UHF RFID Antennas - VI - Quadrifilar antenna (Part I)
Hey there folks! Today I'm heading back to the RFID reader antennas topic. This time, I'm covering another typical antenna found in these readers, which is the quadrifilar antenna. In this particular case, a printed implementation of the quadrifilar antenna. These antennas are composed of four arms, either monopoles or PIFA type elements, where each of the elements is fed with a 90ยบ phase delay in between in order to create a circularly polarized radiation. Another common place for quadrifilar antennas is the helix type antennas used for VHF and UHF band communications and GNSS applications. These are very popular among HAMs and also some commercial applications. Here's some examples: