Investigating the Effect of Geometry on Microstrip Line Structure

Abstract

The microstrip line is arguably the most popular and commonly used transmission line structure on a printed circuit board (PCB) due to its ease of fabrication and the availability of the signals for making circuit connections and probing. To guarantee the integrity of the signal while traveling through the microstrip line, it is very crucial for a board designer to ensure that the line impedance is properly matched. Nevertheless, in order to route the signal on the board to various components, the board designer will need to make necessary bending or tapering of the line which will cause imperfect matching, thus creating mismatch losses. This work will demonstrate the effect of geometry, such as 90°-bend and tapering, on the behavior of the microstrip line using 3-D planar electromagnetic (EM) simulator. Simulation results of a common 90° bend and an actual circuit board trace will be presented and analyzed.