Enhanced performance of an aperture-coupled rectangular microstrip antenna on a simplified unipolar compact photonic band gap (UC-PBG) structure

Recently, the concepts of photonic band gap (PBG) material and unipolar compact photonic band gap (UC-PBG) structure have been proposed by several researchers for improved performance of microstrip antennas and microwave circuits. When etched on high dielectric constant substrate materials they suppress surface waves. The photonic band gap (PBG) substrate normally has periodic air columns micro-machined in the substrate material. However, in the UC-PBG case, a periodic metallic pattern is etched on a grounded dielectric substrate. The metallic pattern consists of square pads separated by capacitive gaps and narrow lines connecting adjacent cells, thereby, creating strong LC coupling. The effect is manifested by a reduced guided wavelength of the propagating modes, and, therefore, reduced lattice period of the UC-PBG pattern. However, the unit cell for creating such a UC-PBG structure seems complex in design and uses more metal or copper area which may increase the cost of production. The authors propose a simpler UC-PBG unit cell design. Its effect on the impedance bandwidth, gain and cross-polarization level performance on an aperture-coupled rectangular microstrip antenna is discussed. The simulation results are reported.