RF photonic apertures
Date
2018
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
For decades, phased array antenna technology has served as the main platform for controlling the directionality and shape of electromagnetic energy in accordance to application specific tasks. Modern development of these systems has shifted focus towards phased arrays that perform all operations through multifunctional apertures, which simultaneously support radar, RF sensing, imaging, and ultra-fast wireless communication links. While technological research and development efforts pertaining to this goal has mostly manifested within military applications, the advent of 5G deployment has spurred recent interest in adopting comparable functionality requirements, and phased array configurations, to satisfy the needs these of next generation wireless communications networks. In particular, the transition to mmW frequency operation in multiple-input multiple-output (MIMO) networks, at a massive scale, drives new systems to be highly integrated, fast scanning apertures, with low size, weight and power (SWaP), to dynamically support multiple users with low latency and fine phase resolution. Unfortunately, the design requirements concomitant with this paradigm shift in commercial wireless communications have exposed many difficulties inherent to the deployment of traditional electronic systems. ☐ In this work, two novel RF photonic aperture designs are proposed for integration into spatially-coherent phased array architectures to facilitate 5G wireless networking. One RF photonic aperture comprises a highly integrated photodiode-coupled phased array transmit antenna which transfers the optical-to-electrical conversion process directly to the antenna’s radiating elements. By directly coupling high-power charge-compensated modified uni-traveling carrier (CC-MUTC) photodiodes at each antenna element, bulky and expensive RF cables, which are fundamentally limited at mmW frequencies by loss, can be replaced with light weight, low-loss, and electromagnetic interference immune optical fibers. As a result, remote deployment of phased array antennas with sufficient RF output powers and beamsteering capability, over multiple 5G spectral bands, is realizable. The efficacy of this approach is presented through low SWaP photonic connected array antennas designed for wide scan operation over 5 – 20 GHz. ☐ The second RF photonic aperture consists of a Ka-band phased array receive antenna coupled to a temporal aperture. By integrating this spatio-temporal aperture into an imaging system, the simultaneous detection of radio waves’ frequency and angle of arrival is enabled through coherent optical processing. This newly developed imaging modality, referred to as k-space tomography, uses fiber-length dispersion in conjunction with a distributed antenna array to provide unique spatio-temporally encoded CCD-captured interferograms, from which a computational tomographic reconstruction of the RF signal environment can be obtained for newly allocated 5G bands. A key aspect of this work is using the sparsity of RF spatial and spectral distributions in the electromagnetic environment to merge this imaging modality with established compressive sensing techniques. By adapting specific characteristics of this methodology, and applying them to k-space tomography, compressive k-space tomography is developed. As a result, reconstruction data size and processing time are reduced significantly, without loss of information, for low latency spatial-spectral utilization mapping.
Description
Keywords
Pure sciences, Applied sciences, Phased array antennas, RF imaging, RF photonics