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Microwaves, Antennas & Propagation, IET

Issue 4 • Date March 18 2014

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Displaying Results 1 - 11 of 11
  • Low specific absorption rate hexa-band coplanar waveguide-fed planar inverted-F antenna with independent resonant frequency control for wireless communication applications

    Page(s): 207 - 216
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1138 KB)  

    Compact low specific absorption rate (SAR) hexa-band planar inverted-F antenna (PIFA) with independent resonant frequency control is presented in this study. Two trapezoidal shaped slots are etched on the coplanar waveguide (CPW)-fed PIFA-radiating plate to create two independent resonant frequencies as well as the fundamental CPW-fed PIFA itself. Three coupled slots are added within the ground plane to create additional three independent resonant frequencies with slight effect on the other resonant frequencies. Multiband (dual, tri, quad, penta and hexa) band capabilities with bandwidth enhancement and acceptable SAR values are realised for different wireless communication applications. The SAR of human head is investigated by using Computer Simulation Technology (CST) 2012 Microwave Studio Hugo Voxel Model. The proposed antennas are fabricated and there is a good agreement between measured and simulated results. View full abstract»

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  • Radiation pattern simulation of antenna array problem with perfectly electrically conducting object in arbitrary shape using novel hybrid method of equivalence principle algorithm and physical optics

    Page(s): 217 - 227
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1598 KB)  

    A hybrid method combining the equivalence principle algorithm (EPA) with physical optics (PO) is proposed to solve electromagnetic radiation of an antenna array with perfectly electrically conducting (PEC) object of arbitrary shape. The main idea of this approach is based on the domain decomposition method which is a scheme for multi-scale problems. An EPA can simulate antenna array accurately, and PO is an asymptotical method to obtain current distribution on a PEC object of arbitrary shape as an electrically large problem. For an antenna array with identical elements, the equivalence principle operator only needs to be calculated and be stored once. Compared with the original EPA, this approach performs with higher efficiency and fewer iterations with acceptable accuracy. Numerical results demonstrate the feasibility of the hybrid method. View full abstract»

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  • Compact in-phase power divider integrated filtering response using spiral resonator

    Page(s): 228 - 234
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (799 KB)  

    A compact in-phase power divider with filtering response is presented in this study. Spiral resonators are meant to realise compact size and bandpass-filtering response. To improve the frequency selectivity of the presented power divider, a source-load cross-coupling is introduced by placing input and output coupling lines. An in-phase power divider with passband-filtering response has been designed, fabricated and measured. The measured return loss and insertion loss of the fabricated power divider are 22 and 1.3 dB at 2.45 GHz, respectively. The 3 dB operating bandwidth of the fabricated power divider is 175 MHz. The total area of the fabricated power divider is 0.15λg × 0.3λg. The measured results verify the predicted attractive features. View full abstract»

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  • Waveguide-integrated MEMS-based phase shifter for phased array antenna

    Page(s): 235 - 243
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1052 KB)  

    This study investigates a new concept of waveguide-based W-band phase shifters for applications in phased array antennas. The phase shifters are based on a tuneable bilateral finline bandpass filter with 22 microelectromechanical system (MEMS) switching elements, integrated into a custom-made WR-12 waveguide with a replaceable section, whose performance is also investigated in this study. The individual phase states are selected by changing the configuration of the switches bridging the finline slot in specific positions; this leads to four discrete phase states with an insertion loss predicted by simulations better than 1 dB, and a phase shift span of about 270°. MEMS chips have been fabricated in fixed positions, on a pair of bonded 300 μm high-resistivity silicon substrates, to prove the principle, that is, they are not fully functional, but contain all actuation and biasing-line elements. The measured phase states are 0, 56, 189 and 256°, resulting in an effective bit resolution of 1.78 bits of this nominal 2 bit phase shifter at 77 GHz. The measured insertion loss was significantly higher than the simulated value, which is assumed to be attributed to narrow-band design of the devices as the influences of fabrication and assembly tolerances are shown to be negligible from the measurement results. View full abstract»

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  • Microstrip bandpass single-pole quadruple-throw switch and independently switchable quadruplexer

    Page(s): 244 - 254
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1433 KB)  

    Two switchable microstrip bandpass circuits are investigated. Owing to the low loading effect from the distributed coupling technique, many channels are obtained without a complicated matching network. Each passband can be turned on and off independently. Both the bandpass single-pole quadruple-throw switch and the switchable quadruplexer consisting of asymmetrical quarter-wavelength resonators, shunt open stubs and p-i-n diodes feature compactness, high isolation and wide stopband. The isolation is better than 35 dB, and the 20-dB stopband extends up to 13 times of the lowest operation centre frequency. To validate this design concept, theory as well as experiment are presented and compared. View full abstract»

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  • Liquid-based dielectric resonator antenna and its application for measuring liquid real permittivities

    Page(s): 255 - 262
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    In this study, a water-based rectangular dielectric resonator antenna is designed and analysed. The compactness of the antenna because of the high relative permittivity of water is demonstrated in both simulation and experiment. In addition, a dielectric resonator antenna-based technique is proposed for measuring liquid permittivities. The resonance frequencies of the antennas with fixed configurations are obtained from finite-element electromagnetic (EM) simulation for liquids with different permittivity values. An analytical model of liquid permittivity as a function of the antenna resonance frequency is then developed. Based on this predictive model, the measurement of the liquid real relative permittivity can be easily achieved by measuring the antenna resonance frequency. The measured permittivity values of distilled water and 10% glucose solution are in agreement with previous data in the literature, demonstrating the effectiveness of the proposed liquid permittivity measurement technique. View full abstract»

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  • Broadband planar circularly polarised antenna for ultra-high frequency applications

    Page(s): 263 - 271
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1140 KB)  

    A broadband circularly polarised (CP) antenna employing a deformed square loop radiator in combination with two spiraled monopoles is presented, for use in multiple ultra-high frequency applications. This combination of radiators provides a broad impedance matching bandwidth which is not accessible using any of these techniques alone. The antenna employs a uniplanar structure that is fed using a coplanar waveguide for simplicity of fabrication. A dual-resonance response is achieved by introducing two spiraled monopoles in combination with a square loop radiator. Subsequently, circular polarisation is achieved by introducing three conducting rectangles into the periphery of the square loop, forming a deformed loop radiator. The increase in the electrical length caused by the introduction of the three rectangles also improves the impedance matching of the antenna, providing a wide impedance bandwidth. The antenna exhibits a 45% (556-882 MHz) -10 dB impedance bandwidth, and a 21% (715-880 MHz) 3 dB axial ratio bandwidth. It has a compact size of 0.28λ × 0.28λ × 0.002λ at 582 MHz, which is the lowest resonant frequency of the antenna. Throughout the operating bands, the gain and radiation efficiency vary from 3.6 to 6.4 dBi and 85 to 90%, respectively. View full abstract»

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  • Inverted-E shaped monopole on high-permittivity substrate for application in industrial, scientific, medical, high-performance radio local area network, unlicensed national information infrastructure, and worldwide interoperability for microwave access

    Page(s): 272 - 277
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    In this study, the simulation and measured results of coplanar waveguide (CPW)-fed inverted-E shaped monopole for application in industrial, scientific, medical (ISM), high-performance radio local area network (HIPERLAN), unlicensed National information infrastructure (UNII), and worldwide interoperability for microwave access (WiMAX) bands are presented. The CPW-fed inverted-E shaped monopole is fabricated on a high-permittivity substrate. The lower band is associated with the longer strips of the inverted-E shaped monopole whereas the higher band is associated with the middle and shorter strips of the inverted-E shaped monopole. The proposed antenna has good agreement between the measured and the simulation results. The proposed antenna has a 10 dB return loss with bandwidth 644 MHz (2033-2677 MHz) in the lower band and 1913 MHz (4815-6728 MHz) in the higher band. The proposed dual-band CPW-fed inverted-E shaped monopole covered the ISM, HIPERLAN, UNII and WiMAX bands. View full abstract»

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  • Printed Newton's egg curved monopole antenna for ultrawideband applications

    Page(s): 278 - 286
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (764 KB)  

    The edge curve of a planar antenna significantly influences its radiation properties. In this study, a novel egg curve-based design of printed monopole antenna of size 40 × 40 mm2 is proposed for ultrawideband (UWB) applications. The egg shape of the proposed antennas is obtained by Newton's diverging parabolas curve referred in this study as Newton's egg curve. The design equations of the proposed antenna are developed. The variation in impedance bandwidth (BW) with various parametric variations of design curve is studied. The proposed Newton's egg curved monopole antenna (NECMA) is designed, fabricated and measured to validate the theoretical design. Good agreement between the simulated results and the measured ones is observed. An empirical formula is also proposed to approximately determine the frequency corresponding to the lower edge of -10 dB operating BW. The results show that the proposed NECMA can obtain the measured BW of 116.55% (2.9-11.0 GHz) along with stable gain of about 2.2-2.9 dBi. The proposed antenna exhibits almost omnidirectional radiation patterns with low cross polarisation in all directions and consistent group delay over the entire UWB bandwidth (3.1-10.6 GHz). View full abstract»

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  • Optimisation of non-uniform time-modulated conformal arrays using an improved non-dominated sorting genetic-II algorithm

    Page(s): 287 - 294
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    This study investigates the synthesis of the radiation patterns of the time-modulated (TM) conformal arrays in real applications, including the optimisation of the layout, the switch-on instants and pulse durations. An improved non-dominated sorting genetic algorithm-II (INSGA-II) is proposed to optimise the non-uniform TM conformal arrays. To maintain a balance between the exploitation and exploration ability, controlled elitism is employed and crossover operator based on the competition and selection among several crossover offspring is used in INSGA-II to effectively explore the search space. Two design instances, including aperiodic TM cylindrical conformal array and airship conformal array, are optimised via INSGA-II, in which both the bandwidth and radiation patterns of the radiating elements are considered during the design process. The design results obtained with INSGA-II are compared with the non-dominated sorting genetic algorithm-II and mutiobjective particle swarm optimisation, and numerical results demonstrate that the proposed INSGA-II exhibits promising potential ability for designing the aperiodic TM conformal arrays. View full abstract»

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  • Bacterial foraging optimisation and method of moments for modelling and optimisation of microstrip antennas

    Page(s): 295 - 300
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (255 KB)  

    A novel technique applying bacterial foraging optimisation (BFO) in conjunction with the method of moments (MOM) is developed to calculate accurately the resonant frequency and bandwidth of rectangular microstrip antenna of any dimension and of any substrate thickness. The resonant frequency results obtained by using (BFO/MOM) algorithm are in very good agreement with the experimental results available in the literature. The computation time is greatly reduced as compared with the classical MOM. Furthermore, the idea of this paper can be used for calculating the various parameters of microstrip antennas of different structures and geometries. View full abstract»

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