البحث — المستودع الرقمي العراقي

المستخلص: هذه الاطروحة تتعلق بتحليل ومعالجة تاثير الضوضاء المحيطية (Clutter) لمنظومة الرادار النبضي، يتطلب رادار الكشف الالي للهدف استعمال عتبة الية (Adaptive threshold) لتحقيق معدل ثابت للانذار الكاذب وذلك لغرض السيطرة على الانذار الكاذب الذي تسببه تغيرات في الضوض | This thesis deals with the analysis and processing of clutter for pulsed radar system. Automatic target detection radar requires adaptive thresholding achieved by Constant False Alarm Rate (CFAR) circuit in order to control the false alarm caused by variations in clutter background.This work focus on worst radar environment that happens when abrupt variation in clutter background merged with multi - interfering target, to detect target in such environments it need robust CFAR algorithm that excise the target spikes and clutter edges from CFAR window in order to give best possible estimation to the noise background. two important algorithms studied which are CA - CFAR and OS - CFAR algorithms in additional to the modified CA - CFAR algorithm. All these algorithms were simulated with mat lab v6.1 and applied them to three different clutter models that represent different environment cases the CA - CFAR family failed to handle model two and three also OS - CFAR family except OSGO - CFAR that handle all models successfully. For modified CA - CFAR family only modified GO - CFAR handle all models successfully and comparing with OSGO - CFAR the modified GO - CFAR need less hardware and processing time because it did not need sorting process that is essential for OSGO - CFAR. Therefore, the modified GO - CFAR is chosen to implement by using FPGA and another important feature in modified GO - CFAR algorithm that is parallel processing since the spike selection process is done at the same time with summing of samples process that make this algorithm much less in processing time from any other algorithm that work in the same environment. The FPGA chip that used to implement modified GO - CFAR algorithm need only three signals from the radar receiver to mach with the receiver circuit correctly which are time base clock signal period reset trigger signal and the pulse duration time. Therefore, the FPGA chip can work effectively with almost any radar receiver system

تصميم وتنفيذ معالج باستخدام TM - CFAR مصفوفة البوابات المبرمجة FPGA == Design And Implementation Of TM - CFAR Processor Using Field Programmable Gate Array

اسم المؤلف: علي هادي عبد الواحد

اسم المشرف: وليد خالد عبد علي

الموضوع العام: هندسة الكهرباء والالكترون والاتصالات

السنة: 2006

الموضوع الدقيق: هندسة الالكترونيك والاتصالات

الدرجة: ماجستير

الجامعة: الجامعة المستنصرية - كلية الهندسة - قسم الهندسة الكهربائية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

اداء التجميع المتعامد لاشارات تقسيم الشفرات المتعدد الوصول ذات الحاملات المتعددة (Rayleigh) عبر قناة الخفوت الترددية الاختيارية من نوع == Performance Of Group Orthogonal Multicarrier Code Division Multiple Access Signal Over Frequency Selective Rayleigh Fading Channel

اسم المؤلف: حارث اكرم ناصر العبيدي

اسم المشرف: مها جورج زيا

الموضوع العام: هندسة الكهرباء والالكترون والاتصالات

السنة: 2006

الموضوع الدقيق: هندسة الكهرباء والالكترونيك

الدرجة: ماجستير

الجامعة: الجامعة المستنصرية - كلية الهندسة - قسم الهندسة الكهربائية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

المستخلص: مع ظهور قنوات الخفوت الترددية الاختيارية المتعددة المسارات. اصبح نظام تقسيم الشفرات المتعدد الوصول (CDMA) يعاني من التداخل بسبب تعدد المستخدمين (MUI) والتداخل بين الرموز(ISI) ولكن مع التصميم المناسب لنظام تقسيم الشفرات فانه يوفر التفريق الى مسارات متعدد | In the presence of frequency selective multipath fading channels, code division multiple access (CDMA) suffers from multiuser interference (MUI), and intersymbol interference (ISI), but when properly designed, it enjoys multipath diversity. Orthogonal frequency division multiple access (OFDMA) is MUI free, and it does not enable the available channel diversity without employing error control coding. But coded OFDMA may achieve lower diversity than a CDMA system employing the same error control codes. In this work, the advantages of OFDMA and CDMA are merged to minimize MUI effects, and also to make the maximum available diversity for every user possible, this system is called group orthogonal multicarrier CDMA (GO - MC - CDMA).In group orthogonal multicarrier CDMA (GO - MC - CDMA) scheme, groups of users share a set of subcarriers. By carefully choosing group subcarriers, there is aguarantees that every user transmits with maximum diversity. MUI is only present among users of the same group, and is suppressed via multiuser detection, which becomes practically feasible by assigning a small number of users per group. The performance of GO - MC - CDMA system is analyzed with 3M bits/sec in two paths frequency selective Rayleigh fading channel. Moreover, simulations are carried out to illustrate the performance of GO - MC - CDMA with number of active users, number of subcarriers, space diversity combining technique, types of spreading code, type of data detection techniques, finally, the effect of near - far problem.