Compact phased array transmitter (TX) and receiver (RX) modules operating at 94 GHz are presented and demonstrated in a 3D radar imaging system. Each module consists of four SiGe ICs and a package that integrates 8X8 dual-polarized antennas and 10-GHz IF power combiners. Each TX and RX IC integrates beam-forming, frequency conversion, LO generation, and digital control functions. The modules have beam steering capabilities in both azimuth and elevation over a range of +/- 32 degrees. A radar imaging system is implemented comprising an evaluation board with one TX module and one RX module, FMCW signal generation and acquisition components, and an FPGA for fast beam steering control. The system can steer TX and RX beams to a given direction and perform a radar measurement in that direction in less than 100us, enabling 3D imaging in real time. Measurement results are presented for the modules and the prototype imaging system.