Yicheng Jiang

Inverse Synthetic Aperture Radar Imaging of Maneuvering Target Based on the Product Generalized Cubic Phase Function

For inverse synthetic aperture radar (ISAR) imaging of a maneuvering target, the Doppler frequency shift for the received signal in a range bin is time varying. In this letter, the received signal is modeled as a multicomponent cubic phase signal, and a new ISAR imaging algorithm based on the product generalized cubic phase function (PGCPF) is proposed. The PGCPF algorithm can estimate the parameters of a multicomponent cubic phase signal, and combined with the range-instantaneous-Doppler technique, high-quality instantaneous ISAR images can be obtained. Results of real data demonstrate the effectiveness of the new method presented in this letter.

ISAR Imaging of a Ship Target Using Product High-Order Matched-Phase Transform

Inverse synthetic aperture radar (ISAR) imaging of a ship target is very important compared with the plane target, and the imaging condition of the ship target is more complicated than that of the plane target due to the complexity of the ships movement. In this letter, the received signal of a ship target is modeled as a multicomponent cubic phase signal, and the product high-order matched-phase transform is proposed to estimate the parameters of each component. Then, the instantaneous ISAR images can be obtained. Results of real data demonstrate the effectiveness of the new method proposed.

A Novel Algorithm for Estimating the Rotation Angle in ISAR Imaging

A novel algorithm for estimating the rotation angle in inverse synthetic aperture radar imaging by generally considering the received signals as cubic phase signals is presented. The rotation angle is determined by the coefficients of the cubic phase signals, and the results of real data demonstrate the validity of the algorithm.

Generalized Omega-K Algorithm for Geosynchronous SAR Image Formation

Geosynchronous synthetic aperture radar (GEO SAR) data focusing is a more challenging and difficult task than the low earth orbit (LEO) SAR due to the strong 2-D coupling of echo signal induced by the orbital trajectory curvature. The range cell migration (RCM) in the GEO SAR configuration is space variant in both range and azimuth directions, hence standard RCM correction (RCMC) functions developed for LEO SAR are inadequate for GEO. In this letter, a curved trajectory model is proposed, taking into consideration the impacts of “stop-and-go” assumption. Based on the range model, a new data transform is derived to deal with the complicated coupling in GEO SAR. From the derivation, we find that the original Stolt mapping is a special case of the proposed “generalized Omega-k” algorithm. In comparison with the original Omega-k algorithm, this new algorithm can correct more complicated RCM effectively. Finally, simulation results show that the proposed imaging algorithm performs well for large scene focusing in an L-Band GEO SAR system.

Bistatic ISAR distortion and defocusing analysis

Bistatic inverse synthetic aperture radar (ISAR) is an efficient geometric configuration of ISAR to image targets traveling along radar transmitters line of sight, but it has the problem of defocusing and distortion because of the time-varying bistatic angle. In this paper, we derive the defocusing term and the distortion term by expanding the bistatic angle using first-order Taylor expansion. In addition, necessary constraints to neglect the defocusing term are provided via point spread function analysis, and a novel method to eliminate distortion based on linked scatterers is proposed. Simulation results validate our theoretical analysis and show the effectiveness of our method.

Efficient Clutter Suppression in SAR Images With Shedding Irrelevant Patterns

Strong clutter reflections of terrain and marine surfaces obscure the contrast between the target-of-interest and clutter (terrain and marine surface reflections) in synthetic aperture radar (SAR) images and consequently hinder the efficiency of image interpretation and analysis. To overcome this problem, this letter proposes an efficient clutter suppression method in SAR images, which is named shedding irrelevant patterns (SIP). The essence is to construct a regression function that can suppress clutter and preserve the target patterns concurrently. We assume that the clutter is irrelevant to the target-of-interest and distinguishable in patterns in terms of image-pixel distribution and intensity (spatial information). Experimental results show the efficiency of the proposed method in both clutter suppression and target pattern preservation.

Three-dimensional shipborne inverse synthetic aperture radar imaging based on single receiver

ABSTRACT Three-dimensional (3D) inverse synthetic aperture radar (ISAR) image can provide additional height information compared to conventional 2D ISAR image. However, since the existing 3D ISAR imaging methods concentrate on the interferometric technique, the height resolution depends on a large number of receivers. In this letter, a novel 3D ISAR imaging method is proposed. Instead of using the interferometry between several receivers, the chirp term caused by the shipborne radar’s rotations is utilized to obtain the height resolution. Therefore, single receiver is enough to reconstructing the 3D image, and hence the hardware complexity for 3D ISAR imaging is reduced. Simulation results validate the effectiveness of the proposed method.

Defocusing and distortion elimination for shipborne bistatic ISAR

ABSTRACT Shipborne bistatic inverse synthetic aperture radar (ISAR), with a stationary and visible transmitter on land and a mobile and stealthy receiver on a ship with complex 3-D rotations is a strategic asset which can provide complementary information to monostatic ISAR. However, it must first overcome the serious problems of defocusing and distortion due to the time-varying bistatic angle. In this letter, an improved cubic chirplet decomposition method is proposed to solve the defocusing problem. By decomposing the ISAR echo into cubic chirplet atoms and estimating the parameters for each term, higher-order defocusing terms can be eliminated. Moreover, a novel method based on linked scatterers is put forward to solve the distortion problem. The method utilizes ‘linked scatterers’ from monostatic ISAR image to calculate and compensate the distortion angle. The effectiveness of the proposed methods is verified by the simulation results.

Three-dimensional aircraft isar imaging based on shipborne radar

A three-dimensional inverse synthetic aperture radar (ISAR) image can provide the target’s information in range, cross-range, and height directions. Because the existing three-dimensional ISAR imaging methods require changing the observing angle, they are highly dependent on radar hardware complexity or target maneuvering movement. In this paper, a new three-dimensional ISAR imaging method based on shipborne radar is proposed. Instead of utilizing multiple radar receivers or uncontrollable target movement, we take advantage of the ship’s known yaw, pitch, and roll rotations, and obtain different observing angles using a single receiver fixed on the ship. To extract the scatterers, a new algorithm called REACT that combines RELAX and adaptive chirplet transform is presented. Subsequently, the errors of the three-dimensional imaging method are analyzed by partial derivative deduction and Monte Carlo simulation. On the basis of the error analysis, a novel best imaging time selecting method based on image quality function that considers both accuracy and resolution is also put forward. Simulation results validate our theoretical analysis and show the effectiveness of our method.

*An approach to ship position estimation and clutter suppression based on GEO satellite/airborne bistatic sar with a multi-receive antenna

ABSTRACT Geosynchronous spaceborne-airborne bistatic synthetic aperture radar (GEO SA-Bi SAR), which employs a geosynchronous orbit (GEO) satellite as a transmitter and an aeroplane that works on the ‘receive-only’ mode as a receiver, is distinct from general bistatic synthetic aperture radar (SAR) systems. In this paper, a GEO SA-Bi SAR system with multi-receive antenna is consider for marine surveillance. First, ship position is estimated in the configuration of GEO SA-Bi SAR with multi-receive antenna, using maximum likelihood (ML) method. Then, according to the estimation result, sea clutter in the signal of a moving point target is suppressed by adaptive beamforming (ABF). Moreover, the performance of our method is analysed and studied in terms of the point target imaging. The simulation results demonstrate the correctness and effectiveness of the proposed method.