Radial transmission-line formalism is a generalization of Marcuvitz-Schwinger theory that permits to solve complex scattering problems in circular geometry. The formalism is exploited in this work ...for the analysis and design of ring loaded slots in circular waveguide whose applications span from microwave filters to mode converters. The scattering problem is formulated in terms of coupled magnetic field integral equations and solved using novel numerical schemes. The method is applied to study a choke flange and a stub filter in circular waveguide. A comparison with commercial software is reported to confirm the effectiveness of the approach.
A waveguide polarizer exploiting two different phase shift phenomena is presented in this letter. Iris-type discontinuities are in fact introduced in a waveguide structure having different ...propagation constants for the two principal polarizations. In this way, the required 90 differential phase shift is obtained combining the iris phase shift with the waveguide one. Several operative conditions arise from the combination of the two contributions. This approach has been used to design a broadband waveguide polarizer for the C-band antenna feed system of the Sardinia radio telescope with -40 dB reflection coefficients and a -35 dB cross polarization level in a 30% bandwidth.
This study presents the design and experimental results of a wide-band passive antenna-feed system developed for the C-band dual-circular-polarisation receiver of the Sardinia radio telescope (SRT). ...The latter is a 64 m diameter shaped radiotelescope under construction designed to operate with high efficiency from 300 MHz to over 100 GHz. The developed C-band antenna-feed system exhibits very high performances in a 30% band centred at 6.7 GHz; for example, the return loss at all electrical ports is higher than 30 dB and the cross-coupling between the two polarisations is lower than -34 dB. The design solutions of all the feed-system components, such as marker injector, polariser, transitions and the ortho-mode transducer (OMT), are reported in the study. In particular, the novel architecture of the OMT that provides an isolation between the two rectangular ports better than 70 dB is described in close detail. The computed and experimental results regarding both the complete system and its sub-assemblies are reported and discussed.
Leaky coaxial cables can be used as distributed radiators for indoor communications. When the number of slots is large, as it is often the case, the application of a full-wave analysis method is very ...demanding in terms of both memory and CPU time. In this paper an analysis technique, based on Bloch wave theory is presented. Slots are viewed as discontinuities in an open waveguide and a suitable basis of orthogonal polynomials is introduced to represent the modal amplitudes pertaining to the continuous spectrum. The radiation properties of the cable are discussed in detail in terms of the excited Bloch waves. Finally, the reflection coefficient at the junction between a uniform and a slotted cable is computed. The results are presented in the form of a chart, for general slot size and spacing.
The joint of a large dielectric radome is described in terms of an equivalent transmission-line circuit thanks to the introduction of an equivalent periodic structure and by Floquet's modal analysis. ...In this framework, all the dielectric layers are modeled with their corresponding generalized scattering matrices, and the compensation grid is described as a parallel lumped admittance. Its value is the design parameter used to obtain the joint compensation. The measurements on a C-band prototype show a significant compensation effect for both polarizations.
The design of a compact dual-band circular corrugated horn for satellite services in the Ku/K-bands is presented in this letter. The horn geometry has been obtained by a suitable design approach, ...which leads to the definition of a good starting point that is subsequently refined by a rapidly converging optimization technique. The tight agreement between measured and simulated data validates the present design.
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