160-GHz to 1-THz Multi-Color Active Imaging With a Lens-Coupled SiGe HBT Chip-Set

This paper presents the concept and implementation of an active all-electronic terahertz multi-color imager with the functionality demonstrated in the frequency range of 160 GHz-1 THz. The proposed terahertz system is realized in the form of two independent highly integrated low-cost transmitter (Tx) and receiver (Rx) modules. Each module consists of a single silicon die with a silicon lens-coupled ultra-wideband on-chip antenna and is assembled onto a low-cost FR-4 printed circuit board using traditional wire-bonding. The chip-set is implemented in a 0.25 μm SiGe HBT BiCMOS process with fT/fmax of 280/435 GHz. The main Tx path is composed of an antenna-coupled harmonic generator and is driven by a × 9 multiplier chain fed from an external reference signal centered around 17-18 GHz. Four identical Tx paths are spatially combined on a single chip to increase the output power. The Rx chip shows a 2 × 2 arrangement of identical antenna-coupled broadband sub-harmonic mixers driven by a single × 9 multiplier chain; similar to that from the Tx circuit. The system operates simultaneously at six harmonics being multiple numbers of 165 GHz. The signal-to-noise ratio in transmission-mode active imaging with a 1-Hz resolution bandwidth is 90 dB for 165-GHz band, 115 dB for 330- and 495-GHz bands, 95 dB for 660- and 820-GHz bands, and 70 dB for 990-GHz band.