In the last decade, radar-based Advanced Driver Assistance Systems (ADAS) have improved safety of transportation. Today, the standardization of ADAS established by New Car Assessment Program (NCAP) is expected to expand its market globally. One of the key technologies of ADAS is the rear-side monitoring system such as Blind Spot Warning (BSW) and Closing Vehicle Warning (CVW). It is required to expand its detection range so that it can monitor not only nearside targets for BSW, but farther targets for CVW. These applications can be achieved using two radar sensors installed at rear-side corner of the vehicle. However, the expanded detection range causes undesirable target detections and decreases target recognition performance. In this paper, a novel solution to improve the performance using DCMP(Directional-Constrained Minimization of Power)-based Beamspace technology using Two-frequency continuous wave (2FCW also known as FSK) is introduced. Combined with IQ detector, 2FCW beat signal output is proportional to the relative speed of an object. IQ detector is a hardware architecture used to distinguish approaching and leaving objects by separating upper and lower carrier frequency by measuring the relative phase of signal components. This method can reduce undesirable targets detection for BSW, but CVW requires farther reduction. The focus area of CVW is different from BSW. To design the focus area for multi-application, it is important to control receiving-directivity properly. The key technology of this paper, DCMP-based Beamspace signal processing, narrows down the objects which exist behind the subject vehicle by steering software receiving-directivity backwards to allow detection of only desirable targets in the CVW focus area. From our experimental result in real world environment, the CVW correct alarm rate is over 99%.