New Technique for Improving Modal Filter Performance by Using an
Electromagnetic Absorber
Abstract
This paper presents a novel technique for improving the performance of a
modal filter by using an electromagnetic absorber. The study considers a
two-conductor modal filter based on a microstrip transmission line. The
authors analyzed the effect of the absorber on the MF performance in
suppressing conducted and radiated interferences (in the near and far
fields). The frequency characteristics of the device were then redefined
into the time characteristics in the Advanced Design System. As an
excitation, the authors used an ultra-wideband interference pulse of 155
ps (at 0.5 level) and then employed N-norms to estimate and characterize
the decomposed pulses. The results show that the use of the absorber can
significantly improve the attenuation of the ultra-wideband
interference. It was experimentally demonstrated that the value of N1
decreased by a factor of 4.31, N2 – by a factor of 6.52, N5 – by a
factor of 1.87. In terms of radiated interference in the near field, the
improvement in attenuation of each norm achieved at least 2.81 times.
The analysis of the characteristics in the far field showed that the use
of the electromagnetic absorber allows reducing the transmission
coefficient on average by 2.25 times at a distance of 1 m. To validate
the measurement results, the electrodynamic simulation of the modal
filter characteristics in the frequency range up to 6 GHz was carried
out and showed full agreement with the experimental results.