This is a balun 1:1 using exclusively transmission lines (in this case Coaxial Cable).
It uses a labmda/2 line lenght to create a different of phase of 180º that compensates the 180º of the dipole and we get a relationship of 4:1.
Two sections of lambda/4 are been added to get a final relationship of 1:1.
This balun only is valid for monoband antennas (or multibands with a multiple of 3 lambdas). And BW of adaptation (dipole+balun) is aprox. 5%.
I like this balun because you can design it with a good accurate.
Remember that: lambda_cable = lambda_air x Speed Factor
Usually, Speed Factor is 0.67 for Rg-58 CU or RG-213. This parameter appears in the cable specifications.