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Original question:

AWR2243: Internal phase changes of the two SYNCIN pins for 20GHz LO

AWR2243: MMWCAS-RF-EVM - LO signal length

James Birchall
Prodigy 20 points
Part Number: AWR2243
Other Parts Discussed in Thread: MMWCAS-RF-EVM,

Tool/software:

Hi All,

I'm working on a design that is a modificationof the MMWCAS-RF-EVM board.

I note as per the 'AWR2243 Cascade' document, that there must be a delay match between the 2x LO outputs of the master (FMCW_CLKOUT and FMCW_SYNCOUT), and the subsequent 4 outputs of the 2 Wilkinson splitters. This all makes sense. 

I note from the Altium design that in particular the 'supplies' to the Wilkinson splitters are not length / delay matched at all, measuring in at 17.151 and 13.018mm for the lines on Layer 3 and do not look to be compensated by lengths on layer 1. Additionally, the delay measurement of each net AWR_1_FMCW_CLKOUT and AWR_1_FMCW_SYNCOUT differ by about 30 ps. I appreciate due to the net naming conventions, that each net delay comprises of  sum of the source to, and both outputs from each Wilkinson divider, but I would have expected the total delay for each net to be equal?

Please could I confirm if there are any internal package delays that need to be taken into account when length matching FMCW_CLKOUT and FMCW_SYNCOUT traces?

Many thanks,

James

  • +1
    TI__Expert 5621 points

    Hi James,

    I'm not sure where exactly you are measuring 17 and 13 mm. I'm measuring slightly higher, but you'll need to simulate the divider with the layer transitions along with the PCB material being used on HFSS to confirm the tolerable phase mismatch and the link budget. Regarding the question, please refer to the following app note page 2, second paragraph AWR2243 Cascade (Rev. B). 

    Regards,

    Aydin 

  • 0 in reply to Aydin Kiasat
    Prodigy 20 points

    Hi Aydin, thanks for your reply,

    I'm happy the 2x 20GHz outputs of the IC are phase matched now - thanks for that reference, I was just surprised that the feed lines to the Wilkinson splitters from the master AWR2243 on the board on layer 3 seemed such different lengths, and given they were on the same layer, surrounded by materials of the same dielectric properties. I'll assume this is compensated for with the structures on Top copper for now.

    Best regards,

    James