The Effect Of Temperature On The Time Response Of A Modal Filter Based On A Microstrip Line with Two Side Grounded Conductors with A Moisture-Proof Coating

The article presents a study of the effect of temperature on the time response of a modal filter based on a microstrip line with two side grounded conductors with and without a moisture-proof coating of an insulating silicon-organic heat-resistant varnish with a layer thickness of 20, 40, 60 and 80µm. It is shown that with a modal filter without a moisture-proof coating, the temperature affects only the mode delays. And with a moisture-proof coating, the temperature affects both the mode delays and their amplitudes. For each thickness of the varnish, the effect of temperature on the time response of the modal filter is different. Thus, the maximum amplitude is reached at a temperature of −50°C with a varnish thickness of 20µm. This is due to its thermal expansion coefficient, which is 10 times greater than that of FR-4 fiberglass. The best results were obtained with 4 layers with a thickness of 80µm. In this case, the effect of temperature on the time response practically becomes close to the time responses without a moisture-proof coating. The results of the work can be useful for designing interference-proof transmission lines on printed circuit boards used under different climatic conditions.