Antenna-on-Chip Radiation Pattern Characterization – Analysis of Different Approaches

Millimeter-wave antenna measurements severely rely on the use of on-wafer probes. For an Antenna-on-chip (AoC), due to the tiny size of the chip (1~2 mm2), the radiation pattern will still be influenced when the probe tip is near the AoC under test (AUT). In addition, the edges of ground plane, the probe body, and the large holder will diffract the radiated fields and cause unexpected results. We have investigated how the probe and the test environment influence the radiation pattern by using a step-by-step approach to analyze the contribution each of the interfering sources. This analysis together with an experimental verification shows that an accurate radiation pattern of AoCs is difficult to characterize using existing probe-fed measurement strategies. To eliminate the large probe tip and body, a system-level approach could be used where the frequency generator is integrated on-chip. Another possible solution for an antenna designer is the bonding wire solution, which is low cost and easy to fabricate. The key rule of the design is that the location of the bond-wires needs to be perpendicular to the E-plane of the AUT.