Abstract: A monostatic radar at 140 GHz frequency band has been developed for scale-model targets imaging and radar cross section(RCS) measurements. The coherent transceiver using all solid state technique adopts a multiplier chain driving by Ka band source as the transmitter to get an output power of about 0.5 mW in the 5 GHz bandwidth and a Schottky diode subharmonic mixer as the receiver to realize coherent detection. This compact range radar has demonstrated good signal-to-noise obtaining100 dB dynamic range with 3 cm resolution. In addition to inverse synthetic aperture imaging of targets, the system can also measure full angle RCS of selected targets with rotation. Measurements were made on 1/720th scale models of aircraft carrier, simulating P-band frequencies according to scaling laws. The results give some references for the full scale RCS used in P-band radar.