Dual circular polarization of tilted beam by a single arm rectangular spiral antenna

A single-arm rectangular spiral antenna has been investigated to obtain dual circular polarization of tilted beam. The proposed rectangular spiral antenna is printed on a finite size dielectric substrate (epsilon(r)=3.27) backed by a finite size-conducting plane. Spiral arm length (L) is varied from L=0.95lambda(o) to L=4.06lambda(o) to choose the length that yields the proper axial ratio and gain. L is chosen to be two values: L-1=1.05lambda(o). and L-2=3.35lambda(o). L-1 radiates axial beam and L-2 radiates tilted beam. Spiral radiates right hand circular polarization (RHCP) in its axial beam (L-1=1.05lambda(o)) due to winding sense. In addition, spiral radiates dual circular polarization (RHCP and LHCP) at tilted beam (L-2==3.35lambda(o)) in one antenna element.