Collaborative Research: SWIFT: SCISRS: Signal Cancellation using Intelligent Surfaces for Radio Astronomy Services

Suny At Albany, Albany NY

Investigators

Abstract

This project investigates use of a reconfigurable intelligent surface (RIS) installed near a radio telescope to help mitigate radio frequency interference (RFI) from other users of the electromagnetic spectrum. The RIS reflects incoming RFI signals towards the telescope in such a way that the reflected RFI cancels out the direct RFI when the two signals combine in the telescope receiver. Better capability to observe in commercial wireless bands and in other bands with active usage, not just in bands reserved for science, will enhance the fidelity of astronomical measurements. Also, the formerly remote locations where radio telescopes were built are experiencing ongoing increases in population density, increased numbers of low earth orbiting satellites, and other effects that increase RFI over time. Improving the ability to remove RFI from astronomical observations helps preserve the value of the investment in these expensive instruments and helps ensure their continued scientific capability. The platform and tools developed in this project will be incorporated into graduate and undergraduate courses at UAlbany as well as a summer school at OVRO. Wireless signals and other datasets captured from the testbed will be made available to the larger community to foster practical research in this field. The primary technical objectives of this project are to accurately estimate the RFI incident at the telescope and to configure the RIS so the reflected signal arriving at the telescope receiver precisely cancels the incident RFI. Cancellation requires control over both amplitude and phase of the reflected signal, which is achieved by tuning the reflecting elements of the intelligent surface. A key challenge tackled in the research is to cancel mobile RFI sources such as airplanes and satellites. Mobile sources stress the ability of the RIS controller to keep up with changes in the direction of RFI and the controller’s ability to keep the surface tuned precisely enough to cancel the RFI. The project combines three areas of innovation to overcome this challenge. At the system level, the RIS controller uses feedback from the telescope, which continually reports the residual RFI it sees, to compensate for estimation errors. At the algorithm level, a novel, low-complexity multi-stage direction of arrival estimation method is combined with an adaptive beamforming algorithm that shapes and steers the reflected RFI. At the hardware level, a 16-channel high-speed processing platform built from Field Programmable Gate Arrays is coupled with a custom fabricated RIS to enable real time RFI estimation and adaptive beamforming. The project will construct an experimental radio telescope at University at Albany, SUNY (UAlbany) based on the Small Radio Telescope (SRT) design from MIT Haystack Observatory. The cancellation approach will be tested on the UAlbany SRT and on one antenna of the large DSA-110 telescope array at the Owens Valley Radio Observatory (OVRO). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.