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Queries about AD9789’s Image

Question asked by WayneQ on Jun 14, 2016
Latest reply on Jul 28, 2016 by danf

Hi, there

 

I met some problems in using AD9789 and need your help here.

The input signal to AD9789 is DVB-T OFDM IQ complex signals. The bandwidth are 8MHz/7MHz/6MHz. The sampling rate are 64/7MSPS, 8MSPS and 48/7MSPS.

Central frequency is 500MHz, interpolation is 32.

 

64/7MSPS sampling rate

P: 0x1b(Register) ->0x41(data)

  0x1a(reg) ->0xa0(data)

  0x19(reg) ->0x00(data)

  Q: 0x18(reg) ->0x80(data)

  0x17(reg) ->0x00(data)

  0x16(reg) ->0x00(dat)

 

8 MSPS sampling rate

P: 0x1b(reg) ->0x4b(data)

  0x1a(reg) ->0x00(data)

  0x19(reg) ->0x00(data)

  Q: 0x18(reg) ->0x80(data)

  0x17(reg) ->0x00(data)

  0x16(reg) ->0x00(data)

 

48/7MSPS sampling rate

P: 0x1b(reg) ->0x57(data)

  0x1a(reg) ->0x80(data)

  0x19(reg) ->0x00(data)

  Q: 0x18(reg) ->0x80(data)

  0x17(reg) ->0x00(data)

  0x16(reg) ->0x00(data)

 

when 8MHz signal inputs, the spur is low, please see Pic1. But the spur/image are high, when 7MHz or 6MHz signal input, please Pic2 and 3.

 

Could you please help with the issue or give some comments on it?

 

Thanks so much!

 

Br,

Wayne

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