Doppler-Hitchhiker: A Novel Passive Synthetic Aperture Radar Using Ultranarrowband Sources of Opportunity

Abstract

Abstract-In this paper, we present a novel synthetic aperture radar imaging modality that uses ultranarrowband sources of opportunity and passive airborne receivers to form an image of the ground. Due to its combined passive synthetic aperture and high Doppler resolution of the transmitted waveforms, we refer to this modality as the Doppler Synthetic Aperture Hitchhiker or Doppler-hitchhiker for short. Our imaging method first correlates the windowed signal obtained from one receiver with the scaled and translated version of the received signal in another window from the same or another receiver. We show that this correlation processing removes the transmitter-related variables from the phase of the resulting operator that maps the radiance of the scene to the correlated signals. We define a concept of passive Doppler scale factor using the radial velocities of the receivers. Next, we show that the scaled, translated, and correlated signal is the projection of the scene radiance onto the contours that are formed by the intersection of the surfaces of constant passive Doppler scale factor and ground topography. We use microlocal analysis to design a generalized filtered-backprojection operator to reconstruct the scene radiance from its projections. Our analysis shows that the resolution of the reconstructed images improves with the increased time duration and center frequency of the transmitted ultranarrowband signals. Our reconstruction method is analytic and therefore can be made computationally efficient. Furthermore, it easily accommodates arbitrary flight trajectories, nonflat topography, and system-related parameters. We present numerical simulations to demonstrate the performance of our imaging method.Index Terms-Filtered-backprojection (FBP), passive imaging, passive radar, passive synthetic aperture radar, ultra-narrowband waveforms.

Synthetic Aperture Inversion for Statistically Nonstationary Target and Clutter Scenes

“…Although, our current treatment focuses on the bistatic configuration, the methods and algorithms presented in this paper can be extended to other SAR modalities [23,47,48,55,56].…”

Radar Imaging of Stationary and Moving Targets

“…For multi-static synthetic aperture imaging exploiting multiple-scattering, see [9]. For a novel passive synthetic aperture imaging modality using ultra-narrowband waveforms, see [10,6,7]. For passive imaging of stationary targets using sparse distributed apertures in multiple-scattering environments, see [11].…”

Signal detection with noisy reference for passive sensing

“…If the signal to be detected is perfectly known and the noise is stationary with zero-mean and white power spectral density, the optimal detector is the matched filter (MF) which maximizes the output signal-to-noise ratio (SNR) [1]. However, the signal may not be known in many practical applications, such as underwater acoustics [2][3][4][5], seismology [6][7][8][9], neurophysiology [10,11], and passive radar [12][13][14][15][16]. Consider for example passive radar.…”