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Output of the singal has an obvious distortion just @>=5 Mhz.

Question asked by cuau on May 25, 2013
Latest reply on May 30, 2013 by Kevin.G

Hi,Kevin.G ,kevintompsett ,KevinL and kevin.liu,

 

MY project is using FPGA to control DDS via SPI .

 

I already sovled the problem with the communication between FPGA and DDS within the help of kevin.G , thank you again!

 

But there is another tough issue.

 

No matter in the mode of PC control through USB  or in the mode of mannul CONtrol VIA SPI, (refrence clock @ 200Mhz,I aware of the configure of the clock!)  the output of the singal has an obvious distortion just >=5 Mhz (It just have a excellent performance @<=1 MHz).

 

I THINK that's terrible! Because My  project want to generate a sin singal between 4Mhz to 6Mhz ,at a high precision(1 HZ) and at a Frequency hopping ( about 770KHZ ),and more inportantly,the output singal should be Random rather than linear.

 

So I guess ti's the problem with the power supply? I power the TB1 &TB2 just from the FPGA board (the 3.3V output pins and 1.8 v output pins ). 

 

Further more, could you give me some Feasible suggestions about my project?

 

Looking forward to your reply timely and comprehensive.

 

THANK YOU very much!!

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