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Reg: ADF4371 SYNTH FREQUENCY LOCKING

Hi Sir,

I'm working on the ADF4371 synthesizer evaluation board using  ACE installer software to write the registers and lock the frequency from 17 to 23GHz. I'm using the STM32 controller and SPI protocol.  

Now I'm facing an offset frequency lock problem. when I loaded register values and tried to lock the desired frequency, there is a problem with the offset in the locking frequency.

Request you to give a solution to the problem I'm facing.

Please find the attached pictures of the Register values loaded, parameter setting GUI, and locked frequency in the spectrum.

  • Hi,

    You need to write Reg0x10 at the end to start autocalibration. Are you following that rule in your writing sequence? 

    Kudret

  • Yes, Sir, I'm following the Register writing Sequence as per the datasheet. First I have started writing from  Reg0x7C. Initializing Registers also should be in that sequence? Because I have written all the registers( followed Reg sequence) in one function and I'm calling that function in the main function.  

  • Hi Sir,

    Can you please help me with the above issue? As I'm running out of time for the project deadline given.

    Rakesh Kumar.

  • Hi,

    If you are referring to a few 2kHz difference on 2 GHz output, this is related with that on-board oscillator is not exactly 100 MHz. Very little deviation on oscillator output is multiplied with N value and it is seen as frequency difference at the output. 

    If you want to get exact frequency, you need to synchronize a signal generator and your spectrum analyzer with 10 MHz reference input and outputs. Then, if you provide 100 MHz from your signal generator to ADF4371 EVB, you will get 2 GHz output exactly. 

    If you want to use external 100 MHz clock from your signal generator, you need to disable on-board oscillator (by removing R20). 

    Kudret