Increasingly, terahertz systems are being used for multi-pixel receivers for different applications from mapping the star-forming regions of galaxies to stand-off radar imaging. Since microstrip patch antennas are too lossy and corrugated horn antenna arrays are difficult to machine at terahertz frequencies, suitable antenna array designs have been one of the key area of research for this field. Moreover, silicon micromachined waveguide housing for front-end integration is becoming very popular for multi-pixel terahertz instruments. This paper describes multi-pixel terahertz instruments with silicon-micromachined front-end and discusses design challenges for integrating terahertz antennas with such systems.@en