Efficient Single-Bit Ternary Digital Filtering Using Sigma-Delta Modulator

Abstract

Abstract-Efficient filtering of sigma-delta bit-streams using a finite-impulse response (FIR)-like digital filter is presented. The filter combines a lowpass sigma-delta modulator system and a ternary FIR filter. Unlike conventional FIR filters, the combination of the two components allows a bit stream to be filtered, with the output being retained in single-bit format.Index Terms-Digital filtering, finite-impulse response (FIR), infinite impulse response (IIR), modulation, sigma-delta, single-bit, ternary filter.

Sigma-Delta Modulation Based Digital Filter Design Techniques in FPGA

“…This section describes input and coefficient encoding techniques that can be exploited to implement fast and efficient DSP algorithms in FPGAs. The techniques can be applied in either a single-bit or multibit environment [10,11]. As outlined above, it is the performance of the multiplyaccumulate (MAC) stages that will have the greatest impact on the overall behaviour of digital filters.…”

“…The advantages of single-bit systems were first identified by the authors of [22] and further developed in [23,24] and [26]. Recently, general purpose short word length (SWL) DSP applications including classical LMS algorithms have been described in [10,35]. In this section we introduce and describe the techniques that have been used to filter whilst maintaining a single-bit output.…”

“…In the last decade various general purpose DSP applications are reported using single-bit sigma-delta modulation encoding including classical FIR filter in [10,[35][36][37][38]. This single-bit approach was first reported for IIR and FIR filtering in [2,3].…”

“…Recently, new DSP design techniques called short word length (SWL) have been reported in [10,11,38,42]. Of these SWL techniques, the so-called single-bit ternary FIR filter was first proposed in [10].…”

Structures for Single-Bit Digital Comb Filtering

“…The tap values are generated via Σ∆ modulation of a target impulse response. The digital Σ∆M used for this purpose must have tri-level output, and must have a flat signal frequency response over the bandwidth of interest [2]. The ternary filter requires operation at an oversampled rate (OSR), a requirement that will be met since the input signal is assumed here to be a Σ∆ modulated bit-stream.…”