Mitigating Effects of Interference in On-Chip Antenna Measurements

Coupling a Chip Antenna to an Antenna Measurement System is typically achieved using a coplanar micro-probe. This micro-probe is attached to a probe positioner that is used to maneuver the micro-probe into position and land it on the chip. Through this process, the chip antenna is supported by a dielectric chuck. Intentional and unintentional radiation from the chip antenna will interact with the micro-probe and dielectric chuck. From design conception, the antenna designer must take steps to reduce ground plane currents on the chip antenna surface to minimize unintended radiation that will interact with both the measurement setup and the surrounding components of the final in-situ design. Even with good design practices, residual ground plane currents will still remain and radiate from the chip antenna. Combined with intentional radiation from the chip antenna in the upper hemisphere, these radiated fields will illuminate the micro-probe and the probe positioner. Scattered fields from both the micro-probe and its positioner will superimpose interference patterns with the desired signal at the spherical measurement probe. In this paper, we evaluate, on a first order, these effects by experimentation on two brands of micro-probes (ACP & Infinity). The residual errors are then evaluated using modal filtering that further reduces these effects and the results are presented. Finally the dielectric chuck is modeled in simulation to evaluate the impact of the chuck on antenna patterns at 60 GHz and the results are presented.