Chip reference antennas: Improving millimeter-wave on-chip antenna measurements

The adoption of millimeter wave phased arrays for a variety of applications, have led to an increased need for on-chip antenna measurements. The antenna elements are tested via micro-probe connections due to their tiny dimensions. For typical wireless applications (e.g. 5G/NR or IEEE 802.11.ad) these phased arrays, are expected to provide near omnidirectional coverage. Even with carefully designed spherical antenna measurement system, the micro-probe and its positioner provide blockage and errors due to scattering. Judicious design of reference antennas can significantly improve the quality of the overall measurement. Consequently, the authors have led the development of a new set of reference antennas specifically designed to aid in calibration and verification of micro-probed antenna measurements [1]. The goal is not only to have a gold standard to monitor the consistent performance of an antenna test range, but to enable accurate on-chip antenna gain calibration using the substitution method [2]. The performance of the reference antennas are directly evaluated based on comparison between measurements and simulations and also via analysis of equivalent source currents using an inverse source technique shown to be effective in identifying and removing effects from feeding and support structures for general antenna measurements.[3,4,5] This paper will elaborate on the effectiveness of the inverse source technique in evaluating scattering for both the single patch and four (2×2) patch geometries shown in Fig 1. And Fig 2., respectively.