Improving Power Amplifier Efficiency of Zero-Crossing Modulation at Sub-THz Frequencies

Utilizing the vast bandwidths available in the THz and sub-THz bands poses significant challenges, particularly with regard to the power consumption of the analog front end. For example, the analog-to-digital converter (ADC) power consumption is suspected to increase significantly due to the increase in bandwidth. As shown in prior work, reducing the ADC’s amplitude resolution down to 1-bit and using tailored modulation schemes, such as zero-crossing modulation (ZXM), can partly mitigate this issue. However, the power amplifier (PA) at the transmitter typically dominates the overall power consumption. Thus, in this work we evaluate the PA efficiency of ZXM under non-linear distortions and propose two techniques to enhance PA efficiency: i) offsetting the in-phase and quadrature components by half a symbol period, and ii) maximizing output power by allowing strong distortions. Our results demonstrate that combining these approaches achieves high amplification efficiency and leads to performance gains in terms of symbol error rate.