Compact Spirograph Planar Monopole Antenna Covering C-/X-Band With Invariant Radiation Pattern Characteristics

This communication presents a novel compact planar monopole antenna configuration: the spirograph planar monopole antenna (SPMA) covering C-/X-Band (4-12 GHz). The antenna has an invariant omnidirectional radiation pattern across the frequency band with no multi-lobe effect and low cross-polarization. The SPMA radiating element size is less than λ/2 at the highest frequency of operation such that it can be used as a beam scanning array element. For the SPMA, it was found that increasing the number of points in the antenna shape miniaturizes the radiating element and increases the impedance bandwidth. A prototype SPMA was fabricated and measured for impedance and radiation performance.