The 1×1 annular ring: Bandwidth enhancement of microstrip asymmetric couple-line bandpass filter with superior matching and lower insertion loss

Electromagnetic Band Gap (EBG) structures which is an exclusive innovation in modern microwave design arena by reason of their high potential and less intricacy of designing in the microwave and millimeter-wave integrated circuits. This paper examines the relationship between the filling factor (FF) of the annular ring structure on couple-line and capacitive coupling for improving the performance. A number of methods, method of moments (MOM) for numerical analysis and uniform distribution with constant aspect ratio (AR) for designing the circuit are used. In like manner, the parametric comparison has been demonstrated considering selectivity, 3-dB bandwidth (3-dB BW), insertion loss and return loss in the passband. Consequently, not only a very wide passband upto 49% increment but also a return loss upto 65 dB which illustrates great matching are achieved. Although, the insertion loss is less than 0.2 dB in the passband, but the selectivity shrinks with expanding bandwidth. In short, remodeling of the selectivity can be done by appropriately choosing the filling factor for annular ring pattern on the couple-line as well as on the transmission line.