In this paper, a scalable architecture is presented which can generate and radiate reconfigurable periodic waveforms in free-space with picosecond time-widths. This is achieved by allowing radiated electromagnetic-fields of fundamental and multiple harmonic frequencies to combine in free-space with the right amplitudes and delays, and quasi-optically construct the time-domain waveform in the desired direction. In this paper, a 4-element array with integrated antennas is presented which is demonstrated to radiate pulse trains of 2.6 ps time-widths as well as pure tones and harmonic frequencies at 107.5 GHz (EIRP=4.5 dBm), 215 GHz (EIRP=5.0 dBm) and any combination of amplitudes and delays of these two harmonics to generate a set of reconfigurable waveforms in free space. No silicon lens or substrate thinning was employed. To the best of the authors' knowledge, this is the sharpest radiated pulses demonstrated in any IC technology. The chip is fabricated in 65nm LP CMOS process.