DGS based legendre low-pass filters for RF/Microwave

Ashwani Kumar, A. K. Verma, Nainu P. Chaudhari

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


The Legendre group of lowpass filters are designed and compared against several known types of filters at fc3dB = 2.5GHz in lumped elements, microstrip and DGS environment. In microstrip format the Legendre Polynomial Product (LPP)-312 and 213 filters have reduced group delay variation in the passband, sharper cut-off and wider impedance matching BW. In the DGS format the measured selectivity of Legendre, LPP-312 and LPP-213 lowpass filters are 28.3dB/GHz, 18.8B/GHz and 18.2B/GHz. Their 20dB rejection BW (RBW) are 6.0 GHz, 7.7GHz and 7.9 GHz; it covers 20dB rejection up to 4fc-5f c in the stopband. The LPP-213 has better than 15dB impedance matching BW (94%) and more than 20dB rejection BW (7.3GHz).

Original languageEnglish
Pages (from-to)80-93
Number of pages14
JournalWSEAS Transactions on Communications
Publication statusPublished - 2014
Externally publishedYes


  • Defected Ground Structure (DGS)
  • Group delay (GD)
  • Legendre LPF
  • Low pass Filter (LPF)


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