JOURNAL OF RADAR
Year:2018 | Volume:5 | Issue:4 |Papers Count:6

Among the various techniques of electronic warfare in the sea, Chaff is very particular due to its easy application, low-cost manufacturing and its impact on the victim radar. Despite the fact that the use of Chaff is dated back to the 1940s, the significant research has not been published on its recognition. It is difficult to study the behavior of Chaff because of the impossibility of Chaff tests in an unechoic chamber. Therefore, the simulation would be a suitable alternative for the study of its behavior. In this paper, the simulation of various features of the target and Chaff are presented in a multi-dimensional space whose features are dependent together. This multi-dimensional space is used to propose a processing structure, based on train and test of the various classifiers, for discrimination between Chaff and the target. Moreover, the comparison between discrimination capability of various classifiers using simulated and real data is carried out and the suitable classifier is concluded for sea applications.

In this paper, the equation of the received signal of a moving target with constant acceleration in a special case of Bi-static SAR, named one-stationary, is derived in a slant range plane. In the one-stationary geometry, usually range curvature and Doppler ambiguity is very large due to wide beam-width and assumption of accelerating movement of the target. Hence, transforms such as Radon and Keystone have little accuracy for both estimating Doppler centroid and removing range cell migration. In this paper, a two-step algorithm is proposed for estimation of Doppler centroid. That is a combination of radon transform and a search algorithm. Then, by extraction of a system of equations, an estimation of target’ s velocity and acceleration is obtained and finally, an image formation algorithm is presented. Compared to usual algorithms, the accuracy of the derived equations and the strength of the proposed algorithm in the presence of noise and clutter are confirmed by simulations.

In this paper، it is demonstrated that shaping of the cathode along the symmetry axis in a relativistic magnetron، leads to a shift in Hull and Hartree curves in such a way that a set of curves is obtained instead of only two curves. This results to excitation of numerous harmonics and so proposing a broadband tube. As an example، without any changes in the anode structure، A6 relativistic magnetron cathode has been subjected to parabolic shaping parallel to the symmetry axis preserving the axial symmetry. To perform a study in this regard، employing a 3D particle in cell simulation، it will be shown that the output power can exceed 400MW while the frequency ranges from 5GHz to 20 GHz.

In this study, the effect of aerodynamic heating has been investigated on the performance of leaky wave antennas in hypersonic projectiles. For this purpose, first the projectile’ s surface temperature is obtained using aerodynamic simulations. Then, with thermal simulation of the leaky wave antenna designed in the X frequency band, its temperature is calculated with the assumption that the upper surface of the antenna lies on the exterior surface of the projectile. The next step is to investigate the changes in antenna’ s performance by studying the changes in its shape and the properties of its materials. The most significant change in the performance is observed for the S11 parameter, which has a frequency shift of around 140 MHz at 1880 Kelvin. Finally, changes of the main beam direction as well as the level of the first sidelobe have been studied with respect to temperature changes

This article describes the first stage in designing and realizing three 100W C-band power amplifier alternatives based on the GaAs-technology for use in TT&C-transmitters. The operational frequency range spanned from 4. 3GHz to 4. 5GHz. A Gysel power divider was used to feed each branch in the second stage. The amplifiers were capable of delivering 100W output power. This distributed design of the microwave SSPA results in built in redundancy and graceful degradation of output power should any individual PA section fail. Each branch includes a current sense alarm indication which is monitored and fed to the RF SSPA controller. The amplified outputs of all the symmetric branches are summed up in a passive combing network which routes the resultant high power to the output of the RF SSPA.

In continuous wave (CW) radar systems, the efficiency of semi-active chaser receiver in the tracking of target is of paramount importance. In a situation where the target and chaser have variable speed (accelerated motion) relative to one another, in the semi-active chaser receiver, the received signal has time varying Doppler frequency shifts. In this paper, semi-active receiver with hierarchical features first acquires an estimation of the parameters of the received signal using the short time-frequency transform (STFT) at the time of the acceleration of the target or chaser. Then, mono-pulse angular tracking accuracy is tested using a matched filter based on the estimated parameters of the received signal. Eventually, providing the required simulation, the proposed method is compared with “ maximum signal spectrum” and “ average signal spectrum” methods. The results imply that the matched filter-based algorithm has a better performance than other algorithms.