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IWR1843: spurious emission

Chenglin Cui
Prodigy 80 points
Part Number: IWR1843
Other Parts Discussed in Thread: AWR1843BOOST

Hello,

We build our board using IWR1843 chip and found radiated spurious emission at around 65GHz.

The chirp setting is 76~76.25GHz and the spurious signal is around 65.76~ 66GHz as shown below.

When I shift the chirp frequency, the spurious signal changes by the same amount.

I measured with 50GHz spectrum analyzer + harmonic mixer and 110GHz UXA analyzer, the signal is same in both case. 

Here are my questions.

a) I`d like to know how this frequency component comes out, please tell me possible reasons.    

b) I need to eliminate this signal or at least reduce 15dB to pass certificate test. Is there any possible solutions?

I`d really appreciate it if you could give me answers or advises as soon as possible.

Best regards,

Chenglin Cui  

  • 0
    TI__Mastermind 30065 points

    Hello Chenglin,

    What certification are you failing?

    We have passed EU RED testing on the AWR1843BOOST, which tested for unwanted emissions between 40GHz - 162GHz, and there were no unwanted emissions in the frequency range that you are seeing this emission. I have attached the report for your reference, see page 55 for reference.

    12554995-E2V2 EN 302 264 v2.1.1 AWR1843 Series Final Report.pdf

    Regards,

    Adrian

  • 0
    TI__Mastermind 30065 points

    Hello Chenglin,

    Can you please confirm the following:

         1. Is OSC-CLK port enabled? If so, could they check with it’s in the disabled state?

         2. If OSC-CLK port is disabled: Could they do a ramp from 80-80.25G and report spurious emission behavior?

    Regards,

    Adrian

  • 0 in reply to aozer
    Prodigy 80 points

    Hello,

    Sorry for the late reply, i took some time to do the test. 

    It is EN 301 091 that we are testing.

    The OSC CLK was enabled. I disabled it and ramp from 76.4-76.65 and 80-80.25. In both case I observed the spurious emission. We are still working on it.

    Regards,

    Chenglin

  • 0 in reply to Chenglin Cui
    TI__Mastermind 30065 points

    Hello Chenglin,

    We also have the passing EN 301 091 on AWR1843BOOST for reference, in this report we also do not have any unwanted emissions around 60-90GHz.

    12554995-E1V2 EN 301 091 AWR1843 Series Final Report.pdf

    It is hard to tell from the plots, was there any change in frequency of the unwanted emission when you changed the TX output frequency? If you change the TX output power, does the emissions level change correspondingly?

    Our characterization team believes this is a measurement artifact as they have seen similar issues like this in the past with Keysight downconverters and signal analyzers. Do you happen to have access to a suitable R&S analyzer like an FSW85?

    Regards,

    Adrian 

  • 0 in reply to aozer
    Prodigy 80 points

    Hello Adrian,

    The unwanted emission changes from 66 to 70G as the output frequency changes from 76 to 80G.

    The power level also changes as the Tx power changes.

    Could you tell me how did you solve the similar issue with Keysight equipment?

    Regards,

    Chenglin