Scheduled System Maintenance:
Some services will be unavailable Sunday, March 29th through Monday, March 30th. We apologize for the inconvenience.
By Topic

Microwaves, Antennas & Propagation, IET

Issue 6 • Date April 26 2011

Filter Results

Displaying Results 1 - 16 of 16
  • Design and demonstration of a metamaterial with electronically tunable negative refraction across the C microwave band

    Publication Year: 2011 , Page(s): 631 - 636
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (505 KB)  

    The design, numerical simulation and experimental measurement of a novel metamaterial with an electronically tunable negative refractive index region are presented. The proposed unit cell is loaded with commercial varactors operating over the C microwave band. Tunability is achieved by applying a static electric field across the series-connected split-ring resonators. A theoretical description of the unit cell is correlated with microscopic and macroscopic simulations of the proposed metamaterial. Two samples of the proposed metamaterial are evaluated in a waveguide measurement. The wideband tunability of the proposed metamaterial is well suited to a variety of microwave applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of channel capacity for fixed broadband multimedia systems at 40 GHz

    Publication Year: 2011 , Page(s): 637 - 643
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (423 KB)  

    The results of a wideband radio channel sounding campaign performed at 40 GHz band are presented. We have used a sounder based on the correlation of pseudorandom m-sequences, but some novelties have been introduced in the classical scheme of this kind of sounders. Different antenna patterns and polarisations have been combined with three groups of actual environments (indoor, outdoor and indoor-outdoor) in order to achieve general conclusions, valid for a wide range of different situations. An expression relating two of the main parameters of the wideband radio channel (coherence bandwidth and delay spread) is fitted to the measured results. The experimental data as well as this expression verify Fleury-s limit, a restriction that has been extended here to define a complete region of valid values. Finally, a theoretical analysis of the channel capacity is conducted. We have stated the theoretical improvement that the channel capacity would experience owing to the use of spatial diversity or multicarrier modulations. The outcomes provide a timely insight into the expectations for the use of high data rate applications in this frequency band even in indoor conditions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Broadband dual planar inverted F-antenna for wireless local area networks/worldwide interoperability for microwave access and lower-band ultra wideband wireless applications

    Publication Year: 2011 , Page(s): 644 - 650
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    An extension of the planar inverted F-antenna (PIFA) concept is proposed, combining two such antennas (one of them fed parasitically) to extend the usable bandwidth to cover the WiFi wireless local area network, worldwide interoperability for microwave access and lower-band ultra wideband spectra. The broad impedance bandwidth is achieved by combining a driven slotted PIFA, having bandwidth-enhanced rectangular strip feed, with a parasitic inverted F-shaped element, hence describable as a dual PIFA. The geometry parameters of these two radiators are selected to enhance the impedance bandwidth and hence to encompass the entire required set of operating frequency bands. The overall optimised dimensions of the antenna are 30 mm 15 mm 8 mm, thus making it compatible with installation on portable wireless electronic devices. The results show that the proposed antenna can achieve a gain between 2.0 and 4.0 dBi across the entire impedance bandwidth 2.4 6.2 GHz (i.e. 88.4 relative bandwidth) for a reflection coefficient of |S11| <; 10 dB. The radiation patterns of the antenna show low-gain broad-beam coverage, as is essential for a wireless electronic device. Computed and experimental results are compared and are shown to be in satisfactory agreement. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of the performance of vegetation barriers to reduce electromagnetic pollution

    Publication Year: 2011 , Page(s): 651 - 663
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (510 KB)  

    Public fear of exposure to electromagnetic fields has led to many countries introducing legislation on the topic. Some have even introduced `sensitive areas` where field levels should be significantly reduced. This study presents an efficient and ecological method to reduce the exposure to electromagnetic fields for the mobile global system for mobile communication (GSM) and universal mobile telecommunications system (UMTS) frequency bands. We propose the use of tree (or bush) barriers as a shielding method around places that may need to be protected. A major measurement campaign has provided a significant amount of data to characterise the performance of such soft walls. The campaign involves seven vegetation species and five different barrier configurations. Furthermore, a parametrical characterisation of the attenuation levels achieved with this method is presented and validated. This aids in choosing the configuration barriers and the vegetation species that provide the desired attenuation levels in exclusion zones. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Identification of V-band frequency-selective surface at 11 m standoff distance with a transceiver chipset

    Publication Year: 2011 , Page(s): 664 - 670
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (539 KB)  

    The authors demonstrate the detection of a millimetre wave frequency-selective surface with a null near 60 GHz at large standoff distances (≥10m) such as would be required for covert security labelling and anti-counterfeiting applications. The authors compare the performance of using lenses and offset parabolic reflector to improve the directivity of a commercial, compact, integrated chipset in a ball grid array package, finding a reduction in beam width from 60 to 5 and 10°, respectively. They measured the power spectrum of the system with no label at distances of 35 cm, 60 cm, 4 m and 11 m finding no appreciable fading effect with the higher-directivity system. The integrated system-measured response of the frequency-selective surface agreed well with that of a standard test set-up (horn antennas and vector network analyser) as well as numerical simulations conducted with a frequency-domain solver (HFSS). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Compact characterisation of ultra wideband antenna responses from frequency measurements

    Publication Year: 2011 , Page(s): 671 - 675
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (594 KB)  

    An approach to give a compact representation of UWB antennas using network analyser measurements and based on the extraction of poles/residues by the singularity expansion method is presented. This work focuses on a Matrix Pencil applied to the measured S21 of two identical antenna links. It also suggests applying the MP algorithm twice (once over each causal signal present on both sides of the time response maximum). This procedure is demonstrated to fully capture the information from the time response of the synthesised antenna link, obtained after a FFT (fast Fourier transform). This allows a perfect reconstruction of the antenna time response with a minimal representation model. The measurements protocol established for experimental results validation is described. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reduced symmetric self-constructing fuzzy neural network beamforming detectors

    Publication Year: 2011 , Page(s): 676 - 684
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    Beamforming technology has been widely used in smart antenna systems that can increase the user's capacity and coverage in modern communication products. In this study, a powerful reduced symmetric self-constructing fuzzy neural network (RS-SCFNN) beamforming detector is proposed for multi-antenna-assisted systems. A novel training algorithm for the RS-SCFNN beamformer is proposed based on clustering of array input vectors and an adaptive minimum bit-error rate method. An inherent symmetric property of the array input signal space is exploited to make training procedure of RS-SCFNN more efficient than that of standard SCFNN. In addition, the required amount of fuzzy rules can be greatly reduced in the RS-SCFNN structure. Simulation results demonstrate that RS-SCFNN beamformer provides superior performance to the classical linear ones and the other non-linear ones (including symmetric radial basis function, SCFNN and S-SCFNN), especially when supporting a large amount of users in the rank-deficient multi-antenna-assisted system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full-wave semiconductor devices simulation using meshless and finite-difference time-domain approaches

    Publication Year: 2011 , Page(s): 685 - 691
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (350 KB)  

    A new numerical method for the full-wave physical modelling of semiconductor devices using a combination of the meshless and finite-difference time-domain (FDTD) approaches is described. The model consists of the electron equations for the active part and Maxwell's equations for the electromagnetic effects, which describe the complete behaviour of a high-frequency active device. The unconditionally stable method by using a semi-implicit meshless approach for the active model and the alternating-direction implicit (ADI)-FDTD approach for electromagnetic model leads to a significant decrease in the full-wave simulation time. Using this technique, we can achieve a 99' reduction in the computation time and obtain an acceptable degree of accuracy in comparison with conventional FDTD approaches. As the first step in the investigation, the authors use the electron flow equations without holes and recombination process as the semiconductor equations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Study of high-frequency electromagnetic transients radiated by electric dipoles in near-field

    Publication Year: 2011 , Page(s): 692 - 698
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (509 KB)  

    The study investigates transient electromagnetic (EM) radiation in the near-field zone of a system of electric dipoles and the usage of the plane wave spectrum (PWS) concept for extraction of a 3-D field from 2-D measurements. Both aspects are important in the modelling and characterisation of radiated emissions in electromagnetic compatibility applications, which are extended here to time domain. Analytical expressions for a set of dipoles excited by short-duration Gaussian pulses, which in the author's approach are used to model EM radiation, are presented and implemented into a Matlab program to calculate the time-dependent distributions of the three electric field components Ex(t), Ey(t), Ez(t). These results are then used to verify the new technique of extraction of the time-domain component Ez(t) of the electric field from measurements of the two other components, Ex(t) and Ey(t). The details of the technique, based on PWS method applied to the time domain, are presented. Very good agreement between the extracted and analytically calculated fields has been achieved. Further verification and comparison has been done by the simulation in the time domain of the system of dipoles using commercial 3-D EM software. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Compensate for the coupled radiation patterns of compact transmitting antenna arrays

    Publication Year: 2011 , Page(s): 699 - 704
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    An effective method is suggested to compensate for the mutual coupling in the coupled array patterns of compact antenna arrays. By using the mutual impedances of the antenna elements, the authors showed that it is possible to design compensation networks that can remove the distortion on array patterns due to the mutual coupling effect. The compensated array patterns enable us to predict the radiation characteristics of compact antenna arrays using the principle of pattern multiplication based on their ideal and isolated element patterns. Equations for the construction of such compensation networks are obtained and the realisation method is discussed. With these compensation networks, further conventional port-decoupling and matching circuits can be designed and connected to their inputs to achieve maximum power transfer from the source to the antenna array. Numerical examples on dipole and monopole arrays demonstrate the validity and accuracy of the method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Very-wideband microstrip antenna for laptop applications

    Publication Year: 2011 , Page(s): 705 - 710
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (769 KB)  

    A very-wideband microstrip antenna is proposed and studied. The antenna has a simple structure comprising a rectangular patch embedded into a notch cut in the finite ground plane edge. The novel structure is bent to reduce antenna height and is divided into two resonators: an open loop and a planar monopole. The former simultaneously excites half- and one-wavelength modes to form a wide bandwidth for lower band operation of the design. In addition, the planar monopole with its inherent broadband property provides the upper-band operation. With a small volume of 45×10×5 mm3, the impedance bandwidth of the proposed antenna is up to 128% impedance bandwidth from 1.80 to 8.23 GHz. Moreover, the non-correlative current paths on the driven elements provide the independence of band adjustment. Owing to the balanced loop structure and the gaps between patch and ground plane, antenna performances are preserved from the integration with an liquid crystal display panel. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multiband-integrated antenna/artificial magnetic conductor

    Publication Year: 2011 , Page(s): 711 - 717
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (874 KB)  

    An artificial magnetic conductor (AMC)-based multiband low-profile antenna for vehicle applications is designed, simulated and measured in this study. The AMC is a simple dual band structure, constructed on a 3.2 mm-thick FR-4 (εr=4.4) board, with the reflection phase and surface wave bandgaps in the 2.0 and 5.8 GHz ranges. A wideband printed circular disc monopole antenna uses this dual-band AMC as a ground plane resulting in a low-profile, multiband and platform-tolerant antenna system. The operating frequency bands covered are GPS (1.57542 GHz), DCS (1.710-1.880 GHz), PCS (1.850-1.990 GHz), UMTS (1.925-2.175 GHz), WLAN (2.4-2.485 GHz), WiFi (5.15-5.825 GHz) and V2X (5.76-5.84 GHz) using a -10 dB reflection coefficient criterion. It is demonstrated that the antenna gain increases significantly when the AMC is used over a large metal ground plane for the antenna. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 24-GHz in-phase/quadrature direct-down converter with integrated quadrature couplers and baluns in standard 0.18 μm cmos technology

    Publication Year: 2011 , Page(s): 718 - 727
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1082 KB)  

    A novel monolithic CMOS radio frequency (RF) direct-down converter architecture is described, that comprises three miniature quadrature couplers (QCs), three miniature baluns and two sub-harmonic mixers (SHMs) for direct-down conversion. The SHMs in conjunction with the QCs and baluns are used to eliminate local oscillator (LO) self-mixing. The circuit was fabricated in a standard 0.18 m CMOS process for 24 GHz applications. At an RF of 24 GHz and intermediate frequency (IF) of 100 MHz, the RF direct-down converter exhibits an amplitude mismatch of only 0.6 dB, a phase mismatch of only 3.53 , a voltage gain of 1.5 dB, and an third-order input intercept point (IIP3) of 6.5 dBm while dissipating 10.05 mW from a 1.5 V supply. In addition, excellent isolations were also achieved. The corresponding LO-to-IF, RF-to-IF, LO-to-RF and 2LO-to-RF isolations are 45.7, 46.5, 61.1 and 60 dB, respectively, at 24 GHz. The chip area was only 1.017 × 0.717 mm2, that is, 0.729 mm2, excluding the test pads. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design of an ultra-wideband monopole antenna with WiMAX, C and wireless local area network

    Publication Year: 2011 , Page(s): 728 - 733
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (799 KB)  

    A compact ultra-wideband (UWB) coplanar waveguide (CPW)-fed printed monopole antenna with single and double band-rejection characteristics are investigated. The antenna has is staircase shaped and is fabricated on a FR4 substrate with an area of 19.5×21×1×mm3. To generate single- and dual-band-notched characteristics, two symmetric and asymmetric quarter wavelength spiral slits cut at the patch are utilised. The simulated and measured results including impedance matching, radiation patterns and gain results are investigated. The measured frequency results show an impedance bandwidth of 8.4 GHz over 2.6 11 GHz for a voltage standing wave ratio less than 2 with two eliminated bands centred at 3.8 and 5.5 GHz to reject the wireless local area network band (5.15 5.85 GHz) and the WiMAX band (3.3 3.6 GHz), along with a major part of the C band (3.7 4.2 GHz). The omni-directional radiation patterns of the fabricated antenna are presented, which show that this design antenna is a good candidate for various UWB applications. The measured gain variation is less than 3 dB over the operating frequency band. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wide band coplanar waveguide-fed bowtie slot antenna for a large range of ground penetrating radar applications

    Publication Year: 2011 , Page(s): 734 - 739
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (702 KB)  

    For the non-destructive sounding of the sub-surface for a large range of applications, a coplanar waveguide-fed bowtie slot antenna operating in a wide frequency band [0.4;1.5] GHz has been designed. The main originality of our work is the extension of the operating frequency band of the uniplanar bowtie slot antenna to frequencies lower than 800 MHz. The shape and the dimensions of the antenna have been optimised in the presence of a soil using numerical simulations based on the finite difference time domain approach. For the characterisation of the sub-surface, a transmission link comprising a pair of bowtie slot antennas that are moved along the soil surface has been studied in details to obtain the system performance in the frequency and time domains. First experimental results have been obtained on a sandy soil in the frequency domain using a vector network analyser. The experimental data have been analysed and compared with simulations results. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wideband antenna array beam steering with free-space optical true-time delay engine

    Publication Year: 2011 , Page(s): 740 - 746
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (630 KB)  

    A 6-12 GHz Vivaldi wideband antenna array made of four sub-arrays (two elements per sub-array) was built to steer the beam with a White cell optical true-time delay (OTTD) engine. The OTTD engine was simulated to produce delays with a time delay increment of 25 ps. The beam is then steered combining the simulated OTTD delays and the measured mutual coupling of a Vivaldi array to a maximum scan angle of ±50°. The results demonstrate that the effect of optical losses and mutual coupling effects of the combined beam steering system is not negligible and must be carefully accounted for when implementing frequency-independent TTD beam steering systems. 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