An Ultra Wideband Printed Helical Antenna with Low Profile

This paper presents a compact ultra-wideband strip helical antenna with circular polarization. In order to achieve circular polarization and impedance matching with helix of 1.1 turns, the helix is made of uniform metallic strip instead of traditional metallic wire. Considering the convenience in manufacture, the uniform metallic strip is firstly printed on a substrate with epsilon(r) = 2.2, h = 0.5 mm, then the substrate is rolled into the shape of cylinder such that a helix is formed. A 50 Omega coaxial cable is directly connected to the helix without an impedance matching section. The ground plane, which is printed on another substrate with epsilon(r) = 2.2, h = 3 mm, is placed under the helix. To demonstrate this method, a 1.1-turns helical antenna is fabricated, measured and analyzed. Measured results show that the proposed antenna has an impedance bandwidth (S-11 <= -10 dB) of more than 70%, and an axial ratio (AR) bandwidth (AR <= 3 dB) of 55%. These wideband circular polarized (CP) characteristics indicate that the proposed antenna has a potential application in wide-band/multi-band wireless communications.