17.7 A packaged 90-to-300GHz transmitter and 115-to-325GHz coherent receiver in CMOS for full-band continuous-wave mm-wave hyperspectral imaging

Millimeter-wave/THz hyperspectral imaging has numerous applications in security, non-destructive evaluation, material characterization, and medical diagnostics [1]. Unlike single-frequency imaging, hyperspectral imaging operates over a wide frequency range and offers spectroscopic information on each imaging pixel. This combines mm-wave/THz high-resolution imaging with spectroscopy and improves detection sensitivity and specificity. In practice, pulse-based imaging supports fast data acquisition, but requires receiver (RX) with real-time wideband sampling (>50GHz). Such instantaneous broadband imaging modality inevitably exhibits severely degraded sensitivity (due to integrated noise) and requires high-end signal sampling, both of which make it very challenging to achieve a low-cost SoC solution. On the other hand, continuous-wave (CW) imaging supports better sensitivity, especially using coherent detection method with a low IF bandwidth [2–5]. Its operation allows for the use of a simplified heterodyne receiver, enabling silicon-based implementations of the entire imaging system. However, there are limited mm-wave/THz integrated electronic systems available that support CW hyperspectral imaging with a large bandwidth (BW), sufficient output power (Pout), and high sensitivity. Some existing CW transmitters (TX) use the harmonics for wideband coverage, which cannot support full-band scanning at any frequency in the band [2]. In this paper, a full-band CW TX/RX chipset is proposed to realize a generic hyperspectral imaging system without knowing the particular band of interest. We therefore optimize its performance to achieve flat TX Pout and RX conversion gain (CG) over a broad BW. Our mm-wave/THz hyperspectral imaging system comprises a 90-to-300GHz TX with a ±2dB Pout variation using a distributed quadrupler architecture and a 115-to-325GHz 4th-subharmonic coherent RX with −115dBm sensitivity (1kHz RBW) using high-order filter-based matching networks (MNs). The TX and RX chips are flip-chip integrated with wideband vivaldi antennas on low-cost organic LCP (liquid crystal polymer) substrates. This packaged wideband system offers a promising solution for low-cost field-deployable hyperspectral imaging.