A 12.8-GS/s Time-Interleaved Sub-Sampling ADC Front End With 38-GHz Input Bandwidth and >39-dB SNDR for 1–32 GHz in 22-nm FDSOI

In this article, we present a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times $</tex-math> </inline-formula> time-interleaved analog-to-digital converter (ADC) front end operating at 12.8 GS/s. We designed for a high tracking bandwidth (BW) of 38 GHz and optimized the SNDR up to the 5th Nyquist zone. This allows covering the targeted Ka-band frequencies of 27–31 GHz allocated for high-throughput Earth-to-satellite communication without the need for a dedicated mixer, enabling a wideband direct RF sub-sampling receiver approach. We employ an inductor-based input network together with co-optimized push–pull buffers and an active bootstrapping concept in the critical first track-and-hold (TH) for BW enhancement and improved linearity. Because the focus of this work lies in achieving a high SNDR at multi-ten-GHz inputs rather than maximizing the sampling rate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f {_{S}}$</tex-math> </inline-formula>, we implement a single 1st-rank TH to eliminate the need for skew and BW mismatch calibration. A prototype of this two-rank TH is implemented in 22-nm FDSOI technology. Measurements of four different chip samples indicate SNDR >39 dB up to 32-GHz input frequency at 12.8-GS/s operation while consuming 87 mW. A sweep of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f {_{S}}$</tex-math> </inline-formula> from 4.8 to 15.2 GHz and ±10% supply variation causes <1.3-dB SNDR fluctuation at a 30.2-GHz input. We estimate the total aperture jitter to about 25 fs, and an input <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${S_{{11}}{\lt }}{-}12$</tex-math> </inline-formula>dB is achieved up to 35 GHz.