This chapter sits in the middle of a long arc of the curriculum.
- Chapter 0 (physics): the origin of radiation in accelerating charges, Coulomb's law, Maxwell's equations.
- Chapter 9 (EM waves and transmission lines): the plane wave, intrinsic impedance, reflection coefficient, characteristic impedance. Antenna feeds are transmission lines; matching the antenna to the line is a transmission-line problem.
- Chapter 18 (waveguides and microwaves): at higher frequencies, guided modes in hollow waveguides feed horns, dishes, and patch arrays. The 60 GHz band lives there.
- Chapter 19 (radar): uses everything from this chapter (especially phased arrays) plus Doppler, range gating, and target detection.
- Chapter 23 (cellular): uses sectoral antennas, MIMO, beam-forming. Friis equation is the daily bread of cell-tower planning.
- Chapter 24 (side channels): uses small loops and near-field probes to capture unintended emissions; the same antenna theory in reverse.
The same equations describe a 1 mm patch on a phone and a 70 m DSN dish. Once you have internalized the parameters and the physics, scaling between them is just substituting numbers. That, more than any specific antenna, is the lasting skill.