## 1 Introduction  
The demand for safety-critical applications (e.g., civil aviation, aircraft landing) using GNSSs has gained extensive and increased interest in recent years. With the advent of the new GNSSs, such as the European Union's Galileo system [1], the USA's modernized GPS [2] and China's Beidou/Compass [3], new radio navigation signals will be broadcast, and more attention has been devoted to the design of the signal structure, which is expected to increase the accuracy, availability, integrity and continuity of service, especially in the field of the safety of life (SOL) applications (e.g., the accuracy needed during the landing of an aircraft). High precision positioning and reliable SOL services represent the main challenges for the upcoming satellite navigation systems. The presence of disturbing signals, such as spurious, harmonic and electromagnetic interferences, will result in serious performance degradation for GNSS receivers. Radio frequency interference (RFI) is one of the biggest threats for satellite navigation systems. Although the satellite navigation system has a certain capability to be immune from interference, since the direct sequence spread spectrum (DSSS) is utilized, due to the low power of the received GNSS signals, the presence of intentional or unintentional disturbing signals, such as spurious, harmonic and electromagnetic interferences, will result in serious performance degradation for GNSS receivers. Among all of the different error sources that can potentially corrupt GNSS signals, RFI is particularly harmful, since, in some cases, it cannot be mitigated by a simple correlation process [4]. The jamming environment is threatening for satellite navigation systems. Many systems rely on the transmission of radio frequency (RF) energy in the L-band. For example, the European Galileo E5a and E5b radio bands, located within 1164-1214 MHz, occupy frequencies already allocated for aeronautical radio navigation services (ARNS), such as tactical air navigation (TACAN), distance measuring equipment (DME) and secondary surveillance radar (SSR) [5]. In addition, other RF transmissions, such as continuous wave (CW) signals originating from the European Digital Video Broadcast Terrestrial (DVB-T) service, can be considered as the main threat for the GNSS signals, since they appear in Radio Navigation Satellite System (RNSS) frequency bands. The presence of RFI and other channel impairments can heavily degrade the reception of useful GNSS signals, which results in poor navigation accuracy or complete loss of tracking for GNSS receivers. Currently, interference detection and mitigation (ID&M) have become very important issues for GNSS applications. Interference can be detected and mitigated through various means. On the hardware side, specialized instrumentation, such as choke rings or active beam-forming antennas, can be used to suppress interference and improve the reception of line of sight (LOS) satellite signals. The main drawbacks of these antenna techniques are their requirements for particular hardware configurations and their computational complexity [6; 7; 8]. In the GNSS receiver, a special front-end architecture design adopts pulse blanker or automatic gain control (AGC) to reduce interference. For example, a specific AGC and analog-to-digital converter (ADC) design performing digital pulse blanking has been implemented in the GPS L5 receiver [9]. In addition, a nonuniform ADC controlled by a digital AGC can be adaptively adjusted based on the interference power strength to obtain an optimized conversion gain of the ADC (_i.e._, the SNR loss in ADC) and improved receiver performance [10; 11]. However, theseapproaches require digital access to the feedback control of the AGC device, which is not a common output of generic analog front-ends used in the GNSS receivers. In the literature, several interference mitigation techniques have been proposed and investigated, and each of them differs according to the operate domain (time, frequency or space).