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    Design and Implementation of Radio Frequency Power Feeding Networks for Antenna Array Applications: Simulation and Measurements of Multiport, Equal and Unequal, Fixed and Reconfigurable Radio Frequency Power Feeding Networks for Narrow and Ultra-Wideband Applications

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    ammar, a.h.a.pdf (33.16Mb)
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    Author
    Ali, Ammar H.A.
    Supervisor
    Abd-Alhameed, Raed A.
    Keyword
    Wilkinson power divider
    Uniplanar power divider
    Multi-layer power divider
    Multi-port power divider
    Ultra-wideband power divider
    Reconfigurable power divider
    Equal and unequal power divider
    Antenna array
    Feeding network
    Quarter-wavelength transformer
    Rights
    Creative Commons License
    The University of Bradford theses are licenced under a Creative Commons Licence.
    Institution
    University of Bradford
    Department
    Faculty of Engineering and Informatics
    Awarded
    2018
    
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    Abstract
    Power dividers are vital components and widely used in radio technology, such as antenna arrays, power amplifiers, multiplexers and mixers. A good example is the well-known Wilkinson power divider with its distinctive feeding network characteristics. A comprehensive review indicated that limited research is carried out in the area of planar multiport and reconfigurable power dividers in terms of the power levels between output ports. The main objectives of this work were to develop a small size power divider, a planer multi-output ports power divider and a power divider with a reconfigurable power division ratio. These power dividers were designed to operate over either an ultra-wideband frequency (3.1-10.6 GHz) or WLAN bands (2.4 or 5.2 GHz). A novel multi-layered topology solved the complexity of interconnecting isolation resistors by introducing an additional layer below the ground layer. The prototype was fabricated and tested to validate the results. The measurements and simulation were in good agreement. Finally, a novel uniplanar power divider with reconfigurable output power level difference was developed. The configurability feature was achieved by tuning the quarter wave transformer using one varactor diode. The power divider was applied to improve a full duplex system cancellation performance at the receiver element caused by interference from in-site transmitting antennas. This study investigated fixed power dividers, multi-output power dividers and reconfigurable power dividers. The measurements validated by the simulation results and applications proved the designed power dividers could be used in practical applications.
    URI
    http://hdl.handle.net/10454/17447
    Type
    Thesis
    Qualification name
    PhD
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      A design procedure for a 1-to-4 Ultra-Wideband Wilkinson power divider

      Ali, Ammar H.; Abd-Alhameed, Raed A.; Hu, Yim Fun; Child, Mark B. (2016-11)
      The design of a physically small, equal phase and equal power, 1-to-4 ultra-wideband Wilkinson power divider is presented. Initially, a 1-to-2 divider was designed and optimized for the 3.1 GHz-to-10.6 GHz range. The 1-to-4 divider was then realized using three 1-to-2 dividers, and further optimized for full band insertion loss, return loss, and isolation. The circuits were constructed using a 0.75 mm thick Rogers RO3035 substrate, and experimentally validated.
    • Thumbnail

      Theoretical and conceptual issues in leadership and complex military operations

      Adeka, Muhammad I.; Shepherd, Simon J.; Abd-Alhameed, Raed A. (2016)
      This paper discusses theoretical and conceptual issues in leadership and how these apply to complex military operations in this global age. It identifies the reason for and the point at which the need for leadership arose among the early humans. It suggests the need for every human activity to be assessed within the context of its relative existence, based on the employment of accepted standards. Thereafter, the subject matter was treated under four main sections; namely, the Elements of Power, Leadership and its Sanctity, Concept of Military Operations, and Analosynthesis. With improvements in technology and mastery over their environments, the homo habilis gained control over their means of subsistence and the basic necessities of life. Their quest for better security and stability, in order to facilitate progressive developments, led to the emergence of community life. This was the stage at which the need for leadership, among humans, became apparent. Lessons on Leadership and Influence dictate that Power and Influence, which is one’s art of getting others to follow one’s lead, are best understood in terms of the interactions among the Elements of Power. The paper identified five enabling factors of power and influence; namely, how power works, how influence works, the TOPS Formula, the influence skills and cultural differences. These would enhance his ability to positively communicate with the led for maximum effect. Defined as a process of influencing a group of individuals to achieve a common goal, leadership is seen as a key variable in the development of human society. Any leader that fails to imbibe some ethical leadership values and principles that would guide his leadership, he would hardly gain the confidence and loyalty of the led. These include respect for others; service to others; justice, fairness and equity for all and sundry; honesty; resourcefulness; and truthfulness/trustworthiness – all leading to the building of a strong, united, virile and prosperous community. It is believed that the crises bedevilling Nigeria today, particularly Northern Nigeria, can be largely attributed to the negation of ethical values/principles on the part of our leaders, both past and present. It is hoped that the Change which Nigerian electorates voted for on 28th March 2015 would make the needed difference. A military operation is a set of activities characterised by mutual belligerent actions; regardless of how the opposing elements are defined, equipped or disposed. Hence, military operations may not be limited to the conventional battlefield; new forms of battlefields and domains of warfare will continue to emerge for as long as human technology is progressive. Currently, a critical analysis yields the existence of five warfare domains; namely, Land, Sea, Air, Space (Strategic Defence Initiative or Star Wars) and Cyber Space. In view of the above, even the concept of military operation, in terms of the troops that execute warfare, must also be re-assessed in tune with the dictates of globalisation. Thus, as opposed to seeing soldiers as some illiterates, dressed in ragtag attire and engaging in a “woo-chebe!” warfare; the contrary should now be the case. Soldiering should be seen as an enterprise for people traversing the entire levels of education/training throughout the social strata of the society; comprising the illiterate and semi-illiterate local informants, highly educated troops, and all shades of professionals and technocrats up to the University Professors, globally. Concomitantly, there is need to also re-evaluate, by reconfiguring and expanding, the concept of the military element of national power into a more suitable gauge of national strength - the socio-military element of national power. That is, the military is no longer expected to function effectively independent of its wider society setting. In a nutshell, for one to succeed as a leader of officers and men in a military operation, one must first of all imbibe the general principles/values of ethical leadership expected of all categories of leaders, as enumerated above. In addition to these, one must then train to internalise those other attributes that would sustain one in leadership position as one confronts an uncertain death; namely, valour, bravery, courage, faithfulness and an existence of a balanced coordination between a healthy mind and a healthy body.
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      Seeing or hearing? Perceptual independence, modality confusions, and crossmodal congruity effects with focused and divided attention

      McIlhagga, William H.; Baert, J.; Bundesen, C.; Larsen, A. (2003)
      Observers were given brief presentations of pairs of simultaneous stimuli consisting of a visual and a spoken letter. In the visual focused-attention condition, only the visual letter should be reported; in the auditory focused-attention condition, only the spoken letter should be reported; in the divided-attention condition, both letters, as well as their respective modalities, should be reported (forced choice). The proportions of correct reports were nearly the same in the three conditions (no significant divided-attention decrement), and in the divided-attention condition, the probability that the visual letter was correctly reported was independent of whether the auditory letter Was correctly reported. However, with a probability much higher than chance, the observers reportedihearing the visual stimulus letter or seeing the spoken stimulus letter (modality confusions). The strength of the effect was nearly the same with focused as with divided attention. We also discovered a crossmodal congruity effect: Performance was better when the two letters in a stimulus pair were the same than when they differed in type.
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