Stepped Impedance Matching Network For The Design Of Harmonic Tuned RF Power Amplifier

This paper presents the design of an efficient, second harmonic tuned RF Power Amplifier (PA) using stepped impedance matching networks. The stepped impedance microstrip line output matching network is designed to offer optimum impedances at fundamental $\left(f_{0}\right)$ as well as at second harmonic frequency $\left(2 f_{0}\right)$. On the other hand, the input matching network offers optimum impedance at fundamental whereas at second harmonic frequency, it differs from the impedance required for optimum performance of the Macom’s CG2H40010F GaN HEMT at $2 f 0$. This condition restricts the amplification of any unwanted signal at $2 f_{0}$. The designed PA delivers 12.4 W of CW power in Class-AB mode of operation at 2.45 GHz with measured Power Added Efficiency (PAE) and drain efficiency of $\mathbf{7 2. 2 \%}$ and $\mathbf{7 3. 1 \%}$ respectively. Measured Gain and input return loss of the amplifier are within $19 \pm 0.6 \mathrm{~dB}$ and better than 10 dB respectively, over $2.37 \mathrm{GHz}-2.65 \mathrm{GHz}$.