Synthesis of cascaded N-tuplet filters


Yildirim N., Sen O., Sen Y.

5th International Conference on Telecommunications in Modern Satellite, Cable and Broadcasting Service, Nish, Serbia And Montenegro, 19 - 21 September 2001, pp.153-162 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Doi Number: 10.1109/telsks.2001.954866
  • City: Nish
  • Country: Serbia And Montenegro
  • Page Numbers: pp.153-162

Abstract

In the theory of Darlington type filter synthesis extraction of transmission zero sections one by one, leading to a cascade of Darlington-A, B, C, D and Brune sections bears serious limitations like numerical accuracy problems, negative and/or extreme element values or impractical topologies or Darlington-C-D and Brune sections. In this paper all such problems are evaded/eased by extracting the transmission zeros as groups to form circuit sections which are readily convertible to multiple coupled resonator forms. In this approach, transmission zeros at s=0 and s=infinity are extracted as groups to form doublets of resonators, the jomega-axis and sigma-axis transmission zeros are extracted as groups to form triplets of resonators, pairs of jomega-axis and sigma-axis transmission zeros and complex transmission zeros are extracted as groups to form quadruplets of resonators, etc. The classical element extraction procedure in transformed frequency domain is revised to cover extraction of complex transmission zeros as forth order section by zero shifting from both s=0 and s=infinity leading to realisation as a quadruplet of resonators. Thus, the theory of cascade synthesis is generalised to include cascaded doublets, triplets, quadruplets and other N-tuplets of resonators as building blocks. It is found out that the limitations due to usual numerical accuracy problems are also reduced a lot and the resulting element value spreads can be controlled to avoid extreme values.