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New Methods for Null Steering in the Field of Adaptive Beamforming

Thesis Info

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Author

Khan, Muhammad Zafar Ullah

Supervisor

Aqdas Naveed Malik

Program

PhD

Institute

International Islamic University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2014

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2244/1/2492S.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726752906

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In this dissertation two categories of adaptive beamforming algorithms have been studied. In first category the adaptive beamforming has been applied for null steering whereas in second category it has been applied for direction of arrival mismatch problem to avoid performance degradation of the beamformers. New algorithms have been contributed in both categories. In case of first category a specific structure has been proposed which provides independent steering of all the available nulls present in the radiation pattern of an array antenna. The idea is based on decoupling of the complex weights employed with each antenna element to provide adaptively by controlling their values. This results in a proposed specific structure. The proposed structure is further improved by incorporating sidelobe suppression capability. Second Order Cone Programming has been used to get the appropriate set of weights to be utilized in the proposed structure. Similarly, the method for improving beam symmetry around the desired signal direction is also incorporated. These additional features are included over the cost of number of steerable nulls. A tailored Genetic Algorithm is proposed to compute the weight vector required to incorporate the proposed structure for beam symmetry. The second part of dissertation is meant for the second category of adaptive beamformers applied for direction of arrival mismatch problem. Performance of these beamformers degrades severely whenever there is a mismatch between the presumed and actual direction of desired signal impinging on an antenna array. A Robust Generalized Sidelobe Canceller has been proposed in this domain as remedial measure to restore the performance. The major advantage of proposed algorithm is that it provides improved results without broadening the main beam. This feature is an added advantage in comparison with the previously existing techniques. For this purpose the blocking matrix present in GSC has been modified without disturbing the quiescent weight vector. This results in robustness against signal look direction error without broadening the main beam. The simulation results confirm the improved performance of the beamformer. Another approach in this domain is based on diagonal loading of signal and data covariance matrices, involved in subsequent computations. The amount of this diagonal loading level is very critical which must not exceed a specific level to ensure the positive definite behavior of signal covariance matrix. This is a standard requirement for the convergence of existing general rank algorithms. Currently, there exists no reliable criterion for deciding the amount of diagonal loading level. In this context a new algorithm has been contributed to decide the amount of diagonal loading. Proposed algorithm is iterative in nature and uses the beam symmetry around the presumed signal direction to decide the level.
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شان الحق حقی

شان الحق حقی
اردو کے بڑے ممتاز شاعر و ادیب، محقق و مترجم اور لغت نویس جناب شان الحق حقی نے ۱۱؍ اکتوبر ۲۰۰۵؁ء کو کناڈا میں داعی اجل کو لبیک کہا، اناﷲ وانا الیہ راجعون۔
مرحوم ایک برس سے پھیپھڑے کے کینسر میں مبتلا تھے، ان کی پیدائش ۱۵؍ ستمبر ۱۹۱۷؁ء کو دہلی میں ہوئی، ان کا خاندانی تعلق شیخ عبدالحق محدث دہلویؒ سے تھا جن کی ذات سے ہندوستان میں علم حدیث کا بڑا فروغ ہوا، علی گڑھ سے انہوں نے بی اے کیا تھا اور دہلی کے سینٹ اسٹیفن کالج سے ۱۹۴۱؁ء میں انگریزی میں ایم اے کیا، اس کے بعد ’’آج کل‘‘ دہلی کے نائب مدیر ہوئے، پھر شملہ میں مترجم کی حیثیت سے کام کیا۔
۱۹۴۷؁ء میں وہ دہلی سے پاکستان چلے گئے، ۱۹۵۳؁ء میں لندن سے ذرائع ابلاغ عامہ کا کورس کیا، عرصے تک ترقی اردو بورڈ پاکستان کے اعزازی سکریٹری رہے اور اس کے مجلہ کے شعبہ ادارت سے بھی منسلک رہے۔
دہلی سے تعلق کی بنا پر ان کی تحریر یہیں کی ڈھلی ہوئی شستہ زبان کا نمونہ تھی، ان کو ٹکسالی زبان اور محاوروں اور ضرب الامثال پر قدرت کا ملہ حاصل تھی، وہ زبان کی صحت کا بڑا خیال رکھتے تھے اور اس کے نوک پلک اور الفاظ کے محل استعمال سے بخوبی واقف تھے، ان کی اس طرح کی تحریروں اور مضامین سے اہل ذوق بہت محظوظ ہوتے تھے۔
نثر و نظم دونوں پر یکساں قدرت تھی، تارپیراہن اور حرف دل رس وغیرہ ان کے شعری مجموعے ہیں، نثر میں افسانہ، ڈرامہ تنقید، ترجمہ اور لغت نویسی ہر ایک میں اپنے جوہر دکھائے ہیں، بچوں کے ادب سے بھی شغف تھا، ان کے لیے پہیلیوں، کہہ مکرنیوں اور نظموں کی متعدد کتابیں لکھیں، لغت نویسی اور ترجمے میں ان کی خدمات بے مثال ہیں، کئی منظوم...

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