This article presents a continuous-time (CT) analog-to-digital converter for wireless communication systems with a high tolerance against blockers. The zero-cancellation technique is introduced to eliminate the peaking in the signal transfer function (STF) to achieve better out-of-band-blocker immunity. An on-chip unary-approximating calibration is implemented to calibrate the mismatch of the outer current-steering digital-to-analog converter. A discrete-time (DT) second-order noise-shaping (NS) 2b/cycle asynchronous successive-approximation-register (ASAR) quantizer further reduces the quantization noise and the excess loop delay, achieving a CT-DT hybrid sixth-order NS without suffering from neither the problem of the CT-DT transfer function matching in a CT multistage NS topology nor the stability issue in a singleloop fully CT sixth-order topology. The prototype is fabricated in 28-nm bulk CMOS and is clocked at 1.7 GHz. With a bandwidth of 85 MHz, the analog-to-digital converter achieves 0-dB peaking STF, 74.4-dB signal to noise and SNDR and 87.5-dB spuriousfree dynamic range, while consuming 61.8-mW power, resulting in an excellent Schreier Figure-of-Merit (FoM S ) of 165.8 dB. Index Terms-2 b/cycle asynchronous successiveapproximation-register (ASAR), continuous-time (CT) analog-to-digital converter (ADC), flat signal transfer function (STF), noise-shaping (NS) QTZ, on-chip digital-to-analog converter (DAC) calibration, out-of-band blocker (OBB).
I. INTRODUCTIONT HE ever more crowded radio spectrum causes great challenges to the design of wireless communication systems, in terms of increasing signal bandwidth (BW) as well as spectral performance. This makes continuous-time (CT) analog-to-digital converters (ADCs) more attractive for use in wireless applications due to their high dynamic range (DR), good power efficiency and implicit anti-aliasing property [1]-[3]. Fig. 1 shows the received spectrum at the antenna of the long-term-evolution advanced (LTE-A) standard [2], [4], [5]. For an inter-band contiguous carrier Manuscript