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CC2650 Bluetooth only works in 2-3 meters ?

Fu Luo
Intellectual 440 points
Other Parts Discussed in Thread: CC2650, CC2541

Hi TI Team

I am using CC2650 (5x5mm) as the MCU in my project. The way I designed the RF part showing as below:

Balun: LFB182G45BG5D920TEMP from Murata (refer to CC2650-MurBal Reference Design)

Antenna: 2450AT42A100, 2.4GHz Antenna from Johanson Technology (refer to CC2541 stamp reference design.)

Trace from the balun output (unbalance port) to the antenna’s feeding point is 50 ohm (specified when manufacturing my board).

The big problem here is: when I use TI sensortag App to check the Bluetooth signal, the signal will be disconnected in only 3 meters’ distance (nothing blocks it in between my phone and my PCB)!

BLE supposes to support 10-15 meters connection. 

I attached my PC board layout. 

U1 is the MCU CC2650, U3 is the balun. R1A is 0 ohm, C1A and C2A are DNM (do not mount).

Could anyone give me some suggestions regarding to debug this Bluetooth issue? Where could possibly be the issue? I thought I already took care of all the matching here, from MCU’s RF_N and RF_P to Balun, Balun to trace, trace to Antenna. They are all 50 ohm matching. What else could be causing this critical failure?

I am looking forward to hearing anything back as soon as possible.

Thanks a lot.

Best regards

Fu