment under the System menu, the default preselector tuning will be quite good.  You may only see a few tenths of a dB difference in amplitude between not preselector centering and preselector centering.  Practically, once you have run the characterization and have run the internal alignments, with X-Series, you should be able to achieve the amplitude specification in high band without preselector centering.  Nevertheless, I don’t have any definitive amplitude difference in specifications when not preselector centering.  App Note 1443 on page 10 has graphs to demonstrate preselector hysteresis for PSA.  

Regards -