"Sensors at sub-millimeter wavelengths, which is loosely defined as 100 GHz to 3 THz, provide unprecedented sensitivity for astrophysics, planetary science, Earth observation, medical imaging or security screening. Heterodyne receivers, which down-convert radio frequency signals to intermediate frequency signals preserving the amplitude and phase information of the incoming radiation, are generally the detector of choice for high resolution sub-millimeter wave spectroscopy. Heterodyne receivers provide both the sensitivity and resolution for such studies. Nevertheless, it is clear that the future instruments will demand heterodyne arrays for higher sensitivity, greater mapping speed, large scale mapping ability, multiple line spectroscopy, and imaging capability. Passive and/or active heterodyne focal plane arrays would have profound impact on medical diagnostics, contraband detections, and astrophysical spectroscopy and imaging applications. However, only a handful of heterodyne array instruments at sub-millimeter wavelengths with a limited number of pixels are currently operational or being developed.This proposal deals with the development of improved heterodyne receiving arrays for instruments at THz frequencies. Such arrays will be enabled by higher levels of component integration with novel array concepts. Front-end architecture, including the choice of mixer elements and local oscillator (LO) injection schemes will be crucial to the overall design of such instruments. However, the novelty of this statement springs up from the efficient integration of the mixer with the antenna element at frequencies as high as 2.7 THz, and from the assembly of all the pixels taking advantage of novel antenna array topologies. The accomplishment of the work plan will not only contribute to the maturity of THz technology; the manufactured devices will be readily available for scientific and industrial purposes."