Modern Antennas2nd-2005

Contents List of contributors xvi Foreword xvii Acknowledgements xx Electromagnetism and antennas – a historical perspective 1 1 Fundamentals of electromagnetism 7 1.1 Maxwell’s equations 7 1.1.1 Maxwell’s equations in an arbitrary medium 7 1.1.2 Linear media 10 1.1.3 Conducting media 12 1.1.4 Reciprocity theorem 14 1.2 Power and energy 15 1.2.1 Power volume densities 15 1.2.2 Energy volume densities 16 1.2.3 Poynting vector and power 17 1.3 Plane waves in linear media 18 1.3.1 Plane waves in an isotropic linear medium 18 1.3.2 Skin effect 24 Further reading 26 Exercises 27 2 Radiation 31 2.1 Plane wave spectrum 32 2.1.1 Spectral domain 32 2.1.2 Electromagnetic field in a semi-infinite space with no sources 34 2.1.3 The far field 39 2.2 Kirchhoff’s formulation 44 2.2.1 Green’s identity and Green’s functions 44 2.2.2 Kirchhoff’s integral formulation 46 2.2.3 Plane wave spectrum and Kirchhoff’s formulation 48 Further reading 49 Exercises 50 3 Antennas in transmission 53 3.1 Far field radiation 54 3.1.1 Vector characteristic of the radiation from the antenna 54 3.1.2 Translation theorem 55 3.1.3 Application: radiation produced by an arbitrary current 55 3.1.4 Radiated power 58 3.2 Field radiated from an antenna 59 3.2.1 Elementary dipoles 59 3.2.2 Plane-aperture radiation 62 3.3 Directivity, gain, radiation pattern 66 3.3.1 Radiated power 66 3.3.2 Directivity 67 3.3.3 Gain 68 3.3.4 Radiation pattern 70 3.3.5 Input impedance 72 Further reading 73 Exercises 74 4 Receiving antennas 79 4.1 Antenna reciprocity theorem 79 4.1.1 Reciprocity theorem applied to a source-free closed surface 79 4.1.2 Relation between the field on transmit and the field on receive 83 4.2 Antenna effective receiving area 84 4.2.1 Definition 84 4.2.2 Relationship between gain and effective receiving area 85 4.3 Energy transmission between two antennas 86 4.3.1 The Friis transmission formula 86 4.3.2 Radar equation 87 4.3.3 Antenna Radar Cross Section (RCS) 89 4.4 Antenna behaviour in the presence of