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New Methods for Null Steering in the Field of Adaptive Beamforming

Thesis Info

Access Option

External Link

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

Similar


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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آصف علی اصغر علی فیضی

جناب اے ۔ اے ۔ اے فیضی
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کلام اقبال اور عشق مصطفے ﷺ

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Effects of Mulching and Farm Manure on Water Use Efficiency, Soil Properties and Crop Growth While Using Brackish Water for Irrigation

In many arid and semi-arid regions, use of brackish ground water has become necessary for irrigation to balance rapidly increasing water demands. Addition of organic material such as farm manure and crop residues would be useful in improving soils that are otherwise deteriorated when brackish water is used for irrigation. Keeping in view role of mulching and farm manure in ameliorating ill effects of brackish water, two years (2009- 2011) field studies were conducted to evaluate the effects of mulching (control, 25, 50, 75 and 100 % soil cover) and farm manure (control, 10, 20 and 30 Mg ha-1) on water use efficiency, soil properties and crop growth. A randomized complete block design with four replications was followed for laying out the experiments. Four field studies were conducted at the research farms of the College of Agriculture D. G. Khan, Sub Campus of University of Agriculture, Faisalabad. In Study-1, two experiments were conducted following cotton- wheat rotation and in Study-2, two experiments were conducted following mung-wheat rotation. Crops were grown during their normal planting seasons, with recommended seed rate and planting methodology. These crops were irrigated with brackish water and measured amount of irrigation was ensured using cut-throat flume. Soil samples collected from 0-15, 15-30, 30-45, 45-60, 60-90 and 90-120 cm soil depth before sowing and at each crop harvest, were analyzed for EC1:5, pH, bulk density, N, P, K and organic carbon concentration. It was observed that the farm manure at 30 Mg ha-1 (FM4) and mulch at 7.6 Mg-1 ha (M5, 100 % SC) produced the maximum cotton, wheat and mung crop yield as compared to control. Whereas economic and marginal analysis indicates that FM4 gave more economical yield as compared to all other levels of farm manure and mulch during both of the years. As for as soil properties were concerned more soil bulk density was found in controlled treatments while less was found in M5 and FM4. Infiltration rate significantly decreased in M5 and FM4 applied plots compared to control. Maximum EC1:5 was obtained in control, where as minimum value was obtained in FM4 (30 Mg ha-1) and M5 (100 % Soil cover). Maximum values of NPK and soil organic carbon (SOC) contents were observed at maximum level of mulching (M5) and farm manure (FM4) as compared to control. The highest values of NPK, SOC, EC1:5, SAR, pH, soil bulk density and salt accumulation was observed at upper soil depth compared to lower soil depth whereas percent increase was more in lower soil depths as compared to upper soil depths. Maximum water use efficiency was obtained in case of FM4 and M5 as compared to control. Minimum salt concentration were observed in case of M5 (100 % soil coverage was done) and FM3 (20 Mg ha-1). Root length density of wheat crop was more in M5 and FM4 as compared to control and in upper soil layers as compared to lower soil layers. It is clear from the results that manuring and mulching improves the water use efficiency, physical and chemical properties of soil, enhance the yield of cotton, wheat and mung crops and also helpful in ameliorating ill effects of brackish water on soil and crop characteristics.