A Cost-Efficient 28 GHz Integrated Antenna Array With Full Impedance Matrix Characterization for 5G NR

A 2 × 2 integrated antenna array operating at 28 GHz with 4 GHz bandwidth is presented. A conventional printed circuit board (PCB) technology is used to realize the antenna board with low fabrication cost by minimizing the number of layers and vias. To overcome limited bandwidth and high mutual coupling, several techniques are used: proximity-coupled feedings, slotted patches, and defected ground. The S-matrix and the radiation patterns of the standalone antenna prototype are measured before being attached to the IC. The performed S-matrix measurement is a very first of a kind among so far reported integrated arrays at 28 GHz. The measurements confirm a mutual coupling level less than -12 dB. This characterization is used to estimate the performance of the driving power amplifiers. The analysis confirms that the antenna array is well matched with the IC output, and as a result, the performance of the array does not degrade under beam scanning. The integrated antenna can be used as a tile module to construct larger arrays in arbitrary configurations.