Design and FPGA Implementation of Configurable Interference Waveforms for Embedded SDR Systems

Radar jamming waveform design is a vital part of radar jamming. Over seven to eight decades of evolution, the field has transitioned from noise signal design to coherent jamming signal design, resulting in a multitude of complex jamming styles capable of achieving deceptive jamming, suppressive jamming, and smart noise jamming, which combines both deception and suppression. For the first time, this article establishes a general formula for unifying jamming waveform design. Building upon this foundation, we systematically categorize jamming techniques, and provide an in-depth summary of the corresponding principles and conduct comparative analysis of their effectiveness against different targets. Finally, we look forward in terms of future research directions in jamming waveform design, including quantifiable jamming effect evaluation indicators, combined jamming styles, and intelligent jamming waveform generation methods to address the continuous advancement of radar technology and the complexity and variability of the electromagnetic environment. In order to fill the gap in the literature by summarizing the current state of the field and highlighting key challenges and opportunities, this review provides a comprehensive overview of radar jamming waveform design, categorizes and compares different jamming techniques, and identifies future research directions.

This paper deals with the design of non-coherent jamming strategies capable of ensuring spectral compatibility with friendly radio frequency (RF) emitters. The goal is achieved via a cognitive approach, which, after recognizing the presence of friendly RF systems within the bandwidth of interest (perception), synthesizes a jamming waveform (action) with spectral notches, that allows to interfere exclusively with opposite emissions. Two methods are proposed for the synthesis of the jamming signal. The former leverages optimization techniques for quadratically constrained quadratic problems (QCQP) where each constraint embeds the interference level tolerable by a specific friendly RF system. The latter is a very computationally efficient approach based on simple projections, allowing a control over the spectral notch positions and widths. At the analysis stage, the performance of the devised jamming techniques is firstly numerically analyzed in terms of spectral occupancy and autocorrelation characteristics. The impact of the quantization process involved in the digital-to-analog conversion (DAC) of the jamming waveforms is also examined, with a particular focus on the spectral shaping impairments resulting from reduced DAC resolution. Finally, waveform transmission and reception is experimentally assessed with software defined radio (SDR) devices.

A minewide low and medium-frequency radio system has been developed and installed in coal and metalliferous mines. The radio system utilizes two robust radio signal transmission modes to establish underground radio coverage areas. The seam transmission mode occurs when layers in the ground form a natural waveguide. The conductor transmission line mode waveguide occurs when electrical conductors, such as AC power distribution cables, are in place in mine passageways. The author describes the development history of MF band technology during the past five decades in South Africa, Europe, and the United States. How EM wave theory guided the design and development of the conductor transmission line repeater network and associated mobile radio equipment is discussed. The safety and cost reduction benefits of a practical radio system are also described. >

Current and leader development characteristics of winter lightning occurring in the coastal area of the Sea of Japan are reviewed. The characteristics of winter lightning are different from those of usual lightning that occurs mainly in summer. The occurrence of upward flashes, the percentage of current polarities, and the median values of current peaks in winter lightning are summarized. Typical current waveforms and the corresponding leader developments of winter lightning observed at the chimney of the Fukui thermal plant are shown. We examined the parameters (peak, duration, charge transfer, action integral) of the current waveforms of winter lightning.

본 논문에서는 슬롯-결합 선로를 이용한 개선된 쉬프만 위상천이기를 제안하고자 한다. 제안된 쉬프만 위상천이기는 일반적인 결합 선로와 결합 선로 바로 밑에 단순한 직사각형 모양의 슬롯으로 이루어졌다. 슬롯과 결합된 결합 선로의 두 독립적인 전송 모드인 우 모드와 기 모드의 임피던스와 위상 특성을 계산하여 제안된 쉬프만 위상천이기의 위상 특성을 해석하였다. 본 논문에서는 일반 결합 선로로는 구현이 어려운 높은 임피던스 비를 갖는 <TEX>$90^{\circ}$</TEX> 쉬프만 위상천이기를 제작하였다. 동작 중심 주파수는 2.4 GHz로 하였다. 실험 결과, 대역폭은 위상 오차 <TEX>${\pm}5^{\circ}$</TEX>의 위상천이기에서 약 74.2 %의 밴드폭을 얻었다. 또한, 측정 반사 특성은 동작 대역에서 15.0 dB 이하이며, 삽입 손실은 1.5 dB 이하로 측정되었다. In this paper, an improved Schiffman phase shifter is proposed using slot-coupled lines. It consists of the typical coupled lines and a simple rectangular slot which is placed in the ground plane underneath the coupled lines. Phase responses of the slot-coupled Schiffman phase shifter are analyzed in consideration of the phase velocity of two independent transmission modes and the characteristic impedance of slot-coupled line. The <TEX>$905^{\circ}$</TEX> Schiffman phase shifters with high impedance ratio is realized at 2.4 GHz, which cannot be implemented with the conventional coupled lines. The measured results show that the bandwidth is around 74.2 % within the phase errors <TEX>${\pm}5^{\circ}$</TEX>. The measured return loss is found to be better than 15.0 dB and insertion loss is less than 1.5 dB over the operating frequency band.

Waveforms and Artifacts

The IEEE has written a new standard on pulse techniques and definitions to replace the withdrawn standards IEEE Std-181-1977 and Std-194-1977. The new Std-181-2003 combines information from both of these withdrawn standards. Relative to the withdrawn standards, the new standard has incorporated new definitions, deleted and clarified previous definitions, provided examples of different waveform types, updated text to reflect electronic computation methods, and incorporated algorithms for computing waveform parameters. This paper introduces Std-181-2003 by describing its contents and changes relative to the withdrawn standards.

The growing use of transcranial electric and magnetic (EM) brain stimulation in basic research and in clinical applications necessitates a clear understanding of what constitutes the dose of EM stimulation and how it should be reported. This paper provides fundamental definitions and principles for reporting of dose that encompass any transcranial EM brain stimulation protocol. The biologic effects of EM stimulation are mediated through an electromagnetic field injected (via electric stimulation) or induced (via magnetic stimulation) in the body. Therefore, transcranial EM stimulation dose ought to be defined by all parameters of the stimulation device that affect the electromagnetic field generated in the body, including the stimulation electrode or coil configuration parameters: shape, size, position, and electrical properties, as well as the electrode or coil current (or voltage) waveform parameters: pulse shape, amplitude, width, polarity, and repetition frequency; duration of and interval between bursts or trains of pulses; total number of pulses; and interval between stimulation sessions and total number of sessions. Knowledge of the electromagnetic field generated in the body may not be sufficient but is necessary to understand the biologic effects of EM stimulation. We believe that reporting of EM stimulation dose should be guided by the principle of reproducibility: sufficient information about the stimulation parameters should be provided so that the dose can be replicated.

The response properties of ampullary electroreceptors of paddlefish, Polyodon spathula, were studied in vivo, as single-unit afferent responses to external electrical stimulation with varied intensities of several types of noise waveforms, all Gaussian and zero-mean. They included broadband white noise, Ornstein-Uhlenbeck noise, low- or high-frequency band-limited noise, or natural noise recorded from swarms of Daphnia zooplankton prey, or from individual prey. Normally the afferents fire spontaneously in a tonic manner, which is actually quasiperiodic due to embedded oscillators. 1) Weak noise stimuli increased the variability of afferent firing, but it remained tonic. 2) In contrast, stimulation with less-weak broadband noise led to a qualitative change of the firing patterns, to parabolic bursting, even though the mean firing rate was scarcely affected. 3) The transition to afferent bursting was marked by the development of two well-separated timescales: the fast frequency of spiking inside bursts at <or=250 spikes/s and the slow frequency of burst occurrences at about 9 (range 5-13) bursts/s. These two timescales were manifested as two regimes in afferent power spectra, bimodal interspike interval histograms, return maps, and autocorrelation functions of afferent spike trains. 4) The stochastic approximately 9-Hz bursts were not simply driven by similar-frequency components of noise stimuli because bursts could be dissociated from stimulus waveforms using high-pass filtered noise, or a 0.1-Hz sine-wave stimulus. 5) Arrhenius plots showed that the threshold noise intensity required to elicit bursting depended on the frequency content of a noise stimulus, being lowest, about 1.2 microV/cm, for stimuli matching the 1- to 20-Hz best response band of these cathodally excited ampullary electroreceptors. This is only slightly higher than previous behavioral estimates of the electrosensory threshold as 0.5 microV/cm. 6) Comparable threshold values for bursting came from an alternate analytical approach, based on correlation times of spike trains. 7) Simultaneous recordings from pairs of afferents showed that their bursting frequencies (bursts/s) always converged as the amplitude of a noise stimulus was raised. Thus the slow timescale of bursting is similar for different electroreceptors, even though their mean spiking rates can differ. In conclusion, the ampullary electroreceptors of paddlefish have two distinct modes of operation: their spontaneous tonic firing is modulated by the weakest stimuli, but they switch to bursting output for less-weak stimuli. We propose that afferent bursting may mediate close-range tracking of planktonic prey.

Real-time digital implementation of radar waveform pulse compression and match filtering on FPGA platform is studied. In this work, different types of radar waveforms including phase coded, linear frequency (LFM) and non-linear frequency modulated (NLFM) signals are generated digitally in Xilinx Virtex-5 FPGA platform. Waveforms with different time bandwidth products are tested both in FPGA platform and computer. Digital matched filtering implementation procedure used in FPGA is presented and comparison of theoretical calculations and FPGA implementation results along with implementation resource utilization are presented. Results indicate that precise generation of real-time waveform matched filtering implementations deviate at most 1 dB on range sidelobe levels from theoretical results. Moreover adopted segmentation and parallel implementation of the received pulse both allows processing of divided pulses without SNR degradation and uses less FPGA resources in general compared to processing full PRI at once.

The operating frequency and instantaneous bandwidth of synthetic aperture radar (SAR) deceptive jamming systems based on digital radio frequency memory (DRFM) is limited and may not be effective when encountering frequency agile or wide-bandwidth radar systems. A vivid false target imaging deceptive jamming signal generator against SAR based on microwave photonics is proposed to solve this limitation. The proposed deceptive jamming method eliminates the reliance on DRFM components for radar jamming systems against SAR. The operational frequency range and the instantaneous bandwidth are extended and high-fidelity false target images can be generated. A proof-of-concept experiment is implemented. SAR jamming waveforms in X and Ku bands are successfully generated. Vivid ship-shaped false targets are constructed in the SAR imaging results. The structural similarity (SSIM) and the peak signal-to-noise radio (PSNR) of generated false target SAR images are 0.7841 and 28.32 dB in the X band, and 0.8500 and 29.58 dB in the Ku band. A quantitative analysis is conducted to evaluate the impact of frequency drifts in the range and azimuth domains on the degradation of false target image quality. The effective deceptive region is also discussed. Experimental results demonstrate that the proposed jamming structure against SAR possesses the capability of vivid SAR false target image generation similar to that of electronic jamming systems while also possessing the large bandwidth advantages of microwave photonic systems.

In order to improve the planning decisions of the urban environment and consider the well-being of the residents, an objective assessment of mental stress in the urban environment is needed. The aim of this study was to investigate the changes in the photoplethysmographic (PPG) and second derivative of PPG (SDPPG) signal parameters related to arterial stiffness during the mental stress assessment. The study was carried out on 15 female and 13 male subjects between the age of 25 and 60 years. The finger PPG signal was recorded with a transmission mode sensor during the subject's inactive state, followed by an arithmetic stress test. The PPG signals were post-processed and the statistically significant increases in an augmentation index related parameter PPGAI, in ‘aging index’ AGI, and in the SDPPG amplitude ratios b/a and decreases in d/a and the slope of the ascending waveform front due to induced mental stress were found ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$p&lt;0.05$</tex> ). The results indicate that the arterial stiffness was increased during the stress test. In summary, the PPG waveform parameters related to arterial stiffness could be considered for the mental stress assessment.

Manufacture and in-service assessment of composite materials can be challenging since there is, yet, no standard method for testing them. Nevertheless, regular inspection is necessary to maintain the structural integrity. This paper describes a nondestructive, broadband noise mapping method that uses a millimeter-wave radiometer to detect defects in composite materials. The $W$ -band system is configured for transmission mode measurement in which an amplified photonic source illuminates a glass fiber reinforced polymer containing machined defects. A high sensitivity radiometer is used for imaging the sample. The radiometer consists of a Schottky diode-based frequency tripler and a fundamental mixer.