A mixed-signal RAM decision-feedback equalizer for disk drives

An analog DFE for disk drives using a mixed-signal integrator

“…When this DFE is used with an analog forward equalizer, a high-speed ADC and digital equalizers are not needed, saving area and power. The use of the mixed-signal integrators reduces the die area as well as power dissipation when compared to previous work [2][3][4][5][6][7]. The performance of the analog DFE, in terms of BER, is comparable to previous DFE implementations.…”

“…Table 1 provides a performance summary for this analog DFE. It also compares the performance of the analog DFE with a similar mixed-signal DFE [5] and a mixed-signal RAM-DFE [7]. Comparison with the DFE in the second column is complicated by the fact that it was fabricated in a different, 2mm CMOS process.…”

“…The ADC consists of 3 pre-amplifiers, 3 comparators and some decoding logic. The preamplifiers and comparators are similar to the ones used in [7]. Only the adaptive loop for coefficient c 1 is shown in the figure, however there are five mixed-signal integrators on the prototype to adapt the coefficients c 0 -c 4 .…”

“…In this DFE, the ISI cancellation and the adaptive loops are realized with analog circuits. Conventional (or "linear") mixed-signal DFE's and a mixed-signal RAM-DFE have proven the feasibility and efficiency of mixed-signal implementations of DFE detectors [5][6][7]. These DFE's use digital integrators in the adaptive loops.…”

Integrated transversal equalizers in high-speed fiber-optic systems

“…At low speed, transversal equalizers can be implemented as digital finite-impulse response (FIR) filters: the input signal is first sampled and digitized, and the delay line can be constructed using a shift register [17] or memory [18]. The maximum data rate of digital FIR filters is limited by the speed of the digitizer and the power consumption and circuit complexity required for the high-speed implementation.…”