The RP-SMA (Reverse Polarity SMA) connector series is a variant of the standard SMA connector used primarily in high-frequency RF systems. The distinctive feature of the RP-SMA connector is its reversed gender interfaces: the male connector has a recessed inner receptacle instead of a pin, and the female connector has a protruding inner pin instead of a receptacle.
The reversed polarity centre conductor was developed mainly as a safety and regulatory measure to prevent the accidental connection of WiFi antennas to non-WiFi devices, thereby avoiding potential device damage or regulatory violations.
The RP-SMA connector is identified by its small threaded interface, similar to the standard SMA connector, but with the gender of the pin and receptacle switched. Although an RP-SMA and SMA connector can be physically mated, the connection would not function electrically due to this difference.