Inverse Class-F Linear PA for Middle Band 5G Applications

It is known that the inverse class-FPA (power amplifier) can lower the
$V_{knee}$
(knee voltage) and improve the efficiency as compared with the class-FPA. However, since the
$V_{knee}$
is low, the linearity tends to deteriorate due to the influence of the nonlinear characteristic of the capacitance between the base and collector of the transistor. In order to improve the linearity, we propose a matching circuit that adjusts the phase of the 2
^nd
harmonic load impedance. It does not apply an unnecessarily low voltage to the collector. We make a prototype of a differential PA module compatible with the 1.735 GHz - 2.0 GHz band and applied the proposed matching circuit. As a result, it was confirmed that the swelling that occurred in the ACLR (adjacent channel leakage ratio) characteristics can be suppressed and the output power that satisfied ACLR
$< \text{-}34\ \text{dBc}$
can be increased (5 dB).