Dual-Polarized On-Chip Patch Antenna with Increased Bandwidth for mm-Wave Radar Systems

This paper presents a straightforward solution to increase the bandwidth of a rectangular on-chip microstrip patch antenna by exciting the fundamental resonance along the long and short edges of the patch. By a suitable combination of both resonances using quarter-wave transformers, the patch will radiate either a vertical or horizontal polarization in dependence on the frequency, ultimately increasing the usable antenna bandwidth. Here, an overall increased antenna mismatch is tolerated to achieve a relatively flat realized gain over a large bandwidth. The prototype fabricated in Infineon's B11HFC SiGe BiCMOS process is characterized in a far-field measurement setup and shows the desired increased bandwidth. Furthermore, the disturbing radiation of on-wafer probes on such far-field measurements is shown. For this purpose, a raster scan of the radiated near-field close to the chip is carried out and evaluated.