In this paper, we establish a model of single antenna GPS intermediate frequency signal by analyzing the characteristics of GPS signal. The array-antenna space-time intermediate frequency(IF) signal is modeled based on the single antenna model. To ensure accuracy of the model, satellite clock error, atmospheric error, receiver clock error and noise are considered in the analysis. We also design a space-time GPS data simulator,
which is flexible, scalable and easy to use. The signal model is validated with spectral analysis and its accuracy verified by space-time adaptive processing.