A 26-32GHz Differential Attenuator with 0.23dB RMS Attenuation Error and 11.2dBm IP1dB in 40nm CMOS Process

This paper presents a 26-32GHz 6-bit differential attenuator in 40nm CMOS process. This attenuator adopts an optimized cascade scheme that incorporates simplified T-type (ST-type), T-type and Π-type attenuator units. Driven by a complete analysis of the pole-zero pattern introduced by the compensation capacitor, the design achieves a state-of-art uncalibrated RMS attenuation and phase error. The design methodology of shunt branches for constant phase and cascade linearity enhancement achieves a high linearity while minimizing the phase variation across the whole frequency band. The attenuator achieves a 31.5dB attenuation range with 0.5dB step and -8.5 to -9.5dB insertion loss in a compact area of 0.54mm×0.23mm. The measured RMS attenuation error remains below 0.23dB without calibration and phase error is less than 5.58◦. IP1dB in the reference state is better than 11.2dBm across 26–32GHz.