Harmonic Suppression of a Three-Stage 25–31-GHz GaN MMIC Power Amplifier Using Elliptic Low-Pass Filtering Matching Network

In this letter, the modified elliptic low-pass filtering (LPF) matching network (MN) is proposed for harmonic suppression of a wideband gallium nitride (GaN) microwave monolithic integrated circuit (MMIC) power amplifier (PA) at millimeter-wave (mm-wave). To investigate the effectiveness of the method at mm-wave, a three-stage 25–31-GHz GaN MMIC PA is designed using a commercial 150-nm GaN HEMT foundry process, with a mask area of
$4.5\times2.6$
mm
²
. Simulated results show that the second harmonic of the PA can be effectively suppressed by using the elliptic LPF MN. Experimental results show that the realized MMIC PA achieves a saturated power-added efficiency (PAE) higher than 26.1% from 25 to 31 GHz, with a peak PAE of 31.5% at 29 GHz. The saturated gain and output power are more than 20 and 34 dBm within the band, respectively.