CC2640R2F: Load Impedance Mismatch

Mark Ackerson

Part Number: CC2640R2F

How much is the CC2640R2F efficiency affected by the load impedance missmatch?

To be specific, customer has an antenna with Return Loss around 7 dB (Antenna Impedance as measured by the Network Analyzer: 21 – j6 Ohms). I understand that the CC2640R2F amplifiers are going to have their efficiency dropped due to the loading, Probably, the effect is not symmetric, as the receiver LNA is a different class than the transmitter power amplifier.

My question: The RL of the antenna causes transmit power loss around 1 dB, and assuming 2 dB loss on the RF path and Balun, as the total radiated power of the system is around – 7 dBm, is it possible that the missmatch is causing the 4 dB drop?

Thanks,
Mark

over 7 years ago

0 Fredrik K over 7 years ago

TI__Guru** 106705 points

Hi Mark,

The datasheet numbers for the CC2640R2F are measured at the antenna feed point on the EVM. If the customer has implemented the balun and RF filter/match as in the reference design, the 7 dB loss is caused by antenna mismatch and efficiency.

A start here would be to do a conducted measurement at the antenna feed point (with antenna and antenna matching disconnected) to verify the conducted power.

Regards,
Fredrik

0 Mark Ackerson over 7 years ago in reply to Fredrik K

TI__Genius 10190 points

Hi Fredrik,

The conducted measurements with a UFL cable at the Balun output are good as compared to the selected output power of the CC2640R2F. Thus, we conclude that the antenna miss-match loss and efficiency has dropped due to the load impedance. Would you agree?

Thanks for the support.

Regards,
Mark

0 Fredrik K over 7 years ago in reply to Mark Ackerson

TI__Guru** 106705 points

Hi Mark,

Yes, it sounds like the antenna mismatch causes the drop in TRP.

Regards,
Fredrik

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CC2640R2F: Load Impedance Mismatch