Analog 28 GHz LoS MIMO Relay System Using a 90° Hybrid Coupler

Abstract

To enlarge the range of wireless fronthaul and backhaul communication links operating close to the millimeterwave (mmW) region, this work 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 lowcomplex 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 (MER) at the last receiver of around 22 dB could be reached for QPSK and 16-QAM modulated signals.