A system and method using a Costas loop to effect accelerated convergence with minimal system complexity. The system comprises an in-phase-limiter and a quadrature-phase limiter, operatively coupled to an EXCLUSIVE-OR gate, for exclusively-ORing an in-phase-sign signal and a quadrature-phase-sign signal...http://www.google.com.tw/patents/US5640425?utm_source=gb-gplus-share專利 US5640425 - Fast-acting costas loop
