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June 2023 Issue

Tunable Wideband High-Order Active Analog Delays With High Delay-Bandwidth Product

by Z. Kabirkhoo, M. Radpour and L. Belostotski

Abstract: This letter describes analog delays based on wideband, high-order, tunable active all-pass filters (APFs) with poles and zeros prescribed by the Padé approximation. The number of inductors in the n th-order APF does not exceed ⌊n/2⌋ for a compact area, low insertion loss, and wide bandwidth. Delay tuning is accomplished via two control lines. The proposed sixth-order APF, implemented in TSMC 65-nm CMOS, exhibits a delay range from 250 ps (BW 10% = 0–8 GHz) to 400 ps (BW 10% = 0–5 GHz) and achieves the state-of-the-art DBW 10% = 2 for wideband APFs. Third- and fourth-order APFs were subsequently designed in GlobalFoundries 22-nm FDSOI CMOS for a 5G beamforming receiver operating from 24.3 to 28.7 GHz. The third- and fourth-order APFs exhibited 9–21 and 21–36 ps delay ranges, respectively, to generate beams from 0° to 35°.