Pulse compression can be performed in direct detection radars by using a newly proposed stepped time intervals coding pulse train and corresponding correlation algorithm. At the receiver end, the envelop-detected signal is processed through a modified cross-correlation algorithm which removes all the range false peaks, leading to a perfect range sidelobe performance. Simulation results demonstrate the validity of the new approach. Furthermore, the approach is easy to be implemented and compatible to the conventional radars. It can be used in direct detection radars where Doppler information is not required or the radars which are difficult to provide coherence, such as short pulse laser radar (also called lidar) and ultra-wide band impulse radar. The proposed approach can also be applied to the upgrade of conventional non-coherent radars.