Chapter 7. Impedance Transformers

  1. Devendra K. Misra

Published Online: 25 AUG 2004

DOI: 10.1002/0471653764.ch7

Radio-Frequency and Microwave Communication Circuits: Analysis and Design, Second Edition

Radio-Frequency and Microwave Communication Circuits: Analysis and Design, Second Edition

How to Cite

Misra, D. K. (2004) Impedance Transformers, in Radio-Frequency and Microwave Communication Circuits: Analysis and Design, Second Edition, John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/0471653764.ch7

Author Information

  1. University of Wisconsin-Milwaukee, USA

Publication History

  1. Published Online: 25 AUG 2004
  2. Published Print: 17 AUG 2004

ISBN Information

Print ISBN: 9780471478737

Online ISBN: 9780471653769

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Keywords:

  • multisection quarter-wave impedance transformers;
  • binomial transformers;
  • Chebyshev transformers;
  • tapered transmission lines;
  • synthesis of transmission line tapers;
  • Bode–Fano constraints

Summary

This 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. The 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.