Development of a microwave low-pass filter based on a microstrip line projection mode

Objectives. Sections of microstrip lines having finite length are widely used to develop integrated circuits and microwave devices for various purposes, such as power dividers, directional couplers, attenuators, and filters. In particular, low-pass filters in the microwave range are comprised of a cascade connection of regular sections of microstrip lines having various geometric parameters. However, modern approaches to calculating microwave filters using commercial software require large computational and time-consuming resources, especially when carrying out electrodynamic analysis of microstrip lines. The work set out to develop an algorithm and a method for calculating filters using a projection approach to the electrodynamic analysis of microstrip lines that reduces the time required to calculate characteristics of microwave filters while maintaining high accuracy of the obtained results.
Methods. The proposed projection approach to the electrodynamic analysis of a microstrip line can be used to rapidly and accurately calculate the main electrodynamic parameters of retardation coefficient and wave impedance across a wide range of changes in the geometrical parameters of the line, as well as its dielectric constant and frequency.
Results. Formulas obtained on the basis of analytical expressions for calculating the electrodynamic parameters of a microstrip line are used to describe the nature of changes in the elements of the scattering matrix of multistage low-pass filters in a given frequency band. A developed computer program was used to calculate the values of the elements of the low-pass filter scattering matrix across a wide range of substrate dielectric constant and frequency parameters. The obtained results were compared with the characteristics of filters calculated using commercial software.
Conclusions. The proposed approach to calculating the electrodynamic parameters of microstrip lines and consequent elements of the scattering matrix of multistage low-pass filters can significantly reduce the calculation time while achieving a sufficiently high accuracy of the obtained results to significantly reduce labor costs when calculating microwave filters in engineering practice.

1. Petrov I.A. Microwave filters with use broadband matching structures. Fizika volnovykh protsessov i radiotekhnicheskie sistemy = Physics of Wave Processes and Radio Systems. 2011;14(1):51–56 (in Russ.).

2. Lamanov Yu.A., Kudryavtseva T.O., Drobotun N.B. Design and Research Process of Microstrip Low-Pass Filters with High Slope Steepness. Doklady Tomskogo gosudarstvennogo universiteta sistem upravleniya i radioelektroniki (Doklady TUSUR) = Proceedings of TUSUR University. 2021;24(2):7–13 (in Russ.).

3. Fel’dshtein A.L. (Ed.). Spravochnik po elementam poloskovoi tekhniki (Handbook of Elements of Strip Technology). Moscow: Svjaz’; 1979. 336 p. (in Russ.).

4. Gupta K.C., Garg R., Chadha R. Mashinnoe proektirovanie SVCh ustroistv (Computer-aided Design of Microwave Circuits): transl. from Engl. Moscow: Radio i svjaz’; 1987. 432 p. (in Russ.). [Gupta K.C., Garg R., Chadha R. Computer-aided Design of Microwave Circuits. Dedham, Mass.: Artech House Inc.; 1981. 636 p.]

5. Lopatin V.V., Khvorenko V.V. Modeling and implementation of a microstrip filter. In: Information Technologies in Science, Industry and Education: collection of papers of the Scientific and Technical Conference. Izhevsk; 2021. P. 166–176 (in Russ.).

6. Kovalenko A.N. Projection method for constructing full-wave models of striplines. J. Commun. Technol. Electron. 2019;64(2):93–99. https://doi.org/10.1134/S1064226919020128 [Original Russian Text: Kovalenko A.N. Projection method for constructing full-wave models of striplines. Radiotekhnika i elektronika. 2019;64(2):108–115 (in Russ.). https://doi.org/10.1134/S0033849419020128 ]

7. Kovalenko A.N., Yarlykov A.D. Numerical analysis of a shielded microstrip line. In: Actual Problems and Prospects for the Development of Radio Engineering and Infocommunication Systems (Radioinfocom-2021): Proceedings of the 5th International Scientific and Practical Conference. Moscow: RTU MIREA; 2021. P. 331–334 (in Russ.).

8. Kovalenko A.N., Yarlykov A.D. Increasing the efficiency of projection models of strip lines. J. Commun. Technol. Electron. 2021;66(9):997–1003. https://doi.org/10.31857/S0033849421090084 [Original Russian Text: Kovalenko A.N., Yarlykov A.D. Increasing the efficiency of projection models of strip lines. Radiotekhnika i elektronika. 2021;66(9):837–844 (in Russ.). https://doi.org/10.31857/S0033849421090084 ]

9. Kovalenko A.N., Yarlykov A.D. Analytical expressions for electrodynamic parameters of the shielded microstrip line. Russian Technological Journal. 2021;9(4):68–76 (in Russ.). https://doi.org/10.32362/2500-316X-2021-9-4-68-76

10. Fusco V. SVCh tsepi. Analiz i avtomatizirovannoe proektirovanie (Microwave Circuits. Analysis and Computer-aided Design): transl. from Engl. Moscow: Radio i svyaz’; 1990. 288 p. (in Russ.). [Fusco V.F. Microwave Circuits. Analysis and Computer-aided Design. Prentice Hall; 1986. 358 p.]

11. Matthaei G.L., Yong L., Jones E.M.T. Fil’try SVCh, soglasuyushchie tsepi i tsepi svyazi (Microwave Filters, ImpedanceMatching Networks, and Coupling Structures): transl. from Engl. Moscow: Svyaz’; 1972. V. 2. 496 p. (in Russ.). [Matthaei G.L., Yong L., Jones E.M.T. Microwave Filters, Impedance-Matching Networks, and Coupling Structures. McGraw-Hill; 1964. 1096 p.]

12. Kostin M.S., Yarlykov A.D. Ustroistva i moduli sverkhvysokikh chastot (Devices and Modules of Ultra-High Frequencies). Moscow, Vologda: Infra-Inzheneriya; 2022. 400 p. (in Russ.).

13. Maloratskii L.G., Yavich L.R. Proektirovanie i raschet SVCh-elementov na poloskovykh liniyakh (Design and Calculation of Microwave Elements on Strip Lines). Moscow: Sovetskoe radio; 1972. 232 p. (in Russ.).

14. Kovalenko A.N. Natural modes of a microstrip line. Radiophys. Quantum Electron. 1978;21(2):128–133. https://doi.org/10.1007/BF01078702 [Original Russian Text: Kovalenko A.N. Natural modes of a microstrip line. Izvestiya vysshikh uchebnykh zavedenii. Radiofizika. 1978;21(2):188–194 (in Russ.).]