Radio astronomical pulsar observations require specific instrumentation and dedicated signal processing to cope with the dispersion caused by the interstellar medium. Moreover, the quality of observations can be limited by radio frequency interferences (RFI) generated by Telecommunications activity. In this paper, we describe two real time algorithms proposed to remove RFI. First method, designed for rather strong RFI, is based on robust power threshold detection. The second one is based on the RFI cyclostationary properties. These algorithms have been implemented in a high performance dedicated backend UNIBOARD.