AN AUTOMATIC GAIN CONTROLLER OF QUADRATURE PHASE SHIFT KEYING DEMODULATOR

摘要

The present invention relates to a digital quadrature phase shift keying (QPSK) demodulator, and in particular, an automatic gain for calculating a magnitude of a modulated signal transmitted by shifting a phase of a carrier according to an information data signal using an approximation of a square root. The present invention relates to an automatic gain control device of a quadrature phase shift demodulator that enables a simple phase shift demodulator to be implemented by implementing a control device. A component receives an I-channel signal I and a Q-channel signal Q, respectively. An absolute value calculator 31 for calculating an absolute value of a signal and outputting an I channel absolute value 32 and a Q channel absolute value 33; An absolute value comparison unit 34 for receiving the I-channel absolute value 32 and the Q-channel absolute value 33 and comparing the magnitudes of the two absolute values and outputting a signal 35 according to the magnitude resu And an output signal 35 of the absolute value comparing unit 34 as a control signal, and receives the I-channel absolute value 32 and the Q-channel absolute value 33 from each other. And a signal magnitude calculator 36 for calculating and outputting a signal size s_magn by summing the doubled values. The automatic gain control device having the above configuration directly calculates the magnitude of the signal using a square root. By using an approximation formula, rather than performing normal operation, a simple logic circuit can be implemented, thereby simplifying and conveniently ASICting the entire QPSk demodulator.