A novel uni-directional, off-axis CPW-fed, matched by unbalanced fork-stub, UWB ring slot antenna printed on single layer PCB with back plane

A rectangular ring slot antenna printed on a single layer substrate capable of providing: uni-omni directional radiation pattern (UODR), linear phase characteristic (LPC), matched impedance bandwidth (IBW) over 58% at -20 dB (VSWR<1.2) is presented. Optimized performances are obtained by using an unusual way of feeding, matching and tuning; the antenna is off-axis fed by CPW structure, matched and tuned by an asymmetric-and-unbalanced fork-stub element.