FM Jamming Research Articles

Research on Radar Jamming for Detection Performance

Radar jamming plays an important role in modern military affairs. The current radar jamming technology is mainly divided into two parts: suppressive jamming and deceptive jamming. This paper applies the jamming effect of multi-false target jamming in deceptive jamming and noise AM jamming, noise FM jamming, and noise PM jamming in suppressive jamming to the radar’s echo signal. Besides, this paper studies their influences from the aspect of target detection results through MTI and the influence of these jamming methods on the radar detection probability through CFAR. The experimental results can directly show the influence of interference measures on detection results and detection probability, and prove the effectiveness of these interference methods.

Method Research and Realization of Noise FM Jamming Based on DDS Technology

Noise FM jamming which has wide jamming band and large noise power is widely used in processing backup jamming to radar, fuze and communication. The paper adopt DDS combines with characteristic of FPGA chip to generate noise FM jamming. The method has large improvement in precision, structure and speed, and has broad application and prospect.

Anti-Jamming Technology of SAR Seeker for Forward Squint of Aircaft

The SAR seeker has the capability of detecting all day long and all-weather. The imaging guidance of SAR can revise the error of inertial navigation, greatly improved the precision of the aircraft. However, the SAR seeker is vulnerable to interference from the other side, which affects imaging and guidance capability. In this paper, the basic principle, model and jamming effect of common noise, FM jamming and pulse jamming are given on the basis of introducing the working principle of SAR seeker. On this basis, this paper focuses on the anti-noise and anti-pulse jamming technology and interference principle of the SAR seeker with forward squint. After analysis, the anti-jamming principle is feasible, and it has the engineering application ability, and can be applied to the aircraft. In addition, from the point of view of the overall design of aircraft, some anti-jamming ideas of SAR seeker are given.

FM jamming cancellation suppression based on noise floor estimation with dynamic threshold

Technique of FM jamming time domain cancellation suppression based on noise floor estimation with dynamic threshold is researched, by using the colored noise NLR filter estimation algorithm instead of the narrowband filtering algorithm, the problem that the target echo signal is lost in the process of jamming amplitude estimation is solved. Through the phase analysis of the jamming signal, the problem of jamming signal amplitude estimation in the background of echo signal is transformed into the problem of useful signals spectral estimation in colored noise background. Combined with the characteristics of the low frequency components of the useful signal, the traditional NLR filtering algorithm is improved by adding the dynamic threshold, so as to achieve the purpose of colored noise’s non-invasive estimation, and then to obtain more accurate jamming signal amplitude estimation. The simulation results show that compared with the traditional jamming cancellation algorithm, this algorithm can improve the SJR of the echo signal better and the anti - jamming ability is stronger.

Rapid frequency control of sonar sounds by the FM bat, Miniopterus fuliginosus, in response to spectral overlap

In the presence of multiple flying conspecifics, echolocating bats avoid jamming by adjusting the spectral and/or temporal features of their vocalizations. However, little is known about how bats alter their pulse acoustic characteristics to adapt to an acoustically jamming situation during flight. We investigated echolocation behavior in a bat (Miniopterus fuliginosus) during free flight under acoustic jamming conditions created by downward FM jamming sounds mimicking bat echolocation sounds. In an experimental chamber, the flying bat was exposed to FM jamming sounds with different terminal frequencies (TFs) from loudspeakers. Echolocation pulses emitted by the flying bat were recorded using a telemetry microphone (Telemike) mounted on the back of the bat. The bats immediately (within 150ms) shifted the TFs of emitted pulses upward when FM jamming sounds were presented. Moreover, the amount of upward TF shift differed depending on the TF ranges of the jamming sounds presented. When the TF range was lower than or overlapped the bat’s mean TF, the bat TF shifted significantly upward (by 1–2kHz, Student’s t-test, P<0.05), corresponding to 3–5% of the total bandwidth of their emitted pulses. These findings indicate that bats actively avoid overlap of the narrow frequency band around the TF.

Novel SREKF-based recurrent neural predictor for narrowband/FM interference rejection in GPS

The GPS provides accurate positioning and timing information that is useful in various applications. A new adaptive neural predictor for GPS jamming suppression applications is proposed. The effective and computationally efficient square-root extended Kalman filter (SREKF) algorithm is adopted to adjust the synaptic weights in the nonlinear recurrent architecture and thereby estimate the stationary and non-stationary narrowband/FM waveforms. Cholesky factorization is employed in Riccati recursion to improve numerical stability because of the propagation of round-off errors in conventional KF equations. The main characteristics of the proposed SREKF-based canceller are their rapid convergence and favorable tracking performance. Simulation results reveal that its SNR improvement factor exceeds the factors of conventional LMS, RLS, ENA and TLFN filters in single-tone CWI, multi-tone CWI, pulse CWI and FM jamming environments, respectively.

New approach for suppression of FM jamming in GPS receivers

A new approach is proposed for the suppression of FM jammers in C/A code GPS receivers. This approach is based on the cascading of the augmented-state approximate conditional mean (ASACM) filter and the discrete wavelet transform (DWT) filter. An ASACM filter for single interference suppression in spread-spectrum systems has been reported in the recent literature. However, the formulation of the ASACM filter and its performance analysis is lacking in the case of suppression of multiple FM interferences. The ASACM filter is formulated here for the suppression of multiple FM jammers. Further, a DWT filter using biorthogonal wavelet is suggested for the suppression of FM jammers. Finally, these two filters are cascaded to get an optimum performance for higher jammer to signal ratio, which is of importance in the GPS, for the case of suppression of multiple FM jammers. The performance of the proposed filters is analyzed through simulation examples for the suppression of single and multiple FM jammers in GPS receivers

Subspace array processing for the suppression of FM jamming in GPS receivers

The mitigation of FM interference in GPS receivers is considered. In difference to commonly assumed wideband and narrowband interferers, the FM interferers are wideband, but instantaneously narrowband, and as such, have clear time-frequency (TF) signatures that are distinct from the GPS coarse acquisition (C/A) spread spectrum code. In the proposed technique, the estimate of the FM interference instantaneous frequency (IF) and the interference spatial signature are used to construct the spatiotemporal interference subspace. The IF estimates can be provided using existing effective linear or bilinear TF methods. The undesired signal arrival is suppressed by projecting the input data on the interference orthogonal subspace. With a multisensor receiver, the distinctions in both the spatial and TF signatures of signal arrivals allow effective interference suppressions. The deterministic nature of the signal model is considered and the known underlying structure of the GPS C/A code is utilized. We derive the receiver signal-to-interference-plus-noise ratio (SINR) under exact and perturbed IF values. The effect of IF estimation errors on both pseudorange measurements and navigation data recovery is analyzed. Simulation results comparing the receiver performances under IF errors in single and multiantenna GPS receivers are provided.

Error Probability for NCFSK with Linear FM Jamming

An expression is derived for the probability of error for a conventional binary, noncoherent, frequency-shift-key (NCFSK) communications system under the influence of bandpass Gaussian noise and a linear frequency-modulation jamming waveform. The resulting integral is expressed in terms of the well-known Q function, which depends upon average signal, noise, and jamming powers. The analytical procedures used can be applied to the analysis of the effects of other types of jamming.