Multilevel QAM demodulator, multilevel QAM demodulation method, and wireless communication system

A multilevel QAM demodulator comprising:

• an oscillator;
• an orthogonal detector converting an input signal into a common phase signal and an orthogonal signal by using an output from the oscillator;
• a phase rotation compensating circuit compensating for a phase rotation of the common phase signal and orthogonal signal;
• and
• a phase noise compensating circuit compensating for a phase noise of a common phase signal and an orthogonal signal which are output from the phase rotation compensating circuit,
• wherein the phase rotation compensating circuit includes
• a first phase rotator rotating a phase of each of the common phase signal and orthogonal signal converted by the orthogonal detector, on the basis of a first phase control signal;
• and
• a first phase difference calculator calculating a first phase difference signal based on a common phase signal and an orthogonal signal which are output from the first phase rotator, the first phase difference signal being used to obtain the first phase control signal, and
• the phase noise compensating circuit includes
• a second phase rotator rotating a phase of each of the common phase signal and orthogonal signal output from the first phase rotator, on the basis of a second phase control signal;
• a second phase difference calculator calculating a second phase difference signal based on a common phase signal and an orthogonal signal which are output from the second phase rotator;
• a first averaging unit averaging the first phase difference signal, and outputting a first average value;
• a second averaging unit averaging an absolute value of the second phase difference signal, and outputting a second average value;
• and
• a phase controller outputting the second phase control signal according to angle information obtained by multiplying the first average value by a correction value calculated using the second average value.

A demodulation method of a multilevel QAM demodulator performing a phase rotation compensation and a phase noise compensation on both a common phase signal and an orthogonal signal which are obtained by quasi-synchronous detection, the demodulation method comprising:

• calculating a phase difference signal based on the common phase signal and orthogonal signal after the phase rotation compensation;
• calculating a phase shift amount indicating a degree of a phase shift based on the common phase signal and orthogonal signal after the phase noise compensation;
• correcting the phase difference signal based on the phase shift amount;
• and
• performing a phase rotation for the phase noise compensation based on the corrected phase difference signal,
• wherein the phase noise compensation is performed after the phase rotation compensation, and
• wherein the phase shift amount is an absolute value of a phase difference signal based on the common phase signal and orthogonal signal after the phase noise compensation.

A demodulation method of a multilevel QAM demodulator including an oscillator;

• an orthogonal detector converting an input signal into a common phase signal and an orthogonal signal by using an output from the oscillator;
• a phase rotation compensating circuit compensating for a phase rotation of the common phase signal and orthogonal signal;
• and a phase noise compensating circuit compensating for a phase noise of a common phase signal and an orthogonal signal which are output from the phase rotation compensating circuit, the demodulation method comprising:
• performing, by the phase rotation compensating circuit, to rotate a phase of each of the common phase signal and orthogonal signal converted by the orthogonal detector, on the basis of a first phase control signal, to calculate a first phase difference signal based on the phase-rotated common phase signal and the phase-rotated orthogonal signal, and to obtain the first phase control signal by using the first phase difference signal;
• performing, by the phase noise compensating circuit, to rotate a phase of each of the common phase signal and orthogonal signal output from the phase rotation compensating circuit on the basis of a second phase control signal, to calculate a second phase difference signal based on the phase-rotated common phase signal and the phase-rotated orthogonal signal, to average the first phase difference signal and output a first average value, to average the second phase difference signal and output a second average signal, and to obtain the second phase control signal according to angle information obtained by multiplying the first average value by a correction value calculated using the second average value.