title: Antennas and Wave Propagation
author:  G.S.N. Raju 
description: <P> <b>Dr G. S. N.</b> Raju is Professor, Department of Electronics and Communication Engineering, College of Engineering, Andhra University, Visakhapatnam, India. A Ph.D from Indian Institute of Technology, Kharagpur, he has 24 years of experience in teaching and research at the undergraduate, postgraduate and Ph.D levels. His main areas of interest are electromagnetic field theory, antennas and wave propagation, radar and microwave communication, and bio- instrumentation. A Visiting Professor in the University of Karlsrube and Padeaborn, Germany in 1994, he is also the recipient of the State Best Teacher Award (1999) and the Best Researcher Award (1994) in Andhra Pradesh. He has published over 100 papers in international journals and proceedings of national and international conferences.</P>
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  CHAPTER 2 
   
  ANTENNA FUNDAMENTALS 
   
   
   
   
   
  In this chapter, the basic concept of an antenna is provided and its working is explained. 
  Next, some critical performance parameters of antennas are discussed. Finally, some common 
  types of antennas are introduced. 
   
  2.1 Introduction 
   
   
  Antennas are metallic structures designed for radiating and receiving electromagnetic 
  energy. An antenna acts as a transitional structure between the guiding device (e.g. waveguide, 
  transmission line) and the free space. The official IEEE definition of an antenna as given by 
  Stutzman and Thiele [4] follows the concept: “That part of a transmitting or receiving system 
  that is designed to radiate or receive electromagnetic waves”. 
   
  2.2 How an Antenna radiates 
   
   
  In order to know how an antenna radiates, let us first consider how radiation occurs. A 
  conducting wire radiates mainly because of time-varying current or an acceleration (or 
  deceleration) of charge. If there is n