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.