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This paper presents a very precise analysis of the impedance variation with feed position of a microstrip line-fed patch antenna. The influence of the inset length and width has been investigated, taking into account finite size of the substrate, various lengths of the feeding microstrip line, losses and finite thickness of metallization. The obtained numerical results are compared with the previously published ones, showing very good agreement. However, the results of the additional analysis confirmed that the mathematical functions proposed in previously published papers (the cosine-squared function and the cosine to the fourth power function) are not really good approximations of the input impedance behavior for this type of the microstrip patch antenna.

U radu se prikazuje nova realizacija mikrotalasnog filtra sa dva nepropusna opsega učestanosti u talasovodnoj tehnici. Četvrttalasni rezonatori realizovani su u planarnoj tehnici, a prilikom istraživanja korišćeni su kao rezonantne prepreke postavljene unutar talasovoda. Razmatraju se rezonatori sa jednom rezonantnom učestanosti i njihove ekvivalentne šeme. Izvršena je detaljna analiza odziva posmatranih rezonatora u cilju projektovanja filtra drugog reda sa jednim nepropusnim opsegom. Ispituje se sprega između dva rezonatora postavljena na istoj štampanoj pločici. Realizovan je filtar drugog reda sa dva nepropusna opsega primenom navedenih rezonatora i predloženog metoda projektovanja. Predloženi metod projektovanja filtara otvara mogućnost za realizaciju filtra višeg reda sa više nepropusnh opsega. Ključne reči: četvrttalasni rezonator, filtar nepropusnik opsega učestanosti, filtar sa dva nepropusna opsega, rezonantna prepreka, talasovodna tehnika SUMMARY NOVEL IMPLEMENTATION OF DUAL-BAND BANDSTOP WAVEGUIDE FILTER USING QUARTER-WAVE RESONATORS Novel implementation of microwave waveguide filter with two rejection bands is presented in this paper. Quarter-wave resonators are implemented in planar technology, and in the research, they are used as resonant septa inserted in the waveguide. Resonators with single resonant frequency are considered, as well as their equivalent circuits. The observed resonator responses are analyzed in details, in order to design second-order filter with a single rejection band. Mutual coupling between the resonators on the same printed-circuit insert is investigated. The second-order filter with two stopbands is implemented using observed resonators and the proposed method for filter design. The proposed method for filter design opens possibility for realization of higher order filters with multi-stopbands.

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