scholarly journals TRC-Based High-Precision Spot Position Detection in Inter-Satellite Laser Communication

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5649
Author(s):  
Qing Li ◽  
Hongyang Guo ◽  
Shaoxiong Xu ◽  
Yangjie Xu ◽  
Qiang Wang ◽  
...  
Keyword(s):  
High Precision ◽  
Signal To Noise Ratio ◽  
Absolute Error ◽  
Light Signal ◽  
Laser Communication ◽  
Complete Space ◽  
Position Detection ◽  
Satellite Laser Communication ◽  
Space Optical Communication ◽  
Four Quadrant

Inter-satellite laser communication (Is-OWC) is one of the main space optical communication technologies currently studied in various countries. In recent years, a kind of Is-OWC communication terminal without independent beacon light has appeared. Such terminals do not have a separate beacon laser with a large divergence angle, but use a narrower communication beam to complete space capture and tracking. Therefore, the energy of the light beam divided by the acquisition, tracking, and aiming (ATP) system is greatly reduced. How to perform high-precision spot position detection under extremely low signal-to-noise ratio (SNR) is a problem that must be faced. Aiming to resolve this problem, this article proposes to use a cosine signal to modulate the intensity of the signal light, so as to convert the problem of detecting a weak light signal into the problem of detecting a line spectrum signal. The authors used the time reversal convolution (TRC) algorithm with a window function to suppress noise and enhance the spectrum line, so as to accurately detect the amplitudes of the weak photocurrents. Finally, by calculating the ratio of the photocurrent amplitude values, the precise spot position is obtained. In the experiment, when the output SNR of the four-quadrant detector (QD) is as low as −17.86 dB, the proposed method can still detect the spot position and the absolute error is limited within 0.0238 mrad.

Investigation of high-precision algorithm for the spot position detection for four-quadrant detector

Optik ◽  
2020 ◽  
Vol 203 ◽  
pp. 163941
Author(s):  
Wang Xuan ◽  
Su Xiuqin ◽  
Liu Guizhong ◽  
Han Junfeng ◽  
Wang Rui
Keyword(s):  
High Precision ◽  
Position Detection ◽  
Four Quadrant

scholarly journals A Method for Improving the Detection Accuracy of the Spot Position of the Four-Quadrant Detector in a Free Space Optical Communication System

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7164
Author(s):  
Xuan Wang ◽  
Xiuqin Su ◽  
Guizhong Liu ◽  
Junfeng Han ◽  
Kaidi Wang ◽  
...  
Keyword(s):  
Optical Communication ◽  
Communication System ◽  
Detection Accuracy ◽  
Free Space Optical Communication ◽  
Free Space Optical ◽  
Optical Communication System ◽  
Detection Model ◽  
Position Detection ◽  
Space Optical Communication ◽  
Four Quadrant

In a free space optical communication system, the beacon light will lose most of its energy after long-distance transmission, and the background light from the universe will strongly interfere with it. The four-quadrant detector (4QD) has been widely used in optical communication systems as a high-precision spot position detection sensor. However, if the light signal falling on the 4QD is too weak, the electrical signal of the output position will be very weak, and it will easily be affected by or even submerged in noise. To solve this problem, we propose a method for improving the spot position detection accuracy. First, we analyzed the solution relationship between the actual position of the spot and the output signal of the 4QD, with a Gaussian spot as the incident light model. The output current signal of the detector was then transimpedance-amplified by an analog circuit and the output voltage signal with noise was digitally filtered. An error compensation factor and the gap size of the detector were introduced into the traditional spot position detection model. High-precision spot position information for the 4QD in a complex environment was then obtained using the improved spot position detection model. Experimental results show that the maximum spot position detection error for this method was only 0.0277 mm, and the root mean square error was 0.0065 mm, when the 4QD was in a high background noise environment. The spot position detection accuracy was significantly improved compared with traditional detection algorithms. Real-time detection can therefore be achieved in practical applications.

scholarly journals High-Precision Dual-Stage Pointing Mechanism for Miniature Satellite Laser Communication Terminals

2021 ◽  
Vol 68 (1) ◽  
pp. 776-785
Author(s):  
Riccardo Antonello ◽  
Francesco Branz ◽  
Francesco Sansone ◽  
Angelo Cenedese ◽  
Alessandro Francesconi
Keyword(s):  
High Precision ◽  
Laser Communication ◽  
Satellite Laser Communication ◽  
Dual Stage

scholarly journals Velody 2—Resilient High-Capacity MIDI Steganography for Organ and Harpsichord Music

2020 ◽  
Vol 11 (1) ◽  
pp. 39
Author(s):  
Eric Järpe ◽  
Mattias Weckstén
Keyword(s):  
Mean Absolute Error ◽  
Signal To Noise Ratio ◽  
High Capacity ◽  
Absolute Error ◽  
Music Technology ◽  
Alternative Methods ◽  
File Size ◽  
User Friendly ◽  
Different Levels ◽  
Better Than

A new method for musical steganography for the MIDI format is presented. The MIDI standard is a user-friendly music technology protocol that is frequently deployed by composers of different levels of ambition. There is to the author’s knowledge no fully implemented and rigorously specified, publicly available method for MIDI steganography. The goal of this study, however, is to investigate how a novel MIDI steganography algorithm can be implemented by manipulation of the velocity attribute subject to restrictions of capacity and security. Many of today’s MIDI steganography methods—less rigorously described in the literature—fail to be resilient to steganalysis. Traces (such as artefacts in the MIDI code which would not occur by the mere generation of MIDI music: MIDI file size inflation, radical changes in mean absolute error or peak signal-to-noise ratio of certain kinds of MIDI events or even audible effects in the stego MIDI file) that could catch the eye of a scrutinizing steganalyst are side-effects of many current methods described in the literature. This steganalysis resilience is an imperative property of the steganography method. However, by restricting the carrier MIDI files to classical organ and harpsichord pieces, the problem of velocities following the mood of the music can be avoided. The proposed method, called Velody 2, is found to be on par with or better than the cutting edge alternative methods regarding capacity and inflation while still possessing a better resilience against steganalysis. An audibility test was conducted to check that there are no signs of audible traces in the stego MIDI files.

scholarly journals Broadband Laser Doppler Frequency Shift Emulator for Satellite Laser Communication

2019 ◽  
Vol 11 (6) ◽  
pp. 1-12
Author(s):  
Jinye Li ◽  
Yuan Yao ◽  
Guozhang Wu ◽  
Jiaqing Hou ◽  
Wenqi Yu ◽  
...  
Keyword(s):  
Frequency Shift ◽  
Doppler Frequency ◽  
Doppler Frequency Shift ◽  
Laser Doppler ◽  
Laser Communication ◽  
Satellite Laser Communication ◽  
Broadband Laser

Pointing and tracking errors due to low-frequency deformation in inter-satellite laser communication

2018 ◽  
Vol 66 (4) ◽  
pp. 430-437 ◽  
Author(s):  
Chao Wang ◽  
Tao Zhang ◽  
Shou-feng Tong ◽  
Ying-chao Li ◽  
Lun Jiang ◽  
...  
Keyword(s):  
Low Frequency ◽  
Laser Communication ◽  
Tracking Errors ◽  
Satellite Laser Communication

Using top-hat beam to improve the performance of the inter-satellite laser communication

Optik ◽  
2017 ◽  
Vol 137 ◽  
pp. 238-243
Author(s):  
Jian Huang ◽  
Ke Deng ◽  
Zhoushi Yao
Keyword(s):  
Laser Communication ◽  
Satellite Laser Communication

scholarly journals Calculations of Signal to Noise Ratio (SNR) for Free Space Optical Communication Systems

2008 ◽  
Vol 5 (1) ◽  
pp. 95-100
Author(s):  
Baghdad Science Journal
Keyword(s):  
Optical Communication ◽  
Free Space ◽  
Communication Systems ◽  
Signal To Noise Ratio ◽  
Full Duplex ◽  
Free Space Optical ◽  
Signal To Noise ◽  
Optical Communication Systems ◽  
Space Optical Communication ◽  
Noise Ratio

In this paper, we calculate and measure the SNR theoretically and experimental for digital full duplex optical communication systems for different ranges in free space, the system consists of transmitter and receiver in each side. The semiconductor laser (pointer) was used as a carrier wave in free space with the specification is 5mW power and 650nm wavelength. The type of optical detector was used a PIN with area 1mm2 and responsively 0.4A/W for this wavelength. The results show a high quality optical communication system for different range from (300-1300)m with different bit rat (60-140)kbit/sec is achieved with best values of the signal to noise ratio (SNR).

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