WL1835MOD: External Antenna with UFL Connector and on-board Chip Antenna

Hi Bhaskar,

Yes your fried is correct. In the RF domain, you cannot have 2 antennas that are connected to the same node. If you want the RF signal to go to the chip antenna, then you need to DNP (do not populate) C7. If you want to send the signal to the U.FL connector, then you need to DNP C8.

Think of it as follows. At 2.4GHz, the impedance should be match to 50 ohms. So looking out of pin 32, with only one path connected it will see 50 ohms. However if you have both paths connected, you will see 2 50 ohm paths in parallel, thus giving an overall impedance of 25 ohms! Thus a mismatch in impedances that will cause lower output power, not to mentions severe receive issues!

Hope this helps.

Thans,
Riz