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Christos G. Christodoulou - One of the best experts on this subject based on the ideXlab platform.

  • Implementation of a cognitive radio front-end using rotatable controlled reconfigurable Antennas
    IEEE Transactions on Antennas and Propagation, 2011
    Co-Authors: Youssef Tawk, Kerry Avery, Joseph Costantine, Christos G. Christodoulou
    Abstract:

    This communication presents a new Antenna system designed for cognitive radio applications. The Antenna Structure consists of a UWB Antenna and a frequency reconfigurable Antenna system. The UWB Antenna scans the channel to discover “white space” frequency bands while tuning the reconfigurable section to communicate within these bands. The frequency agility is achieved via a rotational motion of the Antenna patch. The rotation is controlled by a stepper motor mounted on the back of the Antenna Structure. The motor's rotational motion is controlled by LABVIEW on a computer connected to the motor through its parallel port. The computer's parallel port is connected to a NPN Darlington array that is used to drive the stepper motor. The Antenna has been simulated with the driving motor being taken into consideration. A good agreement is found between the simulated and the measured Antenna radiation properties.

  • implementation of a cognitive radio front end using optically reconfigurable Antennas
    International Conference on Electromagnetics in Advanced Applications, 2010
    Co-Authors: Youssef Tawk, Mohammed Alhusseini, Sameer Hemmady, Alexander R Albrecht, Ganesh Balakrishnan, Christos G. Christodoulou
    Abstract:

    This paper presents a reconfigurable radio front-end Antenna scheme suitable for cognitive radio communications. Our scheme comprises of an UWB Antenna Structure (Antenna-1) and a reconfigurable Antenna Structure (Antenna-2) incorporated together on the same substrate. The UWB Antenna-1 is used for channel sensing while the reconfigurable Antenna-2 is designed to frequency-hop between pre-determined communication channels. The reconfiguration of Antenna-2 is achieved by using photoconductive switches which are selectively illuminated by laser light from a series of integrated laser diodes. A prototype was fabricated and tested to prove the applicability of our proposed radio front-end scheme.

Zongquan Deng - One of the best experts on this subject based on the ideXlab platform.

  • structural design and optimization of large cable rib tension deployable Antenna Structure with dynamic constraint
    Acta Astronautica, 2018
    Co-Authors: Hongxiang Wang, Dewei Tang, Zongquan Deng
    Abstract:

    Abstract The large deployable Antenna has continuously received research interest in space technology. The design of such large Structure has certain inherent challenges, such as limited mass and volume because of the inadequate capabilities of launchers. This constraint affects different aspects, including shapes, dimensions, and stiffness requirements. This study explores a new large cable–rib deployable Antenna Structure with radial ribs and tensioned cables. This Structure has the advantages of high stiffness/mass ratio, which is suitable for constructing large-scale deployable Antennas. A structural optimization method with a dynamic constraint for the maximum stiffness/mass ratio is proposed; this method is based on structural design formulas and the dynamic model of the deployable Antenna Structure. A genetic algorithm is introduced for parameter optimization with frequency constraint. Numerical examples are conducted to demonstrate the effectiveness of the proposed optimization method. By using these analysis methods, a 1.8 m prototype is fabricated and tested. Afterward, the feasibility and dynamic characteristics of the proposed cable–rib tension deployable Structure are validated.

  • modeling and analysis of a large deployable Antenna Structure
    Acta Astronautica, 2014
    Co-Authors: Zhengrong Chu, Zongquan Deng
    Abstract:

    Abstract One kind of large deployable Antenna (LDA) Structure is proposed by combining a number of basic deployable units in this paper. In order to avoid vibration caused by fast deployment speed of the mechanism, a braking system is used to control the spring-actuated system. Comparisons between the LDA Structure and a similar Structure used by the large deployable reflector (LDR) indicate that the former has potential for use in Antennas with up to 30 m aperture due to its lighter weight. The LDA Structure is designed to form a spherical surface found by the least square fitting method so that it can be symmetrical. In this case, the positions of the terminal points in the Structure are determined by two principles. A method to calculate the cable network stretched on the LDA Structure is developed, which combines the original force density method and the parabolic surface constraint. Genetic algorithm is applied to ensure that each cable reaches a desired tension, which avoids the non-convergence issue effectively. We find that the pattern for the front and rear cable net must be the same when finding the shape of the rear cable net, otherwise anticlastic surface would generate.

  • a novel surface deployable Antenna Structure based on special form of bricard linkages
    2012
    Co-Authors: Ji Cui, Hailin Huang, Zongquan Deng
    Abstract:

    In this paper, a novel form of general line-symmetric Bricard linkage (GLSBL) that can be deployed onto arbitrary non-equilateral triangular profile and can be folded onto a bundle compact form with all the six links being parallel and contact to each other is presented. The mobility and detailed kinematic of the mechanism is studied. Using the novel GLSBL, a tripod mechanism using two similar deployable special form Bricard linkages as its bases connecting to three limbs is proposed. The tripod mechanism can be deployed onto triangular prism profile and can also be folded onto a bundle compact form so that it can be used as the basic building modules for the construction of large deployable trussed surface Structures. Using this module, the deployable Structure that can be deployed onto a spherical surface is presented.

Youssef Tawk - One of the best experts on this subject based on the ideXlab platform.

  • Implementation of a cognitive radio front-end using rotatable controlled reconfigurable Antennas
    IEEE Transactions on Antennas and Propagation, 2011
    Co-Authors: Youssef Tawk, Kerry Avery, Joseph Costantine, Christos G. Christodoulou
    Abstract:

    This communication presents a new Antenna system designed for cognitive radio applications. The Antenna Structure consists of a UWB Antenna and a frequency reconfigurable Antenna system. The UWB Antenna scans the channel to discover “white space” frequency bands while tuning the reconfigurable section to communicate within these bands. The frequency agility is achieved via a rotational motion of the Antenna patch. The rotation is controlled by a stepper motor mounted on the back of the Antenna Structure. The motor's rotational motion is controlled by LABVIEW on a computer connected to the motor through its parallel port. The computer's parallel port is connected to a NPN Darlington array that is used to drive the stepper motor. The Antenna has been simulated with the driving motor being taken into consideration. A good agreement is found between the simulated and the measured Antenna radiation properties.

  • implementation of a cognitive radio front end using optically reconfigurable Antennas
    International Conference on Electromagnetics in Advanced Applications, 2010
    Co-Authors: Youssef Tawk, Mohammed Alhusseini, Sameer Hemmady, Alexander R Albrecht, Ganesh Balakrishnan, Christos G. Christodoulou
    Abstract:

    This paper presents a reconfigurable radio front-end Antenna scheme suitable for cognitive radio communications. Our scheme comprises of an UWB Antenna Structure (Antenna-1) and a reconfigurable Antenna Structure (Antenna-2) incorporated together on the same substrate. The UWB Antenna-1 is used for channel sensing while the reconfigurable Antenna-2 is designed to frequency-hop between pre-determined communication channels. The reconfiguration of Antenna-2 is achieved by using photoconductive switches which are selectively illuminated by laser light from a series of integrated laser diodes. A prototype was fabricated and tested to prove the applicability of our proposed radio front-end scheme.

Sujeet K. Chaudhuri - One of the best experts on this subject based on the ideXlab platform.

  • Spherical Vector Wave Method for Analysis and Design of MIMO Antenna Systems
    IEEE Antennas and Wireless Propagation Letters, 2010
    Co-Authors: Mehrbod Mohajer, Safieddin Safavi-naeini, Sujeet K. Chaudhuri
    Abstract:

    In this letter, spherical vector wave approach is employed to investigate the electromagnetic aspects of multiple-input-multiple-output (MIMO) Antennas. The correlation coefficient is introduced as the design and optimization criterion, and a systematic approach is proposed for MIMO Antenna analysis and design. The proposed method is utilized to maximize the system capacity for the given MIMO Antenna Structure.

Abd-alhameed, Raed A. - One of the best experts on this subject based on the ideXlab platform.

  • 8-Port Semi-Circular Arc MIMO Antenna with an Inverted L-Strip Loaded Connected Ground for UWB Applications
    'MDPI AG', 2021
    Co-Authors: Addepalli T., Desai A., Elfergani, Issa T., Anveshkumar N., Kulkarni J., Zebiri C., Rodriguez J., Abd-alhameed, Raed A.
    Abstract:

    yesMultiple-input multiple-output (MIMO) Antennas with four and eight elements having connected grounds are designed for ultra-wideband applications. Careful optimization of the lines connecting the grounds leads to reduced mutual coupling amongst the radiating patches. The proposed Antenna has a modified substrate geometry and comprises a circular arc-shaped conductive element on the top with the modified ground plane geometry. Polarization diversity and isolation are achieved by replicating the elements orthogonally forming a plus shape Antenna Structure. The modified ground plane consists of an inverted L strip and semi ellipse slot over the partial ground that helps the Antenna in achieving effective wide bandwidth spanning from (117.91%) 2.84–11 GHz. Both 4/8-port Antenna achieves a size of 0.61 λ × 0.61 λ mm2 (lowest frequency) where 4-port Antenna is printed on FR4 substrate. The 4-port UWB MIMO Antenna attains wide impedance bandwidth, Omni-directional pattern, isolation >15 dB, ECC 4.5 dB making the MIMO Antenna suitable for portable UWB applications. Four element Antenna Structure is further extended to 8-element configuration with the connected ground where the decent value of IBW, isolation, and ECC is achieved

  • Beam-scanning leaky-wave Antenna based on CRLH-metamaterial for millimeter-wave applications
    'Institution of Engineering and Technology (IET)', 2019
    Co-Authors: Alibakhshikenari M., Abd-alhameed, Raed A., Virdee .s., Khalily M., Shukla P., See C.h., Falcone F., Limiti E.
    Abstract:

    YesThis paper presents empirical results of an innovative beam scanning leaky-wave Antenna (LWA) which enables scanning over a wide angle from -35o to +34.5o between 57 GHz and 62 GHz, with broadside radiation centered at 60 GHz. The proposed LWA design is based on composite right/left-handed transmission-line (CRLH-TL) concept. The single layer Antenna Structure includes a matrix of 3×9 square slots that is printed on top of the dielectric substrate; and printed on the bottom ground-plane are Π and Tshaped slots that enhance the impedance bandwidth and radiation properties of the Antenna. The proposed Antenna Structure exhibits metamaterial property. The slot matrix provides beam scanning as a function of frequency. Physical and electrical size of the Antenna is 18.7×6×1.6 mm3 and 3.43×1.1×0.29, respectively; where is free space wavelength at 55 GHz. The Antenna has a measured impedance bandwidth of 10 GHz (55 GHz to 65 GHz) or fractional bandwidth of 16.7%. Its optimum gain and efficiency are 7.8 dBi and 84.2% at 62 GHz.Partially supported by innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET- 722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1