CC1200: Harmonics

We are not using the recommended matching n/w available with the reference schematic design.

We have bypassed the output with 0-ohm resistor.

Meaning that you have just attached the antenna to the antenna without any matching/ filtering? 

Is this 15.247/ 15.249, target output power? 

Its 15.249 , 903,916 and 927 MHz band.

Yes, we are connecting the antenna directly without any matching /filtering.

We are meeting the Compliance requirement with conducted emission test but failing in radiation emissions 3rd harmonics of 903 and 927 MHz are crossing the limit line. Attached Plot for your ref.

We are targeting 10 dBm o/p power.

FCC 15.249 has -1.2 dBm as max output power? 

The CC1200 has never been designed or tested with only an antenna connected to the PA output. I would recommend to include some match/ filtering on the PA output. Is this a TX only application? 

No its a Tx and Rx Application.

I am keeping a 1.5 GHz LPF filter before the antenna, Will this work to reduce the emissions ?

FCC conducted limit is 40 dbm.

We have configured the chip for 10 dBm O/p.

Sorry 30 dBm

30 dBm is FCC 15.247. FCC 15.249 is -1.2 dBm max. 

If you want a performance that is according to the datasheet you should follow the reference design. 

How are you connecting the LNA pins to the antenna?

We are following the exact reference schematic only differenece we have removed the matching N/W suggested.

As that was giving more loss.

So we bypassed this with 0 ohm short to connect with U.fL connector.

From your first post I got the impression that the PA pin was connected directly to the antenna. Also in the reference design I normally refer to the output of the T filter is connected directly to the SMA, see https://www.ti.com/lit/pdf/tidr180. The schematic snippet is useful since then I'm more sure how you use the chip.

- The pin labeled RF in your schematic: If I understand you correctly this is connected directly to the SMA?

- Could you give the output power you see conducted for the fundamental, 2. harmonic and 3. harmonic?  

- What type of antenna do you use? 

- For the 3. harmonic, the actual limit here will be dependent on the duty cycle of the system, if you have a low duty cycle the limit can be relaxed, see FCC 15.35c. 

We are using 40 % Duty cycle in Packet transmission mode,

We use below the attached antenna

40 % should give a correction factor of 8 dB if I'm not mistaken. I haven't calculated if this enough to pass. It looks like the lab you are using haven't taken this factor into account, please consult with the first before we start looking into other options.