Laird Technologies – S9028PCL12NF – 902-928MHz 9 dBi, LH Circular Polarization Patch Antenna, 12 coax, N-Female, RFID. UHF CIRCULARLY POLARIZED RFID ANTENNASUnless an RFID tag is located very close to a reader antenna, it is usually necessary to use circularly polarized (CP) reader antennas. In most RFID applications the orientation of the tags is random with respect to the reader antenna. Since tags are linearly polarized they would need to be exactly aligned (co-polarized) with a linearly polarized reader antenna for reading to take place successfully. Circularly polarized antennas do away with need to control the tags’ polarized antennas may be either left-hand (LHCP), or right-hand polarized (RHCP). Either type will work equally as well in the reading of RFID tags. The usefulness of deploying a mixture of LHCP and RHCP antennas occurs in situations where interference may be a problem. The signal from a LHCP antenna will not interfere with a RHCP antenna, and vice versa. Examples of this are when antennas connected to two different readers are co-located, or when a bi-static mode reader is used (in bi-static mode the reader uses separate transmitter and receiver antennas). Antennas are available in LHCP and RHCP antennas are weatherproof and UV resistant.