scholarly journals Interperiod coherent integration of the received signal with a variable repetition period of the probing signal

Doklady BGUIR ◽  
2021 ◽  
Vol 19 (7) ◽  
pp. 40-48
Author(s):  
S. R. Heister ◽  
P. G. Semashko
Keyword(s):  
Signal To Noise Ratio ◽  
Doppler Frequency ◽  
Practical Implementation ◽  
Repetition Period ◽  
Signal To Noise ◽  
Integration Algorithm ◽  
Coherent Integration ◽  
Probing Signal ◽  
Frequency Survey ◽  
Quantitative Indicators

Interperiod coherent integration of the received signal provides an increase in the signal-to-noise ratio and is simply implemented with a fixed repetition period of the probing signals. In practice, pulsed radars use a variable repetition period to protect against blind speeds. The algorithms of the interperiod coherent integration with a variable repetition period have been developed and their features have been revealed, which are advisable to take into account in the practical implementation in the radars. These features determine the complexity of the interperiod coherent integration algorithm, the radial velocity (Doppler frequency) survey interval and the spectrum features. An algorithm is developed with simultaneous interperiod coherent integration of the received signal and a single-delay clutter cancelation in the spectral domain in the case of variable repetition period of the probing signals. The quantitative indicators obtained by modeling are presented and a comparative analysis is carried out.

scholarly journals Design of encrypted transceiver Non-coherent OFDM with ability to correct coding bits of information

2019 ◽  
Vol 9 (4) ◽  
pp. 3212
Author(s):  
Kareem J. Thajeel ◽  
Izz K. Abboud ◽  
Laith A. Kunbar
Keyword(s):  
Signal To Noise Ratio ◽  
Doppler Frequency ◽  
Frequency Effect ◽  
Signal To Noise ◽  
Frequency Multiplexing ◽  
Noise Ratio ◽  
Time Spread ◽  
Coding Bits

<p>A differential encrypted transceiver was designed in the signal-to-noise ratio systems. A time"-"spread" frequency-"encoded (TSFE) algorithm was proposed using the orthogonal frequency multiplexing multiplier OFDM. The proposed design was verified under the Doppler frequency effect and there was an improvement in the performance of the signal-to-noise ratio system. As a result, the reliability of decoded data was increased and achieves the ability to correct coding bits of information.</p>

scholarly journals Signal-to-Noise Ratio Analyses of Spaceborne GNSS-Reflectometry from Galileo and BeiDou Satellites

2021 ◽  
Vol 14 (1) ◽  
pp. 35
Author(s):  
Yang Nan ◽  
Shirong Ye ◽  
Jingnan Liu ◽  
Bofeng Guo ◽  
Shuangcheng Zhang ◽  
...  
Keyword(s):  
Global Navigation Satellite System ◽  
Signal To Noise Ratio ◽  
Satellite System ◽  
Integration Time ◽  
Navigation Satellite ◽  
Signal To Noise ◽  
Coherent Integration ◽  
Global Navigation ◽  
Coherent Integration Time ◽  
Global Navigation Satellite

In recent years, Global Navigation Satellite System Reflectometry (GNSS-R) technology has made considerable progress with the increasing of GNSS-R satellites in orbit, the improvements of GNSS-R data processing technology, and the expansion of its geophysical applications. Meanwhile, with the modernization and evolution of GNSS systems, more signal sources and signal modulation modes are available. The effective use of the signals at different frequencies or from new GNSS systems can improve the accuracy, reliability, and resolution of the GNSS-R data products. This paper analyses the signal-to-noise ratio (SNR) of the GNSS-R measurements from Galileo and BeiDou-3 (BDS-3) systems, which is one of the important indicators to measure the quality of GNSS-R data. The multi-GNSS (GPS, Galileo and BDS-3) complex waveform products generated from the raw intermediate frequency data from TechDemoSat-1 (TDS-1) satellite and Cyclone Global Navigation Satellite System (CYGNSS) constellation are used for such analyses. The SNR and normalized SNR (NSNR) of the reflected signals from Galileo and BDS-3 satellites are compared to these from GPS. Preliminary results show that the GNSS-R SNRs from Galileo and BDS-3 are ∼1–2 dB lower than the GNSS-R measurements from GPS, which could be due to the power of the transmitted power and the bandwidth of the receiver. In addition, the effect of coherent integration time on GNSS-R SNR is also assessed for different GNSS signals. It is shown that the SNR of the reflected signals can be improved by using longer coherent integration time (∼0.4–0.8 dB with 2 ms coherent integration and ∼0.6–1.2 dB with 4 ms coherent integration). In addition, it is also shown that the SNR can be improved more efficiently (∼0.2–0.4 dB) for reflected BDS-3 and Galileo signals than for GPS. These results can provide useful references for the design of future spaceborne GNSS-R instrument compatible with reflections from multi-GNSS constellations.

Coherent Integration in Astronomical Interferometry: Theory and Practice

2019 ◽  
Vol 08 (02) ◽  
pp. 1950005
Author(s):  
David Mozurkewich ◽  
Anders Jorgensen ◽  
Gerard T. van Belle
Keyword(s):  
Signal To Noise Ratio ◽  
Performance Model ◽  
Theory And Practice ◽  
Integration Algorithm ◽  
Data Set ◽  
Baseline Phase ◽  
Low Snr ◽  
Long Baseline ◽  
Coherent Integration ◽  
Parameterized Model

Ground-based long-baseline astronomical interferometry operates in a regime where short integration exposures are demanded by working in the presence of a turbulent atmosphere. To reduce piston noise to less than one radian per aperture, these exposure times are on order 10 milliseconds or less in the visible. It has long been recognized that, in the low signal-to-noise ratio (SNR) regime, the visibility SNR is improved by co-adding frames, each rotated by an estimate of its phase. However, implementation of this technique is challenging. Where it is most needed, on low SNR baselines and when combining multiple phases to estimate the phase for a lower SNR baseline, phase errors reduce the amplitude by a large amount and in a way that has proven difficult to calibrate. In this paper, an improved coherent integration algorithm is presented. A parameterized model for the phase as a function of time and wavelength is fit to the entire data set. This framework is used to build a performance model which can be used in two ways. First, it can be used to test the algorithm; by comparing its performance to theory, one can test how well the parameter fitting has worked. Also, when designing future systems, this model provides a simple way to predict performance and compare it to alternative techniques such as hierarchical fringe tracking. This technique has been applied to both simulated and stellar data.

scholarly journals A Jointly Optimized VariableM-QAM and Power Allocation Scheme for Image Transmission

2012 ◽  
Vol 2012 ◽  
pp. 1-14
Author(s):  
Mohamed El-Tarhuni ◽  
Mohamed Hassan ◽  
Akram Bin Sediq
Keyword(s):  
Search Algorithm ◽  
Signal To Noise Ratio ◽  
Image Transmission ◽  
Perceptual Quality ◽  
Practical Implementation ◽  
Signal To Noise ◽  
Look Up Table ◽  
Noise Ratio ◽  
Modulation Level

We introduce an improved image transmission scheme over wireless channels with flat Rayleigh fading. The proposed scheme jointly optimizes bit power and modulation level to maximize the peak signal-to-noise ratio (PSNR) of the reconstructed image and hence improves the perceptual quality of the received image. In this optimization process, the significance of bits with regard to the overall quality of the image is exploited. The optimality of the proposed algorithm is demonstrated using the Lagrange method and verified through an iterative offline exhaustive search algorithm. For practical implementation, a look-up table is used at the transmitter for assigning the bit power and modulation level to each bit stream according to the received signal-to-noise ratio (SNR) observed at the receiver. The proposed scheme has low complexity since the look-up table is computed offline, only once, and used for any image which makes it suitable for devices with limited processing capability. Analytical and simulation results show that the proposed scheme with jointly optimized bit power and variable modulation level provides an improvement in PSNR of about 10 to 20 dB over fixed power fixed modulation (16-QAM). A further reduction in complexity is achieved by using the average signal-to-noise ratio rather than the instantaneous SNR in selecting the system parameters.

scholarly journals Maneuvering Target Detection Based on Subspace Subaperture Joint Coherent Integration

2021 ◽  
Vol 13 (10) ◽  
pp. 1948
Author(s):  
Langxu Zhao ◽  
Haihong Tao ◽  
Weijia Chen ◽  
Dawei Song
Keyword(s):  
Signal To Noise Ratio ◽  
Doppler Frequency ◽  
Computation Complexity ◽  
Target Signal ◽  
Coherent Integration ◽  
Range Cell ◽  
Axis Rotation ◽  
Good Trade ◽  
And Performance ◽  
Range Cell Migration

Range cell migration and Doppler frequency migration induced by the target maneuverability are two difficulties of target signal enhancement and radar detection performance. In order to resolve them, a novel subaperture joint coherent integration (SJCI) algorithm is proposed in this article, which consists of three stages. Firstly, it divides the target signal into several subapertures, in which the Doppler frequency dispersions can be neglected. Afterward, coherent integration within each subaperture is implemented via scaled Fourier transform. Finally, correcting the Doppler frequency shifts and phase differences via axis rotation and phase compensation technology, the joint coherent integration among the subapertures can be achieved effectively. Based on the SJCI algorithm, an upgrade algorithm named subspace SJCI (SSJCI) is presented. Through acceleration space division and subspace translation, the SSJCI algorithm extends the subaperture time and optimizes the computation complexity significantly. Theoretical analyses and performance comparisons demonstrate that the SSJCI algorithm can accomplish a good trade-off among signal-to-noise ratio gain, detection capability, resolution, and computation complexity. In addition, the results of the numerical experiments further verify the effectiveness of the proposed algorithm.

scholarly journals AOCS Requirements and Practical Limitations for High-Speed Communications on Small Satellites

2019 ◽  
Vol 2019 ◽  
pp. 1-16
Author(s):  
Fernando Aguado-Agelet ◽  
Andrés Eduardo Villa ◽  
Marcos Arias-Acuña ◽  
Francisco Javier Díaz-Otero
Keyword(s):  
Signal To Noise Ratio ◽  
Scientific Data ◽  
Transmission Capacity ◽  
Practical Implementation ◽  
Geometrical Parameters ◽  
Radio Link ◽  
Small Satellite ◽  
Signal To Noise ◽  
Small Satellites ◽  
Noise Ratio

In recent years, an increasing number of countries have shown a growing interest in developing their indigenous space capacity building through national small satellite programs. These satellites, which were initially focused on educational and training missions, currently are more scientific and operational-oriented. Thus, small satellite missions are being considered not only as educational tools but also as technological demonstrators or, even, mature enough for commercial and scientific missions, which might generate a huge amount of data to be transmitted to the ground segment. Therefore, an increasing demand on channel capacity will be needed for downloading the generated housekeeping and scientific data for missions based on small satellites. This paper analyses the communication subsystem of a real Cubesat. The influence of geometrical parameters is rigorously calculated both in the signal-to-noise ratio and in the capacity to transmit information. Subsequently, which parameters of the radio link can be modified to increase the transmission capacity, including the pointing requirements and its practical implementation, is studied. Finally, and as a future line, the technical feasibility of using optical links on small satellites that might greatly increase the transmission capacity, including the satellite pointing problems that presents, is presented. In conclusion, this paper presents a rigorous calculation in different frequency bands of the signal-to-noise ratio and the pointing accuracy that is needed to achieve the maximum transmission speed from the satellite to the ground station, and therefore the requirements that the Attitude and Orbital Control Systems (AOCS) must have, as well as the limitations of current systems.

The modification of Kalman filterbased carrier tracking loop for GPS signals in dynamic conditions and high noise levels

2021 ◽  
Vol 64 (1) ◽  
pp. 134-144
Author(s):  
M.M. Kanouj ◽  
◽  
A.V. Klokov ◽  
G.N. Parvatov ◽  
A.I. Potekaev ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Doppler Frequency ◽  
Positioning System ◽  
Tracking Loop ◽  
Noise Levels ◽  
Signal To Noise ◽  
High Noise ◽  
Tracking Method ◽  
Dynamic Conditions ◽  
Matlab Program

This paper discusses the possibility of creating an automated positioning system, including various search objects by means of engineering intelligence, based on the methodology of tracking GPS signals. The traditional tracking methodology is analyzed and a more efficient one is proposed based on a modification of the Kalman filter for environments with low signal-to-noise ratio and in high user dynamic conditions. To achieve tracking of the GPS signals, the data is processed using MATLAB program. A comparative analysis showed that the proposed tracking method improves the tracking performance by 7 dB compared to the traditional tracking and overcomes bit synchronization losses. In addition, the proposed method improves the accuracy of Doppler frequency measurements under dynamic conditions.

scholarly journals Coherent Integration for Radar High-Speed Maneuvering Target Based on Frequency-Domain Second-Order Phase Difference

Electronics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 287 ◽  
Author(s):  
Ke Jin ◽  
Tao Lai ◽  
Yubing Wang ◽  
Gongquan Li ◽  
Yongjun Zhao
Keyword(s):  
Frequency Domain ◽  
Phase Difference ◽  
High Speed ◽  
Doppler Frequency ◽  
Peak Position ◽  
Two Dimensions ◽  
Second Order ◽  
Radar Signal ◽  
Integration Algorithm ◽  
Coherent Integration

In recent years, target detection has drawn increasing attention in the field of radar signal processing. In this paper, we address the problem of coherent integration for detecting high-speed maneuvering targets, involving range migration (RM), quadratic RM (QRM), and Doppler frequency migration (DFM) within the coherent processing interval. We propose a novel coherent integration algorithm based on the frequency-domain second-order phase difference (FD-SoPD) approach. First, we use the FD-SoPD operation to reduce the signal from three to two dimensions and simultaneously eliminate the effects of QRM and DFM, which leads to signal-to-noise ratio improvement in the velocity-acceleration domain. Next, we estimate the target motion parameters from the peak position without the need for a search procedure. We show that this algorithm can be easily implemented by using complex multiplications combined with fast Fourier transform (FFT) and inverse FFT (IFFT) operations. We perform comparisons with several representative algorithms and show that the proposed technique can be used to achieve a good trade-off between computational complexity and detection performance. We present both simulated and experimental data to demonstrate the effectiveness of the proposed method.

scholarly journals A Fast Bistatic ISAR Imaging Approach for Rapidly Spinning Targets via Exploiting SAR Technique

2020 ◽  
Vol 12 (13) ◽  
pp. 2077
Author(s):  
Zhijun Yang ◽  
Dong Li ◽  
Xiaoheng Tan ◽  
Hongqing Liu ◽  
Guisheng Liao
Keyword(s):  
Synthetic Aperture Radar ◽  
Signal To Noise Ratio ◽  
Doppler Frequency ◽  
Synthetic Aperture ◽  
Coherent Integration ◽  
Range Cell ◽  
Isar Imaging ◽  
Imaging Approach ◽  
Spinning Targets ◽  
Aperture Radar

Because of the large range of cell migration (RCM) and nonstationary Doppler frequency modulation (DFM) produced by non-cooperative targets with rapid spinning motions, it is difficult to efficiently generate a well-focused bistatic inverse synthetic aperture radar (ISAR) by use of the conventional imaging algorithms. Utilizing the property of the inherent azimuth spatial invariance in strip-map synthetic aperture radar (SAR) imaging mode, in this work, an efficient bistatic ISAR imaging approach based on circular shift operation in the range-Doppler (RD) domain is proposed. First, echoes of rapidly spinning targets are transformed into the RD domain, whose exact analytical is derived on the basis of the principle of stationary phase (POSP). Second, the RCM is corrected by using an efficient circular shift operation in the RD domain. By doing so, the energies of a scatterer that span multiple range cells are concentrated into the same range cell, and the time-varying DFM can also be compensated along the rotating radius direction. Compared with existing methods, the proposed method has advantages in its computational complexity, avoiding the interpolation and multi-dimensional search operation, and in its satisfactory imaging performance under low signal to noise ratio (SNR) conditions thanks to the two-dimensional coherent integration gain utilized. Finally, several numerical simulations are conducted to show the validity of the proposed algorithm.

Determination of the Best Emulsion for the Microscopy of Crystals

1981 ◽  
Vol 39 ◽  
pp. 32-33
Author(s):  
David A. Grano ◽  
Kenneth H. Downing
Keyword(s):  
Spatial Frequency ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Experimental Situation ◽  
Photographic Emulsion ◽  
Modulation Transfer ◽  
Signal To Noise ◽  
Frequency Space ◽  
Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

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