Design of Miniaturized Wideband Circularly Polarized Patch Antenna with Branch Line Coupler in InFO

In this paper, we proposed a 38GHz compact and wideband circularly polarized patch antenna design with branch line coupler using InFO-WLP (Integrated Fan-Out Wafer-Level-Packaging) technology using vertically connection in InFO-WLP to miniature size. Firstly, we design a branch-line coupler which can provide two same magnitude output but 90 degrees phase difference. After this, it comes to dual-fed square patch antenna. Lastly, we connected branch-line coupler and square patch antenna by TIVs. By orthogonally fed, it becomes a perfect circularly polarized patch antenna. Miniaturized The design concept of miniaturized and compact CP antenna is almost the same as traditional dual-fed CP antenna. What’s difference between them is the proposed antenna is vertically stacked in order to compact size, we also utilize InFO-WLP technology to reduce path loss and power consumption. Additionally, smaller form factor and high quality factor are two of advantages of InFO-WLP. We use two different feeding structure to achieve our goal. One is coupling-fed and the other one is microstrip line-fed. The results suggested that the coupling-fed one’s impedance bandwidth is 33.3%, 3dB axial ration bandwidth is 17.65%, 3dB gain bandwidth is 8.07% and useful bandwidth is 8.07%. And microstrip line-fed one’s impedance bandwidth is 33.1%, 3dB axial ration bandwidth is 32.41%, 3dB gain bandwidth is 12.8% and useful bandwidth is 12.8%.