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Phase Locked signal for antenna measurement

Question asked by skamlesh on Feb 25, 2014
Latest reply on Apr 30, 2014 by OFR_JimP
Dear Sir/Madam,

I am working in antenna far field measurement test range. The instrumentation used for measurement includes 2 signal generator MXG series ( as RF and LO signal source), 2 LO/IF distribution units 85309A, 2 mixers 85320 B  and one PNAX as receiver. The instrumentation is chained such that I can perform the antenna pattern measurement in either Rx or Tx mode. 

The brief introduction of setup is as follows:

a. During Rx mode measurement of Antenna under test:

On feed antenna side, I have one RF signal generator whose output is given to feed side Mixer unit as RF input. The other signal generator is at Test Antenna side and it serves as LO source ( 20 MHz frequency offset). The output of this mixer is passed as *'a2' signal* to PNAX input port and used as *reference signal*. The same signal is used even for *phase locking*. 

n test antenna side, LO signal is sent to LO/IF distribution unit via an amplifier and later as LO source to both mixers ( AUT and feed side). On feed side, the other LO/IF unit is also used to keep the LO level reaching to feed side mixer in desired range.

The 10 MHz signal from the RF source is sent to LO source and then to PNAX through LO source. 

b. During Tx mode measurement of antenna under test, the setup is complementary of first setup.

I want to know the functionality of 10 MHz signal and how phase locking is done. Also, how the phase pattern of antenna is computed through this measurement (preferably with mathematical equations or notions) 

My second question is, if during Tx mode measurement instead of the range RF signal being used to derive the reference signal directly ( I mean RF signal being fed to RF input of mixer) if I have some other external source ( without 10 MHz control) can I still perform the phase locking (using some other horn antenna to capture the signal and using PLL) and compute phase pattern of antenna.

Kindly provide me detailed explanation on above topics as I am in deep necessity to understand these fundamentals. Also, I would be glad if you could reply me directly on my mail or contact me on 080-25375200 number for answer. 

Looking forward for your prompt reply.

Thanks and regards,