Novel microwave microstrip filters using photonic bandgap ground plane with fractal periodic pattern

Abstract

Photonic bandgap (PBG) structures with slots etched in their ground plane have been proposed recently as a good choice for the design of printed microwave filters, absorbers, reflectors, and antennas for many modern applications. In the present work, a microstrip PBG filter was designed to operate as a multifrequency bandstop filter. The conventional profile of the slot patterns used in previous works was either discrete (with circles), continuous sinusoidal, or triangular. These geometries guide the structure to operate as a single wideband filter. In this work, a different periodic pattern of slots is introduced. The configuration is designed using the fractal technique. The self‐similarity of the fractal geometry is found to excite the PBG structure to act as a wide stop‐band filter in more than one frequency region. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 273–276, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20443

Microstrip filter with H-shaped fractal

“…2,3 The fractal geometry concept can also be applied to the design of microstrip filters. 4,5 As a consequence multiband behavior can be achieved.…”

“…One interesting example is the tuning of the second and third harmonics in power amplifiers 10 or oscillators. In the previous design, fractal 4 or continuous profile etched in the ground plane was adopted to reject multiple frequency band. As the ground plane is perforated, the substrate must be suspended so that the circuits cannot be fixed on a metal base for mechanic robustness.…”

1D Koch fractal electromagnetic bandgap microstrip structures with r/a ratios higher than 0.5

“…To solve this limitation, it is necessary to use a geometrical shape different from the above periodic patterns. Recently, fractal techniques have been used for the design of antennas and filters [9–15]. These fractal structures have a self‐similar shape, which can be useful for the development of new patterns.…”

Photonic crystal multi-channel drop filters based on microstrip lines

“…The introduction of a periodic structure in the strip line can create PBGs for the guiding modes propagating along the strip line. These microstrip PBG structures have been used for various purposes, such as improving the performance of microwave antennas [15,16] and filters [17], increasing the output power of microwave amplifiers [18] and suppressing higher order harmonics generated by resonators [19].…”