Defeng Chen

Inverse synthetic aperture radar imaging and cross-range scaling for space objects

Radar imaging based on theorem of inverse synthetic aperture is an important means for space object identification, and cross-range scaling is a key issue. This paper makes a systematic overview on the theorem of ISAR imaging, and then presents the relationship between the observation time and ISAR image cross-range resolution of space objects. An accurate crossrange scaling method for ISAR image of space objects is proposed. Outdoor experiment of ISAR imaging and cross-range scaling for space object show the effectivity of the method.

An improved method for dim space debris detection based on hough transform

An improved integration method is applied to detect dim debris targets in this paper. The algorithm makes full use of prior orbit information to reduce motion uncertainty, and then adopts the Hough line transform to integrate echo energy from multiple pulses. Thus, the detection capability for small-size space debris in the low earth orbit can be effectively improved. The proposed method is easy to be realized in engineering application; its feasibility and effectiveness are further confirmed by simulation experiments.

A novel integration method for nonuniform pulse-train signal

When the nonuniform pulse-train signal is applied to the problem of weak target detection, the traditional long-time integration methods based on FFT are no longer valid. A novel method based on Keystone transform and nonuniform FFT is proposed here to accumulate the echo energy, wherein the former is employed to remove the range walk and the latter realizes the coherent integration of nonuniform pulses. The algorithms effectivity is further evaluated and verified by numerical simulation experiments.

A correction algorithm of migration through Doppler resolution cell for bistatic inverse synthetic aperture radar

When the size of a target or the rotation angle is large, migration through resolution cell may occur in the bistatic inverse synthetic aperture radar (Bi-ISAR) which will affect the imaging quality. A correction algorithm based on the minimum criterion of image entropy is proposed in this paper. The rotating center is estimated according to this criterion. Then the phase compensation term is constructed and the correction of migration through Doppler resolution cell is finished. Finally, simulations are carried out which compare the quality of images based on the maximum criterion of image contrast and the minimum criterion of image entropy. The results show that the proposed method can correct the migration through Doppler resolution cell and improve the imaging quality.

A New Method for Anti-Noise FM Interference

Noise frequency modulated (NFM) interference causes a disaster to almost all types of radar systems. The echo signal and the interference are overlapped because of the strong energy of the NFM interference, and in the radar receiver system nothing could be detected except the interference. Up to now no good method against NFM has been declared, conventional methods are based on the passive radar to track the interference source. Here a new anti-noise FM method is proposed to suppress the NFM interference, the method multiply the echo signal two times by different reference signals, and results show that the method can eradicate NFM effectively which is useful for detecting and tracking the target. Whatpsilas more, in the presence of several interferences from different directions, the passive Radar can not track the interference source but the method supposed here can work well.

Geostationary orbital objects detection based on spaceborne radar imaging

The geostationary orbit is the most significant orbit. Space objects in the orbit could be detected by imaging nearby using spaceborne inverse synthetic aperture radar (ISAR). Based on the analysis of RCS characteristic of geostationary orbital targets, the orbital altitude and revisiting period of space-based radar are designed in detail, so are the antennapsilas size. The relationship between imagepsilas resolutions of spaceborne ISAR and system parameters is discussed. Finally, the accumulated time according to appointed cross range resolution is proposed both in direct orbit and retrograde orbit. The research work is meaningful as a guide to engineering realization.