# SATCOM Earth Station Arrays Anti-Jamming Based on MVDR Algorithm
## 1 Introduction  
Satellite communication is widely used in civilian and military communication due to its advantages of wide coverage, large communication capacity, and no geographical restrictions [1, 2]. With the rapid development of military technology, information warfare has become an important form of modern warfare, and jamming and anti-jamming have naturally become the key combat methods that countries' armies are competing to research. Satellite communication faces three different jamming risks: uplink jamming, downlink jamming, and inter-satellite link jamming [3]. Downlink jamming requires low power, controllable range of influence, and is not easily detected by the other party, making it suitable for local wars under information conditions. Portable small satellite communication ground station antennas have a small diameter, simple structure, and a large number, but they have few anti-jamming measures and weak capabilities. When their downlink is interfered with, the communication quality seriously deteriorates, and even the received signal-to-noise ratio is lower than the threshold, causing communication interruption, so it is urgent to improve their anti-jamming capabilities. Anti-jamming technologies for earth stations mainly include spread spectrum technology, coding and modulation technology, and adaptive nulling antenna technology [4]. Direct sequence spread spectrum [5] spreads the baseband signal over a wide spectrum, effectively resisting narrowband signal jamming. However, the spreading code consisting of pseudo-random sequences has a rate much greater than the information rate, with one information bit width equal to multiple periods of the pseudo-random sequence, resulting in lower spectrum utilization. Frequency hopping technology [6] rapidly and discretelychanges the carrier frequency according to a preset rule, making it difficult for jamming to target the signal frequency, thus ensuring reliable transmission of information. However, its anti-tracking jamming effect is limited. Coding and modulation technology encodes the baseband signal according to certain rules and converts it into a modulated signal suitable for transmission in the channel, effectively improving the reliability and efficiency of the communication system. It is widely used in modern communication. Adaptive nulling antenna technology aligns the nulls with the direction of the jamming signal by weighting the antenna array elements, achieving effective suppression of jamming [7]. Time-domain filtering anti-jamming technology is simple to implement, with low costs and anti-narrowband jamming ability of 10-35 dB, but not ideal for filtering wideband jamming signals. Antenna anti-jamming technology is mature, flexible, and has a high degree of freedom, so multiple satellite earth station antennas can be arrayed and adaptive beamforming technology can be used to improve the anti-jamming ability of the satellite earth station array. The MVDR [8] algorithm is a typical adaptive beamforming technology that minimizes the output power of jamming and noise while keeping the array output power constant, thus effectively suppressing jamming. The MVDR algorithm is a classic spatial filtering algorithm that can improve the receiver's anti-jamming performance by about 40-50 dB. However, the traditional MVDR algorithm is sensitive to errors in the source direction and element, and its beamformer performance severely degrades when errors exist. Based on this, [PERSON] proposed the diagonal loading-based MVDR algorithm [9], which improves the robustness of the MVDR algorithm. Currently, the MVDR algorithm is widely used in radar, communication, sonar, signal processing, and other fields [10]. Reference [11] uses the MVDR algorithm in beam-domain preprocessing to reduce the impact of strong jamming outside the beam domain on high-resolution wave direction estimation algorithms.