Differentially-fed Dual-band Dual-pol Microstrip Antenna on Flexible Substrate for 5G Applications

This paper introduces a compact dual-band, dual-polarized antenna designed on an ultrathin substrate (270 mu m thick) with flexible and conformal capabilities, providing bandwidths across 27.1-28.3 GHz and 36.8-38.2 GHz. To overcome the challenge of controlling coupling in dual-polarized patch antennas on thin substrates, we propose a differential feeding approach for one port to minimize coupling by introducing out-of-phase currents. The antenna's differential feeding is achieved through the design of a wideband coupled-line phase shifter in a T-junction. Notably, exciting only one port differentially avoids high coupling caused by crossed feeding lines. To mitigate resonance differences resulting from asymmetrical feeding, the patch antenna is intentionally designed with asymmetric dimensions, enabling the simultaneous tuning of resonances for both polarizations and frequency bands.