Secondly , comparing with the algorithm that was given by english scholars a . k . nandi and e . e . azzouz in 1995 , this dissertation presents a modified automatic recognition algorithm of six kind of digital modulation types such as 2ask , 4ask , 2psk , 4psk , 2fsk and 4fsk , which only uses four key features , and has a very great exaltation in the rate of correct recognition and the performance of signal to noise , we puts forward the constitution of the best threshold which is applicable to the signal that changes within the scope of the signal to noise rate ( snr ) from 5db to 30db , and the overall success rate is not lower than 92 % when snr is over 7db 其次,针对1995年英国学者a . k . nandi和e . e . azzouz提出的针对2ask 、 4ask 、 2psk 、 4psk 、 2fsk和4fsk这六种常用的数字调制信号识别的算法,提出了一种数字信号调制方式识别算法( dmra )的改进算法。该算法仅利用四个特征参数,就可以识别这六种调制方式,而且在调制识别率和信噪比性能上都有了很大的提高,能够在信噪比不低于7db时,对实际信号的识别正确率高于92 % 。并且提出了最佳门限的设置方法,设置的门限适用于信噪比在5db ~ 30db范围内变化的信号。
