We first consider the propagation characteristics of the infinite loaded line shown in Fig-ure 8.2. Each unit cell of this line consists of a length,d, of transmission line with a shunt susceptance across the midpoint of the line; the susceptance,b, is normalized to the char-acteristic impedance,Z0. If we consider the infinite line as being composed of a cascade of identical two-port networks, we can relate the voltages and currents on either side of the nth unit cell using theABCDmatrix: