An active, non-intrusive, high resolution microwave field probe with applications in high power RF device and circuit design

This paper describes the design, fabrication, and applications of a novel high resolution electric field probe. In essence, the probe consists of a novel miniaturized open-circuited co-axial transmission line that can respond to local normal electric fields with a spatial resolution of about 100 microns. A key aspect of the probe is the use of an active amplifier close to the probe tip. This amplifier not only increases the sensitivity but provides isolation and termination of the unwanted stray pickup from the feeder cable. Results will be presented which show that the probe can resolve the voltage waveforms at individual bond wires in high power transistors. Larger devices have been observed to display substantial spatial variations in this test, which are strongly dependent on the external circuit feeding arrangements.