###### Abstract
In the presence of interference, it is more complicated for signal processing blocks to complete their duties. There are several sensitive blocks in a digital receiver that can be disrupted by even a low power interference. Thus, damage to digital receivers varies from complete packet lost to error increment and QoS reduction [10]. Before the reception chain, the mitigation stage tries to remove the interference while preserving the useful part of the desired signal as much as possible; however, suppressing the interference with minimum damage to the system performance is a very complicated task. Usually, before the mitigation block, a detector tries to accurately characterize and recognize the interference properties [11]. The type, the center frequency, and the bandwidth are common extracted features. After that, the mitigation mechanism is adaptively adjusted for optimum interference cancelation. Thus, generally speaking, the protective box before the receiver chain has two main sub-blocks [12]: the detector and the mitigation block. Structure of these two blocks changes depending on the type of the signal of interest (SoF) and the interference type. Fortunately, some systems already exist to mitigate the negative effects of those RFIs. Especially for the GNSS signals, different methods are designed to detect and suppress interferences [12,13]. Since the GNSS signals are wideband signals, it is easier to detect and suppress interference because the noise and power level are lower than narrowband interference. For this type of receiver, higher jamming to noise ratio (JNR) makes the interference easier to detect [14]. Compared to GNSS signals, which interferences are located on the top of the flat and wideband noise, with a modulated-narrowband signal such as a Digital Video Broadcasting-Satellite-Second Generation (DVB-S2) standard [15], the amplitude level of the signal is much higher than the noise. This research mainly focuses on modulated-narrowband digital communication signals. In a digital transmitter, output bit stream of data source first is mapped into two-dimensional space by the help of constellation modulator. A constellation diagram, such as phase-shift keying (PSK) or quadrature amplitude modulation (QAM), represents the signal as a two-dimensional diagram; however, such a baseband signal is ideal and has a spectrum with very low sidelobe decay rate that does not fit its frequency bandwidth. Thus, it is necessary to limit the effective bandwidth by the help of pulse shaping. Usually, pulse shaping uses raised-cosine filter due to its ability to minimize intersymbol interference (ISI) [15]. Visible interference part is located on the top of the signal power spectrum, thus the existing algorithm used for interference detection in a wideband signal does not work directly with a narrowband signal. Instead of JNR that compares power level of noise with interference power, the jamming to signal ration (JSR) that compares the signal power with interference power must be utilized. Figure 1 displays the visibility of the continuous wave interference (CWI) in different conditions for a modulated signal (narrowband). Target of figure one is to compare effect of JSR and signal to noise ratio (SNR) on detection performance. In Figure 1a, multiple carrier wave interferences (MCWI) with different JSRs is added to the modulated signal. Variation in JSR has an impressive effect on the amplitude of the CWI on top of original signal. Figure 1b tries to explain the effect of different SNRs on clarity of interference, thus the parameters of interference (center and power) are constant and additive white Gaussian noise (AWGN) with variable SNRs is added to the transmitted signal and then CWI (with fixed JSR) is added to the noisy signal. The same interference is utilized with different SNR level, thus only one peak is observed in Figure 1b. As it can be seen, for smaller SNR, the level of noise raises; however, it does not affect the position and visibility of the CWI peaks compared to the power level of the signal.