Anti-jamming Performance Research Articles

An Improved Image Steganography Scheme Based on Partial Preservation Embedding Algorithm for Wireless Visual Sensor Networks

With the continuous improvement of encryption algorithms, some applications based on the architecture of wireless visual sensor networks have gradually shifted their attention to the imperceptibility and antijamming performance of secret images. To reduce the probability of secret images being detected, the current research focuses on hiding secret data in the least-significant bit of the cover image in the spatial domain or embedding data into the coefficients of the high-frequency band in the transformational domain, which usually leads to poor performance in a hostile environment. Therefore, some researchers proposed to substitute the coefficients of the medium-frequency band in the transformational domain with secret information to enhance the anti-interference performance. However, this idea would severely affect the imperceptibility of secret images. As a result, an improved version based on the partial preservation embedding algorithm was designed in this paper. Theory analysis and simulation results indicate that the proposed scheme performs better than the existing methods by directly substituting the coefficients of the medium-frequency band in the transformational domain, especially in the case of strong noise interference.

Research on Signal Processing Method of X-band Multifunctional Phased Array Radar

The signal processing algorithm is an important component of the three major technical fields of radar, and it occupies an important position in the radar system. It is the basis for phased array radar to achieve multi-function. The rapid development of modern signal processing technology has greatly promoted the development and application of radar technology. Modern radar simulation systems can simulate and optimize signal processing algorithms, and quickly adjust system parameters; because it adopts modularization and systematically encapsulated, it can be used repeatedly in different environments or platforms. The continuous development of modern signal processing technology has improved the performance of the radar system, especially in improving the radar's target detection capability and anti-jamming performance. Because signal processing occupies a very important position in radar systems, this paper studies the signal processing in radar systems. This paper analyzes the signal processing process of the multifunctional phased array radar, and conducts corresponding analysis and research on the key technologies.

Phase Transitions in Frequency Agile Radar Using Compressed Sensing

FAR has improved anti-jamming performance over traditional pulse-Doppler radars under complex electromagnetic circumstances. To reconstruct the range-Doppler information in FAR, many compressed sensing (CS) methods including standard and block sparse recovery have been applied. In this paper, we study phase transitions of range-Doppler recovery in FAR using CS. In particular, we derive closed-form phase transition curves associated with block sparse recovery and complex Gaussian matrices, based on prior results of standard sparse recovery under real Gaussian matrices. We further approximate the obtained curves with elementary functions of radar and target parameters, facilitating practical applications of these curves. Our results indicate that block sparse recovery outperforms the standard counterpart when targets occupy more than one range cell, which are often referred to as extended targets. Simulations validate the availability of these curves and their approximations in FAR, which benefit the design of the radar parameters.

Jamming Detection in Broadband Frequency Hopping Systems Based on Multi-Segment Signals Spectrum Clustering

Accurate jamming detection in the broadband frequency hopping (FH) systems plays a vital role in improving the anti-jamming performance of the communication systems. The traditional jamming detection algorithms are prone to misjudge FH communication signals as jamming signals, leading to inaccurate jamming detection. Therefore, this paper proposes a jamming detection algorithm for broadband FH systems based on multi-segment signals spectrum clustering (MSSC). According to the difference in the time-frequency characteristics between FH signals and jamming signals, the proposed algorithm accurately detects the jamming by clustering the spectral components of signals in multiple periods. In addition, a jamming detector suitable for broadband FH systems is designed and the theoretical solution to the threshold factor of signal detection based on the Welch spectrum is also given in this paper. The simulation results show that the MSSC-based jamming detection algorithm proposed in this paper can reduce the jamming false detection probability and significantly improve the estimation accuracy of jamming parameters, effectively overcoming the defects of the traditional FFT-based energy detection and the multi-hop accumulation algorithms whose detection accuracy is sensitive to FH signals.

Numerical simulation of multi output radar orthogonal waveform based on chaos optimization algorithm

Aiming at the problems of low probability of interception and poor anti-jamming performance of multi output radar, the numerical simulation of orthogonal waveform of multi output radar based on chaos optimization algorithm is proposed. Firstly, chaotic frequency coding is applied to multi output radar signal, and different frequency modulation is applied to different sub pulse. At the same time, in view of the low efficiency of numerical simulation algorithm in large space and high dimension optimization, GASA algorithm is used to increase the diversity of chaotic optimization algorithm process. According to the specific working mode, the initial phase of each cycle of multi output radar orthogonal waveform is obtained, and the number of numerical simulation of multi output radar orthogonal waveform is established Model. The experimental results show that the proposed method can improve the radar energy utilization and the signal-to-noise ratio of the echo signal, allocate the transmitting energy reasonably, and keep the structural stability of LFM signal frequency changing continuously with time.

Multi-User Secure Receiving Algorithm Based on Blind Recovery in MIMO Network

In order to optimize the performance of data transmission in multiple input multiple output (MIMO) wireless communication systems, a spread spectrum self-interference system based on channel inverse matrix modulation is proposed. First of all, we improved the spread spectrum method and proposed the DIMMSS(channel inverse matrix modulation spread spectrum) spread spectrum method based on the channel inverse matrix. And a simulation comparison experiment was carried out for the anti-interference ability and anti-eavesdropping ability of this method. Secondly, this paper also proposes two blind despreading methods based on Walsh-hadamard algorithm and cluzeau algorithm. We studied the anti-jamming performance of these two algorithms, and optimized the blind despreading process according to their different characteristics of computational complexity. Experimental results show that compared with ordinary direct sequence spread spectrum, the spread spectrum self-interference system can not only improve the confidentiality and security of the transmitted signal, but also greatly simplify the receiving equipment. It has certain application value in the military and civilian fields.

Dictionary Learning and Waveform Design for Dense False Target Jamming Suppression

For linear frequency modulation (LFM) pulse radars, dense false targets generated by new system jamming seriously damage the performance of such radar systems. In order to avoid the influence of dense false target jamming, an anti-jamming strategy combining waveform design and sparse decomposition are proposed. Specifically, the radar system transmits a random pulse initial phase (RPIP) signal, and uses peak detection method to detect the deception jamming. The phase distribution of the RPIP signal is partially randomly perturbed for a jamming, and we use optimization algorithm to design a phase perturbed LFM (PPLFM) signal with good autocorrelation characteristics. Using the correlation function of the designed signal, the target sample set and the jamming sample set are constructed, and the target echo and the jamming signal are separated using designed dictionary learning method to achieve suppression of dense false target jamming and range side-lobes. The effectiveness of the proposed method is verified by numerical simulation, and the results proved that this proposed method maintains good anti-jamming performance under low signal-tonoise ratio (SNR).

System anti-jamming technology in the design of intelligent single chip computer constant current source of field strength machine

With the development of the electric power industry, the technical level of automatic testing equipment for the reliability of electrical component circuit breakers in the transmission and distribution network is getting higher and higher. The stability and accuracy of the test power supply are the basis for ensuring the pass rate of the test product. Most of the electrical testing and testing equipment has defects such as inaccurate power supply current regulation, low power, and low level of intelligence, which are difficult to meet the testing requirements. Based on the theory of a closed-loop control system, this paper adopts embedded system design technology to realize a high-current, high-power, high-stability digital constant current source system for line detection. This paper studies the rule-based intelligent anti-jamming decision engine design and system anti-jamming performance analysis of NC-OFDM system. We give the design of an intelligent anti-jamming decision engine based on rule-based decision-making, and focus on two intelligent anti-jamming decision-making algorithms: Adaptive Modulation and Coding (AMC) algorithm based on signal-to-noise ratio difference and packet error rate and Adaptive Sub-Band Selection (ASBS) algorithm. Experimental test results show that the output current range is 200 mA to 2000 mA, the system has realized a microstep adjustment of±5 mA, and the absolute error of current measurement is less than 0.3%+4 mA. The system is stable and reliable, and has high practical value in the field of high precision and low power.

Intelligent Reflecting Surface Assisted Anti-Jamming Communications: A Fast Reinforcement Learning Approach

Malicious jamming launched by smart jammers can attack legitimate transmissions, which has been regarded as one of the critical security challenges in wireless communications. With this focus, this paper considers the use of an intelligent reflecting surface (IRS) to enhance anti-jamming communication performance and mitigate jamming interference by adjusting the surface reflecting elements at the IRS. Aiming to enhance the communication performance against a smart jammer, an optimization problem for jointly optimizing power allocation at the base station (BS) and reflecting beamforming at the IRS is formulated while considering quality of service (QoS) requirements of legitimate users. As the jamming model and jamming behavior are dynamic and unknown, a fuzzy win or learn fast-policy hill-climbing (WoLF–CPHC) learning approach is proposed to jointly optimize the anti-jamming power allocation and reflecting beamforming strategy, where WoLF–CPHC is capable of quickly achieving the optimal policy without the knowledge of the jamming model, and fuzzy state aggregation can represent the uncertain environment states as aggregate states. Simulation results demonstrate that the proposed anti-jamming learning-based approach can efficiently improve both the IRS-assisted system rate and transmission protection level compared with existing solutions.

Binary-Sequence Frequency Hopping Communication Method Based on Pseudo-Random Linear Frequency Modulation

To improve the signal detection performance of binary-sequence frequency hopping communication when the complementary channel is jammed, a binary-sequence frequency hopping communication system based on pseudo-random liner frequency modulation (LFM) is proposed. The transmitting end uses the chirp signal to carry out the in-band spread spectrum of the binary-sequence frequency hopping signal, and then sends it out through the radio frequency front end. At the receiving end, the received signal is dehopped and processed by fractional Fourier transform. The source information is obtained by sampling decision. Firstly, a binary-sequence frequency hopping system model based on pseudo-random LFM is constructed. Secondly, the bit error rate expression of anti-partial band jamming and follower jamming under the Rice channel is derived. The results show that this method has at least 5 dB performance gain than binary sequence frequency hopping for different parameter settings under partial band jamming and follower jamming, and the anti-jamming performance is significantly better than the conventional frequency hopping communication.

Single-Antenna-Based GPS Antijamming Method Exploiting Polarization Diversity

The vulnerability of Global Positioning System (GPS) receivers to jammers is a major concern owing to the extremely weak received signal power of GPS. Researches have been conducted on a variety of antenna array techniques to be used as countermeasures to GPS jammers, and their antijamming performance is known to be greater than that of single antenna methods. However, the application of antenna arrays remains limited because of their size, cost, and computational complexity. This study proposes and experimentally validates a novel space-time-polarization domain adaptive processing for a single-element dual-polarized antenna (STPAPS) by focusing on the polarization diversity of a dual-polarized antenna. The mathematical models of arbitrarily polarized signals received by dual-polarized antenna are derived, and an appropriate constraint matrix for dual-polarized-antenna-based GPS antijam is suggested. To reduce the computational complexity of the constraint matrix approach, the eigenvector constraint design scheme is adopted. The performance of STPAPS is quantitively and qualitatively evaluated through experiments as follows. 1) The carrier-to-noise-density ratio (C/N0) of STPAPS under synthetic jamming is demonstrated to be higher than that of the previous minimum mean squared error (MMSE) or minimum variance distortionless response (MVDR) based dual-polarized antenna methods. 2) The strengths and weaknesses of STPAPS are qualitatively compared with those of the previous single-element dual-polarized antenna methods that are not based on the MMSE or MVDR algorithms. 3) The characteristics of STPAPS (in terms of the directions and polarizations of the GPS and jamming signals) are compared with those of the conventional two-element single-polarized antenna array method, which has the same degree of freedom as that of STPAPS.

A superior selective and anti-jamming performance triethylamine sensing sensor based on hierarchical WO3 nanoclusters

Synthesizing materials with specific orientation growth or exposed active facets have emerged as a feasible and low-cost approach to improve sensing performances according to recent literatures. Inspired by this, high ordered WO3 nanoclusters (NCs) were synthesized successfully by a facile and no time-consuming hydrothermal reaction in this work. The ordered WO3 NCs were piled up with by numerous of monocrystalline nanorods that were very close in orientation, and the sensor based on above NCs exhibited excellent triethylamine (TEA) detectability in terms of ultra-high response (137–50 ppm TEA), extremely-fast response speed (1.5 s–50 ppm TEA), low detection limit (500 ppb) to TEA. Moreover, it can not only effectively distinguish amine gas from ordinary volatile organic gas, but also can maintain stable and accurate monitoring toward TEA in mixed gases environment on long-term basis. The unique formation mechanism and superior TEA sensing mechanism of WO3 NCs were discussed in detail.

Research on Fuzzy Adaptive PID Control of Hydraulic System of Pitch–Propeller

Based on the analysis model, a fuzzy adaptive PID control strategy is proposed, which is based on the analysis model, which is based on the analysis model. In this paper, the hydraulic system model of the pitch valve is established by analyzing the flow and the motion equation of the pitch system. Rule table, in order to achieve the PID parameter online tuning. The simulation results show that the fuzzy adaptive PID control has better tracking performance and better anti-jamming robust performance.

Jamming Resilient Tracking Using POMDP-Based Detection of Hidden Targets

This paper considers the anti-jamming optimization problem for tracking multiple moving target flight vehicles in the presence of deception jammers. Since the radar is not able to separate the real target vehicles from a large number of deceptive vehicles, we promote the existing non-anti-jamming tracking model to the anti-jamming partially observable Markov decision process-based (POMDP-based) game tracking model by establishing a new anti-jamming Bayesian tracker. The proposed tracker is able to separate the hidden real target vehicles and establish their accurate trajectories, but the limited radar resources will decrease the accuracy. In order to effectively utilize the limited resources to guarantee the anti-jamming performance, this work deduces the anti-jamming performance gradients with respect to the resource management policy, which can be estimated with the asymptotically vanished biases. With the gradient estimates, the optimal anti-jamming resource management policy can be found with the tolerable complexity. The convergence analysis shows that the algorithm converges to a Nash equilibrium solution with probability 1. Numerical results show that the proposed algorithm can obtain the accurate target trajectories in the presence of jammers.

Design and Realization of Automatic Test System for Anti-Jamming Performance of GNSS Receivers

The performance test is a key part of the anti-jamming the global navigation satellite system (GNSS) receivers in researching and production. To solve the big workload and cumbersome in performance tests, an automatic test system is proposed in this paper. This system, whose core part is software which designs in Microsoft Visual Studio, can automatically control jammer, holder and anti-jamming antenna. The test software can automatically receive data from the navigation receiver and the anti-jamming antenna, can automatically statistics the carrier to noise ratio (CNR) and position information, also can automatically monitor the jam to signal ratio (JSR) in real time. Taking the CNR and the position information as anti-jamming performance test indicators, the software can automatically control the radio frequency (RF) power of jammer by setting the start, stop and step values of the jammer power. The test result shows that it can realize the automatic test after setting the necessary parameter. Also, it can automatically generate test report after completing the test. This system improves the efficiency of the anti-jamming performance test of GNSS receivers.

Synthesis of homogeneous carbon quantum dots by ultrafast dual-beam pulsed laser ablation for bioimaging

Pursuit of an ultrafast and highly efficient method to fabricate homogeneous carbon quantum dots (CQDs) with high quantum yield is a persistent objective for photoluminescence (PL) mechanism and bioimaging. Here, the CQDs were fabricated through ablation of low-cost carbon cloth by ultrafast and highly efficient dual-beam pulsed laser ablation. Unlike previous reports, a single laser beam is divided into double beams by a beam splitter in this work for shortening laser ablation time and improving ablation yield. More importantly, the obtained CQDs are more homogeneous than those obtained by single-beam pulsed laser ablation, and the corresponding quantum yield of emission is as high as 35.4%. The homogeneous CQDs show a stable and excitation-independent PL emission, which is attributed to the electron transition from the π∗ state to the surface state rather than from the π∗ state to the π state based on our experimental evidence. Furthermore, the CQDs have a good stability and excellent antijamming performance, which are well suitable for cell bioimaging. Therefore, a ‘dual-beam pulsed ablation’ technique proposed as an ultrafast method is used to fabricate homogeneous CQDs with high quantum yield for the study of PL emission mechanism and cell bioimaging.

Design of Heterogenous Two-Element Array Antenna on an Electrically Thick Substrate for High Isolation and Low Pattern Correlation Using Modal Difference in Radiation Patterns

In this paper, we propose a novel design of a two-element array antenna on an electrical thick substrate with an extremely narrow array distance. The proposed array consists of a rectangular ring patch printed on a thick substrate and a monopole wire in the center of the substrate. Each element has a modal difference in the radiation pattern, causing high isolation and low correlation between the array elements. From the measurement results, the monopole and patch elements exhibit reflection coefficients of −10 dB and −10.7 dB with peak gains of 3.8 dBi and 6.1 dBi, respectively, at 1.6 GHz. The mutual coupling between the two elements is −20.7 dB. For modal analysis of the antenna pattern, spherical mode decomposition is performed on the radiation patterns of the two elements, and low envelope correlation coefficient levels below 16% are maintained. We also investigate the antijamming performance using a power inversion algorithm in a practical pattern nulling application; a null depth of −47.7 dB and a null width of 33.2° are obtained when the interference signal arrives at the elevation angle of 45°.

Design of Multifunctional Mesosphere-Ionosphere Sounding System and Preliminary Results.

This paper describes a novel sounding system for which the functions of the medium frequency (MF) radar and the ionosonde are integrated on the same hardware platform and antenna structure, namely the middle atmosphere-ionosphere (MAI) system. Unlike the common MF radar, MAI system adopts the pseudo-random (PRN) phase-coded modulation technology, which breaks the limitation of the traditional monopulse mode. Through the pulse compression, only a small peak power is needed to achieve the signal-to-noise ratio (SNR) requirement. The excellent anti-jamming performance is also very suitable for the ionospheric sounding. One transmitting and six receiving modes are adopted for the MF sounding. While neglecting the structure of the T/R switches, the coupling interference between the transmitter and the receiver may also be avoided. Moreover, by employing a miniaturized antenna array composed of progressive-wave antennas for the MF receiving and ionospheric sounding, the MAI system takes account of the requirements of the inversion algorithms of MF radar and the large bandwidth need for the ionospheric sounding concurrently. Such an antenna structure can also greatly simplify the system structure and minimize the difficulty of deployment. The experiments verified the availability of the system scheme and its engineering application significance. Through further analysis of the sounding data, the wind field of the mesosphere, the electron density of D layer and electron density profile from layers E to F were obtained at the identical location. The capability of MAI system can play an important role in studying the interaction and coupling mechanism between the mesosphere and ionosphere.

Spatial Anti-Jamming Scheme for Internet of Satellites Based on the Deep Reinforcement Learning and Stackelberg Game

The anti-jamming communication of the heterogeneous Internet of Satellites (IoS) has drawn increasing attentions due to the smart jamming and high dynamics. This paper investigates a spatial anti-jamming scheme for IoS, with the aim of minimizing anti-jamming routing cost via Stackelberg game and reinforcement learning. Firstly, we formulate the routing anti-jamming problem as a hierarchical anti-jamming Stackelberg game. It has been proved that there is a Stackelberg equilibrium (SE) in the proposed game. Secondly, the spatial anti-jamming scheme for IoS consists of two stages: the available routing selection and the fast anti-jamming decision. To tackle the high dynamics caused by the unknown interrupts and the unexpected congestion, we propose a deep reinforcement learning based routing algorithm (DRLR) to obtain an available routing subset; Furthermore, to make a fast anti-jamming decision, we propose a fast response anti-jamming algorithm (FRA) based on the available routing subset. The user utilizes DRLR and FRA algorithms to empirically analyze the jammer's strategies and adaptively make an anti-jamming decision according to the dynamic and unknown jamming environment. Finally, the simulations have shown that the proposed algorithm has lower routing cost and better anti-jamming performance than existing approaches, and the anti-jamming policies converge to the SE.

Antijamming Receiver With Hybrid Blanking—Clipping for DCSK System

Although investigating performances of existing chaotic communication systems (CCSs) and proposing new CCSs have been extensively investigated, designing antijamming (AJ) receivers for CCSs has been rarely considered. AJ receivers for CCS are of paramount importance in cases that the inherent AJ capability of CCSs does not work well, i.e., when the power of jamming signals is larger than that of chaotic signals. Motivated by this fact, in this article, we consider a differential chaos shift keying (DCSK) system under a Gaussian pulse jamming condition. We propose an AJ receiver with a hybrid blanking-clipping mechanism to enhance the AJ performance of the considered system. We also derive closed-form expressions of the signal-to-interference-plus-noise of the outputs of the blanking and clipping blocks, which are then to be used to obtain optimal blanking and clipping thresholds for additive white Gaussian noise (AWGN) channel. Moreover, an optimal weighting factor used for combining the outputs of the blanking and clipping blocks is also provided. We show that the proposed receiver considerably outperforms existing receivers.