Coupling coefficients of irregular microstrip resonators and selective properties of filters on their basis

Abstract

Frequency-dependent coefficients of coupling between irregular microstrip resonators andtheir role in formation of filter frequency response are studied on the basis of energetic approach. Tworesonator segments and filters are used as samples under investigation. Theoretical analysis carried out in quasi-static approximation shows good agreement between calculated and experimental frequency responses and, thus, allows to conclude tlhat attenuation poles in frequency response are due to compensation of capacitive and inductive interaction between resonator. The data obtained shows a possibility to control the steepness of filter skirt slopes of by appropriate choice of structure parameters. .IntroductionIt is common knowleage that, frequency-selective devices, in particular, filters play critical roles in commuhication and radiolocation systems. Quite often these devices set the overall dimensions of radio engineering equipment, and also influence the quality and the failsafety of their work. It is also known, that in the microwave engineering are widely spread filters due to their compactness, failsafety and ability to be easy manufactured. Good agreement obtained between the quasi-static analysis of microstrip structures and experiments allows to create effective systems for the automated designing MW devices. Now important and actual are the tasks not only on creation of new filter designs, but also on optimization of known ones, in order to achieveextremely high performances in them.The resonators coupling coefficients study not only promotes the solving of such tasks, but also allows to understand regularities in behavior of frequency response (FR) of microstrip structures on changing their design data. In particular, research on frequency-dependent coefficients of coupling between microstrip resonators (MSR) with stepped change in width of a strip conductor, having dumbball shape, are of great interest [l]. Such resonators attract attention of specialists in the area of MW fi-equency-selective devices due to their compactness and higher, in comparison with regular resonators, unloaded quality factor, and also to opportunity of creating designs with the given spectrum of resonant frequencies [2]. Besides, the possibility of effective steepness control of FR slopes in band-pass filters based on irregular resonators allows to realize a given shape of FR with the minimal number of resonators in a device [3]. Thus, the construction of a filter not only becomes more compact, but also, as a rule, has the higher electrical performance in comparison with a filter based on regular MSR's with the same number of resonators. 2.Model and Method of CalculationThe researches was carried out on microstrip segments, consisted of two identical resonators located parallel against each other with the gap S between outside "low-impedance" parts of conductors, having width we (Fig. 1). Width of the middle "high-impedance" part is Wi and its length is la, while a total length of strip conductors of resonator is designated as I , . ...

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