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ADRF6620 PLL locking frequency and Spur

Question asked by yoonjoki on Aug 17, 2016
Latest reply on Sep 30, 2016 by gyaliniz

Hi, I am using ADRF6620-Evalz board to test performance of ADRF6620's internal PLL LO signal's phase noise and spurious emission performance.

 

Here is what I did.

-Connect 20MHz PLL reference clock signal to REFIN port of evalz board

-Set desired LO frequency on ADRF6620-EVALZ software.(2000MHz)

-Enable LO_DRV_EN bit in Register 0x01, Bit 7. to check LO signal

-Connect LO out port to spectrum analyzer to see internally generated LO signal's phase noise and spur.

 

Here is the result I get from this test.

 

 

 

Too many spurs were generated.  ( attached CSV file of this  measured data)

So I checked Lock_detect signal at MUXOUT pin on EVALZ board(to see if it shows logic high, indicating PLL is locked). There was no signal on this lock_detect pin, which means it probably failed to calibrate PLL frequency.

 

Is there a way to lock LO frequency and remove spurs?

 

Please advise.

 

Thank you,

Grace

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