Electromagnetic Bandgap Structures (EBGSs) Assisted Microstrip Bandpass Filter

Abstract

In high performance of wireless communication and advanced modern technologies, the demand for large bandwidth, high efficiency radio frequency devices, ease of installation, low profile antennas with the microwave devices are required tremendously. To meet these requirements the new technique Electromagnetic Bandgap Structures (EBGSs) have been introduced as potential means of improving the performances of existing RF active and passive devices. EBGSs are periodic structures those exhibit distinct passband and stopband properties. These are the unique properties of this structure. The thesis concern the planner EBGS in forms of conventional circular, square, rectangular and dumbbell shaped defected ground structures (DGSs). The investigations into different types of EBGSs that yield better passband, return loss, insertion loss, low ripple and wider stopband have been carried out. The parametric study of different shaped EBGSs have been conducted with their inter element spacing, width, length and the size of the slots. From the investigation, it is clear that 1-D EBGS yield similar performance like 2-D EBGS. It is also found that dumbbell shaped DGS is more compact than the conventional EBGS. For conventional EBGS, it found that etching area is an important factor for producing stopband. In case of dumbbell shaped DGS, narrower slot and its position play important role to produce stopband. The novel design is used in asymmetric coupled line bandpass filters. It is found that EBGSs suppress second and third harmonics by about 40 dB. This illustrates the significance of EBGs in suppression of higher order harmonics of the bandpass filters. It has been found that the non - uniform distribution of EBGSs is more effective to suppress higher order harmonics than the conventional uniform EBGSs. Dumbbell shape DGSs are very effective for simultaneous suppression of both 2nd and 3rd harmonics due to their very wide stopband performances. This phenomenon of dumbbell shaped DGSs has been demonstrated in various designs of asymmetric coupled line bandpass filters.