Multiharmonic triband load coupling network using only transmission-lines for switching-mode power amplifiers

Future multistandard multiband mobile communication terminals demand highly efficient multiband power amplifiers (PAs). In this contribution, for the first time, the design of a compact planar multiharmonic load transformation network (MHLTN) to realise triband highly efficient power amplifiers (PAs) is reported. The proposed switchless MHLTN comprising only transmission-lines is capable to obtain impedance terminations at three distinct bands including up to three corresponding harmonics. The concept of inserting high impedance stubs at specific locations of the network to properly terminate the required harmonic frequencies was used. The idea was validated by implementing a class-E PA using a GaN High Electron Mobility Transistor (HEMT) in a hybrid design for GSM750, GSM1810 and LTE2655 operation. The measured impedances of the passive MHLTN for a triband class-E load coupling network are in good agreement with the desired results. With a triband input matching network, the measurement results have shown 74.0 %, 61.4 % and 46.8 % peak power added efficiency (PAE) with an output power of 40.7 dBm, 39.3 dBm and 38.3 dBm in the lower, middle and upper bands, respectively.