Printed Circuit Board Reverse Engineering Filter Option

Printed Circuit Board Reverse Engineering Filter Option can be useful under conditions where excessive ringing occurs on the TDR response. The filtered response can be used for designs where the minimum (fastest) edge-rate is much larger (slower) than the TDR edge rate.

Enabling the filter function eliminates unnecessary high frequency content on the TDR response for PCB Reverse Engineering TDR Impedance. This will provide a smoother TDR response, making it easier to determine the impedance characteristics of the trace under test. Figure 17 is an example of a filtered TDR response in comparison with the normal, unfiltered TDR response.

To complete differential impedance measurements, two TDR sources need to be injected across two differentially routed signal lines simultaneously. The TDR output edges must be phase aligned so that the output edges have zero time delay (skew) between them and opposite in polarity (odd mode switching).

Edge alignment can be completed by setting the polarity the same and adjusting the head time delays until no visible difference in the time base is observed between the two of Printed Circuit Boards. After aligning the edges, reverse the polarity on one source and apply both signals to the differential line pair.

It is critical to have proper edge alignment and probe placement so the electrical switching characteristics along the two lines will match in time. If this is not confirmed, distorted TDR responses will occur which require to adjust display of Circuit Board Reverse Engineering. A simple method to check the setup and measurements is to apply one signal to measure the single line impedance, which should be similar to a typical TDR impedance response.

Note the impedance value and next connect the second source with the inverse response. Once the second source is applied, it should be visible that the impedance for the single line should drop. The amount of difference will be dependent upon the design of the traces.

The illustration for Figure 18 is an example of a 56 Ω differential impedance measurement for Direct Rambus™. This shows both step responses of which either could be used to extract the impedance after Printed Circuit Board Reverse Engineering.

Tags: pcb assemble reverse engineering,pcb board reverse engineering,pcb card reverse engineering,pcb reverse engineering,pcba reverse engineering,Printed Circuit Board Reverse Engineering,printed wiring board reverse engineering,pwb reverse engineering,pwba reverse engineering