Wideband Frequency-Reconfigurable Spirograph Planar Monopole Antenna (SPMA) Operating in the UHF Band

A frequency-reconfigurable spirograph planar monopole antenna (SPMA) operating in the ultrahigh frequency (UHF) band using RF p-i-n diodes is presented, including experimental verification. The radiating element is compact (0.53λ at 3.1 GHz) such that it can be used as an array element. It has three measured frequency bands with VSWR <;2: case 1, 2.17-3.36 GHz (43.0% impedance bandwidth); case 2, 1.21-2.50 GHz (69.5%); and case 3, 1.07-2.92 GHz (92.7%). Cases 1 and 2 provide contiguous coverage, and case 3 covers almost the entire range of cases 1 and 2. Thus, this antenna provides continuous coverage for 1.07-3.36 GHz (103.4%). This antenna has acceptable omnidirectional radiation patterns with relatively low cross polarization.