فصلنامه رادار
سال دوم شماره 3 (پیاپی 5، پاییز 1393)

In this paper, we deal with the problem of adaptive coherent signal detection in Gaussian interference (clutter plus noise) for surveillance pulse radars. Some of the adaptive radar detectors exploit the AR model for clutter. Most of these detectors have been obtained using the GLR test. This test relies on the maximum likelihood estimation whose accuracy depends on the number of data. Whereas, the length of data is not too long in practical applications, and because of the recursive nature of AR model, in this paper we suggest two methods for estimating the clutter parameters using the Kalman filter based on the initial and secondary data respectively. According to these methods, we propose two adaptive detectors called ARKD and ARKSD. Our investigations show that the proposed Kalman filter-based detectors improve the detection performance especially in low number data.

In this paper, the potential of polarimetric SAR data are evaluated using target decomposition features in order to detect oil spill are evaluated. For this purpose, the value of Power of all of the polarization channels (HH, VV, HV and VH) and decomposition features i.e. Freeman, Yamaguchi, VanZyl and Krogager are computed. Then, to detect oil pollutions, different combinations of these features are then classified using the support vector machine classifier. Thus, in addition to evaluating the ability of each of the used target decomposition methods, the most appropriate method for oil pollution detection is identified. The proposed method is conducted on full polarimetric SAR data acquired from PALSAR sensor of ALOS satellite. Evaluation results indicated that VV polarization is more proper compared to HH polarization for oil spill detection. Among the target decomposition methods, Krogager method with the overall accuracy of 97.3% provides the best result in this field.

In this paper, the operation of helix traveling wave tube in interaction region is investigated by using a three dimensional large signal Lagrangian model. The complete simulation of these tubes is essential for optimum design and minimum manufacturing costs. This 3D code can compute interception current (or body current), beam radius changes in interaction region and the exact path of motion of particles in the beam. Moreover, this model can describe the behavior of the tube in the presence of non-ideal beam. In the helix TWT, the fields in the slow wave circuit are expressed in terms of space harmonics. The expansion coefficients are determined by both a theoretical approach and by a numerical simulation using CST software package. They are used in the 3D code for investigating the effect of different harmonics in beam-wave interaction.

In this paper, the Range Doppler algorithm (RDA) for synthetic aperture radar moving on a ballistic trajectory is presented. The 3-dimensional acceleration and non-uniform trajectory cause decreases in efficiency of conventional imaging algorithms. Therefore RDA provided must be consistent with the acceleration and velocity parameters. Based on 2 dimensional frequency domain expression and ballistic trajectory, the Range Doppler algorithm is presented. To evaluateion the proposed algorithm for the single-point target, SAR image is simulated based on ballistic trajectory simulated and quality parameters of simulation results are computed. For To investigated the capability of the proposed algorithm for extensive targets, SAR image is extracted by consideration of 5 point targets and 17 point targets extracted. The simulation results show the validity of the proposed algorithm in extracting rada images not withstanding 3-dimensional acceleration and ballistic trajectory.

Polarimetric Synthetic Aperture Radar (PolSAR) data classification methods, which are proposed in various studies, useing the information of one polarization base only. In this paper a new method is presented for classification of polarimetric SAR data is presented that this method can use more than one polarization base information. The proposed method is based on polarimetric signatures. In this study, in addition to the polarimetric power signatures, polarimetric signatures were introduced for various PolSAR features were introduced. As the other knowledge-based classification methods, the proposed presented method has two steps. First, extracting reference knowledge and second, classification of data using reference knowledge. Polarimetric signatures for various PolSAR features were used for extracting reference knowledge. Also, pattern recognition matching algorithms were used for classification. To the produce of polarimetric signatures in the segments and to avoid the noisy output, the object-based method was used. A Radarsat-2 image of Petawawa forest area was chosen for this study. According to the results, in comparison to the accuracy of wishart classifier which is 76.34 percent, the accuracy of proposed offered method is 82.12. The aAccuracy of forest species had a significant improvement in the proposed suggested method. The method was successful because of three major factors: fFirst, using a more complete set of polarimetric features., Ssecondly, increasing the feature information using polarimetric signatures, and thirdly, employing contextual information in an object-oriented method.

This paper presents a new lens with polarization diversity. This lens can have right-hand or left-hand circular polarization or linear polarization depending on the direction of the linear polarization of the feed antenna. This ability is achieved by designing a transmit array of aperture- coupled microstrip patch antenna. The sequential rotation method is used for generation of circularly-polarized beam with linearly-polarized cells. These cells are designed in a way that can transmit electric field in both x and y direction. The resulting bandwidth is 5 % with aperture efficiency of about 15%.