选择8510C的放大器要注意什么？

> {quote：title = samtsitrin写道：} {quote}>大家好。
我是一个完整的新手！
>我们使用旧的8510C通过光子晶体发送微波，当我们改用同轴天线作为接收器时，它们的信号非常低。
此VNA输出的最大功率为25dbm（与316mW相同）我不知道8510C。
真的可以输出25 dBm吗？
这在微波频率上是相当大的功率。
但我认为8510系统是由几个不同的组件组成的，所以我想这很有可能。
它不仅仅是大多数现代VNA所能提供的。
在不知道你在做什么的情况下，很难知道你想要建议什么。
您检测到的功率是否太低而无法测量VNA？
如果您发布了系统的框图，以及对您正在做什么，您希望衡量的内容等的某种描述，那么人们可能会有一些建议。
但是你的帖子中没有任何东西可以表明前进的方向。
>一些合作者建议放大器放大信号。
>浏览放大器，我发现例如这两个型号：> 83018A，功率为125mW，增益为27db（便宜！）>和> 83020A，输出功率为1W，增益为30db（昂贵）>所以我的问题是：
看来我们正在支付瓦特的输出，所以这是要注意的参数？
>如果我们选择更便宜的型号，这是否意味着我们的316mW最大VNA信号将被放大125mW，这就是它？
功率只是放大器的一个方面。
增益和带宽可能是功率放大器的另外两个最重要的特性。
噪声系数对放大低信号电平的放大器很重要，但对于高达1 uW的功率电平则不重要。
但是放大器还有许多其他参数，特别是它们的线性度。
如果放大器指定为125 mW，那就是最大功率。
它不增加125 mW。
有很多方法可以组合放大器，但它不是在公园散步。
如果您需要1 W来弥补所有损耗，请购买1 W放大器。
>请帮助，因为我是一名物理系学生，而不是工程师，任何智慧的话都会受到赞赏......你需要确定你需要什么样的力量。
如果你有25 dBm，这还不够，为什么还不够？
而不是看一个放大器的catalgoue，憎恶你需要什么样的规格。
也许您可以在探测器上使用前置放大器。
真的没有足够的信息让任何人帮助你。
我们至少需要一个框图和你想要实现的目标的描述。
戴夫



     以下为原文

  > {quote:title=samtsitrin wrote:}{quote}
> Hello everyone. I am a complete newbie here!
> We are using an old 8510C to send microwaves through photonic crystals and are getting a really low signal when we switch to using a coaxial antenna as receiver. The max power at output for this VNA is 25dbm (is that the same as 316mW) 

I don't know the 8510C. Can it really output as much as 25 dBm? That is quite a bit of power at microwave frequencies. But I think an 8510 system is made up from several different components, so I guess that is quite possible. It is more than most modern VNAs would provide. 

Without knowing what you are doing, it is hard to know what you want to suggest. Is the power you are detecting too low for the VNA to measure? 

If you posted a block diagram of your system, and some sort of description of what you doing, what you hope to measure etc, people might have some suggestions. But there is not really anything in your post to indicate a way forward. 

> Some collaborators suggested an amplifier to amplify the signal. 
> Browsing the amplifiers , I found for example these two models:
> 83018A which gives 125mW and a gain of 27db (cheap!)
>  and
> 83020A which gives 1W output and a gain of 30db (Expensive)
> 
> So my questions are: It seems we are paying for Watts of output so that's the parameter to pay attention to?
> If we go with the cheaper model , does that mean that our max VNA signal of 316mW will be amplified by an additional 125mW and that's it?

Power is only one aspect of an amplifier. Gain and bandwidth are probably the two other most important properties for power amplifiers. Noise figure is important for amplifiers amplifying low signal levels, but not a power levels as high as even 1 uW. But there are many other parameters of amplifiers, specifically how linear they are. 

If an amplifier is specified as 125 mW, that is the maximum power. It does not add 125 mW. There are ways to combine amplifiers, but it is not a walk in the park. If you need 1 W to overall all your losses, buy a 1 W amplifier. 

> Please help, since I am a physics student and not an engineer and any words of wisdom are appreciated...

You need to determine what power you need. If you have 25 dBm, and that is not enough, why is it not enough? Rather than look at a catalgoue of ampliiers, deteremine what specification you need. Perhaps you can use a pre-amplifier on the detector. 

There really is insufficient information for anyone to help you much. We would need at least a block diagram and a description of what you are trying to achieve. 

Dave

戴夫 - 谢谢你的回应。
我们的实验如下：VNA连接到S参数测试装置。
我们通过在端口1使用波导喇叭通过光子晶体结构发送微波（7Ghz-15Ghz）。我们用来收集S21传输，另一个喇叭位于我们晶体的另一侧并连接到端口2并获得了良好的数据。
现在实验正在改变，我们想要使用同轴偶极天线从顶部扫描结构并收集结构不同部分的透射S21数据，以绘制晶体内部的电场强度。
在一些初步试验中，我们发现信号非常低，另一个使用类似设置的研究小组提到他们使用1W放大器来提升信号输出端口1。
8510C的25dbm值是我在显示器上读取的输出功率...我猜这还不够，因为天线收集辐射的效率远低于波导喇叭？
根据你所写的，125mW输出放大器似乎根本没用，因为它的输出比我们目前的VNA本身要少？
谢谢你的建议。



     以下为原文

  Dave-
thanks for responding. Our experiment is the following:
the VNA is connected to the S-parameter test set. We are sending microwaves (7Ghz-15Ghz) through a photonic crystal structure by using a waveguide horn at port 1. We used to collect S21 Transmission with another horn positioned on the other side of our crystal and connected to port 2 and got good data.

Now the experiment is changing, where we want to use a coaxial dipole antenna to scan the structure from the top and collect transmission S21 data in different parts of the structure to map the Electric field intensity inside the crystal. On some preliminary trials we found that the signal is quite low and another research group that uses a similar set-up mentioned they used a 1W amplifier to boost the signal out of port1.

The 25dbm value for the 8510C is what I read on the display for output power...I am guessing it's not enough because the antenna is much less efficient in collecting the radiation than the waveguide horn?

From what you wrote it seems the 125mW output amplifier will not be useful at all, because it's less output than our current VNA itself?

Thanks for your advice.

> {quote：title = samtsitrin写道：} {quote}> Dave->感谢您的回复。
我们的实验如下：> VNA连接到S参数测试装置。
我们通过在端口1使用波导喇叭通过光子晶体结构发送微波（7Ghz-15Ghz）。我们用来收集S21传输，另一个喇叭位于我们晶体的另一侧并连接到端口2并获得了良好的数据。
>>现在实验正在改变，我们想要使用同轴偶极天线从顶部扫描结构并收集结构不同部分的透射S21数据，以映射晶体内部的电场强度。
在一些初步试验中，我们发现信号非常低，另一个使用类似设置的研究小组提到他们使用1W放大器来提升信号输出端口1。
这个水晶有多大？
我不禁感觉你的空间分辨率与你的囊肿大小相比会很差，这让我想知道你会通过扫描看到什么样的优势。
你使用什么尺寸的喇叭天线？
根据尺寸，我们可以计算出增益本来就是多少，因此使用偶极天线可以大致减少多少信号。
> 8510C的25dbm值是我在显示器上读取的输出功率...我猜这还不够，因为天线收集辐射的效率远低于波导喇叭？
是的，天线的增益会低得多。
对于大多数喇叭，喇叭的增益在10到25 dBi之间。
我不认为在喇叭上超过25 dBi是非常实用的。
但是一个人会大约2 dBi，所以会有相当大的损失，特别是如果你用两个偶极子替换了两个角。
如果每一侧最初有25 dBi增益，你可能会损失大约46 dB，现在减少到2 dBi。
>根据你所写的，125mW输出放大器似乎根本没用，因为它的输出比我们目前的VNA本身要少？
是的，就是这样。
使用125 mW放大器是最不明智的。
显然增加功率将提高您的S / N，但您是否尝试过其他技术，如降低IF带宽和/或平均值？
1 W放大器只能为您带来5 dB的改善，但是您可以通过将IF带宽降低10倍来改善问题。这样做的代价是扫描速度较慢。
即使你的喇叭只有10 dBi的增益，你也可能会失去16 dB变成一对偶极子，因为现在每个天线的增益都低8 dB。
在这种情况下，增加5 dB的功率将有所帮助，但它不会恢复到以前的位置。
我想知道你是否可以在端口2（接收器）上使用前置放大器，而不是端口1（源）？
如果您使用的是低噪声放大器而不是功率放大器，那么您可以以更低的成本获得显着的收益。
>感谢您的建议。
我必须补充一点，我从未使用过8510C，但我确信它有能力降低IF带宽，我也希望能够进行平均。
您能否提供其他研究小组正在做的事情的参考？
我将看看论文，看看我是否还有其他想法。
DaveEdited：drkirkby于2013年7月11日上午12:27



     以下为原文

  > {quote:title=samtsitrin wrote:}{quote}
> Dave-
> thanks for responding. Our experiment is the following:
> the VNA is connected to the S-parameter test set. We are sending microwaves (7Ghz-15Ghz) through a photonic crystal structure by using a waveguide horn at port 1. We used to collect S21 Transmission with another horn positioned on the other side of our crystal and connected to port 2 and got good data.
> 
> Now the experiment is changing, where we want to use a coaxial dipole antenna to scan the structure from the top and collect transmission S21 data in different parts of the structure to map the Electric field intensity inside the crystal. On some preliminary trials we found that the signal is quite low and another research group that uses a similar set-up mentioned they used a 1W amplifier to boost the signal out of port1.

How big is this crystal? I can't help feeling your spatial resolution is going to be quite poor in comparision to the size of your cystal, which makes me wonder what advantage you will see by scanning. 

What size horn antenna(s) were you using? From the size we can work out what the gain would have been and so roughly how much the signal would be weaker with dipole antennas. 

> The 25dbm value for the 8510C is what I read on the display for output power...I am guessing it's not enough because the antenna is much less efficient in collecting the radiation than the waveguide horn?

Yes, the gain of the antenna would be much lower. A horn would have a gain of between 10 and 25 dBi for most horns. I don't think its very practical to go beyond 25 dBi on a horn. But a diople would be about 2 dBi, so there would be quite a loss, especially if you have replaced two horns with two dipoles. You could have lost around 46 dB, if each side originally had 25 dBi gain, and is now reduced to 2 dBi. 

> From what you wrote it seems the 125mW output amplifier will not be useful at all, because it's less output than our current VNA itself?

Yes, that is so. You would be most unwise to use a 125 mW amplifier. 

Clearly increasing the power will improve your S/N, but have you tried other techniques like reducing the IF bandwidth and/or averaging? A 1 W amplifier is only going to gain you a 5 dB improvement, but and you can improve matters more than that by reducing your IF bandwidth by a factor of 10. The penalty for doing that is a slower sweep speed. 

Even if your horns were only 10 dBi gain, you could have lost 16 dB changing to a pair of dipoles, since each antenna now has 8 dB less gain. In that case, getting 5 dB more power is going to help, but it wont recover to where you were before. 

I wonder if you could use a pre-amp on port 2 (receiver), rather than port 1 (source)? You could get a significant gain for far less money if you used a low-noise amplifier, rather than a power amplfier. 

> Thanks for your advice.

I must add I have never used an 8510C, but I'm sure it has the ability to reduce the IF bandwidth, and I expect averaging too. 

Can you provide a reference to what the other research group were doing? I'll take a look at the paper and see if I have any other ideas. 

Dave

Edited by: drkirkby on Jul 11, 2013 12:27 AM

戴夫 - 晶体直径约10-15厘米。
根据频率，我们应该能够确定内部的电场模式。
它是一个类似于本文所述的设置：http：//www.lci.kent.edu/muri/nim_papers/negative_index/2006Smithmapping.pdf最新的喇叭天线是17db MA86551 http://www.advancedreceiver.com
/page34.html我们仍计划使用1个喇叭天线和1个偶极扫描天线。
+显然增加功率将提高您的S / N，但您是否尝试过其他技术，如降低IF带宽和/或平均值？
一个1 W的放大器只能让你获得5 dB的改善，但你可以通过将你的IF带宽减少10倍来改善问题。这样做的代价是扫描速度较慢。+你能不能请
告诉我你对减少IF带宽的意思？
你的意思是我们在频率扫描中采取的点数？
我们已经使用相当高的平均值。
+我想知道你是否可以在端口2（接收器）上使用前置放大器，而不是端口1（源）？
如果使用低噪声放大器而不是功率放大器，你可以以更低的成本获得显着的增益。+因此，端口2上的前置放大器可能比端口1上的1W放大器更好吗？
你有任何我应该抬头的模特吗？
我们是否必须以某种方式过滤噪音？
+你能提供其他研究小组的工作参考吗？
我会看一下这篇论文，看看我是否还有其他的想法。+不幸的是，其他小组的论文并没有多谈他们的设置，而是在个人交流中，他们告诉我他们使用了放大器。
谢谢你的帮助。



     以下为原文

  Dave-
The crystals are about 10-15cm in diameter. Depending on the frequency we should be able to determine E-field pattern inside. It is a similar set up as described in this paper:
http://www.lci.kent.edu/muri/nim_papers/negative_index/2006Smithmapping.pdf

The most recent horn antennas were 17db MA86551 http://www.advancedreceiver.com/page34.html
and we still plan on using 1 Horn antenna and 1 dipole scanning antenna. 

+Clearly increasing the power will improve your S/N, but have you tried other techniques like reducing the IF bandwidth and/or averaging? A 1 W amplifier is only going to gain you a 5 dB improvement, but and you can improve matters more than that by reducing your IF bandwidth by a factor of 10. The penalty for doing that is a slower sweep speed.+ 

Could you please tell me what you mean about reducing the IF bandwidth? Do you mean the number of points we take in the frequency sweep? We do use pretty high averaging already.

+I wonder if you could use a pre-amp on port 2 (receiver), rather than port 1 (source)? You could get a significant gain for far less money if you used a low-noise amplifier, rather than a power amplfier.+ 

So a pre-amp on port 2, might work better than a 1W amp on port 1? Do you have any models I should look up? Would we have to filter the noise somehow?

+Can you provide a reference to what the other research group were doing? I'll take a look at the paper and see if I have any other ideas.+ 

Unfortunately the other groups papers don't talk much about their set-up, it's in personal communication that they told me they used the amp.

Thanks for your help.