By Topic

Microwaves, Antennas & Propagation, IET

Issue 14 • Date November 20 2012

Filter Results

Displaying Results 1 - 15 of 15
  • Distance from unconditional stability boundary of a two-port network

    Publication Year: 2012 , Page(s): 1507 - 1515
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    Many parameters are available to show if a linear two-port network is unconditionally stable or not, but none of them shows the distance from the boundary of unconditional stability in the scattering parameter space. Here, the boundary of unconditional stability is demonstrated as hypersurfaces and the distance of the network's parameters from this boundary for the absolutely stable condition is derived using new single stability parameters. The boundary is shown in the S- and Y-dimensions (parameters of scattering and immittance matrices). The unconditional stability safety factor is also introduced to determine the distance from the boundary of unconditional stability for the absolutely stable condition, using scattering parameters. Examples and applications are also demonstrated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • L-shaped strip-fed patch array based on mutual coupling

    Publication Year: 2012 , Page(s): 1516 - 1520
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A novel E-plane patch array with a reduced number of the active elements is developed by making use of strong mutual coupling between passive and active elements. Although only half the number of elements is excited in the proposed array, it can provide similar gain to an ideal conventional array in which all elements are excited; meanwhile the cost and loss are greatly reduced. The operating principle is proved from the points of impedance matrix and electric field distribution. Simulations and measurements show that even when the active element spacing is as large as 1.55λ0 (where λ0 is the free-space wavelength at the centre frequency), the proposed array can still present a gain approximately equal to that of an ideal conventional array with a half-element spacing (0.775λ0). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Cost-efficient electromagnetic-simulation-driven antenna design using co-Kriging

    Publication Year: 2012 , Page(s): 1521 - 1528
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (461 KB)  

    A technique for design optimisation of antennas is presented. The approach exploits coarse-discretisation electromagnetic (EM) simulations of the antenna of interest that are used to create its fast initial model (a surrogate) through Kriging. During the design process, predictions obtained by optimising the surrogate are verified using high-fidelity EM simulations, and these high-fidelity data are used to enhance the surrogate using co-Kriging interpolation that accommodates all EM simulation data into one surrogate model. The co-Kriging-based optimisation algorithm is simple and it is capable of yielding a satisfactory design at a low-cost equivalent to a few high-fidelity EM simulations of the antenna under design. To the best of author's knowledge, this is a first application of co-Kriging to antenna design. The proposed approach is demonstrated using several antenna design cases and compared with other techniques including pattern search and space mapping. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coplanar waveguide-fed slot antenna for wireless local area network/worldwide interoperability for microwave access applications

    Publication Year: 2012 , Page(s): 1529 - 1535
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1003 KB)  

    Owing to the recent demand to incorporate the two communication services, the wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX), therefore dual-band antennas that are designed with sufficient bandwidths to cover both WLAN and WiMAX operating bands are presently very important topics of research. Owing to the difficulty of simultaneously achieving both compactness and wideband, the dimensions of most dual-band slot antenna designs that are reported in recent literature exceed 35×40×mm2. Therefore this study presents a compact (32×32×mm2) coplanar waveguide (CPW)-fed slot antenna design with dual-band operation for WLAN (2.4/5.2/5.8 GHz) and WiMAX (2.3/2.5/3.5/5.7 GHz) applications. To achieve wide 10 dB bandwidth for the lower operating band (58 ), the technique of applying a square-ring slot antenna type with an asymmetric ground plane was used herein, and a broad upper operating band (32 ) was attained by introducing a stub-protruded monopole and loading a double-bent stub into one of the asymmetric CPW ground planes. The process of designing the proposed antenna is explicitly shown, and parametric studies were carried out by simulation. Typical experimental measurements were also conducted and compared with the simulated results. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Passive low-cost inkjet-printed smart skin sensor for structural health monitoring

    Publication Year: 2012 , Page(s): 1536 - 1541
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (625 KB)  

    Monitoring fatigue cracking of large engineering structures is a costly and time-intensive process. The authors' present the first low-cost inkjet-printed patch antenna sensor that can passively detect crack formation, orientation and shape by means of resonant frequency shifts in the two resonant modes of the antenna. For the first time, the effect of non-linear crack shapes on the parallel and perpendicular resonant modes of a patch antenna is quantified with simulation and measurement. This study presents a step towards fully integrated, low-cost, conformal and environmentally friendly smart skins for real-time monitoring of large structures. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fast analysis of electromagnetic scattering from body of revolution using high-order basis functions

    Publication Year: 2012 , Page(s): 1542 - 1547
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (347 KB)  

    Electromagnetic scattering by conducting body of revolution (BOR) is formulated in terms of the electric field integral equation combined with high-order basis function based on curved-wire segment. Owing to the rotational symmetry property of BOR, the currents are represented using high-order basis functions along the generating arc and Fourier series expansion for the periodic azimuthal variation. The method of moment for BOR (BORMoM) is applied to the linear system solved by the direct solver. The parallelisation is carried out in the high-order BORMoM to further reduce the computation time. Numerical results are presented to demonstrate the accuracy and efficiency of the proposed method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Slow-wave slot microstrip transmission line and bandpass filter for compact millimetre-wave integrated circuits on bulk complementary metal oxide semiconductor

    Publication Year: 2012 , Page(s): 1548 - 1555
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1121 KB)  

    In this study, a novel on-chip low-loss slow-wave slot (SWS) microstrip transmission line is proposed. Unlike conventional slow-wave structures such as photonic bandgap and ladder microstrip transmission line, which usually deal with either the substrate, ground plane or the signal line separately, the periodic patterns of SWS structures are etched along both the conductive metal strip and the ground plane of the microstrip line. The proposed structure, unlike other slow-wave structures does not require extra drilling through the substrate or complex three-dimensional multi-layer structures, only requires coplanar slot etching. The proposed SWS microstrip demonstrates excellent size reduction with minimal increase in loss. To show the utility of the proposed method, two second-order rectangular open-loop filters with and without implementing the proposed SWS microstrip have been designed with similar bandwidths and fabricated in the millimetre-wave (mm-wave) range on 65-nm bulk complementary metal oxide semiconductor (CMOS). Both simulations and measurements demonstrate that the on-chip filter implemented using the proposed SWS has a 52.7% reduction in size while suffering only an additional 0.5%dB in transmission loss penalty. To the best of authors% knowledge, this compact filter is the first reported mm-wave filter using slow-wave structure on bulk CMOS. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhancement of intra-body propagation and communication under the Brillouin precursor perspective

    Publication Year: 2012 , Page(s): 1556 - 1564
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    The emergence of the Brillouin precursor is presented as a plausible form to understand classical phenomena observed in intra-body propagation and through-tissue imaging technologies that can be associated with the features of these precursors formation, such as the non-exponentially level decay and the broadening of pulse duration. The authors describe the evolution of different pulses through skin, muscle as well as normal and malignant breast tissues by using both a time-domain and a frequency-domain analysis technique and multi-pole Debye models to characterise the dielectric properties of the considered tissues, in a frequency band designated by the Federal Communication Commission (FCC) for ultra wideband medical applications, 0.5-20-GHz. The Cole-Cole model is also tested for the same frequency range and tissues in order to determine the influence of the dielectric model. The authors tested the influence of one of the main parameters considered critical for precursor emergence: the input pulse configuration. The results reveal that the precursor is a phenomenon to take into account for application in areas where larger signal-to-noise ratios can be of interest. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Exposure of the human brain to an electromagnetic plane wave in the 100-1000 MHz frequency range for potential treatment of neurodegenerative diseases

    Publication Year: 2012 , Page(s): 1565 - 1572
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (614 KB)  

    Radio signals can induce an electric field inside the brain, which might be potentially beneficial in the treatment of neurodegenerative diseases. For instance, a new method for the treatment of Alzheimer's disease in mice through the exposure to the radiation of mobile phones has been successfully demonstrated. In the light of these results, studying the induction of an electric field in the human brain through the controlled exposure to radio signals is of paramount importance for the eventual development of similar treatment techniques in humans. In this study, the authors study the radio signals in 100-1000 MHz as a means for inducing an electric field into the human brain in a non-invasive fashion. A voxel representation of the human body was used for numerical simulations, and the induced electric fields in the brain tissues (white and grey matters) were calculated for different incoming wave polarisations. A quantitative measure of the electric field inside the brain tissues is presented together with the average specific absorption rate. It is shown that the average electric field intensity in the brain has two local maxima at 300 and 600 MHz. These results are important for defining the optimal frequency band and wave polarisation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hybrid differential evolution with artificial bee colony and its application for design of a reconfigurable antenna array with discrete phase shifters

    Publication Year: 2012 , Page(s): 1573 - 1582
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (802 KB)  

    This study proposes a new method of designing a reconfigurable antenna with quantised phase excitations using a new hybrid algorithm, called as differential evolution algorithm (DE)/artificial bee colony algorithm (ABC). The main objective of the reconfigurable design problem is to find the element excitation that will result in a sector pattern main beam with low side lobes. The same excitation amplitudes applying to the array with zero phase should be in a high directivity and low side lobe pencil-shaped main beam. The dynamic range ratio is minimised to reduce the effect of mutual coupling between the antenna-array elements. Additionally, compared with the continuous realisation and subsequent quantisation, experimental results indicate that the performance of the discrete realisation of the phase-excitation value can be improved. In order to test the performances of hybrid differential evolution with the artificial bee colony algorithm, the results of some state-of-the-art algorithms are considered. The experimental results indicate the better performance of the DE/ABC. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Pattern synthesis for multi-feed reflector antennas using invasive weed optimisation

    Publication Year: 2012 , Page(s): 1583 - 1589
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1149 KB)  

    The authors present a new optimisation method for pattern synthesis of multi-feed reflector antennas in this study. By using an invasive weed optimisation (IWO) algorithm, shaped beam antennas are designed. The results of the IWO algorithm for the synthesis of cosecant squared and contoured beam patterns are presented and compared with particle swarm optimisation algorithm results. The far-field radiation patterns of reflector antennas, fed by linear and planar array of conical horn antennas, are provided by a physical optics and the error between desired and provided radiation patterns is calculated by a root mean square method. The results show that the IWO algorithm, which provides good convergence, is stable and adaptive-to-change for different boundary conditions in pattern synthesis applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Instantaneous directivity optimisation in time-modulated array receivers

    Publication Year: 2012 , Page(s): 1590 - 1597
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    As of the periodic on-off modulation of the static excitations, the number and the positions of the active elements in time-modulated arrays can vary significantly within the modulation period and the radiated pattern can drastically differ instant-by-instant. Since the fluctuations of the antenna gain could severely affect the behaviour of the received signal and its correct retrieval, the switching sequence is here properly optimised to keep constant the instantaneous directivity of the main beam, while generating a desired average radiation pattern at the frequency of the impinging signal. This allows one to avoid the spreading of the desired signal power into the harmonics generated by the on-off commutations of the switches. A set of representative results concerned with a benchmark linear case is reported and discussed to show the effectiveness of the proposed approach also in comparison with state-of-the-art solutions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Intelligent z-plane boundary condition-particle swarm optimiser for small array pattern synthesis

    Publication Year: 2012 , Page(s): 1598 - 1607
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1117 KB)  

    This study concerns the radiation performance improvement of small periodic linear phased arrays in the presence of mutual coupling. An approach using a particle swarm optimiser (PSO) coupled with Schelkunoff's z-plane unit circle is proposed, with z-plane zeros constrained using adaptive boundary conditions (termed the intelligent z-plane boundary condition-PSO). It is shown that the proposed optimisation scheme has successfully achieved the target results for a range of problems presented including low-sidelobe scanned beam, and sector-beam pattern synthesis. The approach has consistent and faster convergence when compared with competitive techniques. Results showing significant improvement are presented using a Bowtie dielectric resonator antenna and uniform hemispherical elements. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Self-recoverable antenna arrays

    Publication Year: 2012 , Page(s): 1608 - 1615
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (495 KB)  

    An approach is proposed for a self-recovery algorithm (SRA) to be embedded in an autonomous and reprogrammable controller device that would be used to monitor a system, sense failures of the system components and find a solution to recover the functionality of the system as much as possible. The approach presented here is on the scenario of self-recoverable antenna arrays, perceived as one of the vital interests in today's world of ubiquitous communication. The SRA is presented when run on a desktop computer and an field programmable gate arrays (FPGA) chip, to show the effectiveness of the approach on a few examples. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • New approach to a fast and accurate design of microwave circuits with complex topologies

    Publication Year: 2012 , Page(s): 1616 - 1622
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (823 KB)  

    A robust simulation-driven design methodology of microwave circuits with complex topologies has been presented. The general method elaborated is suitable for a wide class of N-port unconventional microwave circuits constructed as a deviation from classic design solutions. The key idea of the approach proposed lies in an iterative redesign of a conventional circuit by a sequential modification and optimisation of its atomic building blocks. The speed and accuracy of the method presented has been acquired by solving a number of simple optimisation problems through surrogate-based optimisation (SBO) techniques, which offer a satisfactory approximation of the optimal design solution. Two exemplary designs have been supplied to verify the method introduced. An abbreviated wideband quarter-wave impedance matching transformer and a miniaturised hybrid branch-line coupler have been developed. Diminished dimensions of the circuits under construction have been achieved by means of compact microstrip resonant cells. As an SBO engine, an implicit space mapping technique has been utilised. The final results have been acquired in only a fraction of time that is necessary for a direct electromagnetic (EM) optimisation to generate competitive results. An experimental validation of the method proving its high utility has been provided. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IET Microwaves, Antennas & Propagation covers all aspects of microwave and antenna engineering and propagation.

Full Aims & Scope

Meet Our Editors

IET Research Journals
iet_map@theiet.org