A Novel UWB Quadrifilar Plannar Spiral Antenna

With the vast spread of the RFID applications in most field of life's, most researchers pays more attention to the most cheap but challenging technology in the RFID which is the chipless RFID. The challenges in such a technology stems from the need for a reader antenna that achieve an UWB operation, circular polarization, flat gain and a compact size. This is suitable for tags of either linear or circular orientations. This paper discusses the design, the simulation and the measurement of a quadrifilar spiral antenna with four-arms and six-turns that suits the RFID reader specifications. The antenna is fabricated over FR4 material of thickness 1.6 mm using the photolithographic process. The antenna arms are printed on one side of the substrate while the feeding coaxial connector is mounted on the other side without any ground planes. The radiation pattern and the polarization are controlled by adjusting the phase shift between the four arms. The four arms allow a total length less than the longest wavelength, so the antenna size is miniaturized to large extent. The fabricated antenna has a compact size, a high gain and an ultra-wide band (UWB) radiation as well as circularly polarized (CP) radiation. The antenna has wide bandwidth compared to the antennas in literatures. The antenna operates in the range from 1.2 GHz to 12.4 GHz. By comparing the simulated and the experimental results a very promising coincidence is noticed.