Folded aperture coupled patch antenna fabricated on FPC with vertically polarised end-fire radiation for fifth-generation millimetre-wave massive MIMO systems

摘要： The authors proposed a folded aperture-coupled patch antenna (ACPA) on a flexible printed circuit (FPC) with vertically polarised end-fire radiation, suitable for fifth-generation millimetre-wave massive multi-input–multi-output (MIMO) systems. For low-cost implementation, antenna elements were fabricated on a single polyimide substrate. The fabricated FPC was first folded to implement a three-layer ACPA, and then the feed line was bent 90° to achieve end-fire radiation. Measurement of five antenna samples demonstrates that the resonance frequency lies between 27.7 and 28.3?GHz. Each antenna sample has the bandwidth (|S11|?<??10?dB) >1.2?GHz. The measured antenna gain is 2.74?dBi at 28.1?GHz, and the difference between co- and cross-polarised radiation intensities is >15?dB in all directions of interest. To improve the impedance bandwidth and the gain further, they increased the distance between the patch and the aperture of the proposed antenna by folding the fabricated FPC multiple times without an additional layer. Experimental results confirm the bandwidth of 2.64?GHz (26.27–28.91?GHz) and the gain of 3.80?dBi at 28?GHz. Additionally, the 1?×?8-folded APCA array is simulated to verify the feasibility for a practical application of multi-beam massive MIMO technology.