Frequency-domain distribution and band-width of unintentional modulation on pulse

Unintentional modulation on pulse (UMOP) is the basis for specific emitter identification and has been studied for decades. However, the isolated distribution of UMOP in frequency domain has not been investigated. This Letter first gives the signal model of UMOP, and then evaluates its frequency-domain distribution based on sinc-function fitting. Experiments on real-world data validate the effectiveness of the proposed method, and further indicate that UMOP mainly distributes in low frequencies with dramatically limited bandwidth. Furthermore, the proposed distribution density can also serve as a practical UMOP feature which exhibits better recognition performance than conventional spectrum features.