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Limits of Spatial Resolution of phase Encoding Dimensions in MRI of Metals

JOURNAL OF PHYSICAL CHEMISTRY LETTERS 2019年第3期10卷 375-379页

作者： Shekar, S. Chandra Hallinan, Daniel T., Jr. Taylor, Deanne M. Chekmenev, Eduard Y. Florida State Univ Coll Engn Florida A&M Univ Dept Chem & Biomed Engn Tallahassee FL 32310 USA Florida State Univ Aeroprop Mechatron & Energy Ctr Tallahassee FL 32310 USA Florida State Univ Natl High Magnet Field Lab Tallahassee FL 32310 USA Childrens Hosp Philadelphia Dept Biomed & Hlth Informat Philadelphia PA 19041 USA Univ Penn Perelman Sch Med Dept Pediat Philadelphia PA 19104 USA Wayne State Univ Dept Chem Karmanos Canc Inst KCI Detroit MI 48202 USA Wayne State Univ Integrat Biosci Ibio Detroit MI 48202 USA Russian Acad Sci Leninskiy Prospekt 14 Moscow 119991 Russia

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MVDR code receiver for code multiplexing MIMO radar

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ELECTRONICS LETTERS 2019年第1期55卷 49-50页

作者： Kim, E. -H. Baik, K. Sejong Univ Dept Def Syst Engn 209 Neungdong Ro Seoul 05006 South Korea Korea Res Inst Stand & Sci Ctr Med Convergence Metrol 267 Gajeong Ro Daejeon 34113 South Korea

Multiple-input multiple-output (MIMO) radar recently has attracted the attention of engineers and researchers. MIMO radar performance is based on the orthogonality of the transmitted waveforms. A receiver optimisation method is proposed to suppress cross-correlation rather than finding orthogonal waveforms. The method considers two transmitters and is based on the minimum variance distorsionless response (MVDR) algorithm to minimise cross-correlation while maintaining the level of auto-correlation. Performance is evaluated by simulation using random phase code sequences. The proposed method is well suited for single target tracking, or slow moving target detection.

关键词： phase coding MIMO radar array signal processing optimisation correlation methods random codes radio receivers receiver optimisation method minimum variance distorsionless response algorithm random phase code sequences MVDR code receiver multiple-input multiple-output radar MIMO radar performance code multiplexing MIMO radar transmitted waveform orthogonality cross-correlation suppression MVDR algorithm transmitters auto-correlation level performance evaluation slow moving target detection single target tracking

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Implementable phase-coded radar waveforms featuring extra-low range sidelobes and Doppler resilience

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IET RADAR SONAR AND NAVIGATION 2019年第9期13卷 1530-1539页

作者： Dong, Yunhan Def Sci & Technol Grp Intelligence Surveillance & Space Div Sydney NSW Australia

Golay binary complementary sequences are used to code quadriphase waveforms. The Gaussian minimum shift keying coding scheme is used to produce waveforms with constant amplitude, and continuous and differentiable phase. To satisfy spectral requirements, the waveforms are further spectrally optimised by a spectrum-optimisation process, making the final waveforms implementable. The extra-low sidelobe level is achieved by the use of an extended mismatched filter on receive of pulse compression. To improve Doppler tolerance, Doppler-resilient complementary waveforms are derived that provide first-order suppression to the raised range sidelobes introduced by the Doppler frequency shift in returned signals. This study is an expanded version of a conference paper presented at 2018 International Radar Conference held in Brisbane, Australia.

关键词： phase coding minimum shift keying optimisation binary sequences Doppler shift target tracking waveform analysis pulse compression radar signal processing Doppler radar radar constant amplitude continuous phase differentiable phase spectral requirements spectrum-optimisation process final waveforms implementable extra-low sidelobe level extended mismatched filter Doppler tolerance Doppler-resilient complementary waveforms raised range sidelobes Doppler frequency shift 2018 International Radar Conference implementable phase-coded radar waveforms extra-low range sidelobes Doppler resilience golay binary complementary sequences quadriphase waveforms Gaussian minimum shift coding scheme

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A Model of Memory Linking Time to Space

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FRONTIERS IN COMPUTATIONAL NEUROSCIENCE 2020年 14卷 60页

作者： Loffler, Hubert Gupta, Daya Shankar Camden Cty Coll Dept Biol Blackwood NJ 08012 USA

The storage of temporally precise spike patterns can be realized by a single neuron. A spiking neural network (SNN) model is utilized to demonstrate the ability to precisely recall a spike pattern after presenting a single input. We show by using a simulation study that the temporal properties of input patterns can be transformed into spatial patterns of local dendritic spikes. The localization of time-points of spikes is facilitated by phase-shift of the subthreshold membrane potential oscillations (SMO) in the dendritic branches, which modifies their excitability. In reference to the points in time of the arriving input, the dendritic spikes are triggered in different branches. To store spatially distributed patterns, two unsupervised learning mechanisms are utilized. Either synaptic weights to the branches, spatial representation of the temporal input pattern, are enhanced by spike-timing-dependent plasticity (STDP) or the oscillation power of SMOs in spiking branches is increased by dendritic spikes. For retrieval, spike bursts activate stored spatiotemporal patterns in dendritic branches, which reactivate the original somatic spike patterns. The simulation of the prototypical model demonstrates the principle, how linking time to space enables the storage of temporal features of an input. Plausibility, advantages, and some variations of the proposed model are also discussed.

关键词： neural memory temporally precise spike trains subthreshold membrane potential oscillations phase coding gamma-theta code working memory spiking neural networks

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Photonics Improvement of the Time-Bandwidth Product for a Linearly Chirped Waveform

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Journal of Applied Mathematics and Physics 2020年第12期8卷 2955-2963页

作者： Xuan Li Shanghong Zhao Guodong Wang He Li Information and Navigation College Air Force Engineering University Xi’an China

A photonics approach to generate a linearly chirped waveform with increased TBWP is proposed and investigated. The time bandwidth product (TBWP) of the linearly chirped waveform is improved based on optical microwave frequency multiplying combined with temporal synthesis. An integrated dual-polarization modulator and an optical filter are utilized to perform frequency doubling operation by generating an orthogonally polarized optical signal, which consists of an optical carrier in one polarization direction and a second-order chirped optical sideband in another. Then the orthogonally polarized optical signal puts into a polarization modulator (PolM) to perform phase coding process. By driving a Pseudorandom (PN) sequence to the PolM, the time duration of the generated bandwidth doubled linearly chirped waveform can be synthesized to arbitrary length. The approach is verified by simulation. A linearly chirped waveform with central frequency of 8.25 GHz, bandwidth of 500 MHz, time duration of 6.4 ns is used to generate a synthesized waveform with central frequency of 16.5 GHz, bandwidth of 1 GHz, time duration of 819.2 ns. The TBWP of the linearly chirped signal is improved from 3.2 to 819.2. The proposed method features arbitrary large TBWP, and it can be used in a radar system to improve its resolution.

关键词： Linearly Chirped Waveform Time-Bandwidth Product Frequency Multiplying phase coding

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Implementable phase-coded radar waveforms featuring extra-low range sidelobes and Doppler resilience

Implementable phase-coded radar waveforms featuring extra-lo...

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International Conference on Radar (RADAR)

作者： Dong, Yunhan Def Sci & Technol Grp Intelligence Surveillance & Space Div Sydney NSW Australia

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Signal classification against repeat radar jammers with optimized MIMO radar waveforms

Signal classification against repeat radar jammers with opti...

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IET International Radar Conference (IET IRC 2020)

作者： G. Dou S. Zhou H. Liu J. Liu L. Xu H. Ma P. Wang National Laboratory of Radar Signal Processing Xi’an China University of Science and Technology of China Department of Electronic Engineering and Information Science Hefei 230027 China

The digital radio frequency memory (DRFM) repeat jammer, which can transmit signals of close signature to real target returns, is a typical low-cost electronic attacker and poses threats to radar systems. One can optimize multiple-input multiple-output (MIMO) radar waveforms to magnify the difference between deceptive signals and real targets, and in this paper, we examine the performance improvement achieved by designing classification algorithms. The training samples are theoretical target returns and theoretical constant-modulus deceptive signals, both modulated with different Doppler frequencies. Three classifiers, namely the support vector machines (SVM), Naive Bayes and k-Nearest Neighbor (kNN), are considered and the SVM performs the best. With 128-chips phase-coded transmit signals, the waveform optimization algorithm achieves a 6dB signal-to-noise ratio (SNR) improvement at the 90% classification rate.

关键词： jamming radar signal processing support vector machines signal classification MIMO radar signal sampling Doppler radar naive Bayes methods nearest neighbour methods phase coding optimisation radar computing

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Target detection in anechoic chamber based on the interrupted transmitting and receiving of PCM signal

Target detection in anechoic chamber based on the interrupte...

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IET International Radar Conference (IET IRC 2020)

作者： F. Zhao X. Liu A. Xie Q. Wu National University of Defense Technology State Key Laboratory of Complex Electromagnetic Environmental Effects on Electronics & Information System Changsha 410073 P. R. China

phase coded modulation (PCM) signal has been widely used in target detection at the out-field. However, when the PCM signal is utilized in the anechoic chamber for target detection, the target echo returns before the signal is fully transmitted, which results in the signal coupling at the receiver. In this paper, the interrupted transmitting and receiving (ITR) is adopted to solve the problem. Then, the procedure of target detection with PCM signal in anechoic chamber is proposed. The constraints of the ITR parameters are discussed according to the anechoic chamber size and the PCM signal parameters. By conducting the numerical simulations, the effectiveness of the proposed target detection method is verified.

关键词： phase coding radar signal processing echo pulse code modulation object detection anechoic chambers (electromagnetic)

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Intermediate frequency design criterion for reducing spectrum aliasing distortion in binary phase-coded radar system

Intermediate frequency design criterion for reducing spectru...

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IET International Radar Conference (IET IRC 2020)

作者： C. Wang L. Ren W. Li Q. Liu E. Mao Beijing Institute of Technology Beijing China

The binary phase-coded waveform, a kind of pulse compression waveform, is widely used in many radar systems. However, its out-of-band spectral sidelobes will cause distortions in practical radar system. One of the distortions, called spectrum aliasing distortion, will occur when the intermediate frequency (IF) signal at fIF is sampled by a sampling rate fS. An IF design criterion in binary phase-coded radar system is proposed to reduce the spectrum aliasing distortion by using the spectrum property of binary codes. The simulations show that with the suitable design of IF the digital signal processing results will be closer to the designed performance, such as the peak sidelobe level (PSL).

关键词： phase coding pulse compression binary codes signal sampling radar signal processing signal processing

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Dense false-target jamming suppression method by utilizing BI-phase random coded waveform for space time adaptive processing

Dense false-target jamming suppression method by utilizing B...

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IET International Radar Conference (IET IRC 2020)

作者： B. Wang X. Yang Z. Yang T. Lan Key Laboratory of Electronic and Information Technology in Satellite Navigation (Beijing Institute of Technology) China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120 China

The performance of conventional space-time adaptive processing would deteriorated due to dense false-target jamming. Thus, a dense false-target jamming suppression method utilizing bi-phase random coded waveform is proposed. In the proposed method, the phase codes of bi-phase random coded waveform are generated by M sequence codes. Then the generated waveform is applied to the transmitting signal to reduce the correlation among coherent processing intervals. In the following, the matched filter is designed based on the transmitting waveform to suppress the jamming. Finally, the clutter is suppressed by jointly adaptive filtering in space and time domain. Simulation results verify the effectiveness of the proposed method.

关键词： phase coding radar clutter radar signal processing adaptive filters space-time adaptive processing jamming interference suppression matched filters m-sequences random codes

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