G.M. Aristarkhov – Dr.Sc.(Eng.), Professor, Head of Department of Electronics, 

Moscow technical university of telecommunication and informatics

E-mail: g.aristarkhov2010@yandex.ru

O.V. Arinin – Head of Laboratory, 

Department of Electronics, Moscow Technical University of Telecommunication and Informatics E-mail: bishounen99@gmail.com

I.N. Kirillov – Post-graduate Student, 

Department of Electronics, Moscow Technical University of Telecommunication and Informatics E-mail: i.kirillov2009@gmail.com

This article examines the new design principles of one of the integrated microwave electronics basic elements - microstrip filter with increased frequency selectivity. MSFs based on comb structures are among the most compact ones. An increase in their frequency selectivity is traditionally achieved by working attenuation poles forming due to the organization of additional couplings between nonadjacent resonators. The number of attenuation poles formed in the N-resonator structure is limited and does not exceed the value P = N − 2. The purpose of this work is to study the features of constructing MSFs with increased frequency selectivity based on multistep comb and counter-comb structures with a limited number of resonators, in which a much larger number of working attenuation poles is formed without introducing additional electromagnetic couplings between non-adjacent resonators. The procedure of structural synthesis of a two-resonator comb section, which is the circuit basis of band-pass comb MSFs is considered. It is shown that due to the combined use of the effect of inequality of normal waves phase velocities and the step in wave impedances on different areas of the comb section length, it is possible to form working attenuation poles at different places on the frequency axis. The conditions of various operating modes of three-stepped comb sections are determined. It is shown that the implementation of additional steps into the filter structure determines the possibility of a number of additional attenuation poles forming, ensuring the discharge of the spurious passbands spectrum up to the seventh harmonic inclusive. In this paper, we consider the features of constructing higher-order MSFs based on two counter-connected two- and three-resonator comb sections. It is shown that their simultaneous electromagnetic interaction both between the resonators of the base sections and the presence of galvanic connection between the sections determine the formation and splitting of the attenuation poles in the region of high and low frequencies. As a result, N working attenuation poles are formed in these structures, which significantly increase the frequency selectivity of the MSFs. Thus, in these multiconductor structures with additional galvanic coupling between adjacent sections, an increase in the MSF order is realized while preserving the selective properties of the basic two- and three-resonator comb multi-step sections. The minimum distance between the coupled microstrip lines in the structures is Smin ≥ 0.15 mm, which ensures high manufacturability of the MSF. The considered structures combine high compactness, manufacturability and increased frequency selectivity.

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