Lossy Transmission Lines Revisited

Abstract

Two less-known facts about lossy transmission lines are presented here. First, it is impossible to achieve perfect matching, i.e. the reflection coefficient, Γ, cannot vanish at any frequency. Second, for such lines, the magnitude of Γ may show maxima and minima, but the overall envelope will only decay monotonically with frequency.

KEYWORDS:

• Transmission lines
• Lossy lines
• Reflection coefficient
• Matching
• Characteristic impedance

ACKNOWLEDGEMENT

The author thanks Sumantra Dutta Roy for his help in the preparation of this article.

Additional information

Notes on contributors

S. C. Dutta Roy

Suhash Chandra Dutta Roy earned his BSc (Hons) degree in physics in 1956, MSc (Tech) degree in radio physics and electronics in 1959 and DPhil degree for research on network theory and solid state circuits in 1965, all from the University of Calcutta. He served the River Research Institute, West Bengal, as research officer for 2 years, the University of Kalyani as lecturer for 4 years, and the University of Minnesota, USA, as assistant professor for 3 years, before joining the Indian Institute of Technology Delhi (IITD) as associate professor in 1968. He was promoted to a full professorship in 1970. He served the IITD for more than four decades in various capacities – as head of the department and dean of undergraduate studies, and after superannuation in 1998, as IITD Emeritus Fellow, Indian National Science Academy (INSA) Senior Scientist and INSA Honorary Scientist. Currently, he holds the title of INSA Emeritus Scientist. He has held visiting professorships at the University of Leeds, UK, and the Iowa State University, USA, for 1 year each, on sabbatical leave.

He still maintains an active research interest in circuits, systems and signal processing, and still publishes research papers.

Dutta Roy is the recipient of many awards and recognitions, including the Shanti Swarup Bhatnagar Prize, Vikram Sarabhai Award, Pandit Jawaharlal Nehru Award, Fellowship of the IEEE and of all the national academies in science and engineering, and Distinguished Fellowship of the IETE. He has recently been named as the winner of the IEEE Signal Processing Society Distinguished Teacher for the year 2022.

What Professor Dutta Roy values most is the love and appreciation of his large number of direct as well as virtual (through NPTEL lectures on the internet) students and professional colleagues spread throughout the world. Besides the subjects of his research interests, he maintains a deep interest in Indian Classical Music.