Nonlinear Current Anti-Phase Technique in a Linearity-Enhanced 24 GHz-28 GHz GaN MMIC Power Amplifier for 5G mm-Wave Applications

Abstract

This paper proposes a novel nonlinear current anti-phase technique to enhance the linearity of gallium nitride (GaN) power amplifiers, specifically designed for the 24 GHz-28 GHz within the fifth-generation frequency range 2 n258 band. To solve the limited accuracy of conventional gm3 analysis in predicting the third-order intermodulation distortion (IMD3) performance under large dynamic range conditions, a large signal parameter $G_{\mathrm{m}3}$ is developed and analyzed that creates the anti-phase IMD3 current which can be flexibly controlled in both drive stage and power stage with deliberate biasing, enabling effective cancellation of IMD3 at across a large dynamic range. In addition, a shunt of resistive voltage divider was implemented to avoid multiple gate bias supplies. To demonstrate the proposed approach, a class-AB millimeter-wave power amplifier is implemented based on a 0.15 μm GaN-on-silicon carbide high electron mobility transistor technology. Under continuous-wave excitation at 20 V drain bias, the fabricated power amplifier (PA) demonstrates 40.5 dBm-40.9 dBm saturated output power over the 24 GHz-28 GHz frequency range, while the measured power-added efficiency (PAE) remains between 42.5% and 45.5%. Over a large output power back-off (OBO) range of 6 dB-25 dB, the PA achieves excellent linearity, with IMD3 better than −39 dBc. Additionally, at 4 dB OBO, the PA also achieves an IMD3 of −31 dBc and a PAE exceeding 24.5%. Owing to its excellent linearity, the proposed monolithic microwave integrated circuit, when tested with a 64-quadrature amplitude modulation signal featuring a 400 MHz modulation bandwidth and a 14 dB peak-to-average power ratio, provides 26 dBm of average output power. Under these operating conditions, it attains an error vector magnitude of 2.56% and an adjacent channel leakage ratio of −35.5 dBc without applying digital predistortion. The measured and simulated results verify the effectiveness of the high-linearity PA design over a large dynamic range.