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An investigation into mixer in radio communications systems ABSTRACT Software radio is one of the hotspots in radio communication and military research. Due to the processing speed of A/D/A conversion and DSP processor, software radio often adopts inter-specific schemes based on digital conversion technology. That is to say, by using specific DDC&DUC or running relevant algorithm, software radio transforms the sampling rate to enable DSP processors bring real-time signal to success. In this dissertation, the mixer and NCO in the DDC are investigated, some typical cases are focused on., then on the basis of result of logic synthesis, the utilization rate of FLE10K’s logic resource is analyzed In the first place, the dissertation presents Current situation and the trend of the modern radio communication and discusses the problem at present, then gives the theory of radio communication and the function, as well as the principle of the mixer. The dissertation emphases mainly on the design of the mixer. The design of the mixer is discussed from two aspects: the design of the NCO, the design of the multiplier. The design of the NCO includes the design of four function module, that is, Phase accumulator module; module producing the harassing code; accumulator module and module for memory altitude of wave. In the course of design, schematics, VHDL, LPM, MAX+ plusII and FLEX10K are all applied, then on the basis of result of logic synthesis, the utilization rate of FLE10K’s logic resource is analyzed. When we design the NCO, we adopt the technology of the DDS, as a result, we can control the frequency flexibly. Finally we give some typical cases. Key Words: software radio; DDC; NCO; DDS; Mixer; FLE10K ACKNOWLEDGEMENTS Many people have been involved with the compilation of this project. So my thanks goes out to Dave Gray my project mentor at the University of Central England for helping and answering all my questions. To xxxxxx my work mentor xxxxxx and to xxxxxx at GB Spedition for the information to enable my calculations to make sense. I also want to thank my friends for putting up with me constantly talking about this project, their help proof reading and their encouragement, thank you xxxxxx. CONTENTS PAGE ABSTRACT 1 ACKNOWLEDGEMENTS 2 CONTENTS PAGE 4 GLOSSARY 5 LIST OF DIAGRAM 6 1.0 INTRODUCTION 7 1.1 Current situation and trend of the modern radio communication 7 1.2 The questions discussed in this thesis 10 2.0 OVERVIEW 11 2.1 Basic principle of radio communication 11 2.2 The function and principle of mixer 14 2.2.1 The function of mixer 14 2.2.2 The principle of work of the mixer 14 3.0 THE THEORY OF THE ORTHORHOMBIC AND DIGITAL MIXER 16 3.1 The theory and block diagram of the orthorhombic and digital mixer 16 3.2 Mathematical analysis 17 4.0 THE DESIGN AND REALIZATION OF HARDWARE OF THE ORTHORHOMIC AND DIGITAL MIXER 17 4.1 The design of NCO 18 4.1.1 Phase accumulator module 18 4.1.2 Module producing the harassing code 20 4.1.3 Accumulator module 21 4.1.4 Module for storing altitude of wave 22 4.2 The realization of the NCO 23 5.0 THE DESIGN AND REALIZATION OF THE MULTIPLIER 23 5.1 The design of the multiplier with VHDL language 23 5.2 The design of the multiplier with schematic diagram 24 6.0 THE APPLICATION OF MIXER 25 6.1 Several products of mixers 25 6.2 An architecture used for transmission 28 7.0 CONCLUSION 34 REFERENCES 35