Compensated Stepped Microstrip Lines: A Novel Approach for Impedance Discontinuity Mitigation

Abstract

Modern electronic devices operate at frequencies where interconnects function as transmission lines, necessitating meticulous management of characteristic impedance (Z0) to avert signal degradation and power losses. This paper delves into the manipulation of microstrip characteristic impedance through variations in trace inductance and capacitance. It proposes a reference plane cut-out compensation technique to mitigate impedance inconsistencies introduced by component pads of varied sizes, which disrupt the uniformity of the microstrip. The technique involves adjusting capacitance by altering the distance to the reference plane. Experimental validation on a 6-layer printed circuit board (PCB) device confirms the effectiveness of the proposed method in maintaining impedance close to the target value of 50Ω, critical for high-frequency applications. Measurements using a vector network analyzer demonstrate substantial impedance improvement up to 35Ω through compensation, offering insights into practical impedance control strategies for high-frequency dense PCB designs.