Comparing coax launcher and wafer probe excitation for 10 mil conductor backed CPW with via holes and airbridges

An experimental comparison of coax launchers versus wafer probe excitation of a 10-mil conductor backed CPW (coplanar waveguide) is presented. It was found that conductor backing of a CPW can cause a serious moding problem when a coax launcher is used. Introducing via holes can eliminate this problem to some degree. In comparison, wafer probe excitation generally shows a better response but the back metallization causes some moding problems. The transition effect from the coax launcher onto the CPW was modeled numerically, and good agreement with measured data was found.<
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