Novel single-RF MIMO system based on repetitive pulse width modulation

Many alternative systems have been studied based on compact single-RFs for multiple-input multiple-output (MIMO) systems. However, the implementation of such systems has been limited by a lack of robustness in relation to system environment. In this letter, we propose a novel MIMO system based on a repetitive pulse width modulation, which requires a single-RF and switches only, without the need for a phase shifter. The mathematical formulations for the proposed system are derived and the signal difference between our proposed system and a conventional MIMO system is shown mathematically. The performance of the proposed system is verified by comparing its channel capacity with that of a conventional MIMO system.