A high-speed OQPSK module with direct modulation mode in RF

The work presents an efficient satellite OQPSK (offset QPSK) module of direct modulation in RF. The module´s modulation rate can reach 150 Mbps in L band, or 600 Mbps in X band. Compared to the conventional QPSK, the main difference of OQPSK is that its Q-channel digits lag behind the I-channel digits by one half symbol. Thus, OQPSK avoids the 180° phase transitions and therefore has the better power spectrum. The direct modulation in RF is also superior to the conventional IF modulation in terms of structure and reliability. The paper also introduces a time-series analysis method, signal integrity simulation and some design fundamentals for high-speed printed circuit boards involved in the module.