Wideband Digitally Controlled True Time Delay for Beamforming in a 40 nm CMOS Technology

Wideband beamforming is widely required in the sub-6GHz frequency band for 5G commutation and the next generation wireless communication (B5G). The true time delay is the most crucial component, especially in the sub-6GHz frequency band. This paper presents a new true time delay by using an N-path switch capacitor delay cell to break the tradeoff between bandwidth and delay range by introducing tunable sampling clocks. The non-idealities and limitations are discussed as well. In a 40-nm CMOS technology, the implemented true time delay achieves maximum 900ps delay at 3GHz and 500ps delay at 6GHz with 0.15% variation. Reliability of the design is verified by process variation simulation as well. The proposed topology provides a large delay range with a compact size, which is suitable for sub-6 GHz wideband applications.