A Flexible Millimeter-Wave Endfire Antenna Based on Spoof Surface Plasmon Polaritons
Qingfeng Fu, Leilei Liu, Guo Qing Luo
Abstract
A flexible endfire antenna based on spoof surface plasmon polaritons (SSPPs) is proposed at millimeter-wave band. First, due to the strong field confinement of SSPPs, it can ensure that the field distribution of the antenna is almost unchanged when it is bent, so that its impedance characteristics remain relatively stable. Then, to realize the endfire radiation, a symmetrical SSPPs transmission lines fed by a microstrip-slotline structure is proposed. Finally, an endfire antenna operates in the frequency range of 30–50 GHz, over which the average gain of this antenna is 14.9 dBi, and the overall size of this antenna is 9.2λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×2.67λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ×0.016λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Besides, this antenna can still maintain good radiation performance in bending, and its maximum radiation angle changes with a linear correspondence of the bending angle. When the bending angle of the antenna changes from 0° to 30°, the maximum radiation angle increases from 0° to 24°, and the gain fluctuates within 2 dB, which shows that the flexible antenna has good stable radiation performance. The proposed antenna holds the advantages of wide bandwidth, small size and flexibility, and has a good prospect in the future flexible circuit and wearable systems.