I've short question - does anyone know how a general input impedance equation of n-quarter wave transmission lines connected in a cascade looks like ? I'm searching such formula, however there are no concrete information about this.
A properly terminated transmission line has it's specific input impedance. It doesn't matter if it is terminated by a termination resistor or another transmission line with the same impedance.
The fact that they have a quarter wave length only matters if you have a impedance mismatch somewhere (open, short etc,)
It you have an impedance mismatch anywhere, the the length and the loss to the mismatch matters.
General equation for Transmission Lines which are terminated by arbitrary impedance is valid.( see textbooks) So you can calculate one-by-one global Input Impedance of cascaded Transmission Lines.