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Microwaves, Antennas and Propagation, IEE Proceedings

Issue 1 • Date Feb. 1999

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Displaying Results 1 - 18 of 18
  • Rigorous approach to modelling electromagnetic radiation from finite-size printed circuit structures

    Page(s): 29 - 34
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (523 KB)  

    A rigorous full-wave approach, based on the method of moments for modelling arbitrary shaped, finite-size printed-circuit structures, is presented. Based on the field equivalence principle, the dielectric substrate and the etched conductor on the substrate are replaced by the equivalent volume polarisation current and equivalent surface current, respectively. The respective boundary conditions on the conductor and the substrate are applied to formulate the electric-field integral equations. With a proper choice of sub-sectional basis functions and test functions, the currents on the entire finite-size structure are solved. Numerical convergence and close agreement with published experimental results are demonstrated. Through comparison with numerical results obtained from other approaches that made certain there are some interesting findings. View full abstract»

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  • Mode chart and susceptance slope parameter of an E-plane circulator using coupled prism resonators

    Page(s): 23 - 28
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    A three-port E-plane circulator may be constructed by placing either a pair of quarter-wave long cylindrical or prism resonators open-circuited at one end and short-circuited at the other in the H-plane of its junction. In the paper, the mode chart of the prism resonator arrangement is developed, and measurements on its susceptance slope parameter are taken. Since there is more than one solution that will meet the midband frequency of this sort of circulator, the susceptance slope parameter is not single valued. Knowledge of these two quantities satisfies the first classic circulation condition of the device View full abstract»

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  • Efficient 3-D moment-method analysis for reflector antennas using a far-field approximation technique

    Page(s): 7 - 12
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    A full 3-D moment-method analysis is used to model the radiation patterns of 10-15 λ diameter reflector antennas. The moment-method is made computationally efficient by a far-field approximation technique which dramatically reduces the demands of computer memory and CPU time by over 90%, and 80%, respectively. The reflector dishes are discretised with an unstructured 3-D finite-element-type mesh of triangles. The moment-method is applied to rotationally symmetric dishes in order to compare the accuracy of the analysis with results from a more conventional body-of-revolution type moment-method analysis View full abstract»

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  • Design and development of wideband and dual-band microstrip antennas

    Page(s): 35 - 39
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    A study of the wideband and dual-band characteristics of single- and double-notched rectangular patch antennas is presented. A comparative study of the experimental results employing coax, microstrip, aperture-coupled and electromagnetically coupled feed techniques has been made for increased bandwidth and improved crosspolar level. Optimum coax-fed location, input resonant resistance and notch parameters are estimated using the transmission-line model. The experimental radiation patterns were compared with simulated and theoretical patterns and found to be in good agreement. The maximum measured impedance bandwidths of 26.6% in band 1 and 31.7%, in band 2 have been achieved for coax-fed single-notched patches. A double-layered double-notched aperture coupled (composite) patch antenna was also designed, and further improvement in impedance bandwidth of 39% was achieved without significant degradation in radiation characteristics. From the measured and calculated results it can be seen that single- or double-notched composite patches can be designed to yield wide- and dual-band operations suitable for mobile communications View full abstract»

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  • Analysis of a normal-mode helical antenna including non-uniform wire surface current effects

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    Computer modelling of a parasitically excited normal-mode helical antenna (NMHA) is reported and compared with measurements. This structure is particularly suitable for realisation with high-temperature superconductors (HTS). However, attempts to model it using standard method of moments (MOM) techniques are very prone to instability; they also do not give the detailed surface current distribution needed for the evaluation of the benefits of superconductor usage. A MOM program for curved wire structures was written, using polynomial basis functions to describe the average current on a subsection, combined with trigonometric series basis functions to represent the circumferential variation of the surface current density. The results were in excellent agreement with measurements View full abstract»

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  • Numerical analysis of probe-excited multiple-arm printed wire antennas

    Page(s): 70 - 76
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    A unified current integral equation is formulated for N-arm printed antennas with an arbitrary arm shape. The parametric moment method is employed for the current distribution. A succinct expression for the radiation fields is obtained with the help of the saddle point method. The validity of the formulation is verified by comparing the computed current distributions and radiation patterns for two-arm and four-arm Archimedian spiral antennas with published results. Also, the numerical results for a two-arm circular open-loop and a small four-arm Archimedian spiral are given to show potential applications of the present formulation View full abstract»

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  • Effective permittivity of dielectric honeycombs

    Page(s): 55 - 59
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    The effective permittivity of a dielectric honeycomb can be represented by a diagonal permittivity tensor. In the paper, an empirical equation is derived using the FD-TD (finite difference-time domain) method. Which defines the diagonal components of the complex permittivity in terms of the honeycomb material permittivity and the fraction of honeycomb material per unit cell. The impact is investigated of electrically large honeycomb cells on effective permittivity failure. The manner in which the effective permittivity fails proves to favour a honeycomb orientation such that the direction of an incident plane wave's Poynting vector is parallel with the honeycomb's axis. The consequences are considered of an invalid effective permittivity on radar cross-section and planar reflectivity View full abstract»

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  • Analysis of propagation in periodically loaded circular waveguides

    Page(s): 50 - 54
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    A technique is presented for the analysis of propagation in a circular waveguide periodically loaded with irises of finite thickness. The propagation constants of the Floquet modes are determined from the classical eigenvalues of a characteristic matrix instead of a nonlinear determinant equation. Numerical results are presented for the TE0n modes and compared with available data. Excellent agreement is documented View full abstract»

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  • Physical statistical modelling of the land mobile satellite channel based on ray tracing

    Page(s): 45 - 49
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The paper presents a model of the land mobile satellite channel, predicting the statistical fade distribution in a given urban or suburban area described by objective data. The channel modelling is based on a conditional Rician distribution, whose parameters are related to physical parameters such as building height, street width, azimuth and elevation angles of the satellite link. Relationships between Rician and physical parameters are estimated by means of a ray-tracing method based on the uniform theory of diffraction, and statistically varying physical parameters are described by analytical distributions. The model is applied to a typical suburban area, and very good agreement is found between simulations of the fade distribution and radio measurements at L, S and X bands for two elevation angles View full abstract»

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  • Circuit theory of video delay lines

    Page(s): 65 - 69
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    Electromagnetic slow waves guided by single-layer coils and video delay lines are studied from the point of view of circuit theory. The main idea is to introduce into the model the mutual inductance that exists between nearby coil turns. This concept leads to finite-difference, finite-sum equations which pass in the limit into a partial differential equation and an integro-differential equation. The capacitance between adjacent wire turns is taken into account. The decrease of inductance at high frequencies, as computed from the integro-differential equations, is compared with prior computations based on electromagnetic field theory. In this respect agreement between the two theories is complete. A comparison with experiment is made, from which a novel parameter of the coil, termed the series capacitance parameter and measured in Fm, is determined View full abstract»

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  • Designs for an aperture-coupled compact circularly polarised microstrip antenna

    Page(s): 13 - 16
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    Designs of a square-ring microstrip antenna with a cross-strip, and a square microstrip antenna with a cross-slot for circular polarisation (CP) operation, are proposed and experimentally studied. Both the cross-strip and cross-slot are of equal arm lengths, and the two proposed designs can make their respective fundamental-mode patch surface current path much longer than a simple square microstrip antenna of the same size. By adjusting the coupling cross-aperture in the ground plane of the microstrip feed line, the fundamental mode can further be split into two near-degenerate orthogonal modes with equal amplitudes and 90° phase difference. Results show that, for a fixed frequency, a reduction in antenna size of 24~30% can be achieved by using the proposed designs. Details of the proposed antenna design are described, and experimental results for the CP performance are presented and discussed View full abstract»

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  • Microstrip cross-coupled trisection bandpass filters with asymmetric frequency characteristics

    Page(s): 84 - 90
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    A pair of microstrip trisection bandpass filters, consisting of cross-coupled open-loop resonators and exhibiting asymmetric frequency characteristics, are introduced. The utilisation of the microstrip open-loop resonators not only makes the filters compact, but also allows either positive or negative cross coupling to be realised. This results in an attenuation pole of finite frequency on either the high side or the low side of the pass band, so that the frequency response is asymmetric. Two filter designs of this type are described. Theoretical and experimental results are presented View full abstract»

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  • Relationship between photons and electromagnetic waves derived from classical radio principles

    Page(s): 91 - 93
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    A study of the radiation from toroidal aerial systems has shown that the displacement current and vector potential are always emitted in phase-closed loops. The minimal configuration is a `figure of eight' displacement current. On the assumption that these entities may represent photons, the system is linearly translated to the wavelength of pair production. This provides a relationship that is applicable at all frequencies and involves the fine structure constant. It is shown that at the moment of reception or reflection, the electrical component of a photon is equivalent to a virtual electron-positron pair spaced apart by half a wavelength in the direction of the Poynting vector, and the Maxwellian treatment remains valid View full abstract»

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  • System configurations for nine-port network analyser employing symmetrical five-port junctions

    Page(s): 40 - 44
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    A nine-port network analyser that requires only six (instead of eight or ten) power sensors to obtain the unknown scattering coefficients of a two-port device is proposed. Hardware imperfections will naturally affect the performance of this instrument. Monte Carlo simulations have been conducted in order to evaluate the deleterious effects due to the residual mismatches of the constituent components within the nine-port system. The results suggest that improvements in instrumentation accuracy may be achieved simply by modifying the system's overall configuration View full abstract»

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  • Leaky wave radiation of millimetre waves by photoinduced plasma grating in a semiconductor slab

    Page(s): 77 - 83
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    The paper reports investigations on leaky wave radiation of millimetre waves from a periodically photoinduced semiconductor slab waveguide. The photoinduced plasma grating structure is modelled as a permittivity modulated layer by considering the average permittivity as of a uniform plasma occupied thin layer and is systematically analysed using a singular perturbation procedure based on multiple space scales up to second order. The radiation efficiency of a leaky wave is derived and the results are outlined as a function of optically induced plasma density. Experiments have been carried out at 40 GHz by illuminating the grounded silicon slab using the slide of a periodic slit pattern through a xenon arc lamp. The dependence of periodicity on the radiation pattern is also reported View full abstract»

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  • Design method for offset shaped dual-reflector antenna with an elliptical aperture of low cross-polarisation characteristics

    Page(s): 60 - 64
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    The paper presents a design method for an offset shaped dual-reflector antenna (OSDRA) with an elliptical aperture of low cross-polarisation characteristics. This method is a dual-reflector synthesis based on a reflector shaping method using reflector shaping functions and is applied to attain low cross-polarisation characteristics for the OSDRA. The initial values for the reflector shaping are explicitly determined by a reflector system configuration transformation technique. This design method has been verified through measurement of an elliptical aperture antenna for a satellite news gathering system and a very small aperture terminal in the Ku band View full abstract»

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  • Adaptive integral method for hybrid FE/BI modelling of 3-D doubly periodic structures

    Page(s): 17 - 22
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    The adaptive integral method (AIM) is applied to accelerate the boundary integral (BI) portion of a hybrid finite element BI approach for the electromagnetic analysis of three-dimensional doubly periodic structures. Starting from the conventional mixed potential integral equation formulation, AIM is derived using Taylor series expansions for the involved coupling integrals. Implementation issues are discussed that relate to the periodic formulation, and central processing unit timings/memory requirements are given and compared to the conventional BI implementation View full abstract»

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  • Broadband circularly polarised square microstrip antenna using chip-resistor loading

    Page(s): 94 - 96
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    Broadband operation of regular-size and compact circularly polarised microstrip antennas using a chip-resistor loading technique is investigated experimentally. The optimal arrangement is demonstrated of the chip-resistor for broadband operation of circularly polarised microstrip antennas. By introducing the proposed chip-resistor loading technique to a square microstrip antenna with two pairs of slits of different lengths inserted at the patch edges, a compact circular polarisation operation can be obtained. Details of the proposed antennas are described, and experimental results of the circular polarisation performance are presented and discussed View full abstract»

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