JP2004248219A5 - - Google Patents

Claims (6)

In the modulation type identification method for identifying the modulation type of the digital modulation signal of the quadrature amplitude modulation method, the difference between signal points at different amplitude positions is obtained from the constellation information corresponding to the modulation type of the digital modulation signal, and each modulation type is determined. The likelihood calculation signal points for each modulation type are determined from the difference obtained in step (b), and a plurality of likelihood values of the received digital modulation signal are compared with the determined likelihood calculation signal points for each modulation type. A modulation type identification method for discriminating a modulation type having a likelihood calculation signal point from which the smallest likelihood value is obtained from the modulation type of the received digital modulation signal. Amplitude correction means for calculating an average value of amplitude for each observation point of the received signal, calculating an amplitude after correction by correcting the amplitude for each observation point by the average value,
An amplitude difference calculating means for calculating an amplitude difference using the corrected amplitudes before and after the observation point calculated by the amplitude correcting means;
The likelihood for each likelihood calculation identifier is calculated according to the likelihood calculation signal point set in advance according to each amplitude phase modulation type to be the identification category and the amplitude difference calculated by the amplitude difference calculation means. Likelihood calculation means to
Cumulative addition means for cumulatively adding the likelihood for each observation point calculated by the likelihood calculation means for each likelihood calculation identifier over the total number of observation points;
A modulation type identification circuit comprising: identification determination means for identifying the amplitude phase modulation type of the received signal based on the cumulative addition result of the likelihood for each likelihood calculation identifier by the cumulative addition means. 3. The modulation type identification circuit according to claim 2, further comprising phase modulation type identification means for identifying the phase modulation type of the received signal in accordance with the received signal. Amplitude correction means for calculating an average value of amplitude for each observation point of the received signal, calculating an amplitude after correction by correcting the amplitude for each observation point by the average value,
An amplitude difference calculating means for calculating an amplitude difference using the corrected amplitudes before and after the observation point calculated by the amplitude correcting means;
The likelihood for each likelihood calculation identifier is calculated according to the likelihood calculation signal point set in advance according to each amplitude phase modulation type to be the identification category and the amplitude difference calculated by the amplitude difference calculation means. First likelihood calculating means for:
First cumulative addition means for cumulatively adding the likelihood for each observation point calculated by the first likelihood calculation means for each likelihood calculation identifier over the total number of observation points;
Signal normalization means for normalizing the received signal for each observation point;
Delay detection means for performing delay detection according to the reception signal normalized by the signal normalization means and the normalized reception signal obtained by delaying the normalized reception signal by one observation point;
A likelihood is calculated for each likelihood calculation identifier according to a likelihood calculation signal point set in advance according to each phase modulation type as an identification category and a signal after delay detection by the delay detection means. Two likelihood calculation means;
Second cumulative addition means for cumulatively adding the likelihood for each observation point calculated by the second likelihood calculation means for each likelihood calculation identifier over the total number of observation points;
Identification determination means for identifying the amplitude phase modulation type and the phase modulation type of the received signal based on the cumulative addition result of the likelihood for each likelihood calculation identifier by the first cumulative addition means and the second cumulative addition means And a modulation type identification circuit. Transmission path status estimation that estimates the status of the transmission path according to the received signal and adjusts the cumulative addition number of the first and second cumulative addition means or the identification criterion of the identification determination means according to the estimated transmission path status 5. A modulation type identification circuit according to claim 4, further comprising means. Demodulating apparatus characterized by comprising a demodulation means for demodulating the received signal based on the modulation type identified by the modulation type discrimination circuit according to any one of the preceding claims 2.