A novel high-speed NLA-16SQAM modulation module

The paper introduces a novel NLA-16SQAM (nonlinearly amplified superposed quadrature amplitude modulation) module that can transmit satellite data in X-band at a bit rate of 600 Mbps. Different from the conventional QAM, NLA-16SQAM signals are generated by combining two SQPSK signals. First, a serial data stream is split into four parallel streams that form two in-phase and quadrature phase signal pairs. Then the quadrature phase digit signals are set to lag behind the in-phase signals by one half symbol. Each pair of signals is converted from absolute codes into relative codes, and then sent into a SQPSK modulator. Two SQPSK output signals are amplified by their own saturated power amplifier, producing a 6 dB difference in their voltage levels, and they are then sent into a power synthesizer to obtain the NLA-16QAM signals. Not only can the NLA-16SQAM modulation module improve spectral efficiency, but it can also make the best of the precious energy on satellites.