Figure 7. Simulated performance of a two-band asymmetric equal-post section.

A multi-band post-based section

Note, the distance dx = 2 mm between a lateral post and a neighboring sidewall of the waveguide is fixed in all the designs. However, the distance dx is the parameter that affects the frequency response drastically. Detail numerical and experimental study of a transformation of a tri-post resonator response if the distance dx varies is presented [20]. Briefly, a similar transformation of the response from a bandstop one into a singlet-type and a pseudoelliptic ones is revealed even for a symmetric equal-height post-based section. It is not suitable for a frequency-tunable resonator design but a variation of the distance dx for each lateral post separately is a way to achieve a multi-band response. As an example, the simulated frequency response of an asymmetric equal-height post-based section is presented in Figure 7. The section dimensions are hL,C,R =7.2 mm, dxL = 1.0 mm, dxR = 7.6 mm, tx = 0.5 mm, t = 0.5 mm. Here, both the second and the third modes of the resonator are involved in electromagnetic interaction. Each of them provides the resonant coupling between the source and the load at the same time. As a result, a response with two separated singlet pairs TZL/TPL and TZ2/TP is generated.

Conclusions

A novel simple and compact multi-function waveguide resonator is presented in the paper. It is composed of three rectangular partial-height E-plane posts inserted along a rectangular waveguide cross-section. A pair of the posts is mounted symmetrically whereas the third antipodal post is centered. In contrast to known two-post-based designs, the third mode exhibiting a symmetric electric field distribution is exploited as a resonant one. That is why an involving of the third mode into a resonant coupling can be provided both with and without breaking the resonator symmetry. The resonator enables different responses by varying one post height only. The resonator acts as (a) a bandreject element that generates a single transmission zero; (b) a singlet that generates both a transmission zero and a transmission pole simultaneously; (c) a section providing a pseudoelliptic filtering function with two transmission zeros located at both sides of the transmission pole. Besides, a switching waveguide filter providing the ON and the OFF states to allow/block the signal propagation at a given frequency is proposed. The pole frequency of the pseudoelliptic performance for the ON state is equal to the rejection frequency of the performance for the OFF state. Moreover, multi-pole multi-section bandpass filters, a frequency-tunable resonator and a

multi-band post-based section are discussed as well. Measurement data are presented for WR90 waveguide.

Acknowledgements

The author believes a pleasant duty to express her gratitude to Prof. A. Kirilenko for a possibility to use MWD-II software [21] developed under his leadership by Drs S. Steshenko, S. Prikolotin and D. Kulik.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes on contributor

Lyudmila P. Mospan (IEEE SM’11) received the MS degree in radio engineering from the Kharkov State University, Kharkov, Ukraine, and the PhD degree in radio engineering from the Institute of Radiophysics and Electronics of National Academy of Sciences of Ukraine (IRE NASU), Kharkov, Ukraine, in 2001. She is currently a Senior Researcher of the Computational Electromagnetics Lab. of IRE NASU and an Associate Professor at O.M. Beketov National University of Urban Economy in Kharkiv, Kharkov, Ukraine. She has co-authored over 100 journal and conference papers. Her research is focused on microwave computer-aided design and resonance phenomena in waveguides and gratings.

ORCID

Lyudmila P. Mospan http://orcid.org/0000-0002-4895-1409

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