Abstract: To overcome the narrowband interference (NBI) in the direct sequence spread spectrum (DSSS) system, an antijam algorithm based on Fast Fourier Transform (FFT) is introduced. The narrowband interference is detected and suppressed by FFT based on its power distribution different from the DSSS signal in frequency domain. And the synthesizable algorithm is implemented by Verilog HDL to achieve in the FPGA. Simulation and hardware test show that anti-jam block can suppress NBI and get back the original signal.

Key words: DSSS, Narrowband interferenes, Suppresion, FFT, FPGA