A 2.7 W AC-Coupled Hybrid Supply Modulator Achieving 200 MHz Envelope-Tracking Bandwidth for 5G New Radio Power Amplifier

Abstract

Envelope tracking is an effective way to improve the efficiency of radio frequency power amplifiers (PAs). This paper presents a wideband hybrid envelope tracking supply modulator (ETSM) for 5G New Radio (NR) PAs. To reach a wide envelope tracking bandwidth of 200MHz while maintaining high power efficiency, this work utilized a linear amplifier (LA) with accurate frequency compensation and enhanced driving capability. The proposed low-pass sense and control (LPSC) circuit ensures that the switching power amplifier (SPM) only tracks the low-frequency components of the envelope to reduce the switching power loss. The proposed dual-path duty modulator regulates the voltage across the AC-coupling capacitor. This supply modulator circuit is designed and fabricated using 0.18μm BCD technology. When tracking 200MHz bandwidth envelope signals, the prototype ETSM achieves 78.5% efficiency at the output power of 2.7W when taking a realistic 4Ω//600pF load as the PA model.