To enlarge the range of wireless fronthaul and backhaul communication links operating close to the millimeter-wave region, this letter presents a novel line-of-sight (LoS) multiple-input-multiple-output (MIMO) relay system. The analog relay system consists of a simple 90° hybrid coupler to separate two uncorrelated transmit data streams realizing a low complex and cheap system. The functional capability is proven within measurements of two independent 2 × 2 LoS MIMO links at 28 GHz connected by the relay system. A high decoupling of the two independent transmitted data streams of more than 27 dB after the 90° hybrid coupler and a high modulation error rate at the last receiver of around 22 dB could be reached for quadrature phase shift keying (QPSK) and 16-quadrature amplitude modulation (QAM) modulated signals.

中文翻译：

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使用 90° 混合耦合器的模拟 28 GHz LoS MIMO 中继系统


为了扩大在毫米波区域附近运行的无线前传和回程通信链路的范围，本信提出了一种新颖的视距 (LoS) 多输入多输出 (MIMO) 中继系统。模拟中继系统由一个简单的 90° 混合耦合器组成，用于分离两个不相关的传输数据流，从而实现低复杂性和廉价的系统。该功能能力已在由中继系统连接的 28 GHz 两条独立 2 × 2 LoS MIMO 链路的测量中得到验证。对于正交相移键控 (QPSK) 和 16 正交，可以在 90° 混合耦合器之后实现两个独立传输数据流超过 27 dB 的高解耦，以及最后一个接收器处约 22 dB 的高调制错误率幅度调制 (QAM) 调制信号。