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Volume 146
Issue 4
IEE Proceedings - Microwaves, Antennas and Propagation
Volume 146, Issue 4, August 1999
Volumes & issues:
Volume 146, Issue 4
August 1999
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- Author(s): C.R. Lawrence and A.S. Treen
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 241 –246
- DOI: 10.1049/ip-map:19990599
- Type: Article
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p.
241
–246
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It has previously been shown that the electric vector of visible-wavelength radiation can be rotated through 90° by reflecting photons from a suitably aligned diffraction grating. The phenomenon has now been directly extended to the microwave regime, and the use of gratings exhibiting a finite number of grooves has been investigated. While efficient conversion has been obtained from gratings consisting of as few as five grooves, the wavelength dependence of the effect is not in good agreement with an unmodified optical model of the system. Several possible explanations were investigated, and it was deduced that the main error was due to the nonplanar wavefronts produced by the source. An experimental solution to this problem is suggested. - Author(s): R. Malmqvist ; M. Danestig ; S. Rudner ; C. Svensson
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 247 –252
- DOI: 10.1049/ip-map:19990147
- Type: Article
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p.
247
–252
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High-Q active MMIC filters have very low tolerances for temperature drift and process parameter deviations. A theoretical analysis of how these problems limit the Q-value of recursive active MMIC filters is presented. Given that the highest tolerable deviation in filter gain is equal to 1 dB for a temperature drift of 5°C, the Q-value is shown to be limited to 30 if one assumes perfectly impedance matched circuit components. For a non-ideal matching of circuit components, the highest possible Q-value is shown to be also limited by the impedance matching of the filter. It is also found that the maximum allowed deviation in amplifier gain due to on-wafer process parameter deviations when high Q-values, and a stable filter gain are required is very small, even if an automatic Q-controlling system is included. In this analysis, a first-order recursive active filter with a loop electrical length equal to 2π is assumed. The analysis shows that by cascading two first-order filters or by choosing a filter with a loop electrical length equal to n times 2π, a decreased filter gain sensitivity can be achieved. - Author(s): A.A. Zaporozhets
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 253 –256
- DOI: 10.1049/ip-map:19990567
- Type: Article
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p.
253
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The vector parabolic equation method is applied to the modelling of radiowave propagation in the urban environment. As a paraxial version of Maxwell's equations it allows full treatment of 3D electromagnetic scattering which was not possible with scalar versions of the algorithm. The method allows detailed specification of the building geometry and electrical parameters. This approach is particularly useful for accurate modelling of scattering by a single building or a group of buildings at microwave frequencies. The method is validated using an iterative integral equation method and known analytical results. Examples include scattering by a building with hemispherical roof and scattering by a group of buildings with sloping roofs. - Author(s): A. Charles ; M.S. Towers ; A. McCowen
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 257 –262
- DOI: 10.1049/ip-map:19990566
- Type: Article
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p.
257
–262
(6)
Jaumann absorbers show promise as radar absorbing materials (RAMS) for suppressing scattering reflections or reducing the radar cross-section (RCS) of perfectly conducting scatterers. Although various optimised designs are reported in the literature, there is little information on sensitivity of performance to manufacturing errors in the spacers and sheet resistances. The paper reports the findings of some studies using Taguchi methods to evaluate sensitivity and interactions of parameters in Jaumann layers placed on plane and curved (cylindrical) surfaces. The results are favourable, indicating moderate sensitivities to individual parameters and the only strong interactions present between the interlayer spacings. - Author(s): T.J. Willink ; N.C. Davies ; M.J. Angling ; V. Jodalen ; B. Lundborg
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 263 –269
- DOI: 10.1049/ip-map:19990575
- Type: Article
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p.
263
–269
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It is well known that the ionosphere can be highly disturbed in the auroral and polar cap regions. However, efforts to quantify ionospheric effects on high-frequency communications have concentrated mainly on lower-latitude regions. The Doppler and multipath sounding network (DAMSON) has been used in an extensive campaign to measure the channel characteristics on four paths in the auroral region of northern Scandinavia. The conditions observed indicate that robust data modems, used when less-robust, higher-rate modems fail, are required up to 90% of the time. A detailed analysis of the propagation parameters indicates that these modems, designed to operate in these regions, should be able to operate when the Doppler spread exceeds 40 Hz and the multipath spread is greater than 11.5 ms. Multiple propagation modes are common, especially between the lowest and maximum usable frequencies. The distribution of the received signal power in these cases is examined, and it is concluded that laboratory simulations used for robust-modem evaluation should include channel models with dominant modes. - Author(s): A.J. Viitanen and P.P. Puska
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 271 –276
- DOI: 10.1049/ip-map:19990565
- Type: Article
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p.
271
–276
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The general case of a plane wave reflection from a chiral slab backed by a soft and hard surface is considered. Fields in the chiral slab are represented in right-hand and left-hand circularly polarised basis. The same basis is used to derive the reflection dyadic. Expanding fields in circularly polarised vectors are advantageous, because circularly polarised waves are the eigenwaves of the chiral medium; moreover they are not coupled by the boundary condition of the soft and hard surface. However, there is some coupling at the interface of the chiral medium and free space, which complicates the analysis. - Author(s): H. Iwasaki and N. Chiba
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 277 –281
- DOI: 10.1049/ip-map:19990568
- Type: Article
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p.
277
–281
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A new configuration for a circularly polarised microstrip antenna with an omnidirectional pattern is proposed. This antenna consists of two rectangular patches with perturbation segments, which are arranged back-to-back relative to a coplanar waveguide (CPW) on a ground plane. The characteristics of the proposed antenna were clarified by experiments, and the mechanism to produce the circular polarisation was proved by using an electromagnetic simulator. The radiation patterns and input impedances were measured as a parameter of the width of the perturbation segment. Good circularly polarised radiation patterns with an omnidirectional pattern and input impedance characteristics were obtained. - Author(s): C.L. Mak ; K.M. Luk ; K.F. Lee
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 282 –284
- DOI: 10.1049/ip-map:19990569
- Type: Article
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p.
282
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A wideband electromagnetic-coupled single-layer microstrip patch antenna is studied experimentally. With dielectric and foam substrates of total thickness ~ 0.13 λ0, a rectangular patch antenna with impedance bandwidth (SWR ≤ 2) of 49% and 3 dB gain bandwidth of 54% are obtained. It has an average gain of 6.5 dBi and stable radiation patterns across the passband. Furthermore, with the employment of a stacked parasitic patch, a 58% impedance and gain bandwidth is achieved with similar radiation patterns and a higher average gain. A notable structure in the feeding design is that an inverted L-shaped strip is connected to the end of the microstrip line and no matching network is required. - Author(s): A.P. Papachristoforos
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 285 –291
- DOI: 10.1049/ip-map:19990449
- Type: Article
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p.
285
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The method of lines (MOL) is extended for the analysis of different geometries that include both rectangular and cylindrical conductors. The method of analysis is valid for multilevel dielectric structures. The cylindrical conductors can have circular pads and rectangular microstrips that are attached to the pads or the main body of the cylindrical via (buried microstrips). The mixed structures can include many ground planes with circular openings through which the via passes. The results are compared with previous results. - Author(s): Y.X. Guo ; K.M. Luk ; K.W. Leung
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 292 –294
- DOI: 10.1049/ip-map:19990609
- Type: Article
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p.
292
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The mutual coupling between aperture-coupled rectangular dielectric resonator antennas is analysed using the finite-difference time-domain method. The perfectly matched layer is used as absorbing boundary conditions. The voltage excitation source of microstrip structure is based on a simple model, in which the source plane or the terminal plane can be moved very close to the discontinuity so that the computational domain can be reduced substantially. Numerical results are verified by measurements and good agreement between theory and experiment is obtained. The method is highly efficient for the analysis of DR array antennas. - Author(s): D. Kajfez
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 295 –297
- DOI: 10.1049/ip-map:19990692
- Type: Article
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p.
295
–297
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A directional coupler suitable for operation in the low radio frequency range (1–100 MHz) can be built by using a combination of two transformers. An analysis of such a device, under the assumption that the transformers are ideal, leads to explicit equations for the scattering parameters of the directional coupler. Two different applications are analysed, one with a loose coupling and another with 3 dB coupling. - Author(s): K.F. Sabet ; J.-C. Cheng ; L.P.B. Katehi
- Source: IEE Proceedings - Microwaves, Antennas and Propagation, Volume 146, Issue 4, p. 298 –304
- DOI: 10.1049/ip-map:19990558
- Type: Article
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p.
298
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The authors present a wavelet-based formulation of the method of moments for the full-wave analysis of printed circuit antennas and arrays. The rooftop multiresolution basis is introduced for the expansion of planar currents. These basis functions satisfy the boundary and edge conditions in an exact manner. It is shown that wavelet-dominated expansion bases generate highly sparse moment matrices. The resulting sparse linear systems are solved numerically using very efficient computational tools. The fast wavelet transform is exploited for the numerical integration of the Green's function to speed up the filling of the matrix. Extensive results are presented for a microstrip patch antenna and finite size arrays of such antennas. Special emphasis is placed on the solution of large-scale problems, which could not otherwise be treated by conventional moment method implementations.
Polarisation conversion at a textured surface
Theoretical analysis of sensitivity and Q-value for recursive active microwave integrated filters
Application of vector parabolic equation method to urban radiowave propagation problems
Sensitivity analysis of Jaumann absorbers
Robust HF data communications at high latitudes
Reflection of obliquely incident plane wave from chiral slab backed by soft and hard surface
Circularly polarised back-to-back microstrip antenna with an omnidirectional pattern
Microstrip line-fed L-strip patch antenna
Method of lines for the calculation of excess capacitance for a cylindrical via hole in multilayer packaging
Mutual coupling between rectangular dielectric resonator antennas by FDTD
Scattering matrix of a directional coupler with ideal transformers
Efficient wavelet-based modelling of printed circuit antenna arrays
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