A multimodal analysis of the effects of guard traces over near wideband signal paths

Guard traces are used in PCB implementations to avoid interferences between signal strips. These guard traces can affect the integrity of high harmonic content signals such as clock or wideband RF signals. In this paper, the effect of guard traces is analyzed from a multimodal point of view. A multimodal analysis allows a simple interpretation of the phenomena involved in the loss of integrity of signals propagating through strips close to the guard traces. Two guard trace configurations are analyzed, circuitally simulated and measured in order to test the adequacy of the multimodal approach to describe the behavior of signal strips close to guard traces, showing good agreement between theory and experiment.