关于二次谐波测量

大家好，很抱歉再次提问。
这次是关于二次谐波测量。
有关测量设置，请参阅随附的jpg文件。
一些基本的解释。
SG以频率f0产生信号，然后使用低通滤波器（LPF）滤除SG二次谐波，隔离器以减少反射信号，从而稳定SG输出。
2dB ATT改善阻抗匹配。
SA在频率2 * f0处测量二次谐波。
此外，SA和SG 10MHz源被锁定在一起。
在附件中。
（a）用于设置;
（b）用于DUT测量。
在（a）中，SA经过仔细调谐，RBW = 1Hz，SPAN = 100Hz，优化输入衰减器以减少SA混频器失真。
（输入衰减器以2dB步进增加，直到2f0谐波信号电平在1dB内变化）。
在（b）中，SA设置与（a）相同，插入DUT并进行测量。
DUT是无源的，其插入损耗在f0处为0.5dB，在2 * f0处的衰减为15dB。
f0处的LPF（LC型）插入损耗为1dB，2 * f0处的衰减为55dB。
这是我们的测量结果：在设置（a）中，2 * f0处的谐波电平为-65dBm在设置（b）中，2 * f0处的谐波电平为-80dBm我的问题：（1）通常，对于谐波测量，
设置应具有更高的性能，以便正确进行DUT测量。
在我的测量中，我发现DUT结果比设置更好。
这是否意味着设置没有很好地配置/优化？
（2）根据测量结果，似乎2 * f0（15dB）处的DUT衰减与设置（a）和（b）差异完全匹配。
因此，在设置（b）中，我用两个相同的LPF替换LPF并且预期会有改进的结果，但是，我只看到2dB的改进，这是由于LPF损耗（1dB x 2 = 2dB）你的帮助将是
非常感谢！
你的，伊柳



     以下为原文

  Hi, all,

sorry for asking question again.

This time, it is about the second hARMonics measurement.

Please refer to the attached jpg file for the measurement setup.

Some fundamental explanations.

SG generates the signal at frequency f0, then use low pass filter (LPF)to filter out the SG 2nd harmonics, isolator to reduce the reflected signal, hence to stabilize the SG output. 2dB ATT to improve impedance matching. SA measure the 2nd harmonics at frequency 2*f0. Further, SA and SG 10MHz source is locked together.

In the attached file. (a) is for the setup; (b) is for the DUT measurement.  
in (a), SA is carefully tuned, RBW=1Hz, SPAN=100Hz, input attenuator is optimized to reduce the SA mixer distortion. (input attenuator increased in its 2dB step, until the 2f0 harmonic signal level varies within 1dB).
in (b), SA setting is the same with (a), DUT inserted and do the measurement.  

DUT is passive, with its insertion loss being 0.5dB at f0, attenuation at 2*f0 is 15dB.  
LPF(LC type) insertion loss at f0 is 1dB, attenuation at 2*f0 is 55dB.

Here is our measurement result:
In setup (a), harmonic level at 2*f0 is -65dBm
In setup (b), harmonic level at 2*f0 is -80dBm

My questions:
(1) Normally, as for harmonic measurement, the setup should have greater performance in order to do the DUT measurement correctly. In my measurement, I found the DUT result better than the setup. Does this mean that the setup is not well configured/optimized?

(2) From the measurement results, it seems that the DUT attenuation at 2*f0 (15dB) exactly matches the setup (a) and (b) difference. Therefore, in setup(b), I replaced the LPF with two identical LPFs and expected to have improved results, however, I only see the 2dB improvements, which is due to the LPF loss (1dB x 2 = 2dB)

Your help would be highly appreciated!

Yours,
Yiliu   
附件

• SecondHarmonicsMeasurement.JPG24.0 KB