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Create a channel sounder with PSG and PNA

Question asked by JamesChuang on Sep 13, 2006
Latest reply on Sep 13, 2006 by dgun
Hi all,

I am trying to create a UWB channel sounder using PSG, E8257D, and PNA, E8362B, but I am running into some problems.

At first, I can measure the complex frequency response of the channel with just the PNA by connecting an antenna onto port 1 and another one onto port 2, and treating the channel as the DUT.  This approach works great until I have to extend the range up to several hundred meters (cable loss).

As a result, I am now using the PSG as an external source.  I can syncrhonize the stepped sweep without a problem using the trigger inputs and outputs at the back of the instruments; however, I have trouble repeating the same phase offset from sweep to sweep between the two machines even with the 10 MHz reference connected. 

To do a quick test, I set the PNA and PSG both to 3 GHz. The phase offset between the two is constant and perfect.  The phase offset is still constant even if I switch to another frequency.  However, if I go back to 3GHz, the constant phase offset jumps to another value.  Why is this happening?  I thought the two LO would be phase locked when the 10 MHz reference is connected together.  I would like to have repeatable phase offset so that I can manually calibrate out the phase difference between the two instruments.

Any explanation or suggestion on how to do what I want would be greatly appreciated.

Regards,

James Chuang  

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