SAR Signal Reconstruction from Non-Uniform Displaced Phase Centre Sampling

The displaced phase centre (DPC) technique will enable a wide swath SAR with high azimuth resolution. In a classic DPC system, the PRF has to be chosen such that the SAR carrier moves just one half of its antenna length between subsequent radar pulses. Any deviation from this PRF will result in a nonuniform sampling of the synthetic aperture. This paper shows that an unambiguous reconstruction of the SAR signal is also possible in case of such a non-optimum PRF. For this, an innovative reconstruction algorithm is derived, which enables a recovery of the unambiguous Doppler spectrum also in case of a non-uniform sampling of the synthetic aperture. This algorithm will also have a great potential for multistatic satellite constellations as well as the dual receive antennas in Radarsat II and TerraSAR-X

Spaceborne P-Band MIMO SAR for Planetary Applications

The Space Exploration Synthetic Aperture Radar (SESAR) is an advanced P-band beamforming radar instrument concept to enable a new class of observations suitable to meet Decadal Survey science goals for planetary exploration. The radar operates at full polarimetry and fine (meter scale) resolution, and achieves beam agility through programmable waveform generation and digital beamforming. The radar architecture employs a novel low power, lightweight design approach to meet stringent planetary instrument requirements. This instrument concept has the potential to provide unprecedented surface and near-subsurface measurements applicable to multiple Decadal Survey Science Goals

Beamforming P-Band Synthetic Aperture Radar for Planetary Applications

The Space Exploration Synthetic Aperture Radar (SESAR) is an advanced P-band beamforming radar instrument concept to enable a new class of observations suitable to meet multiple Decadal Survey science goals for planetary exploration. The radar is capable of providing unprecedented surface and near subsurface measurements at full polarimetry and fine (meter scale) resolution, and achieves beam agility through programmable waveform generation and digital beamforming. The radars highly flexible modular architecture employs a novel low power, lightweight design approach to meet stringent planetary instrument requirements, all while minimizing cost and development time

Multichannel SAR imaging using wavefront reconstruction

6 pagesThe combination of phased arrays with Synthetic Aperture Radar (SAR), ie. multichannel SAR offers many benefits such as improved ambiguity suppression for Moving Target Indication (MTI) and imaging large swaths [1]-[2], improved Signal-Noise-Ratio (SNR) [3] and the potential to suppress spatial jammers by use of Space Time Adaptive Processing (STAP) [4]. Classical SAR imaging is based on analogue/optical techniques and includes polar format and range-doppler based imaging. More precise imaging algorithms are based on wavefront reconstruction [5], and offer the potential for imaging with greater accuracy. Soumekh [6], has summarised a number of these including spatial MF interpolation, range stacking and time domain correlation. While multichannel SAR imaging has been addressed by [4], there has been no comprehensive study on how different wavefront reconstruction algorithms can be implemented for focussing multichannel data. This work extends these three SAR wavefront reconstruction algorithms to include multiple transmit and receive antennas and provides a quantitative comparison of their Point Spread Functions (PSF).Luke Rosenberg and Doug Gra

Design and Performance Estimation of a Photonic Integrated Beamforming Receiver for Scan-On-Receive Synthetic Aperture Radar

Synthetic aperture radar is a remote sensing technology finding applications in a wide range of fields, especially related to Earth observation. It enables a fine imaging that is crucial in critical activities, like environmental monitoring for natural resource management or disasters prevention. In this picture, the scan-on-receive paradigm allows for enhanced imaging capabilities thanks to wide swath observations at finer azimuthal resolution achieved by beamforming of multiple simultaneous antenna beams. Recently, solutions based on microwave photonics techniques demonstrated the possibility of an efficient implementation of beamforming, overcoming some limitations posed by purely electronic solutions, offering unprecedented flexibility and precision to RF systems. Moreover, photonics-assisted RF beamformers can nowadays be realized as integrated circuits, with reduced size and power consumption with respect to digital beamforming approaches. This paper presents the design analysis and the challenges of the development of a hybrid photonic-integrated circuit as the core element of an X-band scan-on-receive spaceborne synthetic aperture radar. The proposed photonic-integrated circuit synthetizes three simultaneous scanning beams on the received signal, and performs the frequency down-conversion, guaranteeing a compact 15 cm2-form factor, less than 6 W power consumption, and 55 dB of dynamic range. The whole photonics-assisted system is designed for space compliance and meets the target application requirements, representing a step forward toward a deeper penetration of photonics in microwave applications for challenging scenarios, like the observation of the Earth from space

Introducing F-Scan to the concurrent imaging mode

The concurrent imaging mode is a recently proposed technique to increase the imaging capability and flexibility of SAR systems. This mode allows for simultaneous acquisitions of two areas by increasing the pulse repetition frequency (PRF) by interleaving the transmission and reception of two modes in a pulse-to-pulse manner. Due to intrinsic system limitations, this technique applied to current operational systems, such as the German satellite TerraSAR-X, comes along with strong trade-offs in terms of limited swath width and increased ambiguity levels. For future X-band missions, the frequency scanning (F-Scan) technique is one of the most promising methods considered. Therefore, this paper aims to derive timing and interference analyses for the integration of F-Scan with the concurrent imaging concept. Additionally, it will be shown that F-Scan can improve the main critical performance parameters of the concurrent mode

Multichannel SAR imaging with backprojection

© Copyright 2004 IEEEThe use of multiple antennas on a synthetic aperture radar (SAR), i.e., multichannel SAR, offers benefits such as improved ambiguity suppression for moving target indication (MTI) and imaging large swaths (Goodman, N.A. et al. 2002; Ender, J.H.G., 2000), improved signal-to-noise ratio (SNR) (Younis, M. et al., 2003) and the potential to suppress spatial jammers by use of space time adaptive processing (Ender, 1998). The multichannel matched filter (MF) interpolation imaging scheme presented by L. Rosenberg and D. Gray (see Int. Radar Symp. Proc., 2004) offers a good tradeoff between imaging accuracy and computational complexity. However, there are a number of potential problems which affect this algorithm in practice. Backprojection offers a solution to these problems and instead offers a direct tradeoff between accuracy and computation time. We extend the single channel backprojection algorithm to include multiple transmit and receive antennas. An analysis of the performance of the algorithm with varying levels of accuracy is shown, as well as a comparison with conventional MF algorithms

Dynamic Experiment Design Regularization Approach to Adaptive Imaging with Array Radar/SAR Sensor Systems

We consider a problem of high-resolution array radar/SAR imaging formalized in terms of a nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) of the random wavefield scattered from a remotely sensed scene observed through a kernel signal formation operator and contaminated with random Gaussian noise. First, the Sobolev-type solution space is constructed to specify the class of consistent kernel SSP estimators with the reproducing kernel structures adapted to the metrics in such the solution space. Next, the “model-free” variational analysis (VA)-based image enhancement approach and the “model-based” descriptive experiment design (DEED) regularization paradigm are unified into a new dynamic experiment design (DYED) regularization framework. Application of the proposed DYED framework to the adaptive array radar/SAR imaging problem leads to a class of two-level (DEED-VA) regularized SSP reconstruction techniques that aggregate the kernel adaptive anisotropic windowing with the projections onto convex sets to enforce the consistency and robustness of the overall iterative SSP estimators. We also show how the proposed DYED regularization method may be considered as a generalization of the MVDR, APES and other high-resolution nonparametric adaptive radar sensing techniques. A family of the DYED-related algorithms is constructed and their effectiveness is finally illustrated via numerical simulations

Design and performance estimation of a photonic integrated beamforming receiver for scan-on-receive synthetic aperture radar

Synthetic aperture radar is a remote sensing technology finding applications in a wide range of fields, especially related to Earth observation. It enables a fine imaging that is crucial in critical activities, like environmental monitoring for natural resource management or disasters prevention. In this picture, the scan-on-receive paradigm allows for enhanced imaging capabilities thanks to wide swath observations at finer azimuthal resolution achieved by beamforming of multiple simultaneous antenna beams. Recently, solutions based on microwave photonics techniques demonstrated the possibility of an efficient implementation of beamforming, overcoming some limitations posed by purely electronic solutions, offering unprecedented flexibility and precision to RF systems. Moreover, photonics-assisted RF beamformers can nowadays be realized as integrated circuits, with reduced size and power consumption with respect to digital beamforming approaches. This paper presents the design analysis and the challenges of the development of a hybrid photonic-integrated circuit as the core element of an X-band scan-on-receive spaceborne synthetic aperture radar. The proposed photonic-integrated circuit synthetizes three simultaneous scanning beams on the received signal, and performs the frequency down-conversion, guaranteeing a compact 15 cm2-form factor, less than 6 W power consumption, and 55 dB of dynamic range. The whole photonics-assisted system is designed for space compliance and meets the target application requirements, representing a step forward toward a deeper penetration of photonics in microwave applications for challenging scenarios, like the observation of the Earth from space