LPI Radar detection: SNR performances for a dual channel Cross-Correlation based ESM Receiver

Detection of low probability of intercept (LPI) radar signal is an important issue for an electronic support measure (ESM) receiver. In the present work a LPI radar signal is assumed to be phase modulated by a code. The ESM receiver does not have any knowledge of the modulating code and carrier frequency of the LPI radar signal; it can only make general assumptions about the occupied bandwidth. The lack of knowledge of the modulating code strongly constrains the maximum obtainable signal to noise ratio (SNR) by a typical ESM receiver. This paper presents a receiver architecture which allows an improvement of the achievable SNR: the proposed architecture combines in an optimized way a uniform filter bank with the cross-correlation technique: the idea is to use coherent processing on both channels of a dual receiver and then integrate the cross product in order to recover all the energy of the LPI signal. However, since the same signal received is used to demodulate it, nonlinear effects arise and the resultant SNR has to be elaborated. Theoretical SNR performances, derived for a generic case, will be compared with simulations carried out with realistic phase modulated LPI signals. Measurements done on new generation Elettronica SpA (ELT) digital receiver based ESM shall be finally compared with both theoretical and simulation results.