well it is a single ended one , the thing I don't understand that when we design power amplifier for example class E we use port adapter (vary reflection coeff at different freq )so as to determine the optimum load for best output power for example but when designing class F we are now not only caring about load termination at our operating frequency but we also care about other harmonics . at high operating class F we usually don't make open and short circuits we use other load impedance .I don't know how they care about different ones at the same time . I tried to know the optimum at my operating frequencies using port adapter then placing another port adapter at double the frequency but the simulation always fails (I think because of instability issues)