| 摘要 |
PROBLEM TO BE SOLVED: To provide a system that can accurately estimate a carrier frequency of a QAM(quadrature amplitude modulation) signal of a high symbol rate even when the carrier frequency is produced at a frequency largely offset, with respect to object frequency. SOLUTION: A converter converts the QAM signal into an intermediate frequency(IF) signal and digitizes the IF signal at a prescribed sample rate. A complex signal generator extracts a real number component of the digitized IF signal from the digitized IF signal and applies Hilbert transformation to the extracted signal to obtain an imaginary number component of the digitized IF signal. Then the complex signal generator combines the real number component and the imaginary number component into a complex signal. A power unit applies a prescribed power to the complex signal and a fast Fourier transform(FFT) module applies FFT, having a prescribed sample number to the complex signal. A processor extracts the index of sampling after FFT, having a maximum absolute value and estimates the carrier frequency of the QAM signal on the basis of the prescribed power, the extracted index and the prescribed sample rate. |
