International Journal of Infrared and Millimeter Waves, Vol. 20, No. 6, 1999 BRAGG REFLECTORS AND RESONATORS IN MICROSTRIP TECHNOLOGY BASED ON ELECTROMAGNETIC CRYSTAL STRUCTURES Txema Lopetegi, Francisco Falcone, and Mario Sorolla Microwave and Millimeter Wave Group, Department of Electrical Engineering Public University of Navarre, Campus Arrosadia s/n 31006 Pamplona, Navarra, Spain Tel: +34 948 169324 Fax: +34 948 169720, E-mail: mario@upna.es Received March 19, 1999 Abstract Recently, new promising two-dimensional (2-D) Photonic Bandgap Structures (PBG), or more properly Electromagnetic Crystal Structures, for microstrip lines have been proposed. In this paper, we analyze these structures in a manner like a Bragg reflector in optical wavelengths. Joining two of such Bragg like reflectors by means of a conventional microstrip transmission line allows one to design Bragg Resonators. The 2-D periodic pattern of the electromagnetic crystal structure is implemented with circles etched in the ground plane of the microstrip line by means of a numerical milling machine. Simulations have been performed by using HP™ Momentum and MDS software, and in accordance with the measurements give, for the Electromagnetic Crystal Structures, new promising potential applications both in microwave and millimeter wave integrated circuits, and also in the experimentation of expensive short wavelength (including photonic) devices by using simpler and cheaper microwave down scaling. Key Words - Bragg Reflector and Resonator, Photonic Bandgap (PBG), Electromagnetic Crystal Structures, Microstrip Technology. 1. Introduction In recent years there has emerged the requirement to employ broadband structures where the use of local elements for tuning and matching such as slots, diaphragms, stubs, etc. is not reasonable. Instead, distributed elements are used, in which longitudinal dimensions are greater than transversal ones, obtaining better frequency performance. Photonic Band Gap (PBG) structures can be considered in some sense under this classification. These PBG's, or more rigorously for the microwave and millimeter wave region, Electromagnetic Crystals are periodic structures where propagation of electromagnetic waves is not allowed in some frequency bands or directions [1]. Primary research on PBG was realized in the optical frequency bands [2]. One precedent of it was the study of the stop-band reported in holler liquid crystals [31; 1091 0195-9271/99/0600-1091$16.00/0 C 1999 Plenum Publishing Corporation