Chapter 6. Impedance Transformers

  1. Devendra K. Misra Ph.D.

Published Online: 25 MAR 2002

DOI: 10.1002/0471224359.ch6

Radio-Frequency and Microwave Communication Circuits: Analysis and Design

Radio-Frequency and Microwave Communication Circuits: Analysis and Design

How to Cite

Misra, D. K. (2001) Impedance Transformers, in Radio-Frequency and Microwave Communication Circuits: Analysis and Design, John Wiley & Sons, Inc., New York, USA. doi: 10.1002/0471224359.ch6

Author Information

  1. Department of Electrical Engineering and Computer Science, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin, USA

Publication History

  1. Published Online: 25 MAR 2002
  2. Published Print: 1 MAR 2001

ISBN Information

Print ISBN: 9780471412533

Online ISBN: 9780471224358

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Keywords:

  • single-section quarter-wave transformer;
  • multi-section quarter-wave transformers;
  • uniformly distributed reflection coefficients;
  • binomial transformers;
  • Chebyshev polynomials;
  • Chebyshev transformers;
  • transmission line tapers;
  • Bode–Fano constraints

Summary

The chapter begins with the single-section impedance transformer that provides perfect matching at a single frequency. Matching bandwidth can be increased at the cost of a higher reflection coefficient. This concept is used to design multisection transformers. Characteristic impedance of each section is controlled to obtain the desired pass-band response. Multisection binomial transformers exhibit almost flat reflection coefficient about the center frequency and increase gradually on either side. A wider bandwidth is achieved with an increased number of quarter-wave sections. Chebyshev transformers can provide even wider bandwidth with the same number of sections but the reflection coefficient exhibits ripples in its pass-band. This chapter includes a procedure to design these multisection transformers as well as transmission line tapers. The chapter concludes with a brief discussion on the Bode–Fano constraints that provide an insight into the trade-off between the bandwidth and allowed reflection coefficient.