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CC1101 spuries

G.M.
Intellectual 285 points

Other Parts Discussed in Thread: CC1101

Greetings,

our company is developing a couple of products based respectively on

cc1111 and cc1101 chips.

At the moment we need to run EMI and Radio compatibility certification tests for ETSI.

Applicable norms are EN 300-220, EN 301-489-3.

Our application works with the following settings:

- +10 dB Radio power

- 250KBaud/s speed

-868.0-868.6 band

-GFSK modulation

 

We followed the reference design from ezChronos for the cc1111 based product and TI reference designs for antenna pcb for cc1101.

 

During the EMC radiated emission tests we found out the following

non-conformities:

For both cc1111 and cc1101:

Several over-the-limit emission peaks in the frequency bands adjacent to the 868.0-868.6 band.

 

For cc1101 only

Some spurious emission at 816.36, 764.52, 712, 660.12 .... (probably due to our layout)

 

Apparently the first of the two is due to the large emission envelope that spans far beyond the usable band (868.0-868.6). (Please see attached documents)

 

CC1101 setted with +10dBm output power, 250Kbps.

CC111 large emission envelop

Do you have any suggestion where I can try to fix in order to solve this issue?

BR,

 

Giordano

  • 0
    Prodigy 140 points

    Dear Giordano,

    you can find some suggestions on how to configure cc1101 to satisfy ETSI 300 220 in AN050.

    Notice that AN050 is outdated because it refers to ETSI 300 220 V2.1.1 while the current version is V2.3.1.

    The main differences with the previous release are 1) in the definition of the modulation BW and 2) the transient power requirements (significantly relaxed).

    I underline that from AN050 it seams that the maximum bit rate that can be used with cc1101 in the band 868.0-868.6 MHz is 175 kbit/s.

    Regards,

    Matteo

  • 0
    Prodigy 40 points

    I notice that the limit in the graph is the one regarding the en 550122/22 class B devices for EMC compatibility.

    It's likely that is the norm test that failed.

    Stefano

  • 0
    Intellectual 295 points

    Hi Giordana,

    I  know your post is over a year old but I am interested if you found a solution to the resonant peaks around 52 MHz apart near the fundamental frequency.  I am working on getting a CC1110 design through EMI testing at 915 MHz with the same modulation and baud rate as you were using (250 kBaud, GFSK).  I found through testing that our design has what looks to be resonant peaks that are about 52 MHz apart around the fundamental frequency just like you did at 816.36, 764.52, 712, 660.12 MHz frequencies.  Did you find a solution to knock the power down on these frequencies?  Did lowering the baud rate solve your issue?

    The spurious emissions we saw with vertical polarity were 816.36, 764.52, 712, and 660.12 MHz.  The emissions with horizontal polarity were 967.121, 914.881, 862.874, and 810.874 MHz.

    Kind regards,

    JD