In an RFID system, cables act as a bridge between two pieces of equipment allowing for energy to flow from one to the other. The parts that attach to the equipment, the connectors and adapters, are small metallic components found on all coaxial cables, RFID readers, and antennas.
Six coaxial cable connector types are typically found in UHF RFID systems:
(See connectors and counterparts in Connecting Chart below.)
Coaxial connectors are described using type, gender, and polarity. Together, these three characteristics define the connector, as well as dictate to which type of connector each should attach. For example, if a connector is SMA Female (normal polarity), then it must attach to an SMA Male (normal polarity).
Type: RP-TNC, SMA, N-Type, TNC, RP-SMA, or BNC
Gender: Female/Jack or Male/Plug
Polarity: Normal Polarity or Reverse Polarity (RP)
Threading (Female vs. Male)
After determining the type of coaxial connector, the next step is to determine if it is Female/Jack or Male/Plug. The gender solely depends on whether the threading is on the outside of the connector or the inside. If the threading is on the outside, the connector is Female. If the threading is on the inside, the connector is Male. Female and Jack as well as Male and Plug can be used synonymously.
Female/Jack: Threading on the Outside
Male/Plug: Threading on the Inside
Center Pin (Normal vs. RP)
Next, determine if the polarity is normal or reversed. The polarity nomenclature depends on the gender, so whether the connector is Female/Jack or Male/Plug must be determined before moving forward. After factoring in gender, the location of the center pin is the distinguishing factor between normal and reversed polarity. The rule is as follows:
Normal Polarity: Female (outside threading), hole for Center Pin.
Male (inside threading), Center Pin
Reverse Polarity: Female (outside threading), Center Pin.
Male (inside threading), hole for Center Pin
The 3 Rules of Connecting
There are three simple rules for determining if coaxial connectors will join properly.
1. Similar Types Connect.
Example: SMA connects to an SMA, N-Type connects to an N-Type
2. Similar Polarities Connect.
Example: RP-TNC connects to an RP-TNC, SMA connects to an SMA
3. Opposite Genders/Threading Types Connect
Example: BNC Female connects to a BNC Male, RP-TNC Male connects to an RP-TNC Female
Larger, printable version available in A Guide to Cables, Connectors, and Adapters.