Influence of Temperature on the Frequency Characteristics of a Modal Filter based on a Microstrip Line with Two Side Grounded Conductors

For the first time the paper presents the results of the study of temperature influence on the modal filter (MF) reflection| S
11
| and transmission| S
21
| coefficients magnitude frequency characteristics. The MF under consideration is based on a microstrip line with two side conductors grounded at both ends. The study is based on the results of simulations in the TALGAT system and measurements of the fabricated MF layout using the heat-cold chamber ESPEC-SU-262 and the vector network analyzer R&S ZV A40. The results of simulations and measurements at temperatures of -50, 25, and + 150°C for simulation and experiment, as well as for each temperature separately, are presented. A significant influence of temperature on| S
11
| and |S
21
| is shown. As the temperature increases, they decrease. The simulation and experimental results agree well at low frequencies and worse at high frequencies. This occurs due to the unaccounted frequency dependence of the parameters of SMA connectors and measuring cables. At the same time, the results at low frequencies showed the correctness of simulations in the TALGAT system.