Joint Communication and Sensing at D-Band SDR and at 5.8 GHz via Multibeam Arrays

Joint communication and sensing (JCAS) are gaining attention as essential solutions to address the requirements of modern applications while promoting the efficient utilization of spectrum resources. Further, GPS-denied location, navigation, command, and control for unmanned aerial systems (UAS) is important from the standpoint of modern military applications, where GPS is usually not available. In this article, we discuss JCAS using 5.8 GHz industrial, scientific, and medical (ISM) band data communications using a software-defined radio (SDR) approach, where range and direction information is recovered through real-time cross correlation methods across multiple simultaneous receive beams in a single shot. Further, a multifrequency active repeater technique is proposed, where the uplink is at the D-band, and the downlink occurs at 5.8 GHz ISM band, which allows secure and safe command and control of a UAS while allowing location and enhanced security using JCAS in a GPS denied environment. Preliminary experiments using SDR with D-band wireless transmissions for connectivity to a UAS (uplink) ensure that the ground station uses directional transmissions from ground-to-air, making it difficult to detect from ground-based sensors. Further, an active down-converting repeater at the UAS allows omni-directional downlink transmissions at the UAS, making the location of the ISM and array receiver (ground station) difficult to detect from ground-based sensors using direction finding methods. Experimental testbed allows 100 Mbps data rate (up/down) at 147 GHz and 5.8 GHz ISM band, multiple snapshot-based averaging for improved SNR, and 32-beam multibeam digital array receivers for directional and range information over 180° in a single shot. All implementations are real-time and operate on FPGA technology. Ground station uses approximate discrete Fourier transform (DFT)-based beamformers having linear arithmetic complexity for achieving realtime DSP at low arithmetic complexity.