Compact printed quadrifilar helix antenna for universal RFID hand-held reader

• Published in: Journal of electromagnetic waves and applications Vol. 29; no. 7; pp. 891 - 904
• Main Authors: Chiu, Chien-Wen, Ou, Chen-An, Wang, Hwang-Cheng
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 03.05.2015
• Subjects: circularly polarized antenna; miniaturized antenna design; printed quadrifilar helix antenna (PQHA); quadrifilar helix antenna (QHA); UHF RFID reader
• ISSN: 0920-5071; 1569-3937
• DOI: 10.1080/09205071.2015.1026407

This paper presents a compact printed quadrifilar helix antenna (PQHA) for portable UHF RFID reader applications. The circularly polarized PQHA is fed by a feeding network with quadrature-phase and equal amplitude output signals. The quadrature-phase feeding network is composed of a 180° power splitter and two wideband quadrature hybrid couplers implemented by lumped-element circuits. The miniaturized antenna is a one-wavelength resonance type and can preserve high antenna gain. Moreover, the bandwidths of impedance and axial ratio cover the global UHF RFID band (860-960 MHz). The measured impedance bandwidth is about 34.1% and the axial ratio bandwidth covers 700-1,000 MHz. The measured maximum gain is 5.8 dBic and the 3-dB beamwidth is 168°. The height of the entire system is only 79 mm, the radius is 35 mm, and the FR4 substrate for the feeding network is only 80 × 80 × 1.6 mm 3 . The proposed antenna is suitable for handheld UHF RFID reader applications.