Large discrepancy between HFSS simulated microstrip S-parameters and measured results: how to troubleshoot?
Simulating the S-parameters of a 50-ohm microstrip line in HFSS shows significant discrepancies with VNA measurements at high frequencies (> 1 GHz), primarily characterized by large deviations in insertion loss.
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High-frequency discrepancies are typically caused by the following: 1 Material parameters (Dk/Df) not accurately modeled for frequency dependence; 2 Conductor surface roughness model not enabled; 3 Inconsistent port calibration reference planes. First, verify material settings and enable the Huray roughness model, then compare simulated and measured group delay.
Additionally, verify that the mesh is sufficiently fine. At high frequencies, the skin depth decreases, so ensure there are at least 3 to 4 mesh layers across the conductor cross-section. Also, placing radiation boundaries too close to conductors can introduce errors.
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