A Real-time SAR Echo Simulator Based on FPGA and Parallel Computing

This paper designs and implements a SAR (Synthetic Aperture Radar) real-time echo simulator based on multi-FPGA parallel computing. The one-dimensional frequency-domain Fourier transform algorithm is used in the simulator, and the echo signal model and the rapid calculation algorithm of impulse response function are introduced. The pipeline compute structure, multichannel parallel computing and procedure flow design are the key technologies of the simulator, which are also presented in details. And finally, the validity and correctness of the SAR echo simulator are verified through the imaging results of the point-array target and the nature scene target

Attributes of fault-tolerant distributed file systems

Fault tolerance in distributed file systems will be investigated by analyzing recovery techniques and concepts implemented within the following models of distributed systems: pool-processor model and user-server model. The research presented provides an overview of fault tolerance characteristics and mechanisms within current implementations and summarizes future directions for fault tolerant distributed file systems

Hardware-in-the-loop simulation technology of wide-band radar targets based on scattering center model

AbstractHardware-in-the-loop (HWIL) simulation technology can verify and evaluate the radar by simulating the radio frequency environment in an anechoic chamber. The HWIL simulation technology of wide-band radar targets can accurately generate wide-band radar target echo which stands for the radar target scattering characteristics and pulse modulation of radar transmitting signal. This paper analyzes the wide-band radar target scattering properties first. Since the responses of target are composed of many separate scattering centers, the target scattering characteristic is restructured by scattering centers model. Based on the scattering centers model of wide-band radar target, the wide-band radar target echo modeling and the simulation method are discussed. The wide-band radar target echo is reconstructed in real-time by convoluting the transmitting signal to the target scattering parameters. Using the digital radio frequency memory (DRFM) system, the HWIL simulation of wide-band radar target echo with high accuracy can be actualized. A typical wide-band radar target simulation is taken to demonstrate the preferable simulation effect of the reconstruction method of wide-band radar target echo. Finally, the radar target time-domain echo and high-resolution range profile (HRRP) are given. The results show that the HWIL simulation gives a high-resolution range distribution of wide-band radar target scattering centers

RAMPART: RowHammer Mitigation and Repair for Server Memory Systems

RowHammer attacks are a growing security and reliability concern for DRAMs and computer systems as they can induce many bit errors that overwhelm error detection and correction capabilities. System-level solutions are needed as process technology and circuit improvements alone are unlikely to provide complete protection against RowHammer attacks in the future. This paper introduces RAMPART, a novel approach to mitigating RowHammer attacks and improving server memory system reliability by remapping addresses in each DRAM in a way that confines RowHammer bit flips to a single device for any victim row address. When RAMPART is paired with Single Device Data Correction (SDDC) and patrol scrub, error detection and correction methods in use today, the system can detect and correct bit flips from a successful attack, allowing the memory system to heal itself. RAMPART is compatible with DDR5 RowHammer mitigation features, as well as a wide variety of algorithmic and probabilistic tracking methods. We also introduce BRC-VL, a variation of DDR5 Bounded Refresh Configuration (BRC) that improves system performance by reducing mitigation overhead and show that it works well with probabilistic sampling methods to combat traditional and victim-focused mitigation attacks like Half-Double. The combination of RAMPART, SDDC, and scrubbing enables stronger RowHammer resistance by correcting bit flips from one successful attack. Uncorrectable errors are much less likely, requiring two successful attacks before the memory system is scrubbed.Comment: 16 pages, 13 figures. A version of this paper will appear in the Proceedings of MEMSYS2

Research Naval Postgraduate School, v.13, no.1, February 2003

NPS Research is published by the Research and Sponsored Programs, Office of the Vice President and Dean of Research, in accordance with NAVSOP-35. Views and opinions expressed are not necessarily those of the Department of the Navy.Approved for public release; distribution is unlimited

A comparison of DDS and DRFM techniques in the generation of "smart noise" jamming waveforms

This thesis presents a comparison of the effectiveness of 'smart noise' jamming waveforms against advanced threat radars, which are generated using either Direct Digital Synthesis (DDS) or Digital RF Memory (DRFM) based support jamming. The challenge lies in the fact the modern radar employs advanced waveforms, ultralow sidelobe antennas, coherent sidelobe cancelers, and sidelobe blankers to inhibit signals entering through its sidelobes. This thesis compares the effectiveness of using DDS versus DRFM techniques to meet this challenge. In particular, the effect of mismatched frequency on the DDS jamming waveform is described, as is the effect of quantization and multi-signal storage in the DRFM. A quantitative comparison of these jamming techniques against the AN/TPS-70 surveillance radar is madehttp://archive.org/details/comparisonofddsd00watsCaptain, United States ArmyApproved for public release; distribution is unlimited

Optimization of electronic protection testing for the F/A-18 active guidance air-to-air weapon system

The AIM-120A Advanced Medium Range Air-to-Air Missile (AMRAAM) is the premier air-to-air missile in the US arsenal. Although designed to counter threats that employ analog-based Electronic Attack (EA), the new threat of digital-based EA, Digital Radio Frequency Memory (DRFM), places a high priority on the capability to evaluate AMRAAM\u27 s Electronic Protection (EP), which is defined as the capability to counter EA. AMRAAM effectiveness is not only dependent on its own capability to counter EA, but also on the ability of the fighter aircraft radar to counter the same EA while supporting the AMRAAM ( via data links) during the AMRAAM\u27 s intercept profile. In the US Navy, the AMRAAM is carried by the F/A-18. EP testing of the two versions of F/A-18 radar has been limited due to funding constraints and other higher priority testing of the various capabilities associated with the air-to-air and air-to-ground F/A-18 mission requirements. In 1996, the US Navy funded the Weapon System Evaluation program, which includes EP testing of the F/A-18 and AMRAAM weapon system. Current test methods involve captive carriage of the AMRAAM against full-scale targets employing specific EA techniques. Radar data links to the missile are recorded in flight and replayed in the Hard-Ware In The Loop (HWIL) simulator to test missile performance during simulated missile intercept of the same EA threat. Twenty simulations are executed in the HWIL for each test flight to calculate missile probability of guidance (Po). For each HWIL simulation, 50 lethality simulations are executed to calculate probability of weapon effectiveness (PWE), Final products of the test program are a table illustrating Po and a bar chart illustrating PWE against several specific EA threats, including in both cases performance of the missile with perfect aircraft radar support to isolate missile performance. Neither the table nor the chart includes uncertainty associated with the calculated probabilities. A closer look at the test methods revealed that only a few tests of aircraft radar are used to characterize aircraft radar performance versus the EA threat while thousands of simulations are used to characterize AMRAAM performance. For the average number of test runs of each radar mode, the uncertainty associated with the aircraft radar performance calculation was found to be± 43.6% while the uncertainty associated with AMRAAM performance calculation was found to be± 1.39% (using 95% confidence interval). The combined uncertainty is± 44.4%, which spans a wide range of performance for any calculation of Po or PWE. The large uncertainty does not offer a solid foundation on which to base fighter tactics. Three methods of increasing the number of radar performance data were investigated for the purpose of decreasing the uncertainty associated with EP testing. First, synthetic data link file generation was determined to be ineffective because the data link error files were not stationary or ergotic, signal characteristics that are required for accurate generation of data link files. Second, time shift expansion, which involves generation of additional data link files (more radar performance data) from the recorded aircraft radar track files, was found to have some potential to reduce uncertainty. More evaluation would be necessary to quantify effectiveness. However, the effectiveness of time shift expansion would be limited at best because it does not add to the general characterization of aircraft radar performance against EA (no new radar performance runs, only more data from existing runs). Third, the NA VAIR Weapons Division China Lake F/A-18 radar laboratory was researched as a method for generating more radar simulations against EA to more fully characterize radar performance. Utilization of the radar laboratory was determined to be by far the best technique for optimizing weapons system testing. The higher cost associated with more independent aircraft radar runs would reduce the number of test flights per year by one (due to the fixed budget), but the dramatic reduction in uncertainty (from± 44.4% to± 20.5%) would be well worth the cost. Calculating PWE against four types of EA within 20.5% is much more valuable than calculating PWE for five types within 44.4%. The AMRAAM will remain in the US arsenal for many more years, and will face many new threats. The AMRAAM Integrated Project Team should pursue incorporation of the radar laboratory simulations into the EP testing process to significantly improve the accuracy associated with evaluation of weapon system performance. Additionally, NA VAIR should work towards long-term co-development of coupled systems such as the F/ A-18 radar and the AMRAAM to save money and to increase overall performance by allowing optimization of the weapon system through coherent development of system components