Yagi-Uda antennas are end-fire arrays of wires with moderate gain of 5-15 dBi, widely used mainly for TV and radio reception.

For theory see:

Orphanids, S: Electromagnetic Waves and Antennas, 2004-10, chapter 14: http://eceweb1.rutgers.edu/~orfanidi/ewa/ch23.pdf
Kraus, J.D., Marhefka, R.J.: Antennas for all applications, Mc Graw Hill 2003, chapter: End-Fire Antennas (8)

Simulations - 6 element wire Yagi:

yagi_abse The picture shows (click to animate) oscillation of near electric field of 6-element Yagi-Uda antenna consisting of one director, one active dipole and four directors. Note formation of the phase-front.

The same as above, but now the magnetic field is shown.

yagi_j Surface current distribution on elements. Note lagging current at reflector.