Silicon Integrated THz Comb Radiator and Receiver for Broadband Sensing and Imaging Applications

This article presents a fully integrated terahertz (THz) comb/pulse radiator and a broadband frequency-comb heterodyne receiver for sensing and imaging applications. The chipset is fabricated in the GlobalFoundries 90-nm SiGe BiCMOS process. The comb radiator utilizes p-i-n diode sharp reverse recovery to generate THz frequency comb/pulses. The repetition rate of the radiated pulses is locked to a stable off-chip source, which can be adjusted to as high as 15 GHz. By using a low-phase noise off-chip source rather than an on-chip oscillator, low phase noise and high-frequency stability are achieved. The phase noise of 405-GHz tone is −82 dBc at a 10-kHz offset frequency. The radiated tones are characterized from 220 GHz up to 1.1 THz using VDI SAX modules with the measured EIRP of −11, −15, and −36 dBm at 405, 500, and 750 GHz, respectively. In addition, a THz frequency comb detector using a Schottky barrier diode passive mixer is presented. The detector uses a broadband comb as LO for heterodyne detection of any arbitrary spectrum in mm-wave/THz band by adjusting the spacing of the LO comb from 100 s of MHz up to 15 GHz with a resolution of 2 Hz. The receiver chip is characterized from 220 up to 500 GHz with the measured NF of 24.5, 36, and 44 dB at 270, 405, and 495 GHz, respectively. Moreover, a dual-comb technique using the radiator and receiver chips is demonstrated, promising a compact low-cost solution for dual-comb sensing applications. The radiator and receiver chips consume a dc power of 40 and 38 mW, respectively.