Bit-stream signal processing and its application to communication systems

Abstract

The paper describes a digital circuit technique to process directly bit-stream signals from sigmadelta modulation based analogue-to-digital converters and the application of the technique to communication systems. The newly developed adder and multiplier are fundamental processing circuit modules. Using the fundamental modules and up/down counters, other circuit modules, such as oscillators, dividers and square root circuits, can also be realised. Signal processors built from the modules have three advantages over multi-bit Nyquist rate processors. First, single-bit/ multibit converters are not needed at the inputs of the processors because the arithmetic modules directly process the bit-stream signals. Secondly, the physical areas for routing the signals among the circuit modules are small since they are in the form of a bit-stream. Thirdly, the processors are built from a smaller number of logic gates than conventional Nyquist rate processors because of the simple structure of the circuit modules. As an application of the technique to digital signal processing for communications, a QPSK demodulator is presented. In addition to circuit simulations of the demodulator, a useful linear analysis to estimate the influence of the noise components contained in the outputs from the circuit modules on the steady-state demodulation performance is explained.

Improvement of the bit-stream squarer and square root circuit based on ΣΔ modulation

“…Two kinds of bit-stream multipliers are presented in [4,5]. However, only the bitstream multiplier presented in [5] can be used to realize the bit-stream squarer.…”

“…However, only the bitstream multiplier presented in [5] can be used to realize the bit-stream squarer. The input signals of another one are mixed-signals, which couldn't be used in the fully digital bit-stream systems.…”

“…The bit-stream multiplier presented in [5] performs the following operation for two bit-stream signals, xðnÞ and yðnÞ.…”

“…In recent years, a novel bit-stream digital signal processing (DSP) circuit structure based on AEÁ modulation appears [1,2,3,4,5]. The bit-stream DSP circuit structure processes a bit-stream digital signal which comes from a AEÁ modulator.…”

“…With the multi-bit DSP method, it's very easy to realize the high-accuracy squarer, just through connecting two input terminals of the multiplier together. However, the performance of the existing bit-stream squarer realized with the bit-stream multipliers is not perfect [5].…”