On Signals and Channels:

A time-frequency representation of FDMA

A time-frequency representation of TDMA

 On Transmission Line Theory:

Smith trajectory of an impedance transformation

Smith trajectory of a single-stub tuner

Smith trajectory of a double-stub tuner

TEM Transmission line parameters

 On Electromagnetic Properties of Matter:

The atmosphere

A graphical representation of the atmospheric windows

Water

A complete frequency spectrum of liquid water

Comparative absorption spectra of water

The wavelength dependence of the absorption of pure water

On Electromagnet Structures and Devices

Typical Antenna Structures
Giant Antenna Arrays
Structure and beam of a blue-green laser diode
Minature microwave antenna arrays for satellite communication

Miscellaneous:

A nice representation of the electromagnetic spectrum

Another representation of the electromagnetic spectrum