In this paper, we propose a new technique to effectively suppress non stationary jamming in direct sequence spread spectrum (DS/SS) communication systems. This technique combines a new scheme of instantaneous frequency (IF) estimation with the projection based interference suppression. In order to capture jammer subspace, a time-varying autoregressive (TV-AR) modeling is used to estimate the Ifs of the non stationary jammer signals. Orthogonal polynomials are used for the basis function of the TV-AR model to reduce the computational complexity. The jammer subspace is constructed from the models governed by the estimated time-varying IFs. The estimated jamming interference is removed from the received data by subspace projection, resulting in less distortion to the desired signal. The performance of this approach is analyzed and compared with approaches using time-varying notch fltering.