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Honored Contributor I

Signals distorted by the Stratix II EP2S180 Dsp Board


I'm trying to visualize signals generated from my EP2S180 Dsp Board after implementing a design into the FPGA.  

When implementing a simple sinusoidal signal of about 50Hz, I obtain at one of the DACs outputs a sine wave of about 1 MHz with a maximum of 2v peak to peak. 


Questions: I have read that the board has an input cut-off frequency of 1Mhz.  

1- Is there any output bandwidth? (For now, no signal is injected at the ADCs) 

2- What is the reason of this frequency shifting? 


Thanks for your answers!
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Honored Contributor I


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I have read that the board has an input cut-off frequency of 1Mhz. 

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I think, it's Altera's duty to specify the product. As far as I see, the transformer coupling of AD and DA interfaces isn't even mentioned in the User Guide. The parts itself (from Mini-Circuits) have a 0.4 MHz/-3 dB high-pass cut-off. So a 50 Hz signal can't cross it. But that's no reason to get a near full-scale 1 MHz signal, there's most likely a signal generation or DAC connection bug in the design. The factory design (sum of 1.25 + 12.5 MHz sine) should work correctly.