22.1 THz Prism: One-Shot Simultaneous Multi-Node Angular Localization Using Spectrum-to-Space Mapping with 360-to-400GHz Broadband Transceiver and Dual-Port Integrated Leaky-Wave Antennas

The spectrum above 100GHz is expected to spawn a generation of ultra-high-speed wireless links and intelligent sensing and imaging applications. They are meant to be supported through a heterogeneous and dynamically reconfigurable wireless network fabric in 5G and beyond. Such wireless communication and sensing applications require rapid localization and direction finding of mobile nodes [1]. This functionality is paramount for communications-on-the-move applications, wireless link discovery, and rapid beam alignment/tracking at mm-wave and THz frequencies [2]-[9]. The current protocols for direction finding and beam alignment in 5G mm-wave systems are based on iterative algorithms that are often non-scalable, time-consuming, and computationally expensive, posing serious challenges for low-latency applications. Thus there is a need to process such direction-finding methods at the `edge nodes', to enable secure scalable networks with very low latencies [10]. In this article, we present a spectrum-to-space mapping principle, where localization information can be processed at the edge `sensor node' through the spectrum sensing. The conceptual idea is presented in Fig. 22.1.1, which shows an access point (transmitter/receiver) that acts as a THz prism casting different spectral portions of a broadband THz signal across space. If the mapping is unique, multiple edge nodes can simultaneously localize themselves in a single-shot fashion through localized spectrum sensing, avoiding the use of the slow iterative process and bi-directional communication. In this paper, we present a scalable 360-to-400GHz transceiver architecture in 65nm CMOS with frequency-dependent beam synthesis using two dual-port integrated frequency-dispersive leaky-wave antennas. The two antennas when excited/sensed across the two opposite end-ports, cover a 1D spatial angle $across \pm 40^{\circ}$, and enable 2D localization with two such ICs covering both orthogonal basis vectors with a frequency-offset radiation (Fig. 22.1.1). Exploiting the cross-correlation of the spectrum-to-space mapping (Fig. 22.1.1), the system achieves 2D localization accuracy of $\sigma_{\varphi},= 1.9$ ° and $\sigma_{theta}= 1.95^{\circ}$ for a measurement resolution bandwidth (RBW) of 20Hz.