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AD9789 : Glitches appear on frequency change

Question asked by Mathieu on Sep 19, 2012
Latest reply on Oct 9, 2012 by Mathieu

I am using the AD9789 clocked at 2240 MHz and programmed in QDUC Mode to generate a 100MHz-900MHz modulated signal. Baseband signal I,Q is provided by a FPGA with a LVDS interface. So far it works fine.

 

Yet I have noticed a strange phenomenon : On a frequency change a wideband glitch appears in RF exactly at the moment the Frequency Update Register @0x1E is set to 0x80, even though the INSCALE and SUMSCALE registers are set to zero.

 

I have no control on this glitch and it might damage the high power amplifier that follows our modulation system.

 

1/ Are you aware of this glitch phenomenon ?

2/ Is there a way to suppress it ?

 

Thanks in advance to those who can help

 

Mathieu

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