In the super-heterodyne terahertz communication system, the proper design of the critical components like mixers and filters are of great importance for enhancing its performance. In this work, some issues on our newly developed system setup design for 140 GHz wireless communications and the key components subharmonic mixer (SHM) based on Schottky diode, as well as silicon micromachined bandpass rectangular waveguide filters are presented. According to ADS simulation, the optimum conversion loss of the 140 GHz SHM is about 8.2 dB. And the silicon-micromachined rectangular waveguide filters have been fabricated and the measured lowest insertion losses are lower than 0.5 dB.