[问答]

测量短路时导致这些尖峰的原因是什么？

问答对人有帮助，内容完整，我也想知道答案 0 有人让我在我的VNA上测量一个3.5毫米的Maury微波炉。为了使事情尽可能准确，我使用了非常窄的IF带宽（10 Hz），并在测试端口上安装了NMD到3.5 mm的适配器，因此没有柔性电缆。结果让我感到困惑。如果查看图表，会出现一些峰值。我使用了两个非常相似的校准套件（85052B和85033E）并在相同的位置获得相同的尖峰。如果我重新测量校准短路，我看不到这些。事实是\| S11 \| > 0 dB不是一个好兆头，但我知道没有一台仪器是完美的。我一分钟都不相信短片实际上有这些特点。如果我使用测试端口电缆，我几乎一样。任何想法可能是什么？任何想法，如果它可以解决，或者这只是我必须忍受的限制？该仪器去年由Keysight校准，因此完全在校准期内。但是几个月前我对VNA做了一个改变，可能可能就是这个原因。我添加了选项012，它将A和B接收器输入和耦合器输出带到前面板。因此，在端口1耦合器和A接收器之间移除2.4毫米电缆，并用一对2.4毫米到SMA电缆和一个SMA-SMA跳线替换它。同样在端口2 / B接收器上。虽然SMA-SMA跳线是正确的安捷伦部件，但是由专业电缆制造商组成的两根2.4毫米到SMA电缆，因为是德科技没有它们。我附上了一个.s1p文件。文件中有大量的注释，因此如果有人想查看使用了哪些设置，那么它们就在那里。 DaveEdited：drkirkby于2015年1月9日12:32发表spikes.png201.0 KB 以上来自于谷歌翻译以下为原文 Someone asked me to measure a Maury Microwave 3.5 mm short on my VNA. To make things as accurate as I could, I used a very narrow IF bandwidth (10 Hz), and put an NMD to 3.5 mm adapter on the test port, so there were no flexible cables. The results are puzzling me. If you look at the graph, there are some spikes which appear. I've used two very similar cal kits (85052B and 85033E) and get the same spikes in the same positions. If I re-measure the calibration short, I don't see these. The fact that \|S11\| > 0 dB is not a good sign, but I know that no instrument is perfect. I don't for one minute believe the short actually has these characteristics. I get virtually the same if I use test port cables. Any ideas what it could be? Any ideas if it can be resolved, or is this just a limitation I have to live with? The instrument was calibrated by Keysight last year, so is well within its calibration period. BUT there's one change I made to the VNA a few months ago, which might possibly be the reason for this. I have added option 012, which brings the A and B receiver inputs, and coupler outputs, to the front panel. So adding that involved removing a 2.4 mm cable between the port 1 coupler and the A receiver, and replacing it with a pair of 2.4 mm to SMA cables and an SMA-SMA jumper. Likewise on port 2/B-receiver. Although the SMA-SMA jumper is the right Agilent part, the two 2.4 mm to SMA cables I had made up by a specialist cable manufacturer as Keysight did not have them. I've attached a .s1p file. There are tons of comments in the file, so if anyone wants to see what settings were used, they are all there. Dave Edited by: drkirkby on Jan 9, 2015 12:32 AM 附件 short.s1p47.8 KB spikes.png201.0 KB 0
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答案对人有帮助，有参考价值 0 你没有提到模型，但我猜它是8720.这可能是由一个用来调用“采样器反弹”的效果引起的。这是一个复杂的效果，但是在与所需频率相同频率的自生信号反射回DUT回到样本中，重新采样到另一个频率，返回，再次反射，重新采样回到所需的频率并添加或减少在扫描的非常特殊的点。通常这种效应表现为滤波器阻带中S21隔离的限制，但它们也可以出现在反射测量中。首先尝试将6 dB焊盘添加到测试端口，然后再次进行校准。如果原因是采样器反弹，那么有问题的信号将衰减24 dB（4次通过衰减器），而主反射将衰减仅12 dB（两次通过衰减器），因此尖峰将减少。以上来自于谷歌翻译以下为原文 You don't mention the model but I'm guessing it is an 8720. This might be caused by an effect that use to call "sampler bounce". It's a complicated effect but one where self-generated signals at the same frequency as the desired frequency reflect off the DUT back into the sample, resample to another frequency, go back out, reflect again, resample back to the desired frquency and add or subract at very particular points in the sweep. Usually this effect shows up as limitations of the S21 isolation in the stop band of a filter, but they can also show up in reflection measurements. Try adding a 6 dB pad to the test port first, and then making the calibration again. If the cause is sampler bounce, then the offending signal will be attenuated by 24 dB (4 passes through the attenuator), while the main reflection will be attenuated by only 12 dB (two passes through the attenuator) and so the spikes will be reduced.

2018-11-13 10:36:40 评论举报孔德羲