Load-Modulated Single-RF MIMO Transmission for Spatially Multiplexed QAM Signals

TL;DR

This paper introduces a load-modulated single-RF MIMO system for spatially multiplexed QAM signals, offering a compact design that matches conventional MIMO performance without iterative optimization.

Contribution

It presents a novel load design methodology for load-modulated arrays that enables exact reactance calculation and perfect matching, simplifying single-RF MIMO implementation.

Findings

The proposed design accurately computes reactance loads and matches source impedance.

Simulation results show BER performance comparable to conventional MIMO.

The methodology reduces complexity in single-RF MIMO systems.

Abstract

Today, MIMO has become an indispensable scheme for providing significant spectral efficiency in wireless communication and for future wireless system, recently, it goes to two extremes: massive MIMO and single-RF MIMO. This paper, which is put in the latter, utilizes load-modulated arrays with only reactance loads for single-RF transmission of spatially multiplexed QAM signals. To alleviate the need for iterative processes while considering mutual coupling in the compact antenna, we present a novel design methodology for the loading network, which enables the exact computation of the three reactance loads per antenna element and also the perfect matching to the source with the opportunity to select appropriate analog tunable loads. We verify the design methodology by comparing the calculated values for some key parameters with the values from the circuit simulation. In addition, as an evaluation of the proposed architecture, we perform the bit error rate (BER) comparison which shows that our scheme with ideal loading is comparable to the conventional MIMO.