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Microwaves, Antennas & Propagation, IET

Issue 1 • Date January 11 2013

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Displaying Results 1 - 10 of 10
  • Millimetre-wave path-loss variability between two body-mounted monopole antennas

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (433 KB)  

    Variation of on-body millimetre-wave propagation channels with body movements has been studied experimentally. A statistical description of the propagation channel is presented, including path-loss probability distributions, level-crossing rates and average fade durations. The median path losses for the considered practical links with omnidirectional monopole antennas lied within the range of 55-88 dB. The signal variation was found to consist of two superimposed variations, in general: the long-term and short-term fadings, but was dominated by the much stronger long-term fading. The use of a simple two-state Markov process model to describe on-body communication links is also proposed and its limitations are discussed. View full abstract»

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  • Dual band-notched small monopole antenna with novel W-shaped conductor backed-plane and novel T-shaped slot for UWB applications

    Page(s): 8 - 14
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (777 KB)  

    In this study, a novel method for designing a new monopole antenna with dual band-notched characteristic for UWB applications has been presented. The proposed antenna consists of a square radiating patch with a modified T-shaped slot, and a ground plane with two E-shaped slots and a W-shaped conductor backed-plane. By cutting two E-shaped slots in the ground plane, additional resonance is excited and hence much wider impedance bandwidth can be produced, especially at the higher band, which results in a wide usable fractional bandwidth of more than 130% (2.73%13.3 GHz). In order to generate single band-notched characteristic, the authors use a W-shaped conductor backed-plane structure on the other side of the substrate. In addition, by cutting a modified T-shaped slot in the radiating patch and microstrip feed-line, a dual band-notched function is achieved. The measured results reveal that the presented dual notch band monopole antenna offers a very wide bandwidth with two notched bands, covering all the 5.2/5.8 GHz wireless local area network, 3.5/5.5 GHz WiMAX and 4 GHz C bands. The designed antenna has a small size of 12 % 18 mm2. Good voltage standing wave ratio (VSWR) and radiation pattern characteristics are obtained in the frequency band of interest. Simulated and measured results are presented to validate the usefulness of the proposed antenna structure for ultra-wideband (UWB) applications. View full abstract»

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  • Improved reactance domain unitary propagator algorithms for electronically steerable parasitic array radiator antennas

    Page(s): 15 - 23
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (586 KB)  

    In this study, the authors propose four algorithms for directions of arrival (DoAs) estimation of multiple incoming narrowband plane waves onto electronically steerable parasitic array radiator antennas. The constraints on the proposed algorithms are the same as those imposed onto the classic subspace methods allowing superior high-resolution and localisation capabilities even for correlated sources scenarios but with more reduced computations load and processing time than existing schemes. We also demonstrate that estimating the propagator operator through both introduced real-valued orthogonal decompositions techniques not only yields to a faster DoAs estimation with a reduced computational complexity, but also it improves the robustness of the developed algorithms to noise as compared with the classic propagator algorithm. The CraméŕRao bound on the variance of the estimated DoAs by the proposed algorithms is analysed. The achieved performance by the developed methods is studied and compared with conventional antenna arrays. The simulation results confirm that high-resolution DoAs estimation can be achieved with the developed algorithms and prove the validity of the proposed approach. View full abstract»

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  • Comment on 'Analytical equivalence between substrate-integrated waveguide and rectangular waveguide'

    Page(s): 24 - 25
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (77 KB)  

    The authors discuss a recently proposed analytical method for calculation of equivalent width of substrate integrated waveguide. Modifications are made to calculate the final analytical formula more accurately. View full abstract»

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  • Design of miniaturised band-notch ultra-wideband monopole-slot antenna by modified half-mode substrate-integrated waveguide

    Page(s): 26 - 34
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1512 KB)  

    In this study, a compact ultra-wideband (UWB) two-layer printed microstrip line monopole-slot antenna with triple band-rejection characteristics is investigated. The proposed antenna consists of a planar UWB monopole-slot antenna with a size of 40 × 47 × 1.016 mm3 and a modified half-mode substrate-integrated waveguide (M-HMSIW) cavity with folded defected ground structure slot. The antenna is fabricated using two-layer printed circuit board process. To generate band-notched characteristics, M-HMSIW cavity in the bottom layer of the antenna are utilised. By tuning the dimension of M-HMSIW, triple notched bands with sharp rejection can be achieved at WiMAX band (3.3-3.69 GHz), along with a major part of the C-band (3.7-4.2 GHz), lower wireless local area network (WLAN) band (5.15-5.35 GHz), and upper WLAN band (5.725-5.825 GHz). The simulated and measured impedance matching, radiation patterns and gain results of antenna are investigated. The results of the fabricated antenna show that this antenna is a good candidate for various UWB applications. View full abstract»

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  • Specific absorption rate and path loss in specific body location in heterogeneous human model

    Page(s): 35 - 43
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (505 KB)  

    A multi-implant scenario is considered using insulated dipole antennas for specific locations such as the liver, heart, spleen and the kidneys where implants communicate with a pacemaker acting as a central hub. Wireless communication within human body experiences loss in the form of attenuation and absorption, and to identify these losses, the path loss is studied in this paper for an adult and child heterogeneous human model. Link performance is calculated to investigate the applicability of in-body communication. The specific absorption rate for all these locations is also studied to verify compliance with international safety guidelines. View full abstract»

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  • Efficient boundary integral-resonant mode expansion method implementation for full-wave analysis of passive devices based on circular waveguides with arbitrary perturbations

    Page(s): 44 - 53
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    In this study, the efficient full-wave analysis of passive devices composed of circular and arbitrarily-shaped waveguides is considered. For this purpose, the well-known boundary integral-resonant mode expansion (BI-RME) method has been properly extended. Circular waveguides are used for resonant mode expansion, whereas the arbitrary contour is defined by any combination of straight, circular and elliptical segments, thus allowing the exact representation of the most widely used geometries. The proposed algorithm extends previous implementations of the BI-RME method based on circular waveguides by considering circular and elliptical arcs for defining arbitrary geometries. Similarly, it allows the efficient analysis of passive devices based on circular waveguides with arbitrary perturbations, thus providing more accurate results with less computational efforts than a rectangular waveguide-based BI-RME approach. The extended method has been successfully tested with several practical application examples, having compared its performance with the BI-RME method based on rectangular waveguides. View full abstract»

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  • Design of compact planar crossover using Sierpinski carpet microstrip patch

    Page(s): 54 - 60
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (826 KB)  

    The design of a planar four-port microstrip crossover is presented. The design starts by using a half-wavelength square patch and two sets of orthogonal feeding lines. Based on the cavity theory, operation of the patch crossover is analysed. Full-wave simulations and measurements are used to support the analysis. By etching the patch as a Sierpinski carpet, resonant frequency can be lowered significantly, and this property can be employed to reduce the size of the conventional patch crossover. It is shown that the size of the crossover can be reduced by 23% with even a better performance when a second-order Sierpinski carpet microstrip patch is used. Full-wave simulations and measurements are used to validate the proposed design method. The measured data show less than 1 dB insertion loss, more than 10 dB return loss, more than 17 dB isolation and about 0.1 ns group delay deviation across 10% fractional bandwidth centred at 2.4 GHz. View full abstract»

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  • Body-centric ultra-wideband multi-channel characterisation and spatial diversity in the indoor environment

    Page(s): 61 - 70
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (725 KB)  

    This study presents the findings of an empirical channel characterisation for an ultra-wideband off-body optic fibre-fed multiple-antenna array within an office and corridor environment. The results show that for received power experiments, the office and corridor were best modelled by lognormal and Rician distributions, respectively [for both line of sight (LOS) and non-LOS (NLOS) scenarios]. In the office, LOS measurements for tmean and tRMS were both described by the Normal distribution for all channels, whereas NLOS measurements for tmean and tRMS were Nakagami and Weibull distributed, respectively. For the corridor measurements, LOS for tmean and tRMS were either Nakagami or normally distributed for all channels, with NLOS measurements for tmean and tRMS being Nakagami and normally distributed, respectively. This work also shows that achievable diversity gain was influenced by both mutual coupling and cross-correlation co-efficients. Although the best diversity gains were 1.8 dB for three-channel selective diversity combining, the authors present recommendations for improving these results. View full abstract»

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  • Design and analysis of a decade bandwidth 180° hybrid coupler

    Page(s): 71 - 77
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (617 KB)  

    The design and analysis of a decade bandwidth 3 dB 180° hybrid coupler using tandem connection of two similar wideband 8.34 dB hybrids is presented. The designed coupler has return loss better than 12 dB over a decade bandwidth, insertion loss below 6 dB, amplitude balance within ° 1 dB, phase balance of ° 20° and isolation above 18 dB. Gap and overlap ground patterns at the junction of the tightly coupled to uncoupled region are introduced to improve isolation by preventing odd-mode field coupling and preserving equal even- and odd-mode phase velocities across the junction. View full abstract»

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