EETimes has posted chapters 3 and 4 from the book Antennas: Fundamentals, Design, Measurement (Third Edition). There is a little more math than ham radio operators are generally used to, but the material is useful and interesting, if you can plow through it. Here is the available material:
Chapter 3: Antenna Parameters
- Sections 3.1 Antenna Structures; and 3.2 Radiation Pattern.
- Sections 3.3 Directivity and Gain; 3.4 Effective Area and Friis Transmission Equation; 3.5 Beamwidth; 3.6 Minor Lobe; and 3.7 Radiation Resistance and Efficiency.
- Sections 3.8 Input Impedance; 3.9 Bandwidth; 3.10 Polarization; 3.11 Interdependencies of Gain, Beamwidths, and Aperture Dimensions; and References, Problems and Exercises.
Chapter 4:Basic Radiators and Feed Methods
- Section 4.1 Short Dipoles.
- Sections 4.2 Current and Voltage in Longer Antennas; 4.3 The Half-Wave Dipole; and 4.4 Long-Wire Antennas.
- Sections 4.5 Loop Antennas; 4.6 Helical Antennas; and 4.7 Horn Radiators.
- Sections 4.8 Slot Radiators; 4.9 Patch or Microstrip Antennas; 4.10 Surface-Wave and Leaky-Wave Antennas; 4.11 Basic Feed Methods; and References, Problems and Exercises.