This work presents design techniques for the implementation of high-speed analog
integrated circuits for wireless and wireline communications systems.
Limitations commonly found in high-speed switched-capacitor (SC) circuits used
for intermediate frequency (IF) filters in wireless receivers are explored. A model
to analyze the aliasing effects due to periodical non-uniform individual sampling,
a technique used in high-Q high-speed SC filters, is presented along with practical
expressions that estimate the power of the generated alias components. The results
are verified through circuit simulation of a 10.7MHz bandpass SC filter in TSMC
0.35mu-m CMOS technology. Implications on the use of this technique on the design of
IF filters are discussed.
To improve the speed at which SC networks can operate, a continuous-time
common-mode feedback (CMFB) with reduced loading capacitance is proposed. This
increases the achievable gain-bandwidth product (GBW) of fully-differential ampli-
fiers. The performance of the CMFB is demonstrated in the implementation of a
second-order 10.7MHz bandpass SC filter and compared with that of an identical
filter using the conventional switched-capacitor CMFB (SC-CMFB). The filter using
the continuous-time CMFB reduces the error due to finite GBW and slew rate to less
than 1% for clock frequencies up to 72MHz while providing a dynamic range of 59dB and a PSRR- > 22dB. The design of high-speed transversal equalizers for wireline transceivers requires the implementation of broadband delay lines. A delay line based on a third-order
linear-phase filter is presented for the implementation of a fractionally-spaced 1Gb/s
transversal equalizer. Two topologies for a broadband summing node which enable
the placement of the parasitic poles at the output of the transversal equalizer beyond
650MHz are presented. Using these cells, a 5-tap 1Gb/s equalizer was implemented
in TSMC 0.35mu-m CMOS technology. The results show a programmable frequency
response able to compensate up to 25dB loss at 500MHz. The eye-pattern diagrams
at 1Gb/s demonstrate the equalization of 15 meters and 23 meters of CAT5e twistedpair
cable, with a vertical eye-opening improvement from 0% (before the equalizer)
to 58% (after the equalizer) in the second case. The equalizer consumes 96mW and
an area of 630mu-m x 490mu-m
