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： In a GEO-LEO dual-satellite geolocation system, the estimations of the differential time offset (DTO) and differential frequency offset (DFO) are ambiguous at the same time. Aiming at this problem, the ambiguity of the coherent pulse trains signal is analyzed. And, the sequence of the differential time of arrival (TOA) is obtained by the roughly paired pulse trains to avoid the difficulty of the pulse match with high-density in the time domain. The coarse DFO whose ambiguity is eliminated is estimated by the central difference of DTO, and the performance of the coarse DFO estimation is derived. The result shows that the estimation error increases with the increasing of the carrier frequency of the emitter, the increasing of the error of the TOA and the decreasing of the time interval of the differential DTO. The numerical simulations have demonstrated that the coarse DFO estimation error is consistent with the theoretical value, and the estimation accuracy of the DFO approximates the Cramer-Rao lower bound (CRLB) when the coarse DFO estimation without ambiguity is obtained by setting the appropriate differential interval. The new approach is convenient for engineering implementation, and could provide good references for DFO estimation of the radar signal in a long base line location system. [ABSTRACT FROM AUTHOR]

Contrastive analysis of the performance of various polarimetric detectors is the basis of polarimetrie radar detector design in engineering. In this paper, the clutter and the target echo received by polarimetrie radar are modeled. Based on this, ideal detection performances of optimal polarimetrie detector (OPD), polarimetrie whitening filter (PWF), optimal span detector (OSD), polarimetrie matched filter (PMF), power maximization synthesis detector (PMSD) and single channel detector (SCD) are compared by using Monte Carlo simulations. At the same time, implementation difficulties of the six polarimetrie detectors are analyzed according to their test statistics. Simulation and analysis results indicate that PWF, OSD and PMSD have good ideal detection performances and are convenient to implement in engineering. Considering PWF and OSD require prior knowledge of clutter covariance in engineering application, adaptive detection performances of PWF, OSD and PMSD are further compared based on the estimated clutter covariance and its key parameters. Comparison results demonstrate that PWF has best adaptive detection performance when radar observation times is larger than 64. [ABSTRACT FROM AUTHOR]

To solve the serious problem of grate lobe in distributed MIMO radar three-dimensional array, the optimization criterion of minimum PSL (Peak Sidelobe Level) based on the constraint of shading free is derived. The estimation results of PSL are given for different array geometries, different element radar numbers and apertures, and different scanning angles. Numerical simulation results show that the minimum PSL can be achieved by optimal positions perturbed ring array when the distributed MIMO radar is collocated and shading-free. [ABSTRACT FROM AUTHOR]

The approximate fractality of the fractional Fourier transform (FRFr) spectrum of sea clutter and its application of the approximate fractal characteristic of the sea clutter FRFT spectrum in target detection are mainly studied. According to the scale transformational property of FRFT, the approximate fractality of the FRFI spectrum of a self-similar process is studied. Then, an analytical method of approximate fractality is introduced to analyze the FRFT spectrum of real sea clutter. It's found that approximate fractality exists among the sea clutter FRFT spectra of some specific transform orders. Moreover, target echoes can cause the descriptive parameter of approximate fractality, or the Hurst exponent in FRFT domain to change. Therefore, the Hurst exponent in FRVr domain can be used to design the CFAR detection algorithm. By verifying measured data of X-band and C-band radar, the proposed method performs much better than the classical detection method using the Hurst exponent in time domain. [ABSTRACT FROM AUTHOR]

The measured target of close range angle measurement is in the near-field of radar antenna array while that of long range angle measurement is in the far-field. The current angle measurement algorithm based on the assumption of the far-field target is hard to satisfy the accuracy requirement in near-field angle measurement of space rendezvous and docking. In order to achieve near-field high-accuracy angle measurement in microwave rendezvous and docking radar, a new algorithm based on phase difference complex vector matching is proposed. A three-dimensional geometric model is introduced first. Then, phase difference complex vector is constructed, and a function which quantifies the similarity of phase difference complex vector is defined. Based on the above concepts, a nonlinear programming algorithm model for calculating azimuth and elevation angles is established. In addition, the input parameters and processing steps of the algorithm are described in detail. The simulation results and anechoic chamber experiments results demonstrate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

The traditional angle measurement methods of microwave radar are difficult to satisfy accuracy requirements under the rendezvous and docking near-field conditions. To achieve the high-precision angle measuring in a wide range including near-field as well as far-field, a new algorithm based on phase difference complex vector matching was proposed. Firstly, an object function was defined to quantify the similarity of the phase difference complex vector. Secondly, a nonlinear programming model was established to estimate the azimuth and elevation angles and the solving steps of the model were described in detail. Finally, the results of numerical simulation, airborne flight test and anechoic chamber experiment prove the effectiveness of the algorithm with a high precision of 0.12°. [ABSTRACT FROM AUTHOR]

In the presence of suppressive jamming, a target detecting and tracking technique based on new radar observation equation is proposed for radar network. The technique involves two steps, radar observation equation in the presence of suppressive jamming and radar network sequential filtering and tracking. The observation equation is used to calculate the detection probability according to signal-to-jamming ratio ( SJR ) of radar receiver and sensor's targets detection condition is simulated in the presence of suppressive jamming. The radar network sequential filtering algorithm is used to merge serially and compress the measurements from radar network in the presence of suppressive jamming, and the compressed data are tracked by using sequential filtering algorithm based on interactive multiple model (IMM). The detection technique can simulate radar's observed target temporary vanishing phenomenon as a result of low detection probability. It can enhance continuity and stability of radar network target tracking. Simulation results show feasibility and validity of the proposed technique. [ABSTRACT FROM AUTHOR]

Passive multistatic radar imaging algorithm is proposed on the basis of compressed sensing since a image scene usually has a few scattering centers. First, this method is used to construct a reasonable Fourier sparse basis matrix via the prior information constrained by the statistical property of SAR image. Then, the point-enhanced problem is transformed into the optimization problem by the using lp norm method. Finally, a fast recursive algorithm is presented to solve the optimization problem. Numerical simulation shows the method has good imaging performance without the request of enough stations under the location of small rotating angle. [ABSTRACT FROM AUTHOR]

The radar tracking performance for conventional reentry trajectory and glide-reentry trajectory is studied respectively. Based on the Unscented Kalman Filter and target dynamics model, the tracking error including the measurement noise of radar is calculated and the tracking performance is compared. The simulation results indicate that; (1) the gliding reentry trajectory compared with the ballistic reentry trajectory is to be found later and its observation time is shorter for its cross maneuverability and the lower flight altitude; (2) the radar tracking error of glide trajectory is larger than that of ballistic trajectory for the reason of the difficulties in aerodynamic modeling of tracking dynamics for the glide trajectories; (3) the more maneuverable of trajectories, the worse of tracking accuracy under the almost same observation condition of the radar; (4) the effective method for penetration is to make the dynamics model supposed by the defense side most possible mismatch. [ABSTRACT FROM AUTHOR]

The high-resolution polarimetric radars are able to obtain more information of target characteristics than conventional ones, and the operation of exploiting the polarization information can improve the performance of detection and identification remarkably. A polarimetric adaptive algorithm based on generalized likelihood ratio test (GLRT) criterion is presented for detecting range-distributed targets in compound-Gaussian clutter and the theoretical expression of the false alarm probability is derived. The proposed detector ensures the theoretically constant false alarm rate (CFAR) property with respect to both the texture statistics and the clutter covariance matrix. Finally, the simulation results based upon simulated clutter data show that this polarimetric adaptive detector achieves in general a better detection performance than its counterparts under the condition of less secondary data. [ABSTRACT FROM AUTHOR]

The statistical properties of pseudo additive speckle noise in synthetic aperture radar (SAR) image are investigated in this paper. First, the statistical properties of the noise-free signal and the multiplicative speckle noise in SAR image are analyzed, then the approximate probability density function (PDF) of the pseudo additive speckle noise is derived by using the Edgeworth expansion. The parameters involved in PDF of various signals are estimated by using the method of log-cumulants based on Mellin transform. The real SAR images are utilized to analyze the derived PDF, and the results show that the statistical properties of the pseudo additive speckle noise closely approach to Gaussian distribution. [ABSTRACT FROM AUTHOR]

Using the idea of uniformly-accelerating motion modulation for reference, a novel active modulation jamming method of false uniformly-accelerating targets is proposed for countering Synthetics Aperture Radar (SAR)-Ground Moving Target Indication (GMTI) systems. Several key jamming parameters are determined, the jamming imaging result is analyzed, and the influence of reconnaissance errors on jamming performance is discussed. Furthermore, the countering performance of the proposed jamming method against GMTI is investigated by using the tri-antenna interference canceling technique. Simulation experiments have been done based on the raw data. The result shows that, this jamming signal carries the vivid uniformly-accelerating motion features, and is processed coherently in the range direction and partially coherently in the azimuth direction, thus producing a false image of the uniformly-accelerating target. The proposed method is effective and flexible in engineering. [ABSTRACT FROM AUTHOR]

Both P band SAR received silent data and spectrum characteristics of analog television signal are analyzed. In order to suppress analog television signals in P band SAR echoes, a novel interference suppression algorithm is proposed. By splicing multi-pulse SAR echoes in time domain, high frequency resolution of analog television signal can be obtained. Therefore the analog television signal can be identified accurately. By designing filter bank in range-frequency domain according to spectrum characteristics of analog television signals, the discrete spectrum lines of analog television signals are removed and the spectrum of SAR echoes between these discrete spectrum lines are saved. Finally, the proposed algorithm is verified by processing real P band SAR data. [ABSTRACT FROM AUTHOR]

The echo in each range cell of non-uniformly rotating target is multi-component polynomial phase signal. When Fourier Transform (FF) is used for cross-range compressing, the Inverse Synthesis Aperture Radar (ISAR) image of non-uniformly rotating target will be defocused, thus affecting the 3-dimetional imaging quality of Interferometric ISAR (InlSAR). A method based on Match Fourier Transform (MFT) is proposed for non-uniformly rotating target InISAR 3-dimetional imaging. In this method, MFT is used for cross-range compressing of three interferometric antennas' received echoes to obtain focused BAR images. Then the 3-dimetional distribution of target scattering points can be obtained through the interferometry of focused BAR images. Because the phase coefficient ratios of non-uniformly rotating target's polynomial phase signal are determined by the target's rotation parameters completely. It's only need to estimate the phase coefficient ratios of one scattering point's echo to construct the integration path of MFT by this method. It can be adapted to the 3-dimetional InISAR imaging of any order non-uniformly rotating target. The validity of this method is demonstrated by simulation data. [ABSTRACT FROM AUTHOR]

High-accuracy pulse repetition interval (PRI) estimation is meaningful for enhancing the emitter-identification abilities of modern electronic intelligence (ELINT) systems. The maximum-likelihood estimate (MLE) of PRI can be obtained by locating the peak of periodogram of a point process signal used to model the sequence of the time-of-arrival (TOA) measurements. In this paper, a novel two-step numerical search strategy is proposed to search the peak of the periodogram to ensure maximum-likelihood estimation. Simulation results show that our algorithm outperforms the existing methods, especially under the condition of low signal-to-noise ratio (SNR) or high pulse-missing-rate. [ABSTRACT FROM AUTHOR]

High velocity motion of space target can lead to the distortion of one-dimensional range profile in bistatic BAR. To solve this problem, velocity estimation and compensation method is researched. Based on the imaging system of direct intermediate frequency sampling matching filter non-coherent bistatic BAR, the imaging influence caused by high speed motion is researched firstly. Secondly, the redundant dictionary matched with high speed motion target echo is created and the echo is decomposed sparsely based on the sparse character of radar baseband echo. Then, the frequency modulation slope of target echo is estimated and target velocity without ambiguity is estimated based on the frequency modulation slope. With the estimated velocity without ambiguity, compensation phase item is created and the speed compensation is finished finally. Compensation accuracy of this method is high and no velocity ambiguity exists. The compensation method is validated by simulation experiment of space target model with ideal scatters. [ABSTRACT FROM AUTHOR]

In this paper, a receiving technique integrated radar and radar with countermeasure reconnaissance based on signal reconstruction is proposed to resolve the problem of different characteristics between radar and radar countermeasure reconnaissance receiver. First, the intermediate frequency bandwidth is split to several sub-bands by using complex-exponential modulated filter banks. Then a nonuniform dynamic channelization is realized by using the technique for spectrum sensing and signal reconstruction. Finally, the echo of radar and radiation of emitter can be received respectively by using the technique of nonuniform dynamic channelization. A method for designing a high-complexity prototype filter is introduced to satisfy the requirements of the integrated receiver such as instantaneous dynamic range, sensitivity, surveillance bandwidth and frequency resolution. Theoretical analysis and computer simulation have illustrated the validity of this integrated receiving technique. [ABSTRACT FROM AUTHOR]

The parameter estimation of the target and towed radar active decoy (TRAD) within the radar beam is the necessary condition for radar seeker to realize target selection and achieve the beresight steering adjust and accurate tracking. The "closely spaced" target and decoy make radar echoes aliased and the traditional method for parameter measurement and estimation fail. Based on the signal model, that the energy of single target will spill over to adjacent matched filter sampling points when the output of matched filter of radar seeker is sampled actually. Bayesian theory is adopted to obtain the posterior probability density function of estimated parameters from the conditional likelihood function of the observation and the prior distribution of unknown parameters in this paper. Then the Metropolis-Hastings (M-H) sampling algorithm belonged to Markov Chain Monte Carlo (MCMC) is utilized to estimate parameters of target and decoy jointly. At the same time, based on the jamming model and characteristics of TRAD, the M-H sampling is improved. The simulation results under different jamming conditions and dynamic attack scenarios illustrate the performance of proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a new joint radar transmitter and receiver polarization optimization method is proposed based on the optimal detection criterion. First, a fully-polarimetric radar echo model is introduced, and the fully-polarimetric target detection algorithm is designed based on Neyman Pearson criterion, the detection performance is derived and analyzed. Then, a joint radar transmitter and receiver polarization optimization method is proposed to improve the capability of the target detection. Finally, the simulation results demonstrate that the target detection performance can be improved by using this algorithm remarkably. [ABSTRACT FROM AUTHOR]

Combined with sparse SIMO radar array in space domain, the two dimensional sparsity model for radar imaging with high resolution is established in this paper with frequency-stepped chirp signal (FSCS). First, a velocity estimation method for moving targets is introduced for this model based on image entropy criteria, and the accurate velocity estimation is implemented by simple zero-padding for low dimensional data. Second, in combination of the Compressed Sensing (CS) theory, the effective measurement matrix, the sparsity transform matrix and the reconstruction algorithm are designed to obtain the high-resolution range profile (HRRP), then a phase remain character based new imaging method is proposed for SIMO high-resolution sparse radar by two dimensional sparsity processing in the frequency and the space domains. The model can reduce not only the number of sub-pulses in FSCS burst, but also reduce the number of receivers of S1MO high-resolution radar, in the meanwhile, the high quality HRRP and two dimensional images of targets can be achieved. Effectiveness and robustness of the method are proved by the simulation results. [ABSTRACT FROM AUTHOR]

Radar echo of ballistic midcourse targets containing electromagnetic and motion information provides important evidence for target recognition. The problem of wideband radar echo simulation for micro-motion targets in ballistic midcourse is studied, and an echo simulation method based on the scattering center model is proposed in this paper. First, the position variation of each scattering center of circles of micro-motion targets is analyzed. Further, a method to judge the masking effect of scattering centers is proposed based on the physical optical principle by considering the structure of rotary symmetrical targets, under which the precession of the targets is equivalent to the rotation in a two-dimension plane. Therefore, the invisible problem of scattering centers arising from the variation of target attitude can be solved. Comparison between the numerical simulation and measurements in anechoic chamber indicates that the proposed method can effectively simulate radar echo of micro-motion targets, and provide a technical foundation for the feature extraction and recognition of midcourse targets. [ABSTRACT FROM AUTHOR]

Range profile is one of the most important features in UWB radar target recognition, and the technique for target feature extraction based on Multi-station becomes a research direction recently. The mathematical model of ballistic target micro-motion time-profile is derived. Then the range profiles obtained from different radar stations are matched according to the sinusoidal parameter in time-profile image. Based on these data, spatial relative position of scatters on cone-shaped warhead is rebuilt by using the range profiles obtained from three stations. Finally, parameters of cone-shaped warhead are estimated. Simulation results show that the presented method is effective and applicable. [ABSTRACT FROM AUTHOR]

A method is proposed for solving the problem when using Frequency Modulation Continuous Wave(FMCW) in Bi-static ISAR system. Considering coupling terms induced by using FMCW signal, the Discrete Polynomial Phase Transform(DPT) is used to estimate the combined component, then the phases of echo signal are compensated by using compensation functions to eliminate the fixed frequency offset caused by first coupling term and main-lobe expansion induced by second coupling term. The Range Doppler algorithm is used to attain clear target's image. At last, the validity of the proposed compensation algorithm is validated by simulation and focused image is obtained. [ABSTRACT FROM AUTHOR]

In view of the requirement for radar ECM research and the difficulty in getting target radar, the substitutable equivalent reckoning theory used for dense barrage jamming is studied, then mathematical substitutable equivalent reckoning models and simulation model of target radar are established, and also a simulation system of target radar is presented. Based on radar ECM test data, the mathematical substitutable equivalent reckoning model and target radar simulation model are verified, and this provides an efficient and reliable analysis tool for researching into the effect of dense barrage jamming on target radar. [ABSTRACT FROM AUTHOR]

A method for discrimination of midcourse target based on trajectory characteristics is proposed in this paper to recognize motion characteristics of target cluster consisting of warhead and decoys. Radar measure data are used to recover ballistic trajectory. Trajectory characteristics are used to judge the number of intersection points, and single or multiple decoys releasing process can be determined. According to different release processes, recognition methods based on trajectory parameters and weight of intersection are proposed respectively. Then, an integrated midcourse target discrimination strategy based on trajectory characteristics is developed in combination with the number of targets. Numerical simulations have demonstrated the effectiveness of the proposed approach. Some factors such as radar measurement error and radar station location are also considered as the influencing factors in analyzing recognition results. [ABSTRACT FROM AUTHOR]

Three-dimensional sparse distribution of the antennas and squint SAR in distributed-satellite SAR systems makes it difficult to estimate the along-track baseline accurately. Thus, an along-track baseline determination method is proposed based on ephemeris data and radar echoes. The geometric model of squint SAR systems with satellites distributed in three-dimensional space is established after the non-parallel track compensation. And the formula for calculating the along-track baseline is deduced. The squint angle is obtained according to the Doppler centroid estimated from the radar echoes. Compared with some approximate methods, more accurate results can be achieved with this method in the case of long baseline and large squint angle. Simulation results illustrate that accurate velocity estimation and relocation of moving targets can be obtained by using the proposed method to determinate the along-track baseline. [ABSTRACT FROM AUTHOR]

Based on echo model of multi-static ISAR multiple moving targets, the signal parameters of multiple moving targets are estimated and separated by employing time-frequency rate distribution analysis and CLEAN method. After the signal parameters and ISAR images correspond to multiple radars are obtained, the moving parameters of each target are estimated iteratively and then the cross-range scaling of each target is implemented. Furthermore, the constraints of multi-static ISAR multiple target imaging are analyzed. The multiple-static ISAR multiple moving target imaging and cross-range scaling algorithm are verified by simulation experiments. [ABSTRACT FROM AUTHOR]