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

The geometry and loss characteristics of 50-/spl Omega/ striplines operating at a frequency of 1.09GHz, which corresponded to the requirements for an existing military radio system, were estimated 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 allow for smaller geometries but have higher power loss compared to traditional lower dielectric materials. While the striplines produced with higher dielectric materials have more power loss (thermal dissipation), their internal temperature rise is comparable to that of striplines produced on lower dielectric materials. This is due to the fact that the higher dielectric materials also tend to have higher thermal conductivity. Thermal testing and analysis indicate that, while the approach was based on a stripline with characteristic impedance of 50/spl Omega/ and a frequency of 1.09GHz, the thermal analysis that was developed is applicable to both striplines and microstrips of any impedance or frequency.