Problem with ADRF6701

Hi ADI engineer:

  I'm using ADRF6701 in RFID application ,now i intend to use internal VCO generate modulator LO , i found there is a 714MHz frequency output when i only power on ADRF6701 but not start configure the register , when i configure the register , there is nothing frequency output (include the 714MHz), I think it must be the error of register , Attached   is my configuration and schematic , Could you help check it , it is confused with me . Thanks .

attachments.zip
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  • 0
    •  Analog Employees 
    on Dec 8, 2017 10:20 PM

    Hello a Customer

    First, I think 714MHz frequency output when powering on ADRF6701 will be from VCO and is not at a fixed frequency. It will be moving around(you can check it by reducing span of SA), called commonly a free-running frequency before locking by a fixed control voltage.

    It looks some mistakes at register settings. Can you double-check the register settings at INT, FRAC,MOD?

    1. INT(reg.0), Modulus(reg.1),FRAC(reg.2),

        Can you double-check values for them? Based on your information, it is 45 for INT, MOD=2, FRAC=270.

    •      INT should be in 75 ~115 range with 20MHz PFD Frequency(at your case) for 750 ~ 1150MHz LO range by internal PLL and VCO. 
    •      MOD is in 1 ~ 2047 range
    •       FRAC is in 0 ~ (MOD-1) ; it should be smaller than MOD

    Below is the screen shot of ADRF6701 SW (You can download it from the below link) that can be used to get the values for register settings also. You can see the Synth Form(right image) by clicking the number in RF section on main SW.

    (Link for ADRF670X SW : http://www.analog.com/en/products/rf-microwave/iq-modulators-demodulators/iq-modulators/adrf6701.html#product-evaluationkit)

    Thanks

    Tony

Reply
  • 0
    •  Analog Employees 
    on Dec 8, 2017 10:20 PM

    Hello a Customer

    First, I think 714MHz frequency output when powering on ADRF6701 will be from VCO and is not at a fixed frequency. It will be moving around(you can check it by reducing span of SA), called commonly a free-running frequency before locking by a fixed control voltage.

    It looks some mistakes at register settings. Can you double-check the register settings at INT, FRAC,MOD?

    1. INT(reg.0), Modulus(reg.1),FRAC(reg.2),

        Can you double-check values for them? Based on your information, it is 45 for INT, MOD=2, FRAC=270.

    •      INT should be in 75 ~115 range with 20MHz PFD Frequency(at your case) for 750 ~ 1150MHz LO range by internal PLL and VCO. 
    •      MOD is in 1 ~ 2047 range
    •       FRAC is in 0 ~ (MOD-1) ; it should be smaller than MOD

    Below is the screen shot of ADRF6701 SW (You can download it from the below link) that can be used to get the values for register settings also. You can see the Synth Form(right image) by clicking the number in RF section on main SW.

    (Link for ADRF670X SW : http://www.analog.com/en/products/rf-microwave/iq-modulators-demodulators/iq-modulators/adrf6701.html#product-evaluationkit)

    Thanks

    Tony

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