One example includes a machine-readable storage medium encoded with instructions. The instructions are executable by a processor of a system to cause the system to receive at least one target electrical characteristic indicating a target impedance of a passive printed circuit board (PCB) structure. The passive PCB structure is a component of a serial communication channel. The instructions are executable by the processor to cause the system to divide the passive PCB structure into a plurality of elements. Each element has an input and an output. The instructions are executable by the processor to cause the system to determine at least one parameter of each element such that an image impedance of the input and the output of each element equals the target impedance.