The effects of geometry and dielectric material on stripline and microstrip internal temperatures

The geometry and loss characteristics of 50 Ω striplines operating at a frequency of 1.09 GHz were determined using fundamental transmission line theory. These results were then combined with finite element based thermal modeling to estimate the temperature rise within a stripline. The finite element thermal predictions were validated with measurements on a circuit board used in an avionics power amplifier. The results of this analysis showed that higher dielectric materials have higher power loss compared to traditional lower dielectric materials. But, due to the higher thermal conductivity of these materials, they can be used to produce smaller striplines that have a similar internal temperature rise to standard materials. Thermal testing and analysis indicate that, while the approach was based on a stripline with characteristic impedance of 50 Ω and a frequency of 1.09 GHz, the thermal analysis that was developed is applicable to both striplines and microstrips of any impedance or frequency.