Real-time spectrum analyzer is a hot instrument for signal analysis and spectrum monitoring. It has wide applications in wireless communication and high potential for smart reading. However, it is characterized with a high cost. Hence, a designed light version based on already available lab instruments is constructed for use in school lab. In this thesis, a simple oscilloscope and a computer were used in the process. Both instruments communicated through GPIB cable and MATLAB software was used for the processing tasks. In order to test the designed one, a simple signal generator was used. The signal was analyzed in both time domain and frequency domain. Then measurements of the signal over time were updated to a matrix of FFT and were plotted in 3D, showing spectrum variation over time. The application of this project to radio frequency analysis was also discussed.