Beamforming Transmitter IC for Far-Field Wireless Charging

Abstract

This paper introduces a Wireless Power Transfer (WPT) system tailored for far-field charging applications, leveraging beamforming technology. The system comprises a self-phase-shiftable Phase-Locked Loop (PLL) and a high-power, high-efficiency dual-band Power Amplifier (PA). The phase shift PLL is designed to operate with a reference clock frequency of 50 MHz and targets frequencies of 5.8 GHz and 4.8 GHz, specifically suited for beamforming applications, particularly in IoT devices. The PA structure is configured with two stages, incorporating interstage and output baluns for power matching. It directly amplifies the 5.8 GHz PLL output and amplifies the 4.8 GHz PLL output after dividing it by two and then amplifying the resulting 2.4 GHz signal. This system is implemented usig a 130-nm CMOS process and provides VCO gains (KVCO) of 141.72 MHz/V and 83.5 MHz/V at 5.8 GHz and 4.8 GHz, respectively. Power consumption is measured at 210mA and 120mA at a 1.2V supply voltage for 5.8 GHz and 2.4 GHz, respectively. The phase shift PLL enables a phase shift of 5.625° across the full 360° range at frequencies of 5.8 GHz and 4.8 GHz, while the PA achieves output powers of 25.41dBm and 24.48dBm, respectively.