Abstract:Cross ambiguity processing is comm only used for target detection in passive bistatic radar system. However, its th eoretical detection performance on passive bistatic radar is rarely encountered in previous published papers. This paper addresses the theoretical problem of de tecting the presence of a target echo in passive bistatic radar when the bandwid ths of opportunity illuminators are unknown. Analytical expressions are obtaine d for the characteristic function and probability density function (PDF) of norm alized cross ambiguity function (NCAF) when the data samples in the target surve illance and reference channels are contaminated by narrowband uncorrelated white Gaussian noises. The closed form of detection probability and false alarm proba bility for NCAF are derived. They are used to determine which cell in the amb iguity surface exceeds a preset threshold. Results are presented in the form of curves showing the values of input SNRs required to achieve a specified detectio n probability for different system parameters. The detection performance shows that target signal can be detected when SNR in target surveillance channel is large than -20 dB and SNR in direct path channel is large than 5 dB. Furthermore, compared to the detection performance in matched sampling case, the detection probability will be decreased about 0.1 if the mismatch coefficient of sampling is less than 2.

Abstract:Compared to the eyes of the aircraft, airborne weather radar is an imperative avionics equipment for com mercial aviation, which is important and necessary to ensure the flight safety. At present, the key technology of airborne weather radar is mastered by foreign manufactures. This paper gives a comprehensive overview of airborne weather rada r and its related signal processing methods (including precipitation awareness, turbulenc e detection, wind shear detection and ground clutter suppression). The key techn ologies and the problems to be solved are also addressed. Finally, the next gene ration airborne weather radar with enhanced situation awareness and its opening problems are remarked.

Abstract:Inverse synthetic aperture radar (ISAR) is an important approach to derive d etailed information of wideband radar target, where defocusing caused by complex motion and low resolution are two key difficulties. This paper gives a survey o f radar imaging of complex motion target, including modulation effect of micro m otion, procession target imaging, three dimensional motion target imaging and s e parate motion parts imaging. Aiming at improving image resolution, coherent comp ensation among sub bands and fusion imaging are also demonstrated. Then new app r oaches of radar imaging are presented, wherein radar coincidence imaging is irre levant to the relative motion between radar and target, thus avoid compensating complex motions. In THz imaging it is easy to implement large bandwidth and narr ow wave beam; thereby the formulated high resolution images are with more detail s which are beneficial to target recognition. Finally, difficulties and directio ns for these two newly developing techniques are pointed out.

Abstract:Netted radar system can sense the battl e field in multiple levels and can gain rider information than a single rada r system. Due to these features, netted radar system shows great advantages in a nti-deception jamming. Firstly, an introduction to netted radar is given, and i t s potential cooperative electronic counter countermeasures (ECCM) abilities aga i nst deception jamming are analyzed. According to the difference in the fusion st ructure, the existing anti-deception jamming approaches are classified as data f usion-based and signal fusion-based anti-jamming methods. Moreover, data fusi on- based methods are classified as measurement fusion and track fusion. In this pap er, all classes of cooperative anti-deception jamming approaches are presented i n detail. Then, the anti-jamming performance and computational compl e xity of these two classes of methods are analyzed. Finally, based on the analysi s of existing methods, this paper highlights the development direction of the cooperative ant i-deception jamming, and then points out the future research interests.

Abstract:Through analyzing the influence of imaging of 3D rocking ship targets under heav y scale sea, as well as based on the concept of variance, an average Doppler spr ead definition is proposed to estimate the optimal processing time and duration for ISAR. In this algorithm, the ship natural pitching period is estimated th rough the information of the range direction, by which the micro Doppler eff ect is eliminated and a reliable basis for smoothing Doppler spread curve is pro vided. The algorithm can work automatically instead of artificial intervention. The simulation and measured data processing results show that ideal ISAR images can be obtained by using the data segments selected by the proposed algorithm.

Abstract:MIMO-SAR （ multiple input multiple output synthetic aperture radar） is a new kind of SAR s y stem， which combines multiple transmitters and multiple receivers to acquire mo r e equivalent phase centers and more degrees of freedom．By this way， MIMO S AR ex te nds system working mode and improves the performance．However, SAR echo is scatt er ed from a distributed scene. Cross-correlation noise will overlap and interfere n ces will degrade the image. That will make the separation methods used in MIMO r adar fail in MIMO-SAR. Therefore, separation is a key problem to the implementa tion of MIMO SAR. This paper introduces the principle of MIMO SAR and it s ap plications, then reviews the methods proposed in current literatures．The princi p les and constrains of every separation method are pointed out. Some new approach es t o the problem are proposed and discussed．

Abstract:A two-stage reduced-dimension space-time adaptive processing (STAP) method fo r clutter suppression in airborne multiple-input multiple-output (MIMO) radar is proposed. The Doppler filtering method is firstly performed to reduce the dat a dimension in temporal domain. Then the weight vector of the two-dimensional t r ansmit-receive beamformer is decomposed into the Kronecker product of the trans mit and the receive weight vectors. The two low-dimensional weight vectors are res olved respectively to synthesize the final weight vector. The proposed method ca n significantly decrease the training sample requirement and the computational l oad. Under the small sample number condition the method can provide a good clutt er suppression performance, so it has greater value in practical applications. S imulation results verify the effectiveness of the proposed method.

Abstract:The Gaussian mixture cardinalized probability hypothesis density fi lter (GM-CPHD) is a recursive Bayesian filter for track-before-detect multita rge t tracking algorithm in clutter, which propagates the first moment of the multi target posterior density, incorporating track initiation and termination without consideration of measurement-to-track association. Due to the fact that GM-C PHD filer has a great computational complexity: (nm3), where n is the nu mber of targets and m is the cardinality of measurement set, an adaptive gating alg orit hm is proposed . The algorithm reduces the measurement set by using a maximum likelihood adaptive gate, and only the measurements falling into the gate are us ed to update the PHD estimation. Simulation results show that the proposed algor ithm reduces the computational complexity obviously, and obtains a similar perf ormance.

Abstract:From the principle of linear RD algorithm and mod el of airborne spotlight SAR, this paper studies airborne spotlight SAR geolocat ion accuracy. Firstly, the effect of the radar parameters on th e airborne SAR geolocation accuracy is analyzed, and these parameters are mostly platform moti on errors from t he onboard GPS and INS devices. Then, the formulas of airborne spotlight SAR g eolocation errors are given. Finally, simulation results and experimental result s using th e data collected by an experimental airborne SAR are employed to verify the prop osed analysis approach. This paper provides useful reference for the design of the geolocation accuracy of airborne SAR system.

Abstract:When the size of target is b ig or the rotation angle is big, migration through resolution cells (MTRC) may o ccur when employing range Doppler imaging algorithm in inverse synthetic apertu r e radar (ISAR), which can affect the imaging quality. Aiming at the problem of M TRC, the echo after dechirping is researched based on bistatic ISAR turntable mo del. And the cause of MTRC is analyzed. The match Fourier transform(MFT) is used to correct MTRC, which can eliminate the coupling of fast frequency, s low time and solve the image defocusing problem caused by MTRC. Simulation resul t shows that the correction algorithm based on MFT can correct the MTRC of maneu vering target and improve the image quality.

Abstract:Missile-borne step frequency MMW radar can get high resolution range profile, b u t when moving target has radial velocity relative to the radar, it makes the echo signal produce serious deviation and distortion, so it is necessary to mak e compensation in the motion velocity. Firstly, this paper analyzes the image fo rmin g principle of missile-borne step frequency MMW radar and the effect of the tar get v elocity on image forming, then discusses the quadratic velocity estimation algo rithm, which is on the basis of the positive and negative frequency modulation m ethod and the maximum pulse group summation method. It provides a parallel imple mentation scheme of the algorithm on the TMS320C6678 multi core DSP platform, a n d describes the implementation scheme of task allocation, scheduling and inter c ore communication process at the same time. Finally it carries out an algorithm test to 1 000 frames echo signal on multi-core DSP platform, whose result shows t hat the motion compensation algorithm has high accuracy and good real-time perf ormance based on multicore DSP.

Abstract:The angle estimation algorithms of multiple input and multiple out (MIMO) radar are studied. Based on cross array in monostatic MIMO radar, a new algorithm for parameter estimation is proposed by employing quaternion theory to angle e stimation of MIMO radar. Through the construction of quaternion model, the enha ncement matrix, whose rank is equal to the number of targets and has no relatio ns with the coherency of the targets, can be got combining with matrix enh ancement and matrix pencil (MEMP) algorithm. Then the two dimensional angle of coherent targets can be estimated combining with ESPRIT algorithm. This algor ithm, avoiding peak searching which consumes much time and realizing angle esti mation of coherent targets with automatic pairing, has a lower computation compl exity and is more applicable in practice. Simulation results verify that th e proposed algorithm is effective.

Abstract:To address the fea sibility of orthogonal frequency division multiplex (OFDM) radar signal, a real time OFDM radar signal generator based on field programmable gate array (FPGA) a nd fast Fourier transform (FFT) algorithm is proposed on research of synthesis a nd waveform design. Orthogonal multi carrier modulation is implemented with dig i tal signal processing approach. Signal parameters and the modulation scheme are reconfigurable, and can be adapted to different applications and platforms. The design principle and key steps involved in OFDM signal generation are discussed, and test results are provided. Test shows the feasibility of the OFDM signal generator, which is fundamental for theoretical research and applica tion of OFDM radar systems.

Abstract:Circular-scanning SAR is mainly used for scene matching in the precision-guide d mi ssiles, whe r e the motion parameters of radar are one of the key factors to achieve precision - guided. Motion parameters can be directly measured by the GPS and MIU, and also c an be estimated from the measured data. The characteristics of fast velocity,non uniform motion and big strabismus of the circular scanning SAR platform requi re high quality of the SAR image. But the motion parameters measured by the GPS and radar IMU are difficult to meet the accuracy requirements since the large e r rors of motion parameters. By combining the two parameter estimations, accurate estimation and motion compensation are performed for the motion parameters in or der to meet the req uirements of high-resolution images and precision guided.The simulation result s verify the validity of the proposed scheme by improving the quality of circula r-scanning SAR image. The results of measured data prove that the scheme is ver y practical.

Abstract:By analyzing the defects of Jerk model and some modified models for tracking str ong maneuvering targets, and using the current statistics ideas, an adaptive para meter current statistical(APCS) Jerk model is proposed. The adjustment factor bas ed on the innovation vectors is used to adjust the model parameters and filterin g gain, improving the matching degree of maneuvering model with movement of targ et and enhancing the system′s adaptive tracking ability for sudden maneuver. Fu rthermore, the mean value of maneuvering acceleration is modified to fit for the general models of motion. The simulation results also show that the tracking pe rformance of APCS-Jerk model is superior to Jerk model, CS-Jerk model and MCS -Jerk model for tracking highly maneuvering targets.

Abstract:The s ea-land segmentation of SAR image is important in the marine applicatio n s, such as target detection, coastline extraction, etc. According to the charact eristics of SAR image, this paper puts forward a threshold segmentation algorith m combining rough threshold with accurate threshold, and provides a complete set of sea land segmentation scheme. Firstly, Otsu method is used to calculate a ro u gh threshold, and then the rough sea area can be obtained.　Secondly, according to the feature that statistical characteristic of sea area similar to Gauss dist ribution, an accurate threshold can be calculated on the basis of rough threshol d segmentation, then the accurate sea land segmentation image can be obtained. F inally, [JP2]the segmentation result can be improved by the operation of removing spe ckle. The experiment results show that the proposed algorithm has high processin g precision and quick processing speed.[JP]

Abstract:Range align ment is a key step of the motion compensation in inverse synthetic aperture rada r (ISAR) imaging. The quality of the range alignment affects the quality of the resulting reconstructed ISAR image. Based on the conventional Shannon entropy ba sed range alignment method, a new range alignment method using Tsallis entropy i s presented, where the Tsallis entropy is introduced to measure the sharpness of the synthetic range profiles (sum of the shifted range profiles), and estimate the amount of the range shift. The property of Tsallis entropy and the applicabi lity in range alignment are analyzed in detail. Simulated and real data are used to verify the performance of the range alignment method using Tsallis entropy. The results show that, compared with the range alignment method using Shannon en tropy, the range alignment method using Tsallis entropy has good anti noise per formance, and is able to obtain better alignment results.

Abstract:The wavele t is confirmed by modulation frequency, energy attenuation factor of wavelet, th e amplitude and phase of wavelet in seismic theory. Drawing lessons from this th eory in this paper, the Q value is set as a constant in each layer of horiz ontal ly layered medium (Q value is independent of frequency). Firstly, the freque n cy domain equation of the single pass propagation theory of plane wave is solve d . Through the definition of envelope peak instantaneous frequency and the deriva tion of equation, it is shown that Q value is confirmed by the changes of en velope peak instanta neous frequency, the travel time and the wavelet energy attenuation factor. So t he m ethod to estimate Q value using envelope peak instantaneous frequency of VRP(vertical radar profiling) data direct wave of ground penetrating radar is obtained. At last, the effectiveness a nd accuracy of the method are verified using synthetic VRP data, synthesis experimental data and practical data.

Abstract:The sidelob e performance of synthetic impulse and aperture radar(SIAR) is discussed, and particularity of such system is pointed out. The analysis of the conventional process shows that the direction of arrival(DOA) of muti interference is a difficult p roblem for SIAR system . Therefore,a novel method combining focused beam forming and eigenvalue deco mpositio n is presented，and the DOA performance is researched based o n the experimental data. Result shows that the direction of the interference can be measured accurately by using this method. The work is important to desig n and application of the SIAR system.

Abstract:The polar format algorithm(PFA) for bistatic SAR imaging is based on th e planar wavefront assumption which introduces wavefront curvature effect in the focusing process. There is space variant geometry distortion and defocusi n g effect in the focused image via bistatic PFA. Hence, the focused scene size us ing bistatic PFA is usually restricted. A new met hod is proposed to solve the problem of wavefront curvature compensation using t he digital s potlighting technology. Firstly, the digital spotlighting is preprocessed t o divide the original wide beam into several narrow beam phase history data, eac h of which corresponds to different small image patch. And then each narrow beam is compensated and imaged. Finally all these fo cused image patches are mosaiced together to get a full scene image. Theory and simulation results show that the method c an effectively compensate the wavefront curvature effect and enlarge the focused scene size for bistatic PFA.

Abstract:Based on wavelet analysis of the emitters, a new fingerprint feature ext raction method for emitter identification based on wavelet entropy is proposed. Firstly, the signal power spectra are calculated. Secondly, the wavelet coeffici e nts are extracted by continue wavelet transform. Finally, the wavelet entro py is extracted as a feature vector. Using neural network classifier, the compar ative experiments with traditional square integral bispectrum are carried out ba sed on twenty interphones. The experimental results show that the method can achieve individual classification by transferring the signal time frequenc y characteristics to the feature vectors through the entropy of the wavelet coeff icients. Besides, the proposed method is insensitive to noise, and the system re cognition rate is above 95% and more than 80% with SNRs of 20 dB and 5 dB,respectively.

Abstract:RF stealth technology of airborne radar has important signifi cance to improve the viability of the aircraft. The airborne phased search control parameter of array radar is designed. By analyzing th e principle of intercept probability, the relationship between target characteri stics and search performance of radar system are given, and the impact model of dwell time and beam position interval is constructed to optimize the performance under the constraints of target detection and stealth requirement. The search optimal control parameters are obtained for phased array radar to sat isfy stealth requirements.

Abstract:The basic task of an airborne weather radar is to detect the position and intensity of meteorological targets ahead of the plane. The intensity of the meteorological targets can be represented by the physical quantity called reflectivity factor, which is often estimated from the weather radar equation. When observing the middle or long r a nge meteorological targets at low altitude from a high altitude radar platform, due to the incomplete beam filling, the measurement result of the reflectivity f actor is much less than the actual value. This effect seriously lowers down the accuracy of determining the hazard level of the target. This paper fi rstly introduces a beam filling coefficient into the weather radar equation and t hen presents its estimation method based on the real time radar operating parame t ers. The variation of the filling coefficient is fully analyzed under different radar system parameters. Finally, the validity of the proposed method is verifie d by processing the raw data of the simulated meteorological targets. Simulatio n results show an effective improvement of the accuracy of the reflectivity facto r.

Abstract:The sensor information D-S fusion met hod of millimeter wave radar and CCD camera is researched. This pap er discusses information collection and segmentation of millimeter wave radar, c omputing the distance and orientation of the obstacle, judging whether t he obstacle is in region of interested(ROI) of unmanned ground platform or n ot, information collection and segmentation of CCD camera, and calcu lation of width, height and azimuths of obstacle. Space matching is realized thr ough establishing coordinate system and homogeneous transformation among coordinate systems. According to D-S fusion method, obstacle recognition frame is establi shed a t first, and its basic probability distribution value of obstacle index is ascer tained by test. Then fusion results under evidence associative action are calculated according to combination rule of D S evidence method, and di stance, ori e ntation and size of the obstacle in unmanned ground platform ROI are acquire d. At last, the method is verified in unmanned ground platform ROI, and result s how s that the method is validate and more robust.

Abstract:The synthetic aperture radar (SAR) closed-loop test system is constructed to simula te ground-satellite signal transmission process for obtaining SAR system imaging f unction, compression mode and point target characteristics. Those are of great significa nce during HJ 1 C SAR system test. Firstly, the paper presents the SAR echo signal gener ation and the physical implementation of echo simulator, and then provides metho ds to build SAR closed-loo p test systems using echo simulator under wired and wireless manner. Finally, the paper gi ves the point target performance results of HJ-1-C SAR system based on the closed -loop test system. Test results show that the closed-loop test system meets the testing needs of HJ-1-C SAR system and has good engineering application value.