A Novel Energy Efficient Single-RF MIMO Antenna Combining Load Modulated Array and ESPAR

A novel analog energy efficient single-radio-frequency (RF) architecture combining load modulated array (LMA) and electronically steerable parasitic array radiator (ESPAR) is proposed. This architecture exploits the advantage of low peak-to-average power ratio (PAPR) for power amplifier (PA) in LMA and compactness in ESPAR for constructing single-RF multiple-input multiple-output (MIMO) antennas. Therefore, it is superior to conventional MIMO in sixth-generation (6G) integrated sensing and communication (ISAC) system with orthogonal frequency division multiplexing (OFDM) scheme by reducing power consumption on RF chain and MIMO antenna size at the transmitter side. Specifically in this work, the overall system model for the proposed architecture is analyzed where far-field radiation patterns are used to transmit beamspace OFDM symbols. Based on the model, efficient optimization approaches to find the optimal load reactances that excite the required radiation patterns are provided. Simulation results on symbol correlation, PAPR, spectral efficiency (SE), energy efficiency (EE) and sensing accuracy of the proposed architecture are provided. It is shown that MIMO antenna with the proposed architecture has higher SE, EE and smaller PAPR with only minor compromise on symbol and sensing accuracy when compared to conventional MIMO antenna with same size, demonstrating the effectiveness and superiority of the proposed architecture.