RT&L FOCUS AREA(S): Autonomy TECHNOLOGY AREA(S): Electronics OBJECTIVE: To develop low cost radar-on-chip operating at the terahertz frequencies with millimeter range resolution and low power consumption based on integrated circuit technologies. DESCRIPTION: The terahertz part of the electromagnetic spectrum from 0.3 to 1 THz has unique advantages for radar applications, including large bandwidths for improving range resolution and small antenna apertures [1]. It will enable new radar systems for autonomous navigation, security surveillance and screening, biometric vital sign detection, human-machine interfaces, and much more. Prototype THz radar systems mostly using GaAs Schottky diode technology have shown impressive results. However, they are bulky and expensive, and mostly limited to laboratory demonstrations. The aggressive scaling of CMOS integrated circuit (IC) technology driven by Moore's Law has resulted in miniaturization of computational devices. On the analog side, the transistor cutoff frequency fmax has increased steadily to ~350 GHz for 45 nm CMOS nodes [2][3]. However, further scaled nodes (< 45 nm) has not seen more improvement because of increased gate and wiring resistances. In the meantime, SiGe HBT technology has emerged as a viable solution in the THz band with commercial SiGe HBT technology achieving 500 GHz fmax, and 700-GHz fmax for the next technology node. SiGe HBT technology is enabling fundamentally operated circuits above 300 GHz. Furthermore, the speed of SiGe HBT devices is projected to continue to improve with transistor scaling. Theoretical analysis of the performance limits of SiGe HBTs indicates that their operating frequencies should reach 1 THz and beyond. On the system side, these advances have enabled the commercialization of various millimeter-wave systems such as automotive radars. Building on low power RF-CMOS technology, low cost single-chip collision avoidance radars at 77 GHz have become widely available [4]. Besides offering high range resolution, they also include multiple transmitters and receivers in a single-chip form factor that can be electronically configured into coherent beam forming mode for long range detection or MIMO (multiple-input, multiple-output) radar mode for enhanced angular resolution. Based on the above developments, the use of silicon based IC technologies for single-chip THz radars at frequencies greater than 300 GHz is also promising and feasible [5]. The large bandwidth available at the THz frequencies will provide range resolution down to millimeter range that would be impossible to achieve with microwave and millimeter-wave radar systems, and potentially enable new applications such as high-precision secure perimeter tracking and remote gesture recognition [6]. However, past research has shown that systems operating at the THz frequencies cannot be a simple scaling of classic RF design techniques to the higher frequencies because the new operating frequencies are close to or higher than the device fmax. Novel circuit architectures will be required to overcome the device limitations. This STTR topic will explore innovative circuit design techniques in order to enable THz radar-on-chip. PHASE I: Identify IC technology nodes with device characteristics suitable for terahertz frequency operation. The technologies being considered could be silicon-based (CMOS or SiGe), III-V based (GaN or InP), or heterogeneous integration of different technologies. Perform device characterization and modeling of the IC technology nodes. Develop radar system parameters and perform trade study between system size, architecture, operating frequency, antenna structure, range, power consumption, etc. Develop overall system-level models based on optimized parameters selected from the trade study. Design initial circuits implement against the identified technology nodes and develop initial antenna design for the radar system. The radar system should contain 1 transmitter and 1 receiver, and has the following targeted system parameters: >300 GHz, 2% instantaneous bandwidth, 0 dbm TX power, 15 dB RX noise figure, -70 dBc/Hz phase noise at 1 MHz offset. Phase I study should determine the feasibility of developing a THz radar-on-chip. PHASE II: Perform detailed circuit design and IC fabrication against the foundry technology nodes chosen in Phase I. The targeted system parameters should include the following: >300 GHz, 10% instantaneous bandwidth, 3 transmitters (5 dBm TX power each) and 4 receivers (10 dB RX noise figure) in a single chip, -90 dBc/Hz phase noise at 1 MHz offset. Explore use of the spread spectrum modulation code waveforms in addition to convention frequency-modulated continuous wave (FMCW). The detection range should be >100m (or maximum achievable range within the power and noise constraints of the overall system) and range resolution ~1 mm. The IC design should include option to allow multiple chips to operate in parallel and synchronously to improve detection range and angle resolution. Fabricate the ICs through a multi-project wafers service within the STTR budget constraint. Construct a prototype radar system based on the ICs and demonstrate its performance. PHASE III DUAL USE APPLICATIONS: It is expected that THz radar-on-chip will enable a wide range of radar applications including autonomous navigation, security surveillance and screening, biometric vital sign detection, human-machine interfaces, and much more. Low cost of terahertz radar-on-chip ICs will be a key enabler for these applications. REFERENCES: K.B. Cooper, THz Imaging Radar for Standoff Personnel Screening, IEEE Transactions on Terahertz Science and Technology, Vol. 1, No. 1, pp. 169-182, September, 2011. 2. P. Hillger et al, Terahertz Imaging and Sensing Applications With Silicon-Based Technologies, IEEE Transactions on Terahertz Science and Technology, Vol. 9, No. 1, pp. 1-19, January, 2019. 3. K. Sengupta et al, Terahertz integrated electronic and hybrid electronic photonic systems, Nature Electronics, Vol. 1, pp. 622-635. 4. http://www.ti.com/sensors/mmwave/overview.html 5. J. Grzyb et al, A 210 270-GHz Circularly Polarized FMCW Radar With a Single-Lens-Coupled SiGe HBT Chip, IEEE Transactions on Terahertz Science and Technology, Vol. 6, No. 6, pp. 771-783, November, 2016. 6. J. Lien et al, Soli: ubiquitous gesture sensing with millimeter wave radar, ACM Transactions on Graphics, Vol. 35, No. 4, Article 142, July 2016. KEYWORDS: Radar, sub-millimeter wave, terahertz, integrated circuits, CMOS, SiGe, GaN, InP, MIMO, autonomous navigation, human-machine interface
