| 摘要 |
Method and apparatus for the nondestructive testing of metal-clad microwave circuit boards to determine dielectric constant variations within the dielectric sheets of such boards. The method involves using injected microwave energy to measure values related to the average dielectric constant along a plurality of paths in the plane of the sheet. The paths are divided into two intersecting groups, with each path being parallel to the members of its own group. Resulting values are then compared in order to identify dielectric constant variations within the sheet. Measurements may be made by means of phase delay or amplitude/resonance frequency techniques. A preferred apparatus for phase delay measurement is disclosed which includes means for making a simultaneous phase delay measurement along a reference air path.
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