A method for blind detection sub-pulse phase modulated (PSK) radar pulses hidden in the noise is proposed. Indeed, PSK radar signals are known for their low probability of interception: their statistics are similar to the statistics of a noise, and, furthermore, they are usually transmitted with low power, in or below the noise level. The proposed method is based on the successive estimation of the correlation matrix of the received signal and eigenanalysis techniques. We consider a non-cooperative context, hence no a priori information is available (the coding sequence, the pulse duration, the pulse repetition interval, etc., are unknown). A theoretical analysis shows that detection is possible with low signal to noise ratio at the detector input. Experimental results are provided to illustrate the approach. The method is also able to estimate the pulse repetition interval of the PSK radar signal.