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ADF4630-7 PLL unlocked

Question asked by Leo02 on Jan 31, 2018

Hi,

Here is my circuit :

I'm trying to amplify a signal whose the frequency is about 400 MHz and the amplitude is about 5 dBm. This signal is generated by the PLL (ADF4360-7). However the frequency of my amplified signal is about 360 MHz (The frequency is fixed at 360 MHz, it doesn't move on the screen of the spectrum analyzer) and I have nothing at 400 MHz. (The signal is observed on the amplifier (ATF531P8) output).  So, I decided to remove the resistance R36 (0 Ohm) in order to isolate the PLL from the amplifier. The signal observed on the output of the PLL is the frequency that I want to have (400 MHz). Then I used a frequency generator in order to generate a signal whose the frequency is 400 MHz and the amplitude is 5 dBM. I injected this signal on the amplifier input. The signal observed on the amplifier  ouptut has the frequency expected (400 MHz) and it is amplified correctly. So the problem is when the both (amplifier and PLL) are connected together. But I can't identify the source of the problem.

 

Here is the setting of the PLL (register of PLL):

CTRL     0x000FF12C  

N            0x00C0661E  

R            0x00010069  

Here is the link to the datasheet :

http://www.analog.com/media/en/technical-documentation/data-sheets/ADF4360-7.pdf

Thank you very much and have a nice day !

Léo

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