Optimized digital signal processing algorithms applied to radio communications.

Abstract

The application of digital signal processing to radio communications has come of age with the advent of low power, high speed microprocessors and over the past five years, various transceiver architectures, utilizing this new technology have been extensively researched. Due to the flexible nature of a software based transceiver, a myriad of possible applications exist and currently the emphasis is on the development of suitable algorithms. The principal aim of this research is the derivation of optimized digital signal processing algorithms applicable to three separate areas of radio communications. Optimized, as used by the author within this dissertation, implies a reasonable compromise between performance, complexity and numerical processing efficiency. This compromise is necessary since the algorithms are applied to a portable transceiver where power consumption, size and weight are limited. The digital signal processing algorithms described by this research is as follows:- 1. The derivation and assessment of a multirate speech amplitude modulation demodulator which exhibits low distortion (typically less than 2%) for a wide range of modulation indices, carrier frequency offsets and deviations. The demodulator is processing efficient and requires only five multiplications and five decisions for every output sample. 2. The derivation and assessment of a low sampling rate speech frequency modulation demodulator for signals whose bandwidth exceed quarter the sampling frequency. The demodulator exhibits low distortion (typically less than 2%) and is processing efficient requiring eighteen multiplications and three decisions for every output sample. 3. The derivation and assessment of a multirate single-sideband suppressed carrier automatic frequency control system which is a combination of a simple second order adaptive line enhancer and a digital phase-locked loop. The processing efficient automatic frequency control system is suited for low signal to noise power conditions, in both stationary and mobile communication channels.