Millimeter-Wave Thickness-Deviation Measurement System

We measure dielectric slab thickness deviations on the order of tens of microns using a free-space radiating pulse generation and detection system comprised of X-band driven nonlinear transmission line integrated circuits coupled to bow-tie antennas. This is achieved by locking the receiver sampling aperture to the midpoint of a pulse transmitted through the reference material, and then replacing with the material under test to observe a deviation in thickness from the reference. A change in thickness causes the sampling aperture to move along the pulse slope, giving a corresponding change in DC voltage. This technique is applicable to manufacturing process control.