The monostatic/bistatic approximation

Many radar cross section (RCS) prediction codes are limited to one monostatic return per run. However, such codes can calculate multiple bistatic returns per incident angle for a relatively small amount of additional computer resources. This article describes a method of using bistatic returns to generate multiple monostatic predictions for each incident angle computed. Typical results are presented, and show that the accuracy is initially high, and then degrades as the separation angle between the incident and viewing angles becomes large     

Simultaneous bistatic and monostatic detection of tropospheric layers

Utilizing time discrimination techniques, atmospheric layers have been resolved with bistatic and monostatic radars over common regions. The results also indicate the importance of time resolution in bistatic probes to distinguish main beam common volume scattering from that due to sidelobes.     

On the derivation of bistatic RCS from monostatic measurements

The factors which govern bistatic scattering are discussed and the relations between bistatic and monostatic scattering are presented in terms of the combined effect of individual scattering centers on the target. The concept of reradiation lobe patterns of the individual scattering centers is used to define the bistatic pattern in terms of the monostatic pattern and the bistatic angle β. Analytical arguments then demonstrate that for small bistatic angles, the bistatic RCS is very closely approximated by the monostatic RCS measured on the bisector of the bistatic angle and measured at a frequency lower than the true frequency by the factor cos β/2. The limitations to this approximation which are based on the angular width of the lobe patterns reradiated from individual scattering centers are noted. The approximation is of particular value in translating measured monostatic RCS values into bistatic RCS for small bistatic angles.     

单站雷达系统的极化匹配系数

在通讯系统中天线的极化匹配系数这一概念的基础上,根据雷达目标应用中的最优极化状态的分析,提出了单站雷达系统中天线的共极化匹配系数,交叉极化匹配系数和自适应极化匹配系数的新概念,并给出了便于计算的表达式。     

Calibration of bistatic polarimetric radar systems

A calibration technique for laboratory type polarimetric, bistatic instrumentation radars is presented. It describes the errors induced by the standard radiation transfer approach (I-SRT) in a way similar to that for the monostatic case. A 12-term error correction and absolute polarimetric calibration is performed with two external reference targets. Only the polarimetric bistatic reference of the first target must be theoretically determined. The scattering reference of the second target is determined by a measurement during the calibration process (single reference calibration). The simulation of a third cross-polarization measurement is performed by an antenna rotation and a remeasurement of the second target. Thus all data are gained for the determination of the error terms and measurements of unknown objects can be full polarimetrically calibrated. The procedures are shown for an adapted dihedral corner reflector. Misalignment errors are discussed     

双基地MIMO雷达参数估计

文中探讨了双基地MIMO雷达进行参数估计的方法。针对时域噪声为高斯白噪声,存在空间高斯有色噪声的背景,引入时间延迟这个因素构造旋转因子,同时利用匹配滤波器和ESPRIT子空间算法实现目标角度以及多普勒频率的参数联合估计。仿真结果表明这种算法可以消除系统中空间高斯有色噪声的影响,得到较高的估计精度。     

Compressive sensing based high-resolution passive bistatic radar

Passive bistatic radar (PBR) systems using different communication signals can only offer low-resolution target detection due to their inherent low bandwidth. In this paper, compressive sensing (CS) is applied to multichannel FM and GSM PBR to achieve improved range-Doppler resolutions and avoid some limitations of classical multiband PBR processing. In CS context, block-structured time-domain dictionary which is formed from multichannel signals suffers from coherence when fine range resolution is employed. To overcome such a pitfall, this work first transforms the dictionary to spectral domain where only the most important spectral components are retained. Principle component analysis followed by a whitening method are then applied to this spectrally transformed data in order to reduce the dimensionality of problem, thereby reducing the dictionary size and most importantly fulfilling the required condition of dictionary incoherence for better CS-based recovery. Two different block-structured dictionary formations are tested. The performance of the recovery of spatially close targets, in both FM and GSM PBR setups, are reported.     

双基机载雷达任意场景下的杂波几何模型

本文提出一种描述双基机载雷达与杂波散射点几何关系的精确数学模型.文中详细分析了双基机载雷达与杂波散射点在不同场景下的几何关系,并推导了精确的数学表达式来描述这一关系.该模型并未对接收机、发射机的位置坐标加以限制,从而保证了这一几何模型可以适用于任意双基场景下.最后验证了该模型的正确性.     

Spacecraft studies of planetary surfaces using bistatic radar

Spaceborne transmitters have been used in bistatic geometries for a number of planetary surface studies including inference of topography, Fresnel reflectivity, and RMS surface slopes on the Moon, Mars, and Venus. For the Moon and Mars in particular, the bistatic geometry has enabled remote probing in regions and under conditions not obtainable with Earth-based radar systems, yielding information about surface characteristics and properties on scales of centimeters to hundreds of meters that complements monostatic radar observations. A new generation of planetary spacecraft now provides opportunities for further experiments, including more nearly complete definition of the surface scattering function and, possibly, imaging. Targets of interest include the polar regions of Venus (by Magellan) and Mars (by Mars Observer), the enigmatic icy Galilean satellites of Jupiter (by Galileo), and Saturn's largest moon Titan (by Cassini)     

Fully polarimetric bistatic radar scattering behavior of forestedhills

The bistatic radar scattering measurements of forested hills were performed at grazing incidence and at azimuth scattering angles from 28° to 66° from the forward scatter plane. Using pulse-to-pulse switching between orthogonal transmitted polarizations, the radar simultaneously measures two orthogonally polarized components of the scattered wave to obtain full polarimetric information about the scattering process. These are the first fully polarimetric terrain clutter measurements to be conducted at large bistatic angles. The complete Stokes matrix, computed by averaging successive realizations of the polarization scattering matrix, is used to examine the polarization sensitivity of the bistatic clutter. It is found that the polarization state of the EM wave scattered out of the plane of incidence strongly depends on the polarization orientation of the incident electric field. Unlike the monostatic case, these two incident wave polarization states are found to produce substantially different scattered wave behavior when trees are viewed at large bistatic angles. Scattered fields resulting from vertically oriented incident fields are found to be highly polarized and to produce bistatic clutter power levels that are strongly dependent on the polarization of the receiving antenna. In contrast, horizontally oriented incident fields are found to produce weakly polarized scattered waves with bistatic clutter power levels that are insensitive to the polarization of the receiving antenna     

DOA estimation for monostatic MIMO radar based on unitary root-MUSIC

Direction of arrival (DOA) estimation is an important issue for monostatic MIMO radar. A DOA estimation method for monostatic MIMO radar based on unitary root-MUSIC is presented in this article. In the presented method, a reduced-dimension matrix is first utilised to transform the high dimension of received signal data into low dimension one. Then, a low-dimension real-value covariance matrix is obtained by forward–backward (FB) averaging and unitary transformation. The DOA of targets can be achieved by unitary root-MUSIC. Due to the FB averaging of received signal data and the eigendecomposition of the real-valued matrix covariance, the proposed method owns better angle estimation performance and lower computational complexity. The simulation results of the proposed method are presented and the performances are investigated and discussed.     

Developing experimental models for a bistatic subsurface radar

The letter presents preliminary results from a recent experimental investigation to characterise the electromagnetic scattering from conducting objects submerged in a dissipative half-space. The variation of the magnetic field with respect to the depth of the scattering object is discussed. Correlations are also sought between the measured field components and the size of the scattering object.     

双基地雷达的主要性能分析与试验方法研究

双基地雷达的主要性能指标均与收/发两站的布站方式及目标所处的空间位置有关,这与单基地雷达有很大的差异,不能直接采用单基地雷达的试验方法来检验双基地雷达的主要性能指标。为解决双基地雷达的试验与性能评估问题,重点围绕双基地雷达的探测范围、测量精度、分辨力等主要性能进行了理论分析与计算,据此提出了合理可行的双基地雷达主要性能试验方法,有关研究成果已经在一个实用双基地雷达中得到了成功的应用。     

Measurement of target coordinates in three-dimensional bistatic forward-scattering radar

The maximum-likelihood technique is applied to determine the coordinates of moving targets in a three-dimensional bistatic forward-scattering radar. The potential accuracy of the coordinates’ determination is estimated. Simulation results are presented.     

Focusing bistatic synthetic aperture radar using dip move out

The appearance of new synthetic aperture radar (SAR) acquisition techniques based on opportunity sources enhances interest in bistatic geometries. In seismic data acquisition, each source is currently accompanied by up to 10 000 receivers, and in the last two decades, the bistatic geometry has been carefully studied by scores of authors. Rather then introducing new focusing techniques, within the first-order Born approximation (no multiple reflections), seismic bistatic acquisitions are transformed into monostatic ones using a simple operator named "dip move out" (DMO). In essence, the elliptical locus of the reflectors corresponding to a spike in the bistatic survey is forward modeled as if observed in a monostatic one. The outcome of the model, the so-called smile, is a short operator, slowly time varying but space stationary. To transform a bistatic survey into a monostatic one, it is enough to convolve the initial dataset with this smile. Based on the well-known similarity between seismic and SAR surveys, DMO is first described in its simple geometric understanding and is then used in the SAR case. The same processing that is being used for movement compensation can be applied to the bistatic to monostatic survey transformation. Synthetic examples are also provided.     

Direction finding and mutual coupling estimation for bistatic MIMO radar

An algorithm for joint direction-of-departure (DOD) and direction-of-arrival (DOA) estimation in the presence of unknown mutual coupling for bistatic MIMO radar is presented. Based on the special structure of the coupling matrix of uniform linear array (ULA), the angles can be estimated directly by two one-dimensional searches without the knowledge of the mutual coupling matrices. Then the mutual coupling coefficients of the transmitter and the receiver can be solved in closed-form by utilizing the obtained DODs and DOAs, respectively. Numerical examples are given for demonstrating the effectiveness of the proposed method.     

Direction finding with automatic pairing for bistatic MIMO radar

Direction finding is an important issue for bistatic MIMO radar. A two-dimensional direction finding method with automatic pairing is developed. In the presented method, the property of the kronecker product is first utilized to reformulate the cost function in the quadratic form. Then, by constructing the orthogonality constraint of the target DOA to the quadratic form, all target DODs can be first estimated by solving the constrained quadratic form. Moreover, the pth target DOA can be directly estimated by the eigenvector which is related to the pth target DOD. Thus, the target DOD and DOA can be automatically paired. Finally, simulation results demonstrate that the effectiveness of the presented method.     

Quasi-circulator for effective cancellation of transmitter leakage signals in monostatic six-port radar

A quasi-circulator, composed of two branch-line couplers and an asymmetric power combiner, is proposed to effectively cancel the transmitter leakage signals in a monostatic six-port radar. The effective isolation is improved by 12.2 dB at 24 GHz. With the proposed quasi-circulator, the maximum detectable range of the six-port radar is improved by 167 , compared with that of the six-port radar with a conventional branch-line coupler.