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Microwaves, Antennas & Propagation, IET

Issue 8 • Date June 7 2012

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Displaying Results 1 - 18 of 18
  • X-parameters-based closed-form expressions for evaluating power-dependent fundamental negative and positive real impedance boundaries in oscillator design

    Page(s): 835 - 840
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    In this study, an analytical design tool, applicable under large-signal operation, based on X-parameters closed-form expressions, to determine the large-signal boundary between the negative (energy delivered) and positive (energy absorbing) real input impedance regions of the non-linear oscillator block, is presented to be used prior to and/or during non-linear oscillator circuit design. The consistency of the approach is demonstrated since in small-signal operation; the proposed expressions for the gamma equal to unity loci converges to the classic expression, generally referred to as the input or output stability circles. At large-signal levels, while we are not claiming that this formulation provides by itself similar general stability guidance, it can provide relevant information for oscillator design. The validity and usefulness of the proposed expressions as a real-time design aid, thus either minimising or avoiding the necessity for complex and time-consuming harmonic balance simulations, is demonstrated in the study. View full abstract»

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  • Characterisation of resonant structure of relativistic magnetron

    Page(s): 841 - 845
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (587 KB)  

    The authors describe a systematic analysis of relativistic magnetron interaction structure and operating characteristics. The authors have plotted the admittance curves for resonator and interaction space to predict the possible resonant frequency of a relativistic magnetron for the π-mode. Hull cut-off Parabola and BunemanπHartree resonance curves have also been plotted for the resonant structure of a relativistic magnetron using MATLAB. A three-dimensional particle-in-cell (PIC) code, MAGIC3D, is used to simulate the oscillation spectrum, dispersion diagram and the resonant frequency of the resonant structure. A comparative study of simulated eigenmode frequency and calculated from admittance matching criteria has also been performed. View full abstract»

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  • Double-sided open split ring resonator for compact microstrip band-pass filter design

    Page(s): 846 - 853
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (819 KB)  

    A metamaterial structure, called the double-sided open split ring resonator (DOSRR), which combines two open split ring resonators (OSRRs) aligned over the opposite faces of the substrate in an inverted fashion is presented. A study of this resonator from full-wave electromagnetic and circuit simulations is performed. As with the OSRR cell, the DOSRR cell allows a series connection along a microstrip transmission line and it has a small electrical size. Moreover, the DOSRR cell has the ability to add a transmission zero in the out-of-band region without increasing its size. This DOSRR cell is used for the design of compact microstrip slow-wave-type band-pass filters. Two strategies based on circular windows etched at the bottom plane instead of square windows and U-shape slots etched in the microstrip transmission line are designed to increase the stop band and to add extra zeros in order to suppress the spurious band. The experimental results have confirmed the possibilities of this electrically small resonator (DOSRR) and the efficiency of both strategies to improve the out-of-band rejection. View full abstract»

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  • Direct quadrature phase shift keying modulation using compact wideband six-port networks

    Page(s): 854 - 861
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (685 KB)  

    In this study, the operation of a compact six-port network operating as a quadrature phase shift keying (QPSK) modulator with a wide operational bandwidth is presented. The modulation has been accomplished using two types of single-layer six-port networks. The first six-port network uses a novel architecture that is newly introduced herein for use as a QPSK modulator, and employs broadband components previously developed by the same authors. The second six-port network employs the same types of broadband components in a conventional six-port architecture for comparison. The performance of the modulator using both six-port networks is tested using agilent's advanced design system and its wideband operation is verified with measured results. It is shown that the proposed six-port modulator offers accurate QPSK symbol modulation at a symbol rate of 400 Msymbols/s across an octave bandwidth from 4.5 to 9'GHz (66' operational bandwidth). View full abstract»

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  • Compact microstrip ultra-wideband double/single notch-band band-pass filter based on wave's cancellation theory

    Page(s): 862 - 868
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    A novel approach with a new configuration is introduced to design an ultra-wideband (UWB) band-pass filter (BPF) that demonstrates double/single notch-bands using micro-strip transmission lines without using any via-hole. The proposed approach is established using two parallel stepped-impedance resonators (SIR) that provide two paths with different electrical lengths. The mechanism of realising notch-bands within the pass-band of the UWB BPF is developed based on the waves' cancellation theory. To realise single or double notch-bands (DNBs) within the pass-band of a UWB BPF, the conventional tri-section stepped-impedance resonator (TSSIR) is adopted and its fundamental and first spurious resonance frequencies are chosen either to be suppressed or supported. New parallel dual-section T-shaped and TSSIRs are proposed, optimised and fabricated to provide single and DNBss, respectively. The proposed concept avoids using via holes, which is conventionally used in notch filters. In addition, a size reduction of about 75% is reported in comparison with the conventional BPF with a single notch-band accompanied by two transmission zeroes at the lower and upper stop-bands. Moreover, our proposed DNBs BPF demonstrates a comparable performance while being smaller in size (up to a 12.6% size reduction) to that of the latest UWB BPF design that used complicated and expensive multilayer liquid crystal polymer (LCP) technology. View full abstract»

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  • Millimetre-wave-imaging system at 95 GHz - quantitative performance evaluation

    Page(s): 869 - 879
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (996 KB)  

    A quantitative performance evaluation of the millimetre-wave-imaging system developed in the authors' group is carried out. Two parameters, SNRI (image signal-to-noise ratio) and NEΔR (noise equivalence reflectivity difference) of a few common test targets, a copper slab, a leather covered copper slab and a Perspex slab are used in the evaluation of image qualities, hence to characterise the performance of such a system. In the calculation of these two parameters, a convenient four-step procedure developed by the authors is used. For the evaluation of the resolution of the millimetre-wave-imaging system, an indirect approach is used, in which the imager point spread function (PSF) is estimated based on the measurement data of a knife edge. From the imager PSF the imager resolution is calculated. All these parameters have quantitative values and can be used to make performance comparisons. View full abstract»

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  • Small-area and high-inductance semi-stacked spiral inductor with high Q factor

    Page(s): 880 - 883
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (282 KB)  

    In this study, the authors describe the characterisation of spiral inductors and the design of a novel semi-stacked spiral inductor based on low-temperature co-fired ceramics (LTCC). Owing to its semi-stacked nature, the authors obtained a peak quality factor (Qmax) of 43.3 and an effective inductance Leff of 14.41 nH. The authors LTCC spiral inductor occupies a smaller area when compared with conventional LTCC planar inductors of similar number of turns. View full abstract»

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  • Design guidelines for multi-layer dielectric rod antennas fed by Vivaldi antennas

    Page(s): 884 - 892
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1191 KB)  

    Dielectric rod antennas of circular cross-sections have been numerically investigated. Various structures of finite-length rods are compared as functions of their different physical parameters, such as the rods' diameter, length, dielectric constant, multi-layer and finally the effect of corrugation. The far-field radiation pattern characteristics of these various antennas are presented as well. Results indicate that the operating bandwidth of these antennas can be extended by utilising either a core with a high dielectric constant and a cladding layer with a lower dielectric constant or equivalently a corrugated rod of the high dielectric constant material. The simulation of the various types of rod antennas have been compared with the measurement and very good agreement has been achieved. View full abstract»

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  • Compact composite right/left-handed transmission line unit cell for the design of true-time-delay lines

    Page(s): 893 - 898
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (661 KB)  

    This study presents a novel composite right/left-handed transmission line (CRLH TL) unit cell with high time-delay (TD) efficiency for the design of true-time-delay lines (TTDLs). Shorter inter-digital fingers are used in a symmetrical CRLH TL unit cell to reduce the size by 58% and form a compact CRLH TL unit cell. This reduces the left-handed (LH) capacitance, which is compensated by using open-circuited metallic vias on the fingers. A TTDL constructed by cascading a number of compact CRLH TL unit cells is designed and studied using computer simulation, and then fabricated on a PCB for measurements. For performances comparison, two other TTDLs of the same length implemented using the symmetrical CRLH TL unit cells and right-handed transmission line (RH TL) are also designed, fabricated and measured. Simulation and measurement results show that, for the same length of 30%mm, the TTDL implemented using the compact CRLH TL unit cells has much longer time delay than that of using the symmetrical CRLH TL unit cells and the RH TL. View full abstract»

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  • Perfectly conducting tape-helix model for guided electromagnetic wave propagation

    Page(s): 899 - 907
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (467 KB)  

    The homogeneous boundary value problem arising in the propagation of electromagnetic waves guided by an open tape helix modelled to be of infinitesimal tape thickness and infinite tape-material conductivity is shown to be inherently ill posed. It is demonstrated how the ill posed problem may be regularised using the mollification method. The regularised boundary value problem is then solved to yield the approximate dispersion equation which takes the form of the solvability condition for an infinite system of linear homogeneous algebraic equations viz., the determinant of the infinite-order coefficient matrix is zero. For the numerical computation of the dispersion characteristic, all the entries of the symmetrically truncated version of the coefficient matrix are estimated by summing an adequate number of the rapidly converging (after regularisation) series for them. The tape-current distribution is estimated from the null-space vector of the truncated coefficient matrix corresponding to a specified root of the dispersion equation. A comparison of the numerical results with those for the anisotropically conducting model (that neglects the component of the tape-current density perpendicular to the winding direction) of the tape helix reveals that the propagation characteristic computed on the basis of the anisotropically conducting model could be substantially in error even for moderately wide tapes. View full abstract»

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  • Design of multiple band-notch using meander lines for compact ultra-wide band antennas

    Page(s): 908 - 914
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (890 KB)  

    In this study, the design of multiple band notch for compact ultra-wide band (UWB) antennas is proposed. The antenna consists of an elliptical radiator, a microstrip-feed line and a ground plane. Four pairs of meander lines (MLs), working as resonators, are added to the antenna to produce a quadruple band notch characteristic, yet without increasing the overall antenna size. Two types of feeding techniques, direct-connected feed and parallel-coupled feed, are used in the resonators. The centre frequencies and bandwidths of the individual notches can be adjusted independently using the dimensions of the corresponding MLs. For verification, the proposed antenna is also fabricated and measured. The return loss, peak gain, efficiency and radiation pattern of the band-notch antenna are studied using both computer simulation and measurement. The pulse responses of the band-notched antennas are also measured and compared with those of single-, double- and triple-band-notch antennas. View full abstract»

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  • Design of dual-band bandpass filters using H-shaped resonators

    Page(s): 915 - 921
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (569 KB)  

    A new H-shaped resonator configuration is introduced for dual-band bandpass filter applications. This new design provides flexibility in controlling central frequencies and bandwidths of dual-band bandpass filters. The selectivity and the upper stopband performance of dual-band bandpass filters can be improved by virtue of the proposed H-shaped resonators. Experimental design example is given to validate this filter design theory. The proposed filters have compact size, low insertion losses and small group delay variations. The measured results show good agreement with theoretical analysis. View full abstract»

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  • Linearity improvement using a modified derivative superposition method in cascaded stages amplifier

    Page(s): 922 - 928
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (686 KB)  

    A modified derivative superposition (DS) method using cascaded stages transistor is described. It uses the third order intermodulation (IMD3) current generated from the preceding stage to cancel those at the output of the following stage. This analysis demonstrates that an IMD3 minimum occurs near the output power compression point. A balanced X-band linear power amplifier (PA) monolithic microwave integrated circuit (MMIC) using this concept is presented. The results of measurement showed a carrier-to-IMD3 ratio (C/I3) improvement more than 30 dB compared with the conventional cascaded stages configuration. View full abstract»

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  • Uniform impedance ring 0°/180° couplers with arbitrary ring impedances and power division ratios

    Page(s): 929 - 937
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (381 KB)  

    Uniform impedance ring 0°/180° couplers have been developed that possess arbitrary values for the ring impedance and the power division ratio. The power division ratio of the proposed coupler can be adjusted to an arbitrary value for any fixed ring impedance. This makes it possible to obtain a very wide range of power division ratios without any restriction to the line impedance in the design of the coupler. The proposed coupler structure has been analysed rigorously for its scattering characteristics. As a result, general solutions for the coupler are derived in a concise form in terms of the ring impedance and the power division ratio, as well as for the optimum solutions needed to minimise the overall coupler size. The relationships between the coupler size, the ring impedance and the power division ratio also have been investigated. Extensive design and circuit simulation experiments have been conducted in order to analyse the impact of the different ring impedances on the coupler performance under varying power division ratios. An optimum ring impedance value is found from this study and is used to design, fabricate and measure two prototype couplers. View full abstract»

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  • Plane wave scattering by N dielectric coated conducting strips

    Page(s): 938 - 944
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (614 KB)  

    Analytical solution of a plane electromagnetic wave scattered by N dielectric coated conducting strips is presented. The solution of the problem is based on the boundary value method. The scattered field from each coated strip is expressed in terms of an infinite series of Mathieu functions of unknown coefficients which can then be calculated by enforcing the boundary conditions on each coated strip. As scattered fields are written in terms of local coordinates assumed at the centre of each element, the addition theorem of Mathieu function is used to transfer scattered fields from all element local coordinates to the local coordinates at the coated strip where boundary conditions are applied. Owing to the infinite dimensionality of the series involved in the solution, truncation must be performed based on the convergence of the series. Results of a number of interesting examples are then presented. View full abstract»

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  • Sparse-matrix methodology for finite-element time-domain modal non-reflecting boundary condition simulations

    Page(s): 945 - 955
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (738 KB)  

    A sparse-matrix finite-element time-domain (FETD) formulation using a modal non-reflecting boundary condition (MNRBC) is proposed for the modelling of plane wave scattering from cylinders of arbitrary cross-section. Unlike the standard FETD-MNRBC formulation, the proposed formulation does not generate full sub-matrices following the discretisation of the boundary integral. Hence, it requires less computation memory than the standard formulation. The accuracy of the proposed sparse-matrix FETD-MNRBC formulation is demonstrated, in two dimensions, by comparing its bistatic scattering width results with those of the standard FETD-MNRBC formulation, the finite-element frequency-domain method and with analytical or published results. View full abstract»

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  • Compact X-band sige power amplifier for single-chip phased array radar applications

    Page(s): 956 - 961
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (618 KB)  

    An X-band power amplifier (PA) is presented for single-chip phased array radar applications. In this work, the choice of optimum circuit topology for X-band PA design is discussed and possible stability issues for high and low frequencies are analysed. The PA features a two-stage cascode architecture that includes both high-speed (low breakdown) and high breakdown (low-speed) SiGe transistors. It consists of two stages providing a 23.2 dBm saturated output power with a 28 power-added efficiency at 9 GHz. The output 1-dB compression point (P1dB) is higher than 20 dBm in a 3 GHz bandwidth and has a maximum value of 22.2 dBm. The small-signal gain is 25.5 dB with a 3-dB bandwidth of 3.2 GHz (7.3 10.5 GHz). The PA has been fabricated using 0.25 m SiGe BiCMOS process provided by IHP Microelectronics. The PA occupies 1 mm 0.6 mm chip area and consumes 120 mA from a 4 V supply voltage. These results demonstrate comparable or better performance than other reported PAs and suitable performance for single-chip phased array applications. View full abstract»

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  • Single-layer integrated microstrip array antenna for dual circular polarisation

    Page(s): 962 - 968
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (894 KB)  

    A single-layer integrated microstrip array antenna for dual circular polarisation is proposed. It consists of an orthogonal linearly polarised microstrip array antenna and a 90° hybrid circuit using a single-layer substrate. The orthogonally polarised array antenna uses double-sided microwave-integrated circuit (MIC) technology including airbridges, effectively. It has excellent isolation and cross-polarisation suppression performance between the orthogonal modes and flexibility of the antenna size extension. By integrating it with the 90° hybrid circuit, the proposed array antenna can excite the orthogonal circular polarisations [right-hand circular polarisation (RHCP), left-hand circular polarisation (LHCP)] simultaneously. It is possible to easily realise wireless integration modules because of a single-layer structure. The simulated and experimental results show good circular polarisation performance for both the RHCP and LHCP. The design frequency is 10°GHz and the 3°dB axial ratio bandwidths of both the RHCP and LHCP are approximately 10° in the experiment. View full abstract»

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