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Why complex 8 for TmodSink? RRS feed

  • Question

  • Hi,

    First, a bug report. In Tsine brick(sorasdk1.8\inc\sdl), the complex wave is generated by lut with 15bit amplitude and normalized with amplitude NORM_ONE=20000. In TmodSink, the in port is type complex 8, but NORM_ONE is much larger than 127. So the sine wave is not properly generated and will have lots of side peaks in the spectrum.

    Second, why does sora use complex 8 for the TmodSink? Complex 16 is much intuitive, because AD9862 has 14bit Tx path. If this is limited by hardware resource, why dose sora generate redundant tx data with 40M/44M complex 8 instead of 20M/22M complex16 ?

    Thanks,

    Zhice

    Friday, May 24, 2013 5:39 AM

Answers

  • Hello Zhice, you're now working on SORA :) 

    Yes, the bit-width of AD9862 is 14-bit. But SORA gives an interface of 8-bit for history reasons ( YOU dongde :) ). SORA will support 16-bit TX samples in future. Anyway, 8-bit supports about 8*6=48dB SNR, which is enough for most PHY requirements. 


    Danial.F

    • Marked as answer by Qi LuoEditor Monday, May 27, 2013 3:35 AM
    • Unmarked as answer by YANG Zhice Monday, May 27, 2013 12:24 PM
    • Marked as answer by YANG Zhice Monday, May 27, 2013 12:24 PM
    Sunday, May 26, 2013 4:59 PM

All replies

  • Hello Zhice, you're now working on SORA :) 

    Yes, the bit-width of AD9862 is 14-bit. But SORA gives an interface of 8-bit for history reasons ( YOU dongde :) ). SORA will support 16-bit TX samples in future. Anyway, 8-bit supports about 8*6=48dB SNR, which is enough for most PHY requirements. 


    Danial.F

    • Marked as answer by Qi LuoEditor Monday, May 27, 2013 3:35 AM
    • Unmarked as answer by YANG Zhice Monday, May 27, 2013 12:24 PM
    • Marked as answer by YANG Zhice Monday, May 27, 2013 12:24 PM
    Sunday, May 26, 2013 4:59 PM
  • Hi Zhice,

    Thank you for your report.

    Danial is correct, these is no fundamental reason for 8-bit TX. A good news is that we now support 16-bit TX in Sora-MIMO.

    -Jiansong

    Monday, May 27, 2013 3:06 AM
  • Hi Danial, 

    Thanks, sounds very convincing:)

    Zhice

    Monday, May 27, 2013 12:12 PM
  • Hi Jiansong,

    What about the Rx interface? I have not checked it, though it is Complex 16 in the code. It's crucial for me to make sure that it is sampled in 12bit in the hardware.

    By the way, looking forward to see the release of the sora MIMO.

    Thanks,

    Zhice

    Monday, May 27, 2013 12:24 PM