A Bandpass Power Amplifier Applying Transformer-Based Filtering Combiner in 0.5-μm GaAs pHEMT

This letter presents a fully integrated bandpass dual-way differential power amplifier (PA) implemented using 0.5-
$\mu \text{m}$
GaAs pHEMT technology for C-band application. A compact distributed-active-transformer (DAT) filtering combiner is utilized in the PA to trigger promoted harmonic suppression. Additional transmission zero of the combiner is formed by the parasitic capacitance between the transformer windings and the inductance connecting to the center of the primary winding, thereby have the filtering response. The frequency of transmission zero can be controlled by adjusting the inductance, so as to suppress the harmonics. The measured PA achieves a small-signal gain of 26 dB, saturated output power (
$P_{\mathrm {sat}}$
) of 33.3 dBm with 30.6% power-added efficiency (PAE) at 5.4 GHz.