Design and implementation of a software defined radio frequency modulation (FM) transmitter on an FPGA

Abstract

This work was about the design and implementation of a software defined radio (SDR) FM transmitter. SDR provides a number of improvements over traditional analogue modulators particularly in terms of upgradeability, removal of non linear relationships associated with transmitter components and better repeatability and stability. Thus modem telecommunication systems are adopting SDR over the traditional counterparts. The main aim of this thesis was to produce a working prototype capable of transforming an audio input into a frequency modulated signal. This consisted of deriving mathematical models, generating MATLAB simulations for the various blocks which make up the system and finally the actual implementation of the design onto an FPGA using VHDL coding as well as Xilinx IP cores utilizing the results generated from simulation. The actual implementation consisted of deriving the various mathematical models which make up the various blocks of the system. Then from these equations the software algorithm was devised and exhaustively tested on MATLAB. Then an ADC board was fabricated to be used in conjunction with this dissertation and upon completion the work was carried out on the FPGA. This consisted of generating VHDL code and programming various IP blocks accordingly. Afterwards, the actual hardware implementation was extensively tested. The end result was a working prototype capable of generating a fully digital FM modulation. This was carried out by digitizing an analogue audio signal using an ADC, then the necessary filtering which is mandatory by the standards was carried out, after which a stereo multiplexed signal was produced, which was then frequency modulated. The end result was successfully demodulated using a traditional radio which is quite common in the modern household.