Beardell, William L.Ryan, Conor J.Schneider, Garrett J.Murakowski, JanuszPrather, Dennis W.2023-06-022023-06-022023-05-15W. L. Beardell, C. J. Ryan, G. J. Schneider, J. Murakowski and D. W. Prather, "Microwave Photonic Direction-Finding Spectrometer," in Journal of Lightwave Technology, vol. 41, no. 10, pp. 3057-3064, 15 May, 2023, doi: 10.1109/JLT.2023.3242627.1558-2213https://udspace.udel.edu/handle/19716/32818This article was originally published in Journal of Lightwave Technology. The version of record is available at: https://doi.org/10.1109/JLT.2023.3242627In this paper, we propose an architecture wherein the radio-frequency (RF) field at the antenna array is up-converted to an optical carrier and passed through an array of optical fibers, after which an analog Fourier transform is taken in a free-space optical processor. Through the use of multiple temporal dispersion projections, implemented through varied-length optical fiber segments, the locations of RF sources in three-dimensional space spanning angle-of-arrival (AoA) and instantaneous frequency may be determined on a millisecond time scale using commercial computing hardware after detection by a charge-coupled device (CCD) camera. We present a mathematical formulation of the problem, followed by simulated and experimental results showing three-dimensional spatial-spectral localization through the solution to a system of equations brought forth through the use of Fourier optics to process the RF field.en-USoptical signal processingmicrowave photonicsmillimeter wave communicationmultispectral imagingspatial diversityArticle