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Microwaves, Antennas & Propagation, IET

Issue 5 • Date August 2009

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Displaying Results 1 - 23 of 23
  • Three-dimensional double-negative metamaterials resonating at 13.5 GHz

    Publication Year: 2009 , Page(s): 723 - 727
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (511 KB)  

    A three-dimensional double-negative (DNG, epsiv < 0, mu < 0) metamaterial has been designed to operate near 13.5 GHz. The metamaterial was comprised of patterned copper split ring resonators (SRRs) and wires on a Rogers 5880 substrate. The SRRs and wires were each constructed in three orthogonal planes to give a near-isotropic response to an arbitrarily polarised EM excitation. As this material responds to radiation of arbitrary polarisation and direction, it is referred to as a 3E3H structure where all the six components of the EM tensor are present. The simulated losses in the unit cell are large (2 dB/cm), a major contribution being ohmic effects in the SRRs. For many applications, unit cells of lower dimensionality, that is, 2E2H or 1E1H, where only a restricted number of the elements of the EM tensor are needed, can perform nearly as well as 3D DNG materials, but with much lower loss, and thus may be preferred as an alternative to an isotropic 3E3H structure. View full abstract»

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  • Analysing the shielding effect of a concrete wall reinforced with steel plate using generalised surface integral equations

    Publication Year: 2009 , Page(s): 728 - 735
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    The electromagnetic shielding effect of a two-dimensional concrete wall reinforced with steel plate is analysed using a generalised surface integral equation (GSIE) method developed from Huygens' equivalence principle. The wall is divided into small blocks. Each block is analysed independently at first, and its electromagnetic characteristics are expressed by an associated generalised transition matrix defined on the reference surface of that block. In order to find the electromagnetic characteristics of the whole system, a GSIE formulation is established on the reference surface of all blocks, which can be solved efficiently using characteristic basis functions. View full abstract»

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  • Efficient calculation of the Green's functions for multilayered shielded cavities with right isosceles-triangular cross-section

    Publication Year: 2009 , Page(s): 736 - 741
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (485 KB)  

    An efficient calculation of the Green's functions inside multilayered shielded cavities with right isosceles-triangular cross-section is presented. The method is entirely developed in the spatial domain, and it is based on image theory. The idea is to use the spatial-domain Green's functions inside a multilayered shielded square box, in order to accurately obtain the Green's functions for the right isosceles-triangular cavity. Image theory is then used to enforce the boundary conditions along the non-equal side of the triangle. It is shown that the new algorithm is very robust, with limited computational effort. Resonance frequencies and potential patterns of a triangular cavity have been calculated and compared with those obtained by other techniques, showing very good agreement. Finally, a transversal filter inside a multilayered triangular-shaped cavity is designed, manufactured and tested using the developed technique. View full abstract»

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  • Dual band planar soft surfaces

    Publication Year: 2009 , Page(s): 742 - 748
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (610 KB)  

    The design of dual band planar soft surfaces is presented here. Based on previous works, the parameters of a particular planar realisation of soft surfaces are used to create two frequency bands in which surface waves are suppressed. The planar soft surface is made with strips printed over a grounded dielectric slab with grounded vias. The parameters of the soft surface such as the strip width, the period of the vias and the position of such vias across the strip determine the frequency band at which the structure has a bandgap. It is demonstrated that by interleaving two planar soft surfaces with some different parameters over each other, the stopband of each one of them is maintained, and consequently, a dual band operation is obtained. Any of the mentioned parameters can be employed to this aim as shown in this work. The conclusions are supported by experimental results. The agreement between the measurements and the simulation results is good enough to demonstrate the dual band effect. View full abstract»

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  • Ultra-wideband bandpass filter with multiple notch-bands on multilayer liquid crystal polymer substrate

    Publication Year: 2009 , Page(s): 749 - 756
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (743 KB)  

    Novel compact ultra-wideband (UWB) bandpass filters (BPFs) with single or multiple notch-bands to avoid interference from existing radio systems are presented. A compact UWB BPF is proposed and designed based on broadside-coupled stepped impedance resonators (SIRs) at first, and then notch-bands are generated by embedding open-circuit stubs into broadside-coupled SIRs. Because of the harmonic suppression behaviour of SIRs, the proposed UWB BPFs have a wide stopband and high rejection level. The characteristic of the proposed notch-structure was investigated by full-wave simulations. Multilayer liquid crystal polymer (LCP) technology was used to implement the designed UWB BPFs. In the experiments, a UWB BPF with excellent stopband performance was designed to meet the Federal communications commission-defined indoor limits at first, and then UWB BPFs with single, double and triple notch-bands were designed to demonstrate the flexible notch-band, high-selectivity and wideband harmonic suppression performances of the proposed filter. The designed BPFs were fabricated by a multilayer LCP lamination process and measured using a vector network analyser. Good agreement between the predicted and measured results was obtained as presented here. View full abstract»

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  • Microstrip-fed dual-frequency annular-slot antenna loaded by split-ring-slot

    Publication Year: 2009 , Page(s): 757 - 764
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (612 KB)  

    A compact dual-band annular-slot antenna loaded by a concentric split-ring-slot is presented. A stepped microstrip feedline enables the control of the coupling and provides good matching. The annular-slot is connected to the split-ring-slot by a rectangular slot, which increases the surface of the current path, thus notably reducing the resonant frequency for a given size. The embedded split-ring-slot structure allows many resonant modes to be realised. By tuning the key parameters, these operating modes and their bandwidths can be controlled. A wide bandwidth can be realised for either the lower band, upper band or both bands simultaneously, depending on the application. Measured results show that the bandwidths in the region of 45-15% and 32--8.4%, can be provided for the lower and upper bands, respectively. For the case where a wideband response is required for both bands, it is shown that 26 and 32% can be realised. A 30%miniaturisation is also achieved compared with conventional annular ring slot antennas. View full abstract»

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  • Adaptive beamforming using a novel numerical optimisation algorithm

    Publication Year: 2009 , Page(s): 765 - 773
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (659 KB)  

    Currently, the uniform linear array (ULA) is the most commonly used antenna system for different wireless systems like commercial cellular systems. In this study, a ULA adaptive antenna that uses a novel numerical stochastic optimisation algorithm inspired from colonising weeds, designated as invasive weed optimisation (IWO), is introduced. Weeds are shown to be very robust and adaptive to changes in the environment. Thus, capturing their properties leads to a powerful optimisation algorithm. This optimisation algorithm is used for adaptive beamforming; the obtained results are compared with the results obtained from two other optimisation algorithms, that is, the least mean square and genetic algorithms. The reported results show that the IWO is very robust and effective in locating the optimal solution with higher precision and a lower cost function when compared with the other two algorithms. Other advantages of the IWO algorithm is its simplicity and fast convergence, which makes it a practical algorithm for adaptive beamforming. View full abstract»

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  • T-matched dipole antenna integrated in electrically small body-worn wireless sensor node

    Publication Year: 2009 , Page(s): 774 - 781
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (755 KB)  

    A 2.4 GHz antenna for an electrically small body-worn sensor node is presented. Usually, unbalanced antennas are used in such applications. Implementing a balanced antenna in a small node deployed on the body is problematic from the points of view of both design and characterisation. A solution using a T-matched dipole integrated in the node housing is presented. Techniques for characterisation both in free space and on the body are described. Besides antenna port impedance and radiation efficiency, radiated power and radiation patterns of the active antenna fed by a transceiver in a fully functional sensor node are measured. The benefits and drawbacks of the chosen antenna design and characterisation techniques are discussed. View full abstract»

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  • Compact wideband Koch fractal printed slot antenna

    Publication Year: 2009 , Page(s): 782 - 789
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (813 KB)  

    A compact wideband printed slot antenna, suitable for wireless local area network (WLAN) and satisfying the worldwide interoperability for microwave access (WiMAX) applications, is proposed here. The antenna is microstrip-fed and its structure is based on Koch fractal geometry where the resonance frequency of a conventional triangular slot antenna is lowered by applying Koch iterations. The antenna size inclusive of the ground plane is compact and has a wide operating bandwidth. The proposed second iteration Koch slot antenna operates from 2.33 to 6.19 GHz covering the 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands. The antenna exhibits omnidirectional radiation coverage with a gain better than 2.0 dBi in the entire operating band. Design equations for the proposed antenna are developed and their validity is confirmed on different substrates and for different slot sizes. View full abstract»

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  • Design and implementation of low sidelobe substrate integrated waveguide longitudinal slot array antennas

    Publication Year: 2009 , Page(s): 790 - 797
    Cited by:  Papers (18)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (682 KB)  

    Low sidelobe longitudinal slot array antennas are investigated based on substrate integrated waveguide (SIW) technology. The design method consists of the characterisation of the radiating element, the synthesis of the linear array and the development of the planar array including a feeding power divider by performing full-wave electromagnetic simulations for the final accurate design. Two planar slot array antennas are fabricated with a normal printed circuit board (PCB) process. Low sidelobe features are verified by the measured results which are in agreement with the simulated results. For an 8 times 8 SIW slot array antenna, the measured sidelobe levels (SLLs) are below -36 dB in the H-plane and below -25 dB in the E-plane with the Gain of 20.3 dB at 9.9 GHz. And for a 16 times 16 antenna, the SLLs are below -30 dB both in the E-plane and H-plane with the Gain of 24.4 dB at 10 GHz. The achieved design goals on the radiation patterns therefore validate the proposed low sidelobe SIW slot array antennas to be valuable candidates for high performance communication and radar applications. View full abstract»

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  • Distributed fine model evaluation for rapid space-mapping optimisation of microwave structures

    Publication Year: 2009 , Page(s): 798 - 807
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (557 KB)  

    A novel implementation of a space-mapping (SM) algorithm for optimisation of microwave structures and devices is described. The algorithm uses two techniques to speed up the SM optimisation process: the evaluation of the fine model is distributed through independent processing of the fine model response corresponding to consecutive frequency samples using a number of CPUs, and the parameter extraction and surrogate optimisation sub-problems are solved using built-in optimisation capabilities of the coarse model simulator. As a result, the optimisation time of microwave structures can be reduced to values comparable to or smaller than the time necessary for a single fine model evaluation on a single processor. This new implementation can be applied whenever the fine model is evaluated using a frequency-domain simulator. The robustness of this algorithm using microwave design optimisation problems is verified. The efficiency is compared with the standard implementation of the SM algorithm. View full abstract»

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  • Dispersion requirements of low-loss negative refractive index materials and their realisability

    Publication Year: 2009 , Page(s): 808 - 820
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (582 KB)  

    A necessary dispersion requirement is given for the effective relative permeability mur(omega) and permittivity epsivr(omega) as a function of frequency for low-loss homogeneous dispersive materials and negative refractive index materials, in particular, if they exist at some dimensional scale D. The requirements are valid both for isotropic and uniaxial materials, the latter is defined by material properties that are invariant under a rotation about a principal axis. Using asymptotic requirements at zero frequency and Foster's reactance theorem, the general bandgap structure is given for low-loss materials. It is shown that such materials can only be achieved if the material exhibits finite bandgaps separating regions of positive and/or negative refractive index regions. In degenerate cases, the bandgaps shrink to zero but low-loss propagation remains impossible in the neighbourhood of the critical frequencies. The effect of small losses are considered and compared with Stockman's criterion. Losses may be arbitrarily small within a band provided there are no bounds to the size of the real parts of the relative permittivity and permeability at the band edges. A numerical example is given showing the effect of small losses. View full abstract»

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  • Energy tunnelling through an ultrasmall epsilon-near-zero channel in circular waveguide

    Publication Year: 2009 , Page(s): 821 - 825
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    Based on the conservation of complex power technique, the authors demonstrate theoretically that electromagnetic waves can be squeezed and tunnelled through very small circular channel waveguides at cut-off frequency, which mimics the response of epsilon-near-zero (ENZ) materials. Owing to the infinite phase velocity (zero phase delay) of the wave propagating in the ENZ material, this tunnelling phenomenon is shown to be fundamentally independent of the length and location of the channel guide. View full abstract»

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  • Design and implementation of microwave multi-band/multi-level filters using equal-length transmission lines and Yule-Walker scheme

    Publication Year: 2009 , Page(s): 826 - 833
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (463 KB)  

    A new method to design microwave filter with multiple-band/multiple-level response is proposed. The modified Yule-Walker equation is used to define the frequency-domain response of filter in the Z domain. To implement a filter having transfer function in the Z domain, an equal-length transmission-line configuration is employed to emulate the filter. A band-pass filter a dual-band band-pass filter and a dual-level band-pass filter are implemented and their frequency responses are measured to illustrate the validity of this design method. View full abstract»

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  • Characterisation of microwave phase conjugate signal generation using nonlinearly loaded wire frequency selective surface (FSS)

    Publication Year: 2009 , Page(s): 834 - 842
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (830 KB)  

    Both experimental and theoretical information regarding the scattering and phase conjugate mixing properties of a 2D double-periodic array of wires loaded with nonlinear/linear lumped elements have been provided. An experimental means for assessing the phase conjugate energy production capability for the array is given. These investigations enable identification of the fundamental operational characteristics and underlying mechanisms associated with the production of phase conjugate energy by this type of artificial electromagnetic media. Means for enhancing the phase conjugate energy production capability of the structure by using additional linear lumped loads is examined theoretically and limits on the production of phase conjugate energy established. Theoretical far-field prediction of the behaviour of the structure indicates that retro-directive reflector action as well as negative refraction should be possible. View full abstract»

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  • Three-dimensional antennas array for the estimation of direction of arrival

    Publication Year: 2009 , Page(s): 843 - 849
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (418 KB)  

    Direction of arrival (DOA) estimation of multiple sources using an antenna array becomes very important in wireless communications. It is well known that the quality of the DOA estimation depends on the selected technique and algorithm but it also depends on the geometrical configuration of the antenna array used during the estimation. The authors study the influence of the antenna array configurations on the Cramer-Rao bounds(CRB) of the 2D DOA estimation problem as well as on the performance of the well known MUSIC algorithm. For this we consider the most known planar arrays and we propose a 2-L shaped 3D antennas array. It appears that this 3D antennas array outperforms the other configurations as well as that already proposed in Tayem and Kwon (2005), in terms of both the CRB and the MUSIC root mean square estimation error and also removes ambiguities from the estimation MUSIC pseudo spectrum. View full abstract»

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  • Improving the accuracy of the magnetic field integral equation with the use of a new impedance matrix element formulation

    Publication Year: 2009 , Page(s): 850 - 855
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (171 KB)  

    The electric field integral equation (EFIE) and the magnetic field integral equation (MFIE) are widely used in conjunction with method of moments for electromagnetic scattering analysis of three-dimensional conducting objects with closed surfaces. However, the MFIE suffers from an accuracy problem compared with the EFIE with the use of the Rao-Wilton-Glisson (RWG) basis function. This accuracy problem is more serious for objects with sharp edges or corners. To solve this problem, a new technique to compute the impedance matrix elements (IME) of the MFIE using an RWG basis function is presented here. Details to compute the IME and the advantage of this new formulation are displayed. In addition, the relationship between this new IME formulation and the formulation using the low-order curl-conforming basis function for the MFIE is given. Through the computation of the RCS of several relatively small sharp-edged conducting objects, it is shown that the accuracy of the MFIE can be greatly improved by the use of the new IME formulation. View full abstract»

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  • Method of determining feed positions in coupled half-wavelength stepped impedance resonator bandpass filter

    Publication Year: 2009 , Page(s): 856 - 862
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (643 KB)  

    In this study, the input impedance of coupled half wavelength stepped impedance resonator bandpass filter with directly tapped feed structure is deduced, and the method of determining the feed positions in the filter is proposed by using the concept of impedance matching. Two microstrip bandpass filter examples are described for demonstrating the procedure. The simulated and measured results indicate that the proposed method is an effective way for designing similar filters. View full abstract»

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  • Small modified monopole antenna for UWB application

    Publication Year: 2009 , Page(s): 863 - 869
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (821 KB)  

    In this paper, we present a novel modified printed monopole antenna (PMA) for ultra-wideband (UWB) applications. The proposed antenna consists of a truncated ground plane and radiating patch with two tapered steps, which provides wideband behaviour and relatively good matching. Moreover, the effects of a modified trapezoid-shaped slot inserted in the radiating patch, on the impedance matching and radiation behaviour is investigated. The antenna has a small area of 14 times 20 mm2 and offers an impedance bandwidth as high as 100% at a centre frequency of 7.45 GHz for S 11 < -10 dB, which has a frequency bandwidth increment of 18% with respect to the previous similar antenna. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behaviour within the UWB frequency range. View full abstract»

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  • Tunable slotted ground structured bandstop filter with BST varactors

    Publication Year: 2009 , Page(s): 870 - 876
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (481 KB)  

    This paper presents an investigation of a tunable bandstop filter (BSF) using slotted ground structure. A kind of open loop slot resonator is used for the bandstop response and its characteristics according to various dimensions are considered to decide a proper shape for the final design. A barium-strontium-titanate (BST) varactor chip is deployed to tune each resonator and its location is determined by electromagnetic simulation for an optimum frequency tuning. A three-pole tunable BSF of this type is measured at the centre frequency from 4.5 to 5.5 GHz and its rejection is more than 20 dB at the stop band while the insertion loss at the pass band is less than 1.5 dB. View full abstract»

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  • Simple model for the parametric analysis of grid amplifiers

    Publication Year: 2009 , Page(s): 877 - 881
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (405 KB)  

    A simple method for parametric analysis of grid amplifier performances is presented here. The proposed approach is based on the development of an equivalent transmission line model where each element of the grid is represented by an S-matrix derived from a full-wave simulation in an infinite array environment. The proposed technique makes it possible to investigate the dependency of grid amplifier performance on its major parameters taking into account the actual geometry of each part of the circuit while preserving the simulation efficiency. View full abstract»

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  • Wideband homodyne six-port receiver with high LO-RF isolation

    Publication Year: 2009 , Page(s): 882 - 888
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (583 KB)  

    A simple wideband six-port direct receiver architecture exhibiting high isolation between LO and RF ports is presented. The proposed circuit comprises high input impedance power detectors and lumped-element artificial transmission lines. Therefore small size is achieved even at low frequencies, allowing for easy integration in MMIC technology. A proof-of-concept prototype operating in the 0.8-2.4 GHz band has been constructed and measured showing the validness of this approach. View full abstract»

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  • Compact coplanar waveguide-fed ultra-wideband monopole-like slot antenna

    Publication Year: 2009 , Page(s): 889 - 898
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (985 KB)  

    A simple and compact coplanar waveguide (CPW)-fed ultra-wideband (UWB) monopole-like slot antenna is presented. The proposed antenna comprises a monopole-like slot and a CPW fork-shaped feeding structure, which is etched onto an FR4 printed circuit board (PCB) with an overall size of 26 mm times 29 mm times 1.5 mm. The simulation and experiment show that the proposed antenna achieves good impedance matching, consistent gain, stable radiation patterns and consistent group delay over an operating bandwidth of 2.7-12.4 GHz (128.5 ). Furthermore, through adding two more grounded open-circuited stubs, the proposed antenna design features band-notched characteristic in the band of 5-6 GHz while maintaining the desirable performance over lower/upper UWB bands of 3.1-4.85 GHz/6.2-9.7 GHz. View full abstract»

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