فصلنامه رادار
سال پنجم شماره 2 (پیاپی 16، تابستان 1396)

The polarimetric decomposition is one of the most important steps in SAR data processing and analyzing. Conventional decomposition methods use polarimetric information only in a restricted number of polarization bases. This paper presents a new decomposition method based on polarimetric signatures. The proposed decomposition includes two main steps: 1) selection of the reference polarimetric signatures, and 2) Classification of the pixel's polarimetric signature. The presented method was tested on the Radarsat-2 image in C band collected over San Francisco and the Pi-SAR image in L band collected over Niigata University in Japan. The proposed decomposition was compared with Y4O, Y4R, Arii-NNED and Freeman decomposition methods. According to the results of the suggested method, in urban areas especially in areas with a large orientation angle, it is clearly seen that the overestimation of the volume contribution has been reduced and the double-bounce contribution has been increased. In addition, the obtained power values of the proposed decomposition are always positive; therefore, the problem of negative power value cannot be achieved.

Detection and characterization of the constituent scatterers for each pixel in the scene is one of the fundamental goals of microwave remote sensing. Compared with synthetic aperture radar (SAR) sensing, polarimetric SAR (PolSAR) sensing has finer details of the scattering properties of targets and natural background; therefore, it can increase the detectability of single and partial targets. In this paper, a new and fresh look at the target detection issue is taken and an effective technique which simultaneously annihilates interfering background is developed that detects the presence of a scattering mechanism of interest. Several canonical scattering mechanisms are assumed as our signal sources whose combination forms scattering vector of each pixel with appropriate weight fractions. Using this technique leads to the exact detection of partial targets and build-up areas.

In this paper, the reduction of radar cross section of an airplane using overall and partial coverage of fuselage with absorbing material is studied. Specifically, various coverage strategies are tested to achieve minimum radar cross section and minimum mass of the absorbing material. This is important because the weight of absorbent material is usually great, around 13 Kg per square meter, even for a small thickness of 3mm. Therefore, it is extremely important to find effective strategies for covering the fuselage. Using the moment method and ray tracing method in the CST software package, the monostatic and bistatic RCS of an airplane with partial coverage of RAM are calculated. It is shown how partial coverage of the fuselage can affect the RCS. For instance, the head-front radar cross section of the studied airplane without any RAM coverage was found to be at 1.925 GHz. When only the wings are covered with RAM, the cross section is reduced to . When the body (without wings) is covered, the average mono-static radar cross section is reduced to . When all parts are covered with RAM, the average mono-static radar cross section is further reduced to . Furthermore, the effects of partial coverage of the wings are studied.

This paper addresses architecture, signal processing algorithm and receiver(RX) network planning in MIMO passive radar based on GSM transmitter of opportunity. Design constraints should be derived, before RX network planning. Receiver nodes in MIMO networks may receive direct path signal of different transmitters from main lobe or back lobe. The main subject of this paper is derivation of admissible distance between transmitter and receiver nodes in each situations and RX network planning. In this paper, limiting constraints in minimum distance between transmitter and receiver, in both case of using or not using regeneration approach is studied in passive radar networks. Target detection range is investigated in different distance between transmitter and receiver. finally, RX network planning algorithm is proposed and applied to a typical scenario.

This paper presents a technique to improve mean-squared error of chirp rate and central frequency estimation in high signal to noise ratios in Discrete Phase Transform and Improved Discrete Phase Transform methods. The estimation of chirp signal parameters is used in many signal processing fields such as intercept radars, SARs, ISARs, and disrupting enemy radars. Increasing the estimation accuracy of chirp signal parameters in these applications is of great importance. In this paper, in order to increase the estimation accuracy of chirp signal parameters in Discrete Phase Transform and Improved Discrete Phase Transform methods, instead of periodogram frequency estimation, the proposed technique is used. Simulation results show that this technique reduces the computational complexity of these methods and increases the estimation accuracy of chirp signal parameters.

In this paper a C-band, low phase noise voltage controlled oscillator is presented based on substrate integrated waveguide (SIW) resonator. As the SIW resonator plays a great role on the noise performance of the voltage controlled oscillator, the effects of some parameters on the performance of the SIW are investigated. Considering various techniques of excitation and tuning, an SIW resonator is designed in the frequency range of 5 to 6.3 GHz. The resulting tunable resonator has a quality factor of 240 at 5.5 GHz, when simulated on RO4003 substrate. The voltage controlled oscillator can oscillate from 5.3 GHz up to 6.3 GHz. The tuning voltage for this frequency range is between 2 and 20 Volts. The oscillator phase noise is better than -112dBc/Hz at 100 KHz offset from the 5.5 GHz carrier.