Time-based ADCs using VCOs for Digital Intensive RF Receivers
Speaker: SeongHwan Cho
Series: Topical Seminars
Location: Engineering Quadrangle B205
Date/Time: Tuesday, June 7, 2011, 4:00 p.m. - 5:00 p.m.
In this talk, time-based ADCs using voltage-controlled oscillators (VCOs) will be presented for digital-intensive RF receivers. First, an RF bandpass ADC for direct RF sampling receiver is introduced. Unlike conventional delta-sigma bandpass ADCs that require accurate DACs and high speed analog circuits, the proposed architecture provides bandpass function by time-interleaving 1st-order VCO-based ADCs. The use of VCO-based ADC has the advantage that its resolution is determined by time-resolution rather than the voltage resolution, thus making it attractive for future low-voltage CMOS processes. Next, a direct conversion receiver that consists of an LNA, a mixer and VCO-based ADCs will be shown. The use of VCO-based ADC provides high sampling rate, wide dynamic range and inherent anti-alias filtering that eliminates the need for VGA and analog filters. Experimental results of direct RF sampling receiver and direct conversion receiver implemented in 65 and 90nm CMOS will be presented.
SeongHwan Cho received the B.S. degree in electrical engineering from KAIST, Korea, in 1995, and the S.M. and Ph.D. degrees in EECS from MIT, Cambridge, MA, in 1997 and 2002, respectively. In 2002, he joined Engim, Inc., where he was involved in data converters and phased-locked loop (PLL) design for IEEE 802.11abg WLANs. Since November of 2004, he has been with KAIST in the department of EE, where he is now an associate professor. His research interests include mixed-signal and analog circuits for low power communication systems and bio/health-care devices. Prof. Cho was the co-recipient of the 2009 IEEE Transactions on Circuits and System Society Guillemin-Cauer Best Paper Award. Prof. Cho serves on the Technical Program Committee of several IEEE conferences, including ISSCC, Symp. on VLSI and A-SSCC. He has served as guest editor of JSSC and is currently an associate editor of IEEE Trans. On Circuits and Systems-I.