Simulation and Optimization of Digital Baseband Signal Transmission Systems with Matched Filtering in MATLAB

In the digital communication system, in order to reduce the bit error rate under the condition of limited channel bandwidth, it is necessary to use the shaping filter for pulse shaping before signal transmission. This process improves the spectral characteristics of the signal and produces a waveform suitable for channel transmission. In this paper, MATLAB is used to realize the simulation design of the raised cosine roll off filter, square root raised cosine filter and Gaussian filter, and their influence on signal quality is analyzed without considering the noise, and the optimal filter is selected for signal processing. The simulation results show that the amplitude-frequency characteristics, bandwidth efficiency and intersymbol interference suppression ability of the transmission filter are affected by rolling coefficient and bandwidth. In general, choosing a roll down factor between 0.3 and 0.8 can minimize out-of-band interference and spectrum leakage, resulting in a smoother and more continuous signal. This method effectively improves the noise resistance and bit error rate of the signal, significantly reduces ISI, improves bandwidth utilization, and enhances the anti-interference ability and stability of the communication system.