Millimeter-Wave Patch Antennas With Ultralow Profile of 20 μm on Flexible Substrate

In applications of flexible communication electronics, the requirement for ultralow profile of antenna is gradually approaching a limit. In order to achieve a higher flexibility, it is necessitated to limit the vertical distance to 10 $\mu \text{m}$ scale between the integrated antennas and the electrode ground (GND). Such a small Section height results in a severely reduced radiation efficiency and a narrowed bandwidth. In this article, the enhancement of radiation efficiency and bandwidth of a millimeter-wave (mmWave) patch antenna with 20 $\mu \text{m}$ profile height are studied. On the metal GND, by properly opening two (or one) resonant slots with a width of 100 $\mu \text{m}$ , strong resonance coupling between the patch antenna and the slots can be induced, leading to a greatly enhanced radiation efficiency. Meanwhile, the spectra width of TM10 mode of the patch antenna can also be effectively broadened by the mode coupling, giving rise to a greatly improved radiation bandwidth. The physical mechanism and the sensitive factors to maximize bandwidth, antenna gain, and front-to-back ratio are discussed.