Design and implementation of a 24-GHz frequency-modulation continuous-wave radar front-end system is presented and discussed, and its hybrid planar and waveguide building blocks are fully integrated on one single substrate. A flexible and compact integration methodology on the basis of the substrate-integrated-circuits concept is deployed to design such a microwave front-end system-on-substrate. In this study, it is found that this surface-volume hybrid integration scheme not only enables the complete system integration of planar and nonplanar microwave circuits, but also combines respective advantages of such structures in connection with microstrip lines (planar) and waveguides (nonplanar). Design strategies of the system building blocks including mixers, power dividers, and antenna arrays are discussed together along with the measured results. To verify the developed radar prototype, laboratory-based target-range measurements are conducted.