harmonics don't go down with carrier power on cc1101

Please send schematics and layout.

Regards,
Richard

Hi Richard,

The schmatics and layout are available at circuithub.com/.../atlas-tag-v1_7
If you want them in another format, let me know how (I can upload or email the Eagle files).

Thanks, Sivan

DN025 SWRC112 CC1101EM_JTI_Balun_868_915_MHz_1_0.zip

Hi,

Two main points in the layout:

1. The GND around the IPC does not look too good. Need more GND vias.

2. The power routing to the chip should go to the decoupling caps first and then to the chip. When the decoupling cap is placed far away from the chip, the GND return loop currents become large and these become unwanted radiators.

Are you using the 0433BM15A0001 balun ?

If the vias are too far from the IPC then the unwanted emissions will increase.

Attached the board design used for the evaluation of the JTI IPC at 433 MHz.

Regards,

   Richard

Yes, this is the balun+filter unit that I am using.

I will try to improve the layout according to your suggestions (what is IPC?). I was aware of point #2 and tried to follow it, but perhaps I did not do it so well. Thanks for the hints.

However, I asked about something else really. I did not ask why the harmonics are at that level when I transmit at 10dBm. What surprized me is that when I programmed PATABLE to drop the signal's power to 0dBm, the 434 fundamental signal did go down by 10dB to 0dBm, but the harmonics did not. They stayed about the same, perhaps even rose a bit.

Is this normal for the CC1101? It seems that at low power, the PA stage becomes more nonlinear than at full power.

Thanks, Sivan