Ultra-Wideband Bandpass Filters with Hybrid Microstrip Slotline Structures

Microstrip UWB filter with W-shaped slotline resonator

Li and Zhu [1] experimented with various microstrip structures to realize ultra-wideband (UWB) filters.  These structures typically include microstrip lines that couple with slots in a metallic ground plane, such as the one showed here.

Dimensions s and t were varied experimentally to optimize performance of the filter.  FEKO models were constructed for:

• s = 1.05 mm
  
• t = 1.1 mm

Standard Roger's RT/Duroid 6010 substrate specifications were used in the setup of the simulation:

• ε = 10.8
• h = 0.635 mm

FEKO's implementation of the planar Greens function features the ability to model the slots in the ground plane as magnetic triangles, which means that only the slots are meshed and not the ground plane itself, saving significantly on simulation resources.

S-parameters for UWB-filter simulated with FEKO's magnetic slots method

Surface currents on the UWB-filter at 7GHz