Method of increasing spatial resolution of the scanning near-field microwave microscopy

Abstract

In this article we propose methods for the measurement of electric intensity of a microwave field above the surface of microwave circuits. Using miniaturized coaxial antennas and a special probe positioning system, we measure both the amplitude and the phase of the induced field above the device under test. We introduce a position/signal difference method to further increase the spatial resolution down to about 30 μm—about one order better than contemporary microwave scanning devices utilizing coaxial antennas. The effect is theoretically analyzed and experimentally verified. The probes are calibrated in a well-defined field standard to allow quantitative characterization of the measured field. Performance of our scanning system utilizing these methods is demonstrated using a PCB finger capacitor.