We present the performance characterization of a large-format, sub-millimeter resolution, real-time focal plane array (FPA) sensor for THz imaging. With the aid of in-house hybrid electromagnetic modeling tools, the FPA is optimized for diffraction limited image resolution and conjugate impedance matching for highest THz sensitivity. The sensor operates in the 0.6-1.2 THz band with 5 frames-per-second image acquisition speed and with pixel responsivity of 1,000 V/Watt. The simulated images are verified by imaging of various objects at ~0.7 THz and the results are presented to highlight the overall imaging performance of the THz FPA sensor.