GaN-based digital transmitter chain utilizing push-pull gate drivers for high switching speed and built-in DPD

Abstract

This paper presents a fully digital transmitter chain, including a modulator and a digital microwave power amplifier (PA) MMIC. It uses push-pull drivers for the gates of the class-D final stage for improved switching speed. To the authors' knowledge this is the first time this approach is implemented on a GaN HEMT process. The performance of the flexible and compact chip is evaluated with modulated baseband signals at a 900 MHz carrier. For encoding the IQ signals into a binary stream, a modulation scheme with a built-in DPD is used, resulting in a higher line-up efficiency as no additional computational power is dissipated. ACLR values of more than 43.5 dB are reached almost fulfilling the 3GPP spectral requirements. A comparison of achieved signal quality to other publications is given.