Design and Performance Investigation of a Temperature Compensated Transmitter With GaN HEMTs for Phased-Array Applications

Abstract

This article presents a temperature compensated transmitter for phased-array applications. The high-temperature effects on each individual transmitter building block are studied and compensated to mitigate the performance variations. Furthermore, a new active, tunable, and variable gain phase shifter VGPS) architecture is proposed, which features low-performance variation with temperature and high gain without compromising the phase shift range. A temperature sensor is designed to adaptively adjust the critical dc bias voltages to minimize the variation of the active devices. A class- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{F}^{-1}$ </tex-math></inline-formula> power amplifier PA) is designed, as the last stage in the transmitter chain, and its performance variation is compensated through the VGPS stage by adaptively tuning its characteristics. Gallium-nitride (GaN)-on-silicon-carbide (SiC) high-electron-mobility transistors (HEMTs) are adopted as the active devices and a voltage-controlled capacitor (varactor) used in the VGPS stage. The transmitter is prototyped on a piece of Rogers 4003C substrate, and the system performance is measured. The transmitter has the minimum and the maximum small-signal gain of 5.2 and 31.5 dB, respectively, with the maximum variation of < 2.3 dB across the temperature range and the frequency range of 2–2.1 GHz. The insertion phase variation also remains below 6.5° across the phase shift, temperature, and frequency range. The maximum output power and power added efficiency (PAE) are measured to be 33 dBm and 58%, respectively, at the maximum ambient temperature of 220 °C. The measurement results also show that the transmitter is able to transmit 64-QAM signals with the data rate of 120 Mb/s at the maximum ambient temperature of 220 °C.