A kind of high resolution radar signal (inter pulses Costas freguency hopping,or Costas FH) and a kind of direct digital synthesis (DDS) technique were introduced.A uniform expression of inter pulses Costas FH radar signal and stepped frequency pulsed radar signal was presented. A method to generate Costas FH radar signal from the signal set produced by DDS using so called "frequency selecting matrix"was also presented. The result shows that by using this method, certain flexibility of implementation of radar system, including software and hardware, may be increased.