Ridge waveguide probe for estimation of the scattering parameters of a device at millimeter- and sub-millimeter-wave frequencies

In this study, we investigate a novel approach for on-wafer testing of active and passive circuits at Y-band and higher. This represents an alternative approach to the conventional coaxial- or CPW-based probes used at lower frequencies. The measurements based on coaxial probes at these high frequencies are unreliable and non-repeatable due to the small size of the fragile probe tips. The small dimensions of coaxial probes are needed to avoid over-moding and radiation from the fingertips of the probe. However, at high MMW and sub-MMW frequencies manufacturing tolerances limits the minimum size of such coaxial probes which inevitably leads to unreliable mode conversion and probe radiation. Another limitation in utilization of coaxial probes is that the smooth physical connection of the probes with on-wafer lines is very hard to achieve due to the small dimensions of the probes and the lines. Besides, the probe tips tend to deform after a number of measurements resulting in unreliable measurements.