الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
 |  | from | 136 |  |  |
| | | from | 136 | | |
المستخلص
Digital signal processor in modem radars is adopted with a circuit, which can accomplish a constant false alarm probability.
The function of the constant false alarm rate circuit is to adjust the detection threshold adaptively to prevent the signal processor from entering the saturation state and from being overloaded by extraneous clutter or noise. It can be described that, it is the stare of observing the noise or clutter backgrounds in vicinity of the target, and adjusting the threshold in accordance with the measured background to extract true targets from noise and clutter background. Modeling and simulation of different CFAR schemes can be obtained by either statistical or analytical methods.
In this thesis, both statistical and analytical simulation techniques are applied over all the CFAR schemes to describe their behavior and their reflection on the detection probability of the true targets. Detection probability is computed over all CFAR schemes at various values of SNR and false alarm probability. The cell averaging (CA-CFAR) gets the highest detection probability at different values of SNR. In addition, two-dimensional CFAR technique is applied over all CFAR schemes by taking not only range cells but also azimuth resolution cells as well. The results record higher detection probability for the two-dimensional CA-CFAR scheme .than that of the conventional one-dimensional technique. The study of the influence of pulse jamming and interfering targets on the two-dimensional CA-CFAR scheme to find out an optimal detector is considered. Acceptable results are clarified in this case to prove that the CA-CFAR scheme is indeed an optimal detector.
The contribution of this thesis is the proposal of a new two-dimensional automatic censoring cell averaging CFAR detector based on ordered data variability (2D-ACCA-ODV). This algorithm is applied for performance enhancement. Comparisons take place among the conventional one-dimensional CFAR technique, two-dimensional CFAR technique, ACCA-ODV technique and 2D-ACCA-ODV technique. The results revealed that the detection probability maintains obvious enhancement for all CFAR schemes. Superior improvement in detection probability is clarified when applying the novel two-dimensional ACCA-ODV algorithm. CFAR schemes performance arrangement emphasizes that CA-CFAR has the superior detection probability, and greatest of selection GO-CFAR is the nearest scheme to the CA-CFAR. Ordered Statistics and the smallest of selection SO-CFAR alternatively compete in the third and fourth degree in the schemes • performance arrangement. Eventually, for realistic practical considerations, it is shown that the implementation of CFAR is not very difficult but in’general, the actual performance will be function of target clutter and statistics. An experimental CA-CFAR circuitry is designed. The CA-CFAR scheme is selected over all other CFAR schemes for its practical facility. Theoretical and practical results are very close.