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Microwaves, Antennas and Propagation, IEE Proceedings

Issue 3 • Date 3 June 2005

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Displaying Results 1 - 11 of 11
  • Optimal synthesis of difference patterns subject to arbitrary sidelobe bounds by using arbitrary array antennas

    Page(s): 129 - 137
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (327 KB)  

    Two new approaches to the optimal synthesis of difference patterns are proposed that can deal in an effective fashion with arbitrary sidelobe bounds. The first approach, which amounts to solving a convex programming problem, can be applied to completely arbitrary (fixed geometry) arrays and it is capable of taking into account additional constraints. The second approach, which amounts to solving a simpler linear programming problem, can be applied to uniformly spaced linear or planar arrays, and allows results about the uniqueness of the solution to be inferred. Numerical examples show the flexibility and effectiveness of the proposed procedures. View full abstract»

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  • Gain enhancement in linear and circularly polarised microstrip patch antennas using shorted metallic patches

    Page(s): 138 - 148
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (506 KB)  

    The influence of shorted metallic patches (SMPs) in the design of linear and circularly polarised microstrip patch antennas is investigated. The SMP structure consists of square patches connected to the ground plane by shorting pins. Effects of different parameters such as the dimension, and position of the SMPs on the performance of patch antennas are studied. It is shown that the implementation of the SMP in the patch design has led to significant improvements in gain and radiation patterns. The SMPs have also been incorporated in four element circularly polarised arrays to increase the gain and improve the axial ratio and impedance bandwidths. A comparison of the experimental results with simulation data demonstrates their good agreement. View full abstract»

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  • Useful multilayered microstrip pole extraction technique

    Page(s): 149 - 154
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    The paper presents a unified approach for the fast evaluation of the locations of poles in multilayered microstrip technology. For the first time, good initial values and functional expressions with high order of convergence for multilayered pole extraction have been derived. Numerical comparison with conventional methods of extraction shows that this proposed method is indeed very accurate and extremely fast in convergence, even for high loss substrate. View full abstract»

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  • Air-filled square coaxial transmission line and its use in microwave filters

    Page(s): 155 - 159
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (277 KB)  

    A suspended coaxial transmission line with an air propagation medium is presented. The transmission line is made only of metal, thereby avoiding dielectric and radiation losses. Short-circuit stubs suspend the centre conductor of the coaxial structure which is used in the design of two dual-mode narrowband microwave filters. Stacked layers of copper sheets are used to form the square coaxial transmission line, which has low loss and low dispersion. View full abstract»

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  • Ring filters and their application to new measurement technique on inherent-ring-resonance frequency

    Page(s): 161 - 166
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (495 KB)  

    A ring filter is proposed as a wide-banded filter. It consists of a ring and two short stubs that are connected at the 90° and 270° points of the ring. Since the characteristic impedances of all the transmission line sections have an effect on the bandwidths of the ring filters, their relations are studied. On the basis of the study, one having more than 100% fractional bandwidth is selected and tested. The measured results are in good agreement with the simulated ones. As an application of the ring filter, a new and simple method to determine an inherent-ring-resonance frequency is introduced. The ring filter may be seen in such a way that two filters are connected in parallel. Therefore, if the two powers of the two filters are out of phase at the output, the excited power cannot be delivered. That can be used for determining the inherent-ring-resonance frequency and its condition is derived. Also, an effective loss tangent at a frequency of interest may be obtained correctly using the method suggested. To verify the method, two ring filters have been fabricated in microstrip lines and the measured results also show good agreement with the predicted ones. View full abstract»

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  • Tolerance analysis of bypass-, cross- and direct-coupled rectangular waveguide band-pass filters

    Page(s): 167 - 170
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1864 KB)  

    Tolerance analyses of bypass-, cross- and direct-coupled rectangular waveguide filters are presented. It is found that, contrary to common belief, standard direct-coupled waveguide filters are not less sensitive with respect to their passband behaviour than filters with cross or bypass couplings. Moreover, they are considerably larger than bypass-coupled TM110-mode cavity designs, which always present the shortest solution and allow a simple implementation of transmission zeros. The general approach of the tolerance analysis is verified through measurements of a large number of fabricated direct-coupled seven-pole inductive-iris filters. It is concluded that both the path and the radius of the manufacturing end-mill cutter influence the return loss and passband spread of the fabricated filter components. View full abstract»

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  • Efficient method for design and analysis of rectangular waveguide band-pass filters with multiple inductive circular posts

    Page(s): 171 - 178
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (222 KB)  

    A set of integral equations for surface electric currents on inductive circular posts in a rectangular waveguide is solved by Galerkin's method. Elements of the impedance matrix are initially expressed as infinite-range improper integrals and then are transformed into eigenmode series and supplementary rapid converging series. The method can be effectively used for development of rectangular waveguide band-pass filters with many inductive circular posts. View full abstract»

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  • Smaller offset broadwall longitudinal waveguide slots: a new analysis using a new idea

    Page(s): 179 - 182
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    The paper employs the method of moments with the Rao, Wilton and Glisson basis functions for analysing waveguide slots and their arrays, when they precisely ride on the waveguide broadwall central line or are located with a very small offset from the central line. The whole waveguide structure with slots cut on conducting walls is considered as a complete antenna system in the formulation of the electric field integral equation. The integral equation is then solved using the method of moments. A comparative study is performed to investigate the effects of the offset distance, which was never reported due to the difficulty in the previous numerical techniques. Numerical results of the slot radiating power patterns in the E- and H-planes are provided and concluding remarks made. View full abstract»

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  • Measured equation of invariance with non-uniformly distributed line sources as metrons

    Page(s): 183 - 188
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (283 KB)  

    In the paper, δ functions are employed as simple yet effective metrons to generate measured equation of invariance (MEI) coefficients in the MEI method. Compared with the widely used sinusoidal functions, δ functions greatly reduce the time for the computing of measuring functions and alleviate the ill-conditioning phenomenon of the matrix equations for the determination of MEI coefficients, hence enabling one to interrelate more nodes in the MEI. In this way, the accuracy of the solutions for electrically large scatterers can be improved progressively. It is also found that non-uniformly distributed δ metrons produce more accurate and stable results compared to uniformly distributed metrons. Numerical results for two-dimensional scattering problems are presented to show the accuracy and efficiency of the proposed method. View full abstract»

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  • Numerical dispersion and dissipation error of the 2-D PLCDRC-FDTD method for plasmas

    Page(s): 189 - 194
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (225 KB)  

    Recently, a new finite-difference time-domain (FDTD) method for dispersive media called the piecewise linear current density recursive convolution FDTD (PLCDRC-FDTD) method has been published. The numerical dispersion relation of the 2-D PLCDRC-FDTD method for plasma is derived. With the numerical dispersion relation, the numerical dispersion error and dissipation error caused by the PLCDRC-FDTD method are investigated by comparing the real part and imaginary part of a numerical index of refraction with those of an analytic index of refraction. The relationships between the numerical dispersion, dissipation errors and different parameters (i.e. EM wave frequency, plasma frequency, collision frequency) are studied. View full abstract»

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  • Approach for determination of extrinsic resistance for equivalent circuit model of metamorphic InP/InGaAs HBTs

    Page(s): 195 - 200
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    An improved extraction procedure for determination of the extrinsic resistances of metamorphic InP heterojunction bipolar transistors (HBTs) is presented. This method is a combination of the test structure method and an analytical method but it does not require numerical optimisation. The main advantage of this method is that the extrinsic base resistance and the collector resistance can be obtained by using cutoff mode S-parameter measurements. Bias-dependent empirical models for the intrinsic resistance and extrinsic base-collector capacitance over the whole region of operation are also presented. Good agreement is obtained between simulated and measured results for a metamorphic InP HBT with a 5×5 μm2 emitter in the frequency range 50 MHz-40 GHz over a wide range of bias points. View full abstract»

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