2 Replies Latest reply on Mar 1, 2016 5:52 PM by MichaelF_56

    Wideband Emissions During FCC Testing

      During FCC testing, it was discovered that there are wideband emissions around channel 36 (2402 MHz) for the 2.2.2 SDK build.

      The waveform vacillates between the wideband (~4Mhz) and normal bandwidth (~2MHz).

       

      It appears that the order of the test being sent to the module using the Bluetool has an impact on the modulation issue.

      1) If you do Set_tx_carrier_freq_arm in Bluetool (ch0, prsrb9, LE mod, 4dB power) without doing another test first, the wideband waveform is not seen:

      a.      For V2.2.2 you don’t get obvious shoulders (See blue line ignore green):

      222settx.jpg

      b.      For V2.2.0 you get shoulders but the higher frequency shoulder is not as sharp.

      220settx.jpg

       

      2) If  you do LE_Transmitter_test only , you get:

      a.      V2.2.2: Shoulders are present:

      222transmittest.jpg

      b.      V2.2.0: Shoulders are present, but high frequency shoulder is not as sharp

      220transmittest.jpg

       

      3) If you first do LE_Transmitter_Test then LE_Test_end then do Set_tx_carrier_freq_arm:

      a.      V2.2.2: No shoulder waveform is seen, but in about 1 minute, the very wide band waveform appears (green) and this vacillates back and forth 

      222wideband.jpg

      b.      V2.2.0: Shoulder waveform is seen, but in about 1 minute, the  very wide band waveform appears

      220wideband.jpg

       

      4) Doing a wide sweep of the advertising channels we see:

      a.      V2.2.2 - Way wider Ch37 than Ch38 and Ch 39 (disregard Wifi signal)

      222fullspectrum.jpg

      b.      V2.2.0 – Looks like the correct BW for all 3 channels

      220fullspectrum.jpg