Design Of Single/Dual Circularly Polarized Slot Printed And Microstrip Antennas

As a key component of the wireless radio systems, the antenna has criticalinfluences on the performance of the system. For the purpose of flexible orientation ofboth the transmitting and receiving antennas without causing a severe polarizationmismatch, the circularly polarized (CP) antennas have aroused wide attention in thefields of radar, wireless communication and navigational systems. In this paper, themethods for broadening the bandwidth and radiating the CP wave are also introduced.Three wideband CP antennas are designed, including a wideband dual-CP microstrippatch antenna, two wideband CP slot antennas fed by microstrip-line and coplanarwaveguide (CPW) respectively. They are analyzed and optimized by the Ansoft HFSS13.0. The simulated and measured results show that the designed antennas have goodbroadband and single/dual CP radiation performances.Firstly, a broadband CP antenna with two slot-rings is presented. Two circularslot-rings are linked over the corner. By tuning the sizes of the slot-rings and thedistance between them, both the VSWR and the axial-radio bandwidths can beenhanced. The bandwidth is broadened by merging the two bands, which are generatedby the two slot-rings with different radius. The bandwidth meeting|S11|≤-10dB and3dB axial-ratio (AR) simultaneously is21.5%.Secondly, a CPW-fed broadband circularly slot printed antenna is presented. Theantenna ground is slotted with a circular aperture. By adjusting the lengths and widthsof two arms of the L-shaped orthogonal stubs and the disturbed stubs, the proposedantenna excites two orthogonal resonant modes with equal amplitudes and90°phasedifference for CP radiation. An antenna is fabricated based on simulations andoptimizations. The measured results show that the3dB axial ratio bandwidth with|S11|<-10dB is24%and the antenna has good performance on CP radiation.Finally, a broadband dual CP microstrip patch antenna has been simulated. Theantenna, which works from2.25GHz to2.75GHz, consists of an orthogonal couplingnetwork and a dual-fed microstrip patch antenna. The impedance bandwidth of theantenna is500MHz (20%) and the axial-radio is less than3dB. Left hand and righthand CP performances can be obtained by feeding from port1and2, respectively.Good directional radiation characteristics with less affection of cross polarization anddual-CP characteristics during working band can be obtained.