Temperature dependence of microstrip bandpass filter for extreme climates

In general designers of the microstrip bandpass filter, depend on the manufacturers' specification, even though such specifications are restricted to standard environmental conditions. The electronic devices are usually designed for room temperature performance. Due to the temperature expansion, the constitutive parameters of the geometries need further modifications, because it is not only reduces the filter performances but also greatly shortens their lifetime. In this paper, the dimensional change of microstrip parallel coupled band pass filter is analyzed for the temperature variation from - 50°C to 80°C, using different dielectric substrates such as FR-4 epoxy, alumina and silicon with copper. The designed parameter values of the band pass filter are determined by MATLAB and the performance of the filter under different temperature conditions are studied with the help of Ansoft HFSS. There is a shift of frequency from its initial value and corresponding changes in upper cut off frequency, lower cut off frequency and center frequency which are shown in table form and graphically.