A 25 µm spatial resolution broadband microwave voltage probe

Abstract

The present generation of voltage probes have demonstrated a spatial resolution of 100 μm at 6 GHz bandwidth. This paper presents results of a contactless voltage probe having 25 μm spatial resolution and instantaneous bandwidth up to 7 GHz. The probe is constructed from a miniaturized open-ended coaxial cable of 20 μm inner conductor diameter and 300 μm outer diameter. Capacitive coupling between the open-end coaxial cable and the device under test (DUT) generates a signal which feeds a miniaturized microwave amplifier. This concept introduces a new dimension into the process of designing microwave circuits which allows high accuracy, spatially resolved, voltage measurements. The improved probe design offers more flexibility in terms of the range of devices that can be measured, extending beyond large power microwave transistors to medium and small scale microwave active devices.