如何比较两个波形发生器

嗨Lokesh，源谐波在与DUT中的其他音调混合时会降低多音测量精度，从而产生干扰被测失真信号的信号。
对于双音三阶测量，当一个源（2f1）的二次谐波在DUT中与来自另一个源（f2）的音调混合时产生这种情况，从而产生与三阶互调失真相同频率的信号
信号（2f1-f2）。
换句话说，由DUT从两个入射音产生的三阶失真信号出现在频率（2f1-f2,2f2-f1）处，这也是混合一个音调和二次谐波产生的差分产物。
其他语气。
因此，如果其中一个音调的二次谐波入射到DUT上，则DUT将以互调频率产生一个信号，该信号将加到我们试图测量的信号上，从而导致测量误差。
该误差的大小取决于入射谐波信号的水平和DUT中混合过程的效率。
因此，最好使用低谐波失真规格的信号源进行IMD测量。
由于安捷伦没有为E4422B指定谐波失真，因此很难将33250A与E4422B进行比较以用于IMD测量。
这是因为谐波失真不仅作为频率的函数而且作为输出功率的函数而改变。
但是，根据E4422B数据手册中给出的典型值和33250A数据手册中的规格判断，我怀疑E4422B的谐波失真性能优于33250A。尽管谐波失真是选择的主要因素。
在IMD测量中使用的源还有其他变量。
杂散（非谐波）失真，源交叉调制（多音调发生器的因素）和输出功率也可能影响测量质量。
谢谢！穆勒



     以下为原文

  Hi Lokesh,

Source harmonics degrade multitone measurement accuracy when they mix with other tones in the DUT to produce signals that interfere with the distortion signals being measured. For two-tone third-order measurements, this occurs when the second harmonic of one source (2f1) is mixed in the DUT with the tone from the other source (f2), producing a signal at the same frequency as the third order intermodulation distortion signal (2f1 – f2). In other words, the third-order distortion signal generated by the DUT from the two incident tones occurs at the frequencies (2f1 – f2, 2f2 – f1) which are also the difference products that result from mixing one tone and the second harmonic of the other tone. Therefore if the second harmonic of one of the tones is incident upon the DUT, the DUT will generate a signal at the intermodulation frequency that will add to the signal we are trying to measure, thus causing an error in the measurement. The magnitude of this error depends upon the level of the incident harmonic signal and the efficiency of the mixing process in the DUT.

For this reason, it is best to use sources with the low harmonic distortion specifications for IMD measurements. It is difficult to compare the 33250A with the E4422B for use in an IMD measurement as Agilent does not specify harmonic distortion for the E4422B. This is because harmonic distortion changes not only as a function of frequency but also as a function of output power. However, judging by the typical values given in the E4422B data sheet and the specifications in the 33250A data sheet, I would suspect that the harmonic distortion performance of the E4422B is superior to that of the 33250A.

Although harmonic distortion is the main factor in selecting sources to use in an IMD measurement there are other variables. Spurious (non-harmonic) distortion, source cross-modulation (a factor for multitone generators) and output power may affect the quality of your measurements as well.

Thanks!
Mueller

谢谢Stephen，这是一个非常好的和明确的回复。这个主题（IMD测量）是否有来自安捷伦的任何具体教程/讲座？。你的工程直觉也是正确的，我从E4422B获得的IMD结果比
33250A。（那是你真正的螺柱工程师，帽子:-)问候，Lokesh



     以下为原文

  Thanks Stephen,
That was a really nice and clear reply.
Is there any specific tutorial/talks from agilent on this topic(IMD measurement)?.
Also your engineering Intuition is really correct, The IMD results that I got from E4422B was more superior than 33250A.(That is a really stud engineer in you, hats off:-)

Regards,
Lokesh

嗨Lokesh，以下是有关安捷伦IMD测量的两项资源。
他们都专注于使用安捷伦PNA-X网络分析仪进行IMD测量，但是您可能会发现一些有用的一般信息和理论。调制失真（IMD）测量具有更高的速度和准确度。
网络研讨会.http：//www.home.agilent.com/agilent/eventDetail.jspx？cc = US＆amp; lc = eng＆amp; ckey = 1665457＆amp; nid = -11143.0.00＆amp; id = 1665457＆amp; pselect = SR.GeneralMaking Accurate Intermodulation
使用PNA-X网络分析仪进行失真测量。
应用笔记1408-17.http：//cp.literature.agilent.com/litweb/pdf/5989-7265EN.pdf谢谢！穆勒



     以下为原文

  Hi Lokesh,

Here are two resources regarding IMD measurements from Agilent. They are both focused on making IMD measurements using the Agilent PNA-X Network Analyzer but there is some general information and theory that you may find useful.

Intermodulation distortion (IMD) measurements with improved speed and accuracy. Webinar.
http://www.home.agilent.com/agilent/eventDetail.jspx?cc=US&lc=eng&ckey=1665457&nid=-11143.0.00&id=1665457&pselect=SR.General

Making Accurate Intermodulation Distortion Measurements with the PNA-X Network Analyzer. Application note 1408-17.
http://cp.literature.agilent.com/litweb/pdf/5989-7265EN.pdf

Thanks!
Mueller