Design and Implementation of an Educational FM Transmitter with FPGA Using SDR Techniques

Abstract

The basic purpose of Software Defined Radio (SDR) systems is to use a digital signal processor to numerically handle radio signals. The use of a processor like a Field Programmable Gate Array (FPGA) to perform tasks like modulation, demodulation, signal creation, and line coding on these systems dramatically decreases the demand for analog circuit-based hardware. FPGAs are digital integrated circuits with a wide range of applications which are made up of links between programmable logic blocks. It's aimed at assisting the creator realize the logic functions that the designer needs. In consequence, the user may change the function of each logic block. VHSIC Hardware Description Language (VHDL) is commonly used in FPGA programming. In this study, VHDL code was created, and a FM transmitter was implemented on a FPGA board (CMOD A7) in this research. The sound card interface on the PC used to send and receive the signals while suitable ADC and DAC cards are used on the FPGA side for the same purpose. Audacity program was used to playback the sample wav files while HDSDR SDR program was used to monitor and record the signals in wav file format. Finally, using the MATLAB code, the recorded transmitter signal was demodulated offline, and the output was stored to the hard drive. The demodulated signal obtained is identical to the initial modulation signal, indicating that the modulation was correctly executed. As a result, a perfect foundation for the development and training of SDR systems using FPGA has been established.