In order to research on the design and implementation of a modernized GPS civil signals simulation system,a brief review of the modernized GPS signals is introduced,including the signal structure and characteristics of L2C,L5 and L1C signals.The design and implementation of the main modules of the simulation system is described in detail.The simulation system is mainly composed of parameter setting,system initialization,signal generator,noise generator,disturbance generator,signal synthesis,low-pass filter,A/D conversion and storage.The simulation results based on Matlab are then presented,and the power spectral density（PSD） of all navigation signals is analyzed.The simulation system completes the physical layer simulation of a modernized GPS new civil signal and can provide a controllable signal source for designing and testing of modernized GPS civil receivers,especially for the signal processing algorithm design of the GPS software receiver.
