The Experts below are selected from a list of 5883 Experts worldwide ranked by ideXlab platform

Chuangjiashih Shih - One of the best experts on this subject based on the ideXlab platform.

  • polarization diversity ring slot antenna with Frequency Agility
    IEEE Transactions on Antennas and Propagation, 2012
    Co-Authors: Chuangjiashih Shih
    Abstract:

    A design for polarization-diversity slot antennas with switchable Frequency is described. The antenna structure is mainly composed of a radiating annular slot backed with a reflector and a quasi-lumped coupler with two different operating modes, quadrature hybrid mode and T-junction power divider mode. The resonant Frequency of the slot antenna and the operating frequencies of the two modes of the coupler can be tuned with variable capacitors. First, the effects of changing capacitance values on the performances of the antenna and coupler are respectively analyzed. Then, according to the simulation results, validated with experiments, a reconfigurable antenna prototype integrating with several diodes and their related dc-bias networks is constructed. The prototype is designed to be with three working frequencies, and moreover it can provide one linear polarization and two circular polarizations at each working Frequency. Details of measured antenna performances are shown.

Bishoy I. Halim - One of the best experts on this subject based on the ideXlab platform.

  • smart Frequency Agility control system using compact microstrip crlh tl array structure for communication and radar applications
    Loughborough Antennas and Propagation Conference, 2016
    Co-Authors: Bishoy I. Halim, Hassan M. Elkamchouchi, Yasser M. Madany
    Abstract:

    Metamaterials represent a new paradigm in electromagnetic science and technology. They have already leaded to many unprecedented microwave applications, which may be classified in three categories: guided-wave, radiated-wave and refracted-wave applications. Radiated-wave applications cover several types of novel antennas and reflectors, which may be 1D or 2D, passive or active, and static or dynamically tuned. Progress in metamaterial technologies places challenging demands on material properties and therefore structured electromagnetic materials. The development of composite right / left-handed transmission lines (CRLH-TLs) has received considerable attention due to the unique propagation characteristics. The CRLH-TLs are the metamaterials with both of the RH and the LH properties. In this paper, study and design of smart Frequency Agility control system has been introduced and investigated. The proposed CRLH-TL has been evaluated using a commercial software. The final proposed system with smart control unit has been fabricated and the scattering characteristics have been illustrated using network analyzer to meet the multifunction operation requirements for communication and radar applications.

  • Investigation and design of smart Frequency Agility control system using compact CRLH-TL for communication and radar applications
    2016 IEEE/ACES International Conference on Wireless Information Technology and Systems (ICWITS) and Applied Computational Electromagnetics (ACES), 2016
    Co-Authors: Yasser M. Madany, Hassan M. Elkamchouchi, Bishoy I. Halim
    Abstract:

    Metamaterials is a rapidly evolving field of research that covers a vast range of artificial structures and electro-magnetic properties. Resulting from this, there is no universally accepted definition of what is meant by a meta-material. It is generally agreed that metamaterials are artificial media with unusual properties not found in their constituent materials. The composite right / left-handed transmission lines (CRLH-TLs) are the metamaterials with both of the RH and the LH properties. In this paper, study and design of smart Frequency Agility control system has been introduced and investigated. The proposed CRLH-TL has been evaluated using a commercial software. The final proposed system with smart control unit has been fabricated and the scattering characteristics have been illustrated using network analyzer to meet the multifunction requirements for communication and radar applications.

Yasser M. Madany - One of the best experts on this subject based on the ideXlab platform.

  • smart Frequency Agility control system using compact microstrip crlh tl array structure for communication and radar applications
    Loughborough Antennas and Propagation Conference, 2016
    Co-Authors: Bishoy I. Halim, Hassan M. Elkamchouchi, Yasser M. Madany
    Abstract:

    Metamaterials represent a new paradigm in electromagnetic science and technology. They have already leaded to many unprecedented microwave applications, which may be classified in three categories: guided-wave, radiated-wave and refracted-wave applications. Radiated-wave applications cover several types of novel antennas and reflectors, which may be 1D or 2D, passive or active, and static or dynamically tuned. Progress in metamaterial technologies places challenging demands on material properties and therefore structured electromagnetic materials. The development of composite right / left-handed transmission lines (CRLH-TLs) has received considerable attention due to the unique propagation characteristics. The CRLH-TLs are the metamaterials with both of the RH and the LH properties. In this paper, study and design of smart Frequency Agility control system has been introduced and investigated. The proposed CRLH-TL has been evaluated using a commercial software. The final proposed system with smart control unit has been fabricated and the scattering characteristics have been illustrated using network analyzer to meet the multifunction operation requirements for communication and radar applications.

  • Investigation and design of smart Frequency Agility control system using compact CRLH-TL for communication and radar applications
    2016 IEEE/ACES International Conference on Wireless Information Technology and Systems (ICWITS) and Applied Computational Electromagnetics (ACES), 2016
    Co-Authors: Yasser M. Madany, Hassan M. Elkamchouchi, Bishoy I. Halim
    Abstract:

    Metamaterials is a rapidly evolving field of research that covers a vast range of artificial structures and electro-magnetic properties. Resulting from this, there is no universally accepted definition of what is meant by a meta-material. It is generally agreed that metamaterials are artificial media with unusual properties not found in their constituent materials. The composite right / left-handed transmission lines (CRLH-TLs) are the metamaterials with both of the RH and the LH properties. In this paper, study and design of smart Frequency Agility control system has been introduced and investigated. The proposed CRLH-TL has been evaluated using a commercial software. The final proposed system with smart control unit has been fabricated and the scattering characteristics have been illustrated using network analyzer to meet the multifunction requirements for communication and radar applications.

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

  • effective bandwidth sf cw sar increase using Frequency Agility
    IEEE Aerospace and Electronic Systems Magazine, 2006
    Co-Authors: K Morrison
    Abstract:

    The use of a Frequency-agile waveform is proposed as a way of providing significantly increased bandwidth for a stepped Frequency continuous wave (SF-CW) SAR, than is provided by traditional imaging schemes. The range resolution is set by the bandwidth of the transmitted waveform, and is built up as a set of monotonically increasing stepped frequencies. As these frequencies are sampled sequentially, a constraint with SF-CW waveforms is the time restriction available to build up the bandwidth, imposed by the spatial sampling requirements along the aperture to avoid grating-lobe effects. To address this problem, an approach is outlined which allows the Frequency spectrum to be greatly undersampled to provide a greater effective bandwidth. It was found that randomizing the set of frequencies omitted from sweep to sweep allowed significant thinning before the appearance of significant unwanted image artifacts due to the under-sampling. This scheme allows great flexibility in the choice of bandwidths that can be realized for a particular imaging scenario. Their application is considered from the point of view of operation from UAV SAR platforms

  • increasing the effective bandwidth of an sf cw sar using Frequency Agility
    IEEE International Radar Conference, 2005
    Co-Authors: K Morrison
    Abstract:

    The use of a Frequency-agile waveform is proposed as a way of providing significantly increased bandwidth for a stepped Frequency continuous wave (SF-CW) SAR, than is provided by traditional imaging schemes. The range resolution is set by the bandwidth of the transmitted waveform, and is built up as a set of monotonically increasing stepped frequencies. As these frequencies are sampled sequentially, a constraint with SF-CW waveforms is the time restriction available to build up the bandwidth, imposed by the spatial sampling requirements along the aperture to avoid grating-lobe effects. To address this problem, an approach is outlined which allows the Frequency spectrum to be greatly under-sampled to provide a greater effective bandwidth. It was found that randomizing the set of frequencies omitted from sweep to sweep allowed significant thinning before the appearance of significant unwanted image artifacts due to the under-sampling. This scheme allows great flexibility in the choice of bandwidths that can be realized for a particular imaging scenario. Their application is considered from the point of view of operation from UAV SAR platforms.

Rozeha A. Rashid - One of the best experts on this subject based on the ideXlab platform.

  • LCN Workshops - Experimental studies of the ZigBee Frequency Agility mechanism in home area networks
    39th Annual IEEE Conference on Local Computer Networks Workshops, 2014
    Co-Authors: Mohd Adib Sarijari, Mohd Sharil Abdullah, Anthony Lo, Rozeha A. Rashid
    Abstract:

    A normal home environment consists of various wireless technologies, in particular WiFi and ZigBee, which usually operate in the ISM 2.4-GHz band. In addition, some of the home appliances (e.g., a microwave oven) may operate in this crowded ISM band. WiFi-based, ZigBee-based devices and home appliances operating at the same Frequency and physical space can cause harmful interference to one another, particularly to ZigBee technology. Therefore, the ZigBee Frequency Agility mechanism is introduced by the ZigBee Alliance to ZigBee networks for resolving such harmful interference. In this paper, we experimentally study the performance of the ZigBee Frequency Agility mechanism using a home area network (HAN) testbed. The measurement results show that this mechanism can effectively overcome interference caused by WiFi-based devices. However, in the extreme case, when all the channels are occupied, the mechanism is not effective as expected. In addition, it is observed that the response time for the ZigBee Frequency Agility mechanism to perform channel switching is depending on packet-error-rate (PER) and send-packet-counter thresholds. Low thresholds can reduce channel-switching time but increases signaling overhead. Thus, in order to obtain optimum performance, self-adaptive PER and send-packet-counter thresholds based on interference level are desired rather than static ones.

  • experimental studies of the zigbee Frequency Agility mechanism in home area networks
    Local Computer Networks, 2014
    Co-Authors: Mohd Adib Sarijari, Mohd Sharil Abdullah, Rozeha A. Rashid
    Abstract:

    A normal home environment consists of various wireless technologies, in particular WiFi and ZigBee, which usually operate in the ISM 2.4-GHz band. In addition, some of the home appliances (e.g., a microwave oven) may operate in this crowded ISM band. WiFi-based, ZigBee-based devices and home appliances operating at the same Frequency and physical space can cause harmful interference to one another, particularly to ZigBee technology. Therefore, the ZigBee Frequency Agility mechanism is introduced by the ZigBee Alliance to ZigBee networks for resolving such harmful interference. In this paper, we experimentally study the performance of the ZigBee Frequency Agility mechanism using a home area network (HAN) testbed. The measurement results show that this mechanism can effectively overcome interference caused by WiFi-based devices. However, in the extreme case, when all the channels are occupied, the mechanism is not effective as expected. In addition, it is observed that the response time for the ZigBee Frequency Agility mechanism to perform channel switching is depending on packet-error-rate (PER) and send-packet-counter thresholds. Low thresholds can reduce channel-switching time but increases signaling overhead. Thus, in order to obtain optimum performance, self-adaptive PER and send-packet-counter thresholds based on interference level are desired rather than static ones.