The TX path of the impedance transformation network is shown in the figure below. It is clear that this network is a fully-differential PInetwork(i.e., shunt-C, series-L, shunt-C). So it is the task of the designer to select values for CB, LMID, and CTUNE to transform 50 Ω(the impedance seen looking back into the balun and lowpass filter) into the desired differential TX load impedance, as listed in Table2.2 Differential PA Load Impedance vs Output Power and VDD on page 9. This design task is readily accomplished with the aid of aSmith Chart or simple impedance matching application.