scholarly journals An Improved Descalloping Method Combined With Imaging Parameters for GaoFen-3 ScanSAR

2020 ◽  
Vol 12 (5) ◽  
pp. 822
Author(s):  
Lihua Zhong ◽  
Xiaolan Qiu ◽  
Bing Han ◽  
Yuxin Hu
Keyword(s):  
Thermal Noise ◽  
Signal To Noise Ratio ◽  
Antenna Pattern ◽  
Statistical Characteristics ◽  
Periodic Signal ◽  
Frequency Filtering ◽  
Working Mechanism ◽  
Imaging Parameters ◽  
Modulation Model ◽  
Specific Working

Due to the specific working mechanism of alternately transmitting and receiving signals between multiple adjacent swaths, scanning synthetic aperture radar (ScanSAR) will cause periodical wavelike modulation of the intensity image along azimuth direction, which is known as scalloping. Conventional descalloping methods are achieved by proper azimuth antenna pattern (AAP) correction and multi-looking techniques but are limited by the accuracy of Doppler centroid estimating and the thermal noise. Another type of method extracts and suppresses the scalloping texture on the image, but the scanning parameters of ScanSAR are insufficiently considered. The period of scalloping on the image is related to the period of switching between subswathes. While the harmonics can be calculated by the period of a periodic signal, an improved frequency filtering method combined with imaging parameters is proposed. The scalloping modulation model of ScanSAR combined with imaging parameters is constructed, and the harmonics of scalloping texture are accurately calculated and filtered. For the low signal to noise ratio (SNR) image, the antenna pattern is modified according to SNR to avoid scalloping caused by noise. For non-uniform scenes, scalloping suppression is achieved by using the scalloping features acquired by uniform scenes. To separate the non-uniform scenes from uniform scenes, we still use the characteristics of harmonics caused by scalloping. Our descalloping method achieves accurate suppression of scalloping without sea-land segmentation and ship mask and the residual scalloping is reduced from 1.0 to 0.3–0.5 dB. The residual scalloping and statistical characteristics of the image are analyzed to demonstrate the effectiveness of the proposed method.

scholarly journals Stochastic resonance in periodically driven bistable systems subjected to anomalous diffusion

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
F. Naha Nzoupe ◽  
Alain M. Dikandé
Keyword(s):  
Stochastic Resonance ◽  
Signal To Noise Ratio ◽  
Planck Equation ◽  
Relevant Information ◽  
Periodic Signal ◽  
Signal To Noise ◽  
Periodically Driven ◽  
Loop Area ◽  
Bistable Systems ◽  
Noise Ratio

AbstractThe occurrence of stochastic resonance in bistable systems undergoing anomalous diffusions, which arise from density-dependent fluctuations, is investigated with an emphasis on the analytical formulation of the problem as well as a possible analytical derivation of key quantifiers of stochastic resonance. The nonlinear Fokker–Planck equation describing the system dynamics, together with the corresponding Ito–Langevin equation, is formulated. In the linear response regime, analytical expressions of the spectral amplification, of the signal-to-noise ratio and of the hysteresis loop area are derived as quantifiers of stochastic resonance. These quantifiers are found to be strongly dependent on the parameters controlling the type of diffusion; in particular, the peak characterizing the signal-to-noise ratio occurs only in close ranges of parameters. Results introduce the relevant information that, taking into consideration the interactions of anomalous diffusive systems with a periodic signal, can provide a better understanding of the physics of stochastic resonance in bistable systems driven by periodic forces.

scholarly journals On the Performance Analysis of Switched Diversity Combining Receivers over Fisher–Snedecor ℱ Composite Fading Channels

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3014
Author(s):  
Weijun Cheng ◽  
Xiaoting Wang ◽  
Tengfei Ma ◽  
Gang Wang
Keyword(s):  
Fading Channels ◽  
Error Probability ◽  
Signal To Noise Ratio ◽  
Multipath Fading ◽  
Performance Criteria ◽  
Statistical Characteristics ◽  
Diversity Combining ◽  
Systematic Analysis ◽  
Average Bit Error Probability ◽  
Switched Diversity Combining

In some emerging wireless applications, such as wearable communication and low-power sensor network applications, wireless devices or nodes not only require simple physical implementation approaches but also require certain reliable receiver techniques to overcome the effects of multipath or shadowed fading. Switched diversity combining (SDC) systems could be a simple and promising solution to the above requirements. Recently, a Fisher–Snedecor ℱ composited fading model has gained much interest because of its modeling accuracy and calculation tractability. However, the performance of SDC systems over ℱ fading channels has not yet been analyzed in the open literature. To this end, this paper presents a systematic analysis of SDC systems over ℱ fading channels, including dual-branch switch-and-stay combining (SSC), multibranch switch-and examine combining (SEC), and SEC with post-examining selection (SECps) systems. We first investigate the statistical characteristics of univariate and bivariate ℱ distributions. Then, these statistical expressions are introduced into the above SDC systems and the statistical metrics of the output signal-to-noise ratio (SNR) for these systems are deduced in different ℱ fading scenarios. Thirdly, certain exact and novel expressions of performance criteria, such as the outage probability, the average bit error probability and average symbol error probability, as well as the average channel capacity for SSC, SEC, and SECps are derived. To find the optimum performance, optimal analysis is performed for the independent and identically distributed cases. Finally, numerical evaluation and simulations are carried out to demonstrate the validity of the theoretical analysis under various ℱ fading scenarios. According to the obtained results, the multipath fading parameter has more influence on the performance of SDC systems than the shadowing parameter, the correlation coefficient, or the average SNR. Importantly, the SDC systems can provide switched diversity gains only when the switching threshold is not too large or too small compared to the average SNR.

Stochastic resonance in an array of integrate-and-fire neurons with threshold

2018 ◽  
Vol 32 (16) ◽  
pp. 1850169 ◽  
Author(s):  
Bingchang Zhou ◽  
Qianqian Qi
Keyword(s):  
Stochastic Resonance ◽  
Additive Noise ◽  
Signal To Noise Ratio ◽  
Array Size ◽  
Periodic Signal ◽  
Signal Parameter ◽  
Input Noise ◽  
Integrate And Fire ◽  
Noisy Input ◽  
Better Than

We investigate the phenomenon of stochastic resonance (SR) in parallel integrate-and-fire neuronal arrays with threshold driven by additive noise or signal-dependent noise (SDN) and a noisy input signal. SR occurs in this system. Whether the system is subject to the additive noise or SDN, the input noise [Formula: see text] weakens the performance of SR but the array size N and signal parameter [Formula: see text] promote the performance of SR. Signal parameter [Formula: see text] promotes the performance of SR for the additive noise, but the peak values of the output signal-to-noise ratio [Formula: see text] first decrease, then increase as [Formula: see text] increases for the SDN. Moreover, when [Formula: see text] tends to infinity, for the SDN, the curve of [Formula: see text] first increases and then decreases, however, for the additive noise, the curve of [Formula: see text] increases to reach a plain. By comparing system performance with the additive noise to one with SDN, we also find that the information transmission of a periodic signal with SDN is significantly better than one with the additive noise in limited array size N.

Stochastic resonance and stability for an ecological vegetation growth system driven by colored noises and multiplicative signal

2016 ◽  
Vol 30 (24) ◽  
pp. 1650308 ◽  
Author(s):  
Kang-Kang Wang ◽  
Ya-Jun Wang ◽  
Jian-Cheng Wu
Keyword(s):  
Stochastic Resonance ◽  
Multiplicative Noise ◽  
Signal To Noise Ratio ◽  
Periodic Signal ◽  
Expansion Process ◽  
Correlation Times ◽  
Vegetation Growth ◽  
Growth System ◽  
Speed Up ◽  
The Stability

In this paper, we investigate the steady-state properties and the transition rate for an ecological vegetation growth system induced by the terms of the colored multiplicative and additive noises. Numerical results indicate that the multiplicative noise and the additive one can reduce the stability of the ecological system and slow down the development velocity of the vegetation, while two noise self-correlation times can increase the stability of the system and speed up the expansion process of the vegetation system. With respect to the stochastic resonance (SR) phenomenon caused by noise terms and a multiplicative weak periodic signal, the results show that the additive noise always enhances the SR effect, two noise self-correlation time terms can produce SR phenomenon, but play opposite roles in enhancing or inhibiting the SR effect under different parameter conditions. In particular, the two self-correlation times can keep up the maximum of the signal-to-noise ratio (SNR) invariant in specific situations. Analogously, the multiplicative noise can not only improve the SNR, but also restrain the SR phenomenon in different cases.

scholarly journals Shielding of Piezoelectric Ultrasonic Probes in Hall Effect Imaging

1998 ◽  
Vol 20 (3) ◽  
pp. 206-220 ◽  
Author(s):  
Han Wen ◽  
Eric Bennett ◽  
David G. Wiesler
Keyword(s):  
Hall Effect ◽  
Electromagnetic Interference ◽  
Thermal Noise ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Excitation Pulse ◽  
Signal To Noise ◽  
Coherent Noise ◽  
Electrical Pulses ◽  
Coupling Mechanisms

This paper addresses significant sources of electromagnetic noise in Hall effect imaging. Hall effect imaging employs large electrical pulses for signal generation and high sensitivity ultrasonic probes for signal reception. Coherent noise arises through various coupling mechanisms between the excitation pulse and the probe. In this paper, the coupling mechanisms are experimentally isolated and theoretically analyzed. Several methods of shielding the probe from electromagnetic interference are devised and tested. These methods are able to reduce the noise to levels below the random thermal noise, thereby improving the signal-to-noise ratio in HEI by two orders of magnitude.

scholarly journals Reaching thermal noise at ultra-low radio frequencies

2020 ◽  
Vol 642 ◽  
pp. A85 ◽  
Author(s):  
F. de Gasperin ◽  
G. Brunetti ◽  
M. Brüggen ◽  
R. van Weeren ◽  
W. L. Williams ◽  
...  
Keyword(s):  
Thermal Noise ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Galaxy Cluster ◽  
Cosmic Ray ◽  
Radio Halo ◽  
Cosmic Ray Acceleration ◽  
The Galaxy ◽  
Background Turbulence ◽  
Post Shock

Context. Ultra-low frequency observations (< 100 MHz) are particularly challenging because they are usually performed in a low signal-to-noise ratio regime due to the high sky temperature and because of ionospheric disturbances whose effects are inversely proportional to the observing frequency. Nonetheless, these observations are crucial for studying the emission from low-energy populations of cosmic rays. Aims. We aim to obtain the first thermal-noise limited (∼1.5 mJy beam−1) deep continuum radio map using the Low Frequency Array’s Low Band Antenna (LOFAR LBA) system. Our demonstration observation targeted the galaxy cluster RX J0603.3+4214 (known as the Toothbrush cluster). We used the resulting ultra-low frequency (39–78 MHz) image to study cosmic-ray acceleration and evolution in the post shock region considering the presence of a radio halo. Methods. We describe the data reduction we used to calibrate LOFAR LBA observations. The resulting image was combined with observations at higher frequencies (LOFAR 150 MHz and VLA 1500 MHz) to extract spectral information. Results. We obtained the first thermal-noise limited image from an observation carried out with the LOFAR LBA system using all Dutch stations at a central frequency of 58 MHz. With eight hours of data, we reached an rms noise of 1.3 mJy beam−1 at a resolution of 18″ × 11″. Conclusions. The procedure we developed is an important step towards routine high-fidelity imaging with the LOFAR LBA. The analysis of the radio spectra shows that the radio relic extends to distances of 800 kpc downstream from the shock front, larger than what is allowed by electron cooling time. Furthermore, the shock wave started accelerating electrons already at a projected distance of < 300 kpc from the crossing point of the two clusters. These results may be explained by electrons being re-accelerated downstream by background turbulence, possibly combined with projection effects with respect to the radio halo.

scholarly journals Performance Analysis of Reconfigurable Intelligent Surface-Aided Full-Duplex Cooperative NOMA System

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xiang Zhao ◽  
Jinyong Sun
Keyword(s):  
Performance Analysis ◽  
Outage Probability ◽  
Multiple Access ◽  
Signal To Noise Ratio ◽  
Access Point ◽  
Full Duplex ◽  
Statistical Characteristics ◽  
Signal To Noise ◽  
Outage Performance ◽  
Analytical Results

The outage performance of a reconfigurable intelligent surface- (RIS-) aided full-duplex cooperative nonorthogonal multiple access (NOMA) system is studied in this paper. Based on the statistical characteristics of the signal-to-noise ratio of the reflection channel from the access point via RIS to the near user, and the cooperative channel from the near user to the far NOMA user, the outage probability of both the near and far users is derived. Through the comparison with the outage performance of conventional cooperative NOMA without employing RIS, the superiority of the proposed scheme is demonstrated. Finally, the correctness of the analytical results is validated with simulation.

scholarly journals Does a Standalone, “Cold” (Low-Thermal-Noise), Linear Resistor Exist Without Cooling?

2018 ◽  
Vol 17 (04) ◽  
pp. 1850030
Author(s):  
Jiaao Song ◽  
Laszlo B. Kish
Keyword(s):  
Thermal Noise ◽  
Cold Resistance ◽  
Signal To Noise Ratio ◽  
Noise Temperature ◽  
Low Noise ◽  
Natural Question ◽  
Signal To Noise ◽  
Nonlinear Resistor ◽  
Technology Corporation ◽  
Thermal Cooling

Classical ways of cooling require some of these elements: phase transition, compressor, nonlinearity, valve and/or switch. A recent example is the 2018 patent of Linear Technology Corporation; they utilize the shot noise of a diode to produce a standalone nonlinear resistor that has [Formula: see text]/2 noise temperature (about 150[Formula: see text]K). While such “resistor” can cool its environment when it is AC coupled to a resistor, the thermal cooling effect is only academically interesting. The importance of the invention is of another nature: In low-noise electronics, it is essential to have resistors with low-noise temperature to improve the signal-to-noise ratio. A natural question is raised: can we use a linear system with feedback to cool and, most importantly, to show reduced noise temperature? Exploring this problem, we were able to produce standalone linear resistors showing strongly reduced thermal noise. Our must successful test shows [Formula: see text]/100 (about 3[Formula: see text]K) noise temperature, as if the resistor would have been immersed in liquid helium. We also found that there is an old solution offering similar results utilizing the virtual ground of an inverting amplifier at negative feedback. There, the “cold” resistor is generated at the input of an amplifier. On the other hand, our system generates the “cold” resistance at the output, which can have practical advantages.

A Novel Frequency Locked Loop Based on Stochastic Resonance

2013 ◽  
Vol 347-350 ◽  
pp. 1763-1767
Author(s):  
Wei Tong Zhang ◽  
Zhi Qiang Li ◽  
Wen Ming Zhu
Keyword(s):  
Stochastic Resonance ◽  
Thermal Noise ◽  
Signal To Noise Ratio ◽  
Dynamic Performance ◽  
Tracking Accuracy ◽  
Carrier Synchronization ◽  
Signal To Noise ◽  
Frequency Discriminator ◽  
Simulation Results ◽  
High Dynamics

Frequency locked loop (FLL) plays an important role in carrier synchronization because of its excellent dynamic performance. However, it performs inadequately in low signal-to-noise ratio (SNR). In this paper, the principle of stochastic resonance (SR) is briefly introduced and a SR processor is proposed. Based on traditional FLL, the SR processor is added before frequency discriminator in order to weaken the effect that thermal noise brings to FLL. The paper investigates the processing effect of SR. Simulation results show that the performance of improved FLL is greatly improved. It can tolerate rather high dynamics and tracking accuracy of frequency achieve 0.2Hz even with CNR as low as 25 dBHz, which verified the validity of above ideas.

STOCHASTIC RESONANCE IN THE NONAUTONOMOUS CHUA'S CIRCUIT

1993 ◽  
Vol 03 (02) ◽  
pp. 553-578 ◽  
Author(s):  
V. S. ANISHCHENKO ◽  
M. A. SAFONOVA ◽  
L. O. CHUA
Keyword(s):  
Stochastic Resonance ◽  
Signal To Noise Ratio ◽  
Modulation Frequency ◽  
External Noise ◽  
Statistical Characteristics ◽  
Chua’S Circuit ◽  
Chua's Circuit ◽  
Coherent Interaction ◽  
Parameter Variations ◽  
Dynamics Method

The dynamics of the nonautonomous Chua's circuit driven by a sinusoidal signal and additive noise is investigated numerically via the "two-state" dynamics method. The possibility of realizing the phenomenon of stochastic resonance (SR) is established. The SR is characterized by an increase in the signal-to-noise ratio (SNR) due to the coherent interaction between the characteristic frequencies of the chaotic bistable Chua's circuit and the modulation frequency of the input. The SNR can be controlled by both external noise and system parameter variations in this circuit. The statistical characteristics of the "chaos-chaos" type intermittency and their correlation with the optimal conditions for SR are investigated.

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