Design and Characterization of a 24 GHz Transceiver with Adaptative Power Control for 5 G mmWave Systems

Abstract

The progression towards 5 G communications in millimeter-wave (mmWave) bands imposes stringent requirements on the linearity and power stability of the radio frequency (RF) chain. This paper presents the design, modeling, and experimental characterization of a complete 24.2 GHz transceiver featuring a closed-loop power control system. The system employs a Software-Defined Radio (SDR) for the generation and demodulation of a 5 G waveform at a 5 GHz intermediate frequency (IF). Frequency conversion to the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{R F}$</tex> band is performed by a subharmonic mixer, which utilizes an internal frequency multiplier to generate a 24.2 GHz RF carrier from a 9.6 GHz local oscillator (LO) signal supplied by a synthesizer. The output power is monitored in real-time by an RMS power detector, the output of which feeds a digital control loop implemented in a microcontroller. Theoretical analysis of the mixing cascade, signal quality metric (EVM), and control algorithm is presented. Experimental results characterize the open-loop system performance, including the compression point and EVM degradation, and demonstrate the effectiveness of the control loop in maintaining a constant output power and ensuring linear operation against variations in input power and chain gain.