J. Uher

Analysis and design of circular ridged waveguide components

A fast and efficient radial mode-matching technique (RMMT) is applied to the analysis and design of components in circular ridge waveguide technology. Five different structures are investigated with respect to their performance as filters and polarizers. For fast computation, pie-shaped metal ridges and septa are assumed to better fit the cylindrical coordinate system. In practice, the pie-shaped structures are approximated by rectangular cross-section metal inserts. The validity of this approximation is investigated by comparing with measurements and finite-element analysis. It is found that for thin etchable inserts, the measured filter response is in excellent agreement with the theoretical prediction and that for polarizers, the axial ratio response is not particularly sensitive to the ridge shape. Differences between computed and measured results occur only at return loss and isolation levels beyond 25 dB. A central processing unit time comparison with HFSS (4.0) results in a 10-min versus 3-h advantage in favor of the RMMT.

Field Theory Design of Ferrite-Loaded Waveguide Nonreciprocal Phase Shifters with Multisection Ferrite Or Dielectric Slab Impedance Transformers

Impedance-matched ferrite-loaded waveguide nonreciprocal phase shifters are designed using the method of field expansion into eigenmodes, which includes higher order mode interaction between the step discontinuities. Computer-optimized Ku -band ferrite stepped design examples, of 45° and 90° nonreciprocal differential phase shifts, attain typically about 2° phase error and less than -25 dB input reflection within a bandwidth of about 5 percent. Compact designs are achieved by thicker uniform ferrite slabs with dielectric transformer sections at each end. The theory is verified by comparison with available results from measurements and other methods.

Magnetically tunable rectangular waveguide E-plane integrated circuit filters

A rigorous field theory method is described for the computer-aided design (CAD) of magnetically tunable E-plane metal-insert filters, where the waveguide sections are symmetrically loaded with ferrite slabs, and for large-gap finlines filters on a ferrite substrate. The design method is based on field expansion in suitably normalized eigenmodes which yields directly the modal scattering matrix of all discontinuities. The theory includes both higher-order mode interaction and the finite thickness of the metal inserts. Optimized data are given for magnetically tunable Ku-band metal insert and finline filter examples. The metal-insert type achieves a tuning range of its operating midband from about 14.1 to 15.7 GHz. The theory is verified by measurements. >

Computer-aided design and improved performance of tunable ferrite-loaded E-plane integrated circuit filters for millimeter-wave applications

The modal scattering matrix method is applied to the rigorous computer-aided design of low-insertion-loss magnetically tunable E-plane metal-insert filters with improved characteristic, where only the resonator sections are loaded with ferrite slabs, and large-gap finline filters on a ferrite substrate of moderate width. The design method is based on field expansion in suitably normalized eigenmodes, which yields directly the modal scattering matrix of key building block discontinuities, which in turn are appropriately combined for modeling the complete filter structure. The theory includes both the higher order mode interaction of all discontinuities involved and the finite thickness of the metal inserts, or metallization. Optimized data are given for magnetically tunable Ku-band (12-18 GHz), Ka-band (26-40 GHz), and V-band (50-75 GHz) metal-insert and finline filter examples. The theory is verified by measurements on the Ku-band metal insert and finlines filters, utilizing ferrite materials. >

H-plane waveguide filters with E-plane dispersive inverters for high-power applications

Conventional H-plane waveguide filters are supplemented with E-plane stubs which simultaneously act as impedance inverters and create transmission zeros (attenuation poles) at prescribed frequencies. Due to the utilization of E-plane stubs, the filter can be manufactured as two identical halves joined in the center plane of the components. Since current in the housing is minimal in this plane, E-plane fabrication facilitates high-power applications. The different steps in the design of such filters are outlined. It is concluded that E-plane stub inverters are not only more compact than H-plane stubs but also display better return-loss behaviour. The individual designs are verified by independently developed and/or commercially available software packages.

Fast and efficient mode-matching analysis of ridged circular waveguide polarizers

A fast and efficient mode-matching technique is applied to the analysis and design of polarizer components in ridged circular waveguide technology. Two different structures (the septum polarizer and the longitudinal-ridge polarizer) are investigated with respect to the validity of approximating the rectangular-cross-section septa by conically shaped ridges in theory. Measurements of two different prototypes demonstrate, first, that the axial ratio response is not potentially critical to this approximation and, second, that some differences occur with respect to return loss and isolation performance, but that these difference have only been encountered beyond the 25 dB margin. A CPU time comparison with HFSS results in a ten-minutes-versus-three-hours advantage of the mode-matching technique.

Analysis of branch line coupler in suspended stripline with finite metallization thickness

An efficient analysis of a branch line coupler in suspended stripline technology is described. The finite metallization thickness on the stripline is fully accounted for by a rigorous full-wave technique. This is based on an improvement of the transverse resonance technique (TRT), which allows a resonator of fixed dimension to be considered. In this manner all the advantages of the TRT are kept (no complex modal spectra need to be computed), while repeated field analyses for searching for the resonant dimensions of the structure are avoided. The theory has been checked successfully against both experiments and theoretical results based on different numerical methods.<<ETX>>

Ferrite tunable millimeter wave printed circuit filters

Designs for millimeter-wave magnetically tunable E-plan integrated circuit filters are described. The filters combine the advantages of printed circuit technology with the high-power capability of ferrite-loaded waveguides. Computer-optimized design data based on the rigorous modal S-matrix method are given for Ka-band tunable metallic and finline type filters. The theory is verified by measured results in Ku-band.<<ETX>>

Fast and accurate design methods for complex waveguide feed systems

This paper presents the individual design steps for the fast and accurate design of complex waveguide feed system components. Rather than using general electromagnetic codes for the analysis, targeted mode-matching routines are employed which are flexible enough to allow an attached optimization algorithm to vary individual parameters within a wide range. The so-obtained design dimensions can be verified or fine-optimized for manufacturing tolerances. The advantages of using mode-matching-based algorithms are discussed, and the design engineer is provided with some optimization guidelines. Typical results of the software packages are presented in form of three design examples involving a circular septum polarizer feed, a diplexer configuration and an entire Ku-band feed system.

Design and measured performance of advanced Satcom dielectric lens antenna

This paper describes design techniques and presents calculated as well as experimental performance of a multiple-beam dielectric lens antenna for the Ka-band Advanced Satcom application. The lens is spherical on the outside and zoned on the inner surface. A dual-CP, single-horn-per-beam mode of operation is assumed. In order to examine mutual-coupling effects, however, a 19-element feed cluster, with only one element active, was built and tested. Primary and secondary radiation patterns are presented. Superior electrical performance of the lens and excellent agreement of experimental and predicted results are demonstrated.