Timing markers used in the measurement and testing of a printed circuit board's controlled impedance

摘要

Testing of a printed circuit board (PCB) impedance measurement region is performed using time domain reflectometry (TDR) that measures reflections and time delays of pulses injected into an impedance measurement region (impedance coupon). Timing markers are used to give both visual and electrical indications of precisely where the desired impedance measurement region (impedance coupon) begins and ends. The timing markers are placed on either end of the impedance coupon to be measured and give explicit start and end points to the PCB impedance measurement region. The timing markers may be in any form which has a discernable impedance difference from the PCB impedance measurement region.