Patent ID: 8774645

Claim:
A method for controlling a bias point of a Differential Quadrature Phase Shift Keying (DQPSK) demodulator, comprising: step 1: applying a first bias voltage to an I-path of the DQPSK demodulator, applying a second bias voltage to a Q-path of the DQPSK demodulator, and applying identical pilot voltage signals to the I-path and the Q-path respectively; step 2: executing filtering processing on an I-path differential current signal of the DQPSK demodulator collected by a balance receiver and determining a bias point real-time value θ I of the I-path, and executing filtering processing on a Q-path differential current signal of the DQPSK demodulator collected by the balance receiver and determining a bias point real-time value θ Q of the Q-path; and step 3: performing feedback control to the first bias voltage according to the bias point real-time value θ I , and performing feedback control to the second bias voltage according to the bias point real-time value θ Q , so that θ I reaches an expected bias point value of the I-path and θ Q reaches an expected bias point value of the Q-path; executing the step 2 and the step 3 cyclically at preset regular intervals, so that θ I remains consistently the expected bias point value of the I-path and θ Q remains consistently the expected bias point value of the Q-path.