IR active jammers or the directed infrared counter measures(DIRCM)generate IR signals which attack the guidance signals passed to the sensors in IR-guided weapons. They provide IR signals with appropriate frequency, phase and intensity which will be superposed on those produced by the IR energy of the target passing through the reticle. When both the jamming signal and the modulated target energy signals are received by the missile"s IR sensor, they cause the tracker to produce incorrect guidance commands and push the target out of the field of view (FOV). In this paper, the seeker signals of a crossed four slits or crossed array detectors (CAT) infrared seeker will be simulated. Then the active jammer signal is modeled and simulated. After that, the effect of all the active jammer parameters will be discussed and simulated. Finally, the conditions or the ranges of these parameters in which the active jammer can affect the seeking process will be stated.

One of the important parts of the infrared seeker is the counter countermeasure part. Seeking in a field of view with the existence of jammers is not simple and needs effective algorithms. In this paper, several methods of the detection in a crossed array trachers (CAT) seeker will be designed, simulated and evaluated. These methods depend on detecting the appearance of the flare using analzing the two channels signals.