On the Novel Approach to Parallel Coupled-Line Bandpass Filters that Have Diverse Wavelenght Impedance Scaling I/O Transformers

Abstract

This paper presents a practical novel approach of realization of parallel coupled-line band-pass filters in the scope of expanding their capabilities by using various electrical-length I/O transformers. Resonators have properties of half-wavelength or full-wavelength, with steps in half of length. This approach allows the filters to be full-differently impedance-scaled. In particular, it was important to obtain arbitrary microwave filters of narrow or moderate bandwidths for TEM rods' diameters or strip width. This is the first ever in-depth study of the design with impedance-scaling levels with various I/O transformers. The method of synthesis and transformations provides accurate results and agreements in bands, and impedance level with theoretical filter functions. Several designs and one experiment confirm and verify the extended filter design. There are many filter transformation possibilities and this paper presents more thoroughly only two selected ones.