Pulse Compression (PC) is applied in radar systems to enhance range resolution and simultaneously preserve a high duty cycle. PC phase coded radars suffer from unwanted side-lobes at the Matched Filter (MF) output which may mask weak nearby signals. Different methods have been applied to deal with this problem. Each method is designed and applied particularly for certain phase coded signal. In this paper, a generic mathematical formula for a Side-Lobe Cancelling (SLC) Optimum Filter (OP-F) in phase coded pulse compression waveforms is presented. The derived filter followed the MF and can be applied to any type of phase coded signals with any length. The validity of the derived formula is verified for Barker, polyBarker and polyphase coded signals. The enhanced detection performance of the OP-F over MF alone is verified though receiver detection curves. Also, Implementation issues of the OP-F in either time and frequency domain are discussed.