The performance of a wideband bandstop transmission line filter employing a series overlay inductor over two stubs resonating at respectively one half and one quarter of the centre frequency, is described. The structure contributes seven transmission zeros to the stopband and the performance compares to that of a Cauer filter. The structure has the advantage of having impedance levels that are readily realizable.

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By employing open circuited stubs with a length ratio of 1:2:3 separated by three unit elements, it is shown that a pseudo-elliptic frequency response can be obtained with a compact structure. It has an electrical performance comparable to that of a Cauer filter, but is realizable in etched form for very wide bandwidths and very high rates of cutoff.Introduction: It was previously shown that an elliptic-function-like bandstop response can be obtained by making use of open circuit shunt stubs and a series shorted stub [1], or open circuit shunt stubs and unit elements [2] with a stub length ratio of 1:2:4. Such filters can be made to have high rates of cutoff, and are realizable for bandwidth ratios of the order of 7:1. These filters have seven transmission zeros periodically interspersed, as shown in table 1.

A variety of profiles for the cross section of wideband TEM horns have been proposed, employing an optimal impedance function or exponential taper in order to minimize reflection losses. In this article, an elliptic longitudinal sectional profile, combined with an optimal impedance function, is proposed and evaluated.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1548–1551, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22488

This paper describes a new pseudo-elliptic structure that has the same number of transmission zeros as comparable Cauer filters. The filter differs from previous structures in that it has two three-section stepped stubs which contribute an additional transmission zero, ensuring even better performance and substantially increased range of realizable stopband attenuation levels.