Online ISSN
1751-8733
Print ISSN
1751-8725
IET Microwaves, Antennas & Propagation
Volume 2, Issue 7, October 2008
Volumes & issues:
Volume 2, Issue 7
October 2008
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- Author(s): T.A. Denidni and M. Nedil
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 641 –649
- DOI: 10.1049/iet-map:20060199
- Type: Article
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p.
641
–649
(9)
The design and realisation of a 4×4 Butler matrix for multibeam antenna arrays operating at 5.8 GHz are described. The matrix is implemented on a single layer slotline structure to avoid using air bridges as required in coplanar waveguide technology. In this design, a new hybrid coupler and a crossover using slotline technology were designed and fabricated, and they are used to build a new Butler matrix. To examine the performances of the proposed matrix, numerical simulations and experimental measurements were carried out; the comparison between simulated and experimental results shows a good agreement. - Author(s): M.D. Migliore
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 650 –658
- DOI: 10.1049/iet-map:20070197
- Type: Article
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p.
650
–658
(9)
The objective of the study is to clarify some physical limitations in the performance of statistical RADAR systems using multiple antennas. In particular, it is shown that the performance of the recently proposed statistical multiple-input multiple-output (MIMO) RADAR is limited by the Number of Degrees of Freedom (NDF) of the scattered field. Furthermore, the true nature of statistical RADAR systems (single-input multiple-output, multiple-input single-output, MIMO) is not related to the number of transmitting/receiving antennas, but to the NDF of the scattered field exploited by the system. - Author(s): E. García ; J.A. Murphy ; E. de Lera ; D. Segovia
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 659 –667
- DOI: 10.1049/iet-map:20070229
- Type: Article
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p.
659
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(9)
Infinite circular corrugated waveguide is analysed to investigate its ability to support modes with backward wave behaviour. Such waveguides provide an alternative structure, easier to manufacture than those already reported based on rectangular symmetry with corrugated walls or filled with frequency selective surfaces. The corrugations if sufficiently deep provide a guiding structure with the required series capacitance and shunt inductance to allow left-handed propagation within some frequency bands. These backward waves are analysed using the surface impedance model of propagation in corrugated waveguides to predict their properties. Interpreting the physical meaning of the analysis, the authors discuss how backward waves are related to resonances in corrugated structures. The relationship between power flows in the guide and the behaviour of the group velocity for such guides is shown. A full wave simulator is also applied to validate these results and the case of a dielectric filled waveguide is considered showing the improved ability to support left-handed modes. The authors present the results of a parametric study of how left-handed propagation depends on the corrugation depth. Potential applications of backward waves in corrugated circular waveguides are proposed. - Author(s): Z.Y. Huang and G.W. Pan
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 668 –676
- DOI: 10.1049/iet-map:20070259
- Type: Article
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p.
668
–676
(9)
An important advance in the finite difference time domain (FDTD) algorithms is Berenger's perfect matched layer (PML), along with its derivatives. In recent years several new explicit and implicit FDTD algorithms have appeared on the scene, of which each requires a specific PML. To simplify programming, the authors derive a universal uniaxial PML formulation, which is universally applicable to the Yee FDTD, FDTD with higher-order stencils and implicit FDTD algorithms. Numerical results show the efficiency and versatility of the new method. - Author(s): S. Liu ; M. Liu ; W. Hong
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 677 –685
- DOI: 10.1049/iet-map:20070291
- Type: Article
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p.
677
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A modified piecewise linear current density recursive convolution (PLCDRC) finite-difference time-domain (FDTD) for anisotropic magnetised plasma is proposed. The method is derived using two recursive conclusion. The electric field is time-shifted in the first convolution and the current density is time-shifted in the second convolution. The computation of the current density and the electric field employ the piecewise linear approximation technique. Like PLCDRC FDTD, the method has more accuracy over CDRC FDTD. Moreover, it is faster in computation velocity than PLCDRC FDTD. The high efficiency and accuracy of the method are confirmed by computing the reflection and transmission through a magnetised plasma layer, with the direction of propagation parallel to the direction of the biasing field. The bistatic radar cross-section of conducting sphere covered with magnetised plasma is also calculated. Then, the numerical dispersion relation of the new PLCDRC FDTD scheme is derived. The numerical dispersion error and dissipation error caused by the new PLCDRC-FDTD method are investigated by comparing the real and imaginary parts of the numerical wave number with those of the analytical wave number. Finally, the stability of the new PLCDRC-FDTD method is discussed. This method can also be used in other frequency dispersion electromagnetic problem if it is modified slightly. - Author(s): A.K. Hamid and F.R. Cooray
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 686 –695
- DOI: 10.1049/iet-map:20070190
- Type: Article
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p.
686
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An exact solution to the problem of scattering of electromagnetic waves from a perfect electromagnetic conducting spheroid is presented, using the method of separation of variables. The formulation of the problem is realised by expanding the incident as well as the scattered electromagnetic fields in terms of appropriate spheroidal vector wave functions and imposing the appropriate boundary conditions at the surface of the spheroid. This generates a set of simultaneous equations, the solution of which yields the unknown coefficients associated with the expansion of the scattered electromagnetic field. Results are presented in the form of normalised bistatic and backscattering cross-sections for spheroids of different axial ratios, sizes and admittances, for both transverse electric and transverse magnetic polarisations of the incident wave. - Author(s): M. Okumura ; T. Imura ; Y. Kamata ; N. Kamo ; A. Sugawara ; T. Takano
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 696 –703
- DOI: 10.1049/iet-map:20070311
- Type: Article
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p.
696
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A novel design is proposed to reduce the number of driven elements by replacing them with passive elements or wires in an array antenna. The study is based on the analysis of electromagnetic wave fields by considering of the coupling between the half-wavelength dipoles. An array antenna of two driven elements and two passive elements is considered as a model. After optimising the element arrangement, the antenna gain can match that of the equivalent four‐driven element case. The simulation result is confirmed by an experiment that uses dipoles with simplified matching technique. Feeding networks in a high-power radiating system are analysed in terms of the length and matching of feed lines, and the number of amplifiers. - Author(s): Y.H. Cho
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 704 –710
- DOI: 10.1049/iet-map:20070251
- Type: Article
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p.
704
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The transverse magnetic plane-wave scattering equations for infinite and semi-infinite rectangular grooves (RGs) in a conducting plane are proposed in terms of the overlapping T-block method and Floquet theorem. By utilising the Floquet theorem and taking the limit of multiple RGs as the number of RGs becomes infinity, the simultaneous solutions of infinite RG are then analytically obtained. Combining the analyses of infinite and large number of RGs yields approximate yet numerically efficient scattering equations for semi-infinite RG. Numerical computations are performed to verify that the solutions converge fast and agree with the mode-matching method. - Author(s): J.-W. Lee and B. Lee
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 711 –717
- DOI: 10.1049/iet-map:20070099
- Type: Article
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p.
711
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In order to increase the radio-frequency identification (RFID) operation distance, read range analysis was performed based on a simple equivalent circuit of the ultra high frequency (UHF)-band passive RFID tag. The analysis shows that a tag with a large Q-factor leads to an increased input voltage in the tag chip and thus enhances the efficiency. Based on this analysis, a compact (37.5 mm ×44 mm) RFID antenna employing inductive coupling between the radiation and feeding portions was designed. Simple adjustments of the two structural parameters of the antenna allowed for easy control of the antenna resistance and inductive reactance, from which a high Q-factor requirement could be readily satisfied. For a conjugate match to the tag chip impedance of 11−j127 Ω, a Q-factor of 11.5 was achieved. The designed RFID tag has a 3 dB radar cross-section (RCS) bandwidth of ∼6.5%, which is wide enough to handle the impedance detuning caused by the material properties of the attached objects. The designed RFID tag antenna was fabricated and a reading range test in an anechoic chamber was performed using two methods. When a measured RCS of the RFID tag was used, the detection distance was 9.8 m for a reader sensitivity of –65 dBm and 4.7 m for a tag sensitivity of –11 dBm. Using a commercially available tag chip, the range test resulted in 4.3 m, which is compatible with the derived range equations. The tag antennas having lower Q-factors (77+j100 Ω and 55+j155 Ω) have also been fabricated, and their measured read ranges were 2.6 and 1.1 m, respectively. - Author(s): C.H. See ; R.A. Abd-Alhameed ; P.S. Excell ; N.J. McEwan ; J.G. Gardiner
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 718 –724
- DOI: 10.1049/iet-map:20070356
- Type: Article
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p.
718
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A novel internal triple-band folded planar antenna for mobile handsets is introduced, formed by modifying the geometry of a rectangular patch antenna to include a shorting pin, folded sides, a shorted microstrip stub and a notch. The size of the antenna is successfully reduced to a volume of 34×34×7 mm3. The antenna is mounted on a finite ground plane of 50×100 mm2. The impedance bandwidth achieved was 29.7% (equivalent to return loss≤−10 dB); this covers the DCS1800, PCS1900 and UMTS 2000 bands. The characteristics of the proposed antenna, including impedance bandwidth and far field radiation patterns are discussed theoretically and experimentally; the simulated and measured results show good agreement. The tuning effects of the geometry parameters on impedance matching of the proposed antenna are also investigated. - Author(s): H. Nakano ; S. Sasaki ; H. Oyanagi ; J. Yamauchi
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 725 –730
- DOI: 10.1049/iet-map:20080022
- Type: Article
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p.
725
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The characteristics of an Archimedean spiral (ARSP) antenna backed by an extremely shallow cavity (0.07 wavelength at the lower operating design frequency of 3 GHz) are analysed. It is revealed that the presence of the cavity causes noticeable variation in the antenna characteristics at low frequencies. To restore the wideband characteristics inherent to the ARSP, a ring-shaped strip absorber (R-ABS) is placed under the spiral arms. It is found that the wideband antenna characteristics are successfully restored with the use of the R-ABS. Subsequently, the R-ABS is divided into two arc-shaped strip absorbers and the volume of each is reduced by decreasing the arc-angle phisARC from 180° (corresponding to an R-ABS) to 0° (corresponding to a cavity without an absorber). It is shown that when the arc-angle is chosen to be greater than phisARC=90°, the antenna characteristics obtained for phisARC=180° are reproduced. Theoretical results are confirmed using results from experimental work. - Author(s): W. Tong ; Z. Hu ; H. Zhang ; C. Caloz ; A. Rennings
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 731 –736
- DOI: 10.1049/iet-map:20070180
- Type: Article
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p.
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A novel realisable dual composite right/left-handed (D-CRLH) coplanar waveguide (CPW) transmission line (TL) in GaAs MMIC technology demonstrated by theoretical analysis and experimental results is presented. A D-CRLH TL is the dual of the conventional CRLH TL in the sense that it consists of series LC parallel tanks and shunt LC series tanks. However, an ideal D-CRLH TL cannot be realised because of unavoidable parasitic effects. The measured results indicated that a real D-CRLH TL exhibits a fundamentally different frequency response at higher frequency band in that a real D-CRLH TL cannot provide unlimited left handed (LH) bandwidth. Instead, it has triple bands; right-handed (RH) passband at lower frequencies (DC-2.9 GHz), LH passband at intermediate frequencies (5.1–14.3 GHz) and RH passband at higher frequencies (above 14.3 GHz). The reported fully integrated D-CRLH CPW TL metamaterial has a very compact size of 2.2 mm2 which leads to a small loss 1.5 dB within 3 dB LH passband. - Author(s): Y.H. Liu and X.P. Zhao
- Source: IET Microwaves, Antennas & Propagation, Volume 2, Issue 7, p. 737 –744
- DOI: 10.1049/iet-map:20070198
- Type: Article
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p.
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A more directional and higher gain patch antenna with an anisotropic negative permeability medium (NPM) cover is proposed. The patch antenna operates at the frequency where the permeability of split-ring resonator (SRR) is negative, and then the sideward radiation can be forbidden. It leads to a significant enhancement of designing the high gain antenna. We investigate numerically and experimentally the performance of the antenna when NPM composed of SRR is placed above the patch antenna. The measured result has a good agreement with the simulation. Compared with the conventional antenna, the result shows that the beam of antenna with the NPM cover becomes more convergent, half-power beamwidth is smaller by almost 30° in the H-plane and 10° in the E-plane and the gain is higher by 4.03 dB. Moreover, NPM cover can have applications in the other types of antenna such as monopoles, dipole antennas, leak-wave antennas and aperture antennas.
Experimental investigation of a new Butler matrix using slotline technology for beamforming antenna arrays
Some physical limitations in the performance of statistical multiple-input multiple-output RADARs
Analysis of the left-handed corrugated circular waveguide
Universally applicable uniaxial perfect matched layer formulation for explicit and implicit finite difference time domain algorithms
Modified piecewise linear current density recursive convolution finite-difference time-domain method for anisotropic magnetised plasmas
Scattering of electromagnetic waves by a perfect electromagnetic conducting spheroid
Theoretical and experimental study on a partially driven array antenna with simplified dipole elements
Transverse magnetic plane-wave scattering equations for infinite and semi-infinite rectangular grooves in a conducting plane
Design of high-Q UHF radio-frequency identification tag antennas for an increased read range
Internal triple-band folded planar antenna design for third generation mobile handsets
Cavity-backed Archimedean spiral antenna with strip absorber
Study and realisation of dual-composite right/left-handed coplanar waveguide metamaterial in MMIC technology
Investigation of anisotropic negative permeability medium cover for patch antenna
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