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Different amplitude for different frequencies using AD9910 EVAL BOARD

Question asked by Rahul..gupta on Jul 25, 2011
Latest reply on Jul 25, 2011 by DSB

Hello Forum,

 

I am using AD9910 EVAL BOARD using its GUI interface. I am new to it and first of all I tried to get a frequency of 1MHz using the 25 Mhz on board crystal as Refclk( resistors shorted and capacictors removed and jumper set accordingly ). PLL was not enabled.

 

But

1. I could not get exact 1 MHz frequency for its corrosponding FTW. Frequency was about 877 KHz.

2. The Amplitude of differnt frequencies say ( 1Mhz and 2 MHz) were differnt.It was observed that as i kept on increasing frequency,

     amplitude decreased. Phase value was set to 0 degrees in GUI.

 

 

Then I enabled the PLL and set its multiplication factor to 40 to obtain a system clock of 1000 MHz in GUI. Again I found that the FTW corrosponding to a particular frequency say 80 MHz came out to give a fequency output of 65 MHz and amplitudes for different frequency outputs were different.

 

How can I get two different frequencies (FSK) with the same amplitude level??

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