Typical passive millimeter wave (PMMW) sensors with focal plane array (FPA) are placed on a rectangular grid to sample the image plane. Since the sensors must be made large enough to sense PMMW wavelengths, the sensor density that can be achieved is limited. In fact, the sensors may not be spaced closely enough to sample the image at Nyquist density. A novel design scheme based on focal plane array is reported in this paper for 3 mm PMMW imaging. Image resolution and imaging speed have improved by using large aperture lens and multi-channel receiving array. The arrangement of feeds and scanning model can realize Nyquist sampling rate on focal plane array(FPA) so that the image can be reconstructed as reliably as possible, which means super resolution algorithms can be implied in both vertical and horizontal directions.