Modulation classification of BPSK and QPSK signals using a two element antenna array receiver

Modulation classification is a technique that automatically identifies the modulation type of a received signal. It has found a variety of military and commercial applications. In some practical cases such as signal interception, the intercepted signal is very weak and a long observation time is needed to maintain an acceptable probability of correct identification. This paper presents an algorithm using a two element antenna array receiver for BPSK and QPSK classification to increase the probability of correct classification for a short data record. The approach is to perform the generalized likelihood ratio test. The unknown phase shift between the two received signals due to the spatial separation of the antenna elements is estimated using maximum likelihood or linear least squares technique. It is then used in the likelihood ratio test for classification. Simulations show that the proposed classifier has high accuracy and is superior to the classifier that has only one received antenna.