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AD9789 Hamornic issue

Question asked by kmkim on Aug 21, 2013
Latest reply on Aug 23, 2013 by danf

I have designed direct up conversion VSB modulator using AD9789+AD9516+ADF4350+FPGA and most of circuits are same with ADI evaluation board.

It is added a RF amp circuit only.

FDAC-2.4GHz

DAC OUT CH- 4CH

 

1)There are four harmonics existing as the attached photo #1.2

The harmonics are appearing even changing the CH.

The harmonics frequency are 6, 12, 16, and 22MHz.

The harmonics also reduced to two when DAC output to reduce to 2CH.

The harmonics frequency are 6, 10MHz.

 

2)There is noise on high channels like attached photo #3,4

    The channels which I tested were MA66 to 69.

    The noise disappear when DAC output reduce to 2CH.

 

3)It is detected such frequency from DAC out and it is assumed CLK RATE 150MHz

  I think it H/W problem. Please check circuit diagram. photo#4

 

DAC setting values are same as attached.

And, Please advice for me above problem 1) & 2) caused by H/w or S/W.

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