Product-Based Pulse Integration to Combat Noise Jamming SOHAIL AHMED Air University, Islamabad Pakistan A novel radar pulse integration technique is proposed in which the received signals in various returns from the target during one scan are multiplied with each other instead of the conventional summing up. Using the Mellin transform, mathematical expressions are derived that pave the way for computation of probability of detection and probability of false alarm in the context of this technique. Analytical and simulation results show that the proposed product-based pulse combining is more resistant to noise jamming, as compared to conventional noncoherent pulse integration, under certain conditions. Manuscript received May 12, 2013; revised September 16, 2013, August 8, 2013; released for publication March 5, 2014. DOI. No. 10.1109/TAES.2014.130322. Refereeing of this contribution was handled by S. Blunt. Author’s address: Institute of Avionics and Aeronautics, Air University, E-9, Islamabad 44000, Pakistan, E-mail: (sohailahmed71@hotmail.com). 0018-9251/14/$26.00 C  2014 IEEE I. INTRODUCTION Pulse integration [1] is employed in radar receivers to combine the signals received in multiple pulses from the target within one scan in order to increase the signal-to-noise ratio (SNR). Increased SNR translates into increased probability of detection and reduced probability of false alarm. Three main types of pulse integration techniques have been proposed [2]: coherent, noncoherent, and binary. In coherent pulse integration, phase information of the signals received in various pulses is retained when they are added, while in noncoherent pulse integration (NCPI), only the magnitudes of the signals are combined. In the context of binary pulse integration, binary detection decisions are made on each pulse and then the multiple decisions are combined using appropriate criteria. While coherent integration yields maximum SNR gain, a noncoherent scheme offers the advantage of simplicity. Barrage or noise jamming [1], whether an electronic countermeasure or accidental, has the potential of deteriorating the detection performance of a radar by superimposing Gaussian noise in the receiver bandwidth. Due to raised noise floor, the probability of false alarm can increase to an unacceptably high level. While modern radars exploit techniques such as space-time adaptive processing or features offered by cognitive radars [3–5], conventional antijamming techniques continue to form part of the electronic counter-countermeasure (ECCM) suite. Frequency hopping or agility [1] is one such technique that is often employed to rapidly change the carrier frequency of the radar, thus avoiding certain jammed frequencies. As far as the author is aware, in the published literature the performance of the aforesaid pulse integration techniques has not been evaluated when the radar is assumed to be operating in the presence of noise jamming. Very little work indeed has focused on antijamming techniques in radars [6, 7]. Hence, in this contribution, we focus on the antijamming performance of radar pulse integration. Specifically, we propose a novel noncoherent technique of pulse integration in which the signals received in multiple pulses returned from a target during the same scan are combined noncoherently by multiplying, instead of adding, the detector’s multiple outputs. The proposed scheme is motivated by various diversity schemes proposed for frequency-hopping noncoherent frequency-shift-keying-based communication signals [8, 9], whose detection process is similar to conventional noncoherent pulse integration. In addition to SNR gain, these combining schemes exploit diversity and suppress the jamming effect through various signal-processing operations. This fact suggests that diversity offered by pulse integration can be used in conjunction with frequency agility and a suitable combining scheme to suppress jamming effects. Hence, we choose product combining [8, 9] because of its attractive antijamming performance and simple implementation, and apply it for IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS VOL. 50, NO. 3 JULY 2014 2109