Ultraviolet spectroscopy analysis of aircraft plume region is a new breakthrough in high-speed aircrafts detection technology. The main difficulty lies in obtaining spectral information and flow field information of aircraft plume. Firstly, based on the high-temperature radiation of high-temperature alumina particles and the secondary combustion theory of unburned fuel, the flow field of the tail flame is simulated. The simulation chamber adopts a variety of solutions and network convergence methods. The temperature, pressure and gas density distribution of the tail flame field can be obtained by simulating the tail flame flow field. Secondly, the atmospheric channel characteristics of ultraviolet detection are studied in this paper. The calculation of spectral irradiance of the plume target and the earth background ultraviolet radiation reaching the pupil of the camera is very important for the design of the detection system. Combining the absorption and scattering characteristics of the atmosphere to the ultraviolet wave band, the ultraviolet imaging detection scheme for the target tail flame is established. For the research of ultraviolet detection channel, the atmospheric radiation transmission software MODTRAN is selected to carry on the preliminary simulation research. The absorption and scattering of all atmospheric molecules and the absorption and scattering effects of aerosols and clouds are calculated by calculating the path transmittance, atmospheric emissivity, single or multiple scattering of solar and lunar emissivity and direct transmission of solar radiation.
In the present work, we show that intensity modulated
light source may be received with the help of Van cittert & Zernike
theorem interstellar observation method. And show that Poisson
probability density distribution of photon received can be used to verify
information, and introduce a photon probability theory mathematical
method to decide pulse light symbol threshold, which are already
present but unexploited in communication systems. These investigation
show that pulse light Photonic and wave decision method has huge
application potential in interstellar distance communication systems.
In recent years, with the rapid development of digital chip, high speed sampling rate analog to digital conversion chip can be used to sample narrow laser pulse echo. Moreover, high speed processor is widely applied to achieve digital laser echo signal processing algorithm. The development of digital chip greatly improved the laser ranging detection accuracy. High speed sampling and processing circuit used in the laser ranging detection system has gradually been a research hotspot. In this paper, a pulse laser echo data logging and digital signal processing circuit system is studied based on the high speed sampling. This circuit consists of two parts: the pulse laser echo data processing circuit and the data transmission circuit. The pulse laser echo data processing circuit includes a laser diode, a laser detector and a high sample rate data logging circuit. The data transmission circuit receives the processed data from the pulse laser echo data processing circuit. The sample data is transmitted to the computer through USB2.0 interface. Finally, a PC interface is designed using C# language, in which the sampling laser pulse echo signal is demonstrated and the processed laser pulse is plotted. Finally, the laser ranging experiment is carried out to test the pulse laser echo data logging and digital signal processing circuit system. The experiment result demonstrates that the laser ranging hardware system achieved high speed data logging, high speed processing and high speed sampling data transmission.
Narrow pulse laser ranging achieves long-range target detection using laser pulse with low divergent beams. Pulse laser ranging is widely used in military, industrial, civil, engineering and transportation field. In this paper, an improved narrow pulse laser ranging algorithm is studied based on the high speed sampling. Firstly, theoretical simulation models have been built and analyzed including the laser emission and pulse laser ranging algorithm. An improved pulse ranging algorithm is developed. This new algorithm combines the matched filter algorithm and the constant fraction discrimination (CFD) algorithm. After the algorithm simulation, a laser ranging hardware system is set up to implement the improved algorithm. The laser ranging hardware system includes a laser diode, a laser detector and a high sample rate data logging circuit. Subsequently, using Verilog HDL language, the improved algorithm is implemented in the FPGA chip based on fusion of the matched filter algorithm and the CFD algorithm. Finally, the laser ranging experiment is carried out to test the improved algorithm ranging performance comparing to the matched filter algorithm and the CFD algorithm using the laser ranging hardware system. The test analysis result demonstrates that the laser ranging hardware system realized the high speed processing and high speed sampling data transmission. The algorithm analysis result presents that the improved algorithm achieves 0.3m distance ranging precision. The improved algorithm analysis result meets the expected effect, which is consistent with the theoretical simulation.
For satellite navigation and positioning receivers are susceptible to the influence of the multipath, this paper used multipath estimating delay lock loop (MEDLL) technology for BOC (n, n) multipath signal tracking. Through the analysis of multipath signal model, it is concluded that all the multipath signal can be expressed by its amplitude, phase and delay. Then in odor to get the accurate direct signal, this paper applied MEDLL algorithm to estimate the received signal. Finally, the simulation show that this algorithm can realize multipath signal track demodulation and accurate data demodulation under a low signal noise ratio environment (SNR= -20db).
Pulse laser radar imaging performance is greatly influenced by different kinds of clutter. Various algorithms are developed to mitigate clutter. However, estimating performance of a new algorithm is difficult. Here, a simulation model for estimating clutter discrimination algorithms is presented. This model consists of laser pulse emission, clutter jamming, laser pulse reception and target image producing. Additionally, a hardware platform is set up gathering clutter data reflected by ground and trees. The data logging is as clutter jamming input in the simulation model. The hardware platform includes a laser diode, a laser detector and a high sample rate data logging circuit. The laser diode transmits short laser pulses (40ns FWHM) at 12.5 kilohertz pulse rate and at 905nm wavelength. An analog-to-digital converter chip integrated in the sample circuit works at 250 mega samples per second. The simulation model and the hardware platform contribute to a clutter discrimination algorithm simulation system. Using this system, after analyzing clutter data logging, a new compound pulse detection algorithm is developed. This new algorithm combines matched filter algorithm and constant fraction discrimination (CFD) algorithm. Firstly, laser echo pulse signal is processed by matched filter algorithm. After the first step, CFD algorithm comes next. Finally, clutter jamming from ground and trees is discriminated and target image is produced. Laser radar images are simulated using CFD algorithm, matched filter algorithm and the new algorithm respectively. Simulation result demonstrates that the new algorithm achieves the best target imaging effect of mitigating clutter reflected by ground and trees.
In free space optical homodyne receiver that analyze Residual carrier COSTAS loop, Inter-satellite LEO-GEO laser communication link frequency analysis, result from Doppler frequency shift 10GHz in the maximum range, LEO-GEO inter-satellite laser links between Doppler rate of change in the 20MHz/s. The optical homodyne COSTAS receiver is the application in inter-satellite optical link coherent communication system. The homodyne receiver is the three processes: Scanning frequency, Locked frequency and Locked phase, before the homodyne coherent communication. The processes are validated in lab., and the paper presents the locked frequency data and chart, LO laser frequency with triangle control scanning and receiving optical frequency is mixed less 100MHz intermediate frequency, locked frequency range between 100MHz and 1MHz basically, discriminator method determines mixing intermediate frequency less 1MHz between the signal laser and the LO laser with the low-pass filter due to frequency loop and phase loop noise. When two loops are running, the boundary frequency of laser tuning is fuzzy, so that we must be decoupling internal PID parameters. In the Locked frequency and phase COSTAS loop homodyne receiver gave the eye-diagram with Bit error rate 10E-7.
In free space optical homodyne receiver that analyze Residual carrier COSTAS loop, in
the pointing and communication phase with laser terminal analyze free space link optical power
penalty and pointing power penalty. In the conforming bit error rate with BPSK homodyne
receiver dues to the minimum receiver optical power, in the same way the relation between
receiver optical power and homodyne locked phase error variance, and the relation between
receiver optical power and homodyne optimum equivalent noise loop bandwidth, all the more loop
filter design parameter is variable with receiver optical power. In simulation COSTAS loop
homodyne locked phase error deviation and loop bandwidth, when the receiver power is more
-50dBm and less -40dBm in the signal trace, COSTAS loop parameter is not appreciable on the
whole. Locked phase loop is integrated in the relation between baseband phase error deviation and
carrier frequency shift, when baseband phase error is 10 degree, carrier frequency shift about