scholarly journals Reference frequencies comb generation for microwave photonics ADC with signal spectral-interval estimation

2019 ◽  
Vol 30 ◽  
pp. 14005
Author(s):  
Victor Kulagin ◽  
Vladimir Cherepenin ◽  
Sergey Kontorov ◽  
Denis Prokhorov ◽  
Victor Valuev
Keyword(s):  
Numerical Simulation ◽  
Input Signal ◽  
High Speed ◽  
Frequency Comb ◽  
Interval Estimation ◽  
Microwave Photonics ◽  
Intermediate Frequency ◽  
Spectral Interval ◽  
Frequency Noise ◽  
Reference Frequency

Formation of a reference frequency comb in a circuit comprising a highly stable continuous laser and an amplitude Mach- Zehnder modulator with two independent RF inputs working with large modulation index for use in a high-speed microwave photonics ADC with spectral-interval estimation is investigated by numerical simulation. In such ADCs, the entire spectrum of the input signal is divided by microwave photonics elements into spectral intervals, each of which uses a microwave photonics converter to transform the signal to an intermediate frequency (for each part of the spectrum of the microwave input signal, its own reference frequency is used for heterodyning). The requirements for a multimode source of optical reference frequencies for high-speed microwave photonics ADC are formulated. To study the characteristics of such a source, numerical modeling is carried out. It is shown that the frequency noise of the laser can be partially suppressed due to their compensation when converted to an intermediate frequency. Experimental study of the reference frequency comb generator layout showed a good agreement of the obtained characteristics with the results of numerical simulation.

Numerical Simulation of In-Pipe Turbulent Noise

2014 ◽  
Vol 607 ◽  
pp. 565-568
Author(s):  
Juan Xu ◽  
Zong Rui Hao ◽  
Zhong Hai Zhou
Keyword(s):  
Numerical Simulation ◽  
Flow Rate ◽  
High Speed ◽  
Frequency Noise ◽  
Straight Pipe ◽  
Flow Around A Cylinder ◽  
Variable Diameter ◽  
Structure Of Flow ◽  
Diameter Pipe ◽  
Parabolic Relationship

Numerical simulation is used to explore the turbulence noise in pipes generated by high-speed fluid. The characteristics of turbulent noise and its influencing factors are analyzed for different pipe structures and flow rates. The results showed that there is a parabolic relationship between the Overall Sound Pressure Level (OASPL) and the flow rate as the flow rate increases in the pipe. The OASPL of a variable diameter pipe is 20dB higher than that of the straight pipe with a built-in cylinder under the same flow rate. The structure of flow around a cylinder can effectively weaken turbulence noise and reduce high-frequency noise.

Numerical simulation of high-speed civil transport inlet operability with angle of attack

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 1223-1229
Author(s):  
Ge-Cheng Zha ◽  
Doyle Knight ◽  
Donald Smith ◽  
Martin Haas
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Angle Of Attack

Numerical Simulation of High-Speed Crack Propagating and Branching Phenomena

2016 ◽  
Vol 37 (7) ◽  
pp. 729-739
Author(s):  
GU Xin-bao ◽  
◽  
ZHOU Xiao-ping ◽  
XU Xiao ◽  
Keyword(s):  
Numerical Simulation ◽  
High Speed

Numerical Simulation of Flowfield around High Speed Trains Passing by each other at the same Speed

2011 ◽  
Vol 97-98 ◽  
pp. 698-701
Author(s):  
Ming Lu Zhang ◽  
Yi Ren Yang ◽  
Li Lu ◽  
Chen Guang Fan
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Flow Field ◽  
Point Source ◽  
High Speed ◽  
Stokes Equations ◽  
Field Structure ◽  
Vehicle Speed ◽  
Mesh Method ◽  
High Speed Trains

Large eddy simulation (LES) was made to solve the flow around two simplified CRH2 high speed trains passing by each other at the same speed base on the finite volume method and dynamic layering mesh method and three dimensional incompressible Navier-Stokes equations. Wind tunnel experimental method of resting train with relative flowing air and dynamic mesh method of moving train were compared. The results of numerical simulation show that the flow field structure around train is completely different between wind tunnel experiment and factual running. Two opposite moving couple of point source and point sink constitute the whole flow field structure during the high speed trains passing by each other. All of streamlines originate from point source (nose) and finish with the closer point sink (tail). The flow field structure around train is similar with different vehicle speed.

Active Attenuation of Low Frequency Noise Radiated from Tunnel Exit of High Speed Train

1994 ◽  
Vol 13 (2) ◽  
pp. 39-47
Author(s):  
Min Liang ◽  
Toshiya Kitamura ◽  
Katsushi Matsubayashi ◽  
Toshifumi Kosaka ◽  
Tatsuo Maeda ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Pressure Wave ◽  
High Speed ◽  
Outer Space ◽  
Low Frequency ◽  
Close Relation ◽  
Frequency Noise ◽  
High Speed Train ◽  
Low Frequency Noise ◽  
Active Cancellation

A pressure wave occurs at the instant when a high speed train enters into a long tunnel. The wave propagates downstream to the tunnel exit and low frequency noise is radiated from the exit to outer space. The low frequency noise causes a lot of problems1 to the residents living near the exit and has a close relation with the pressure gradient of the pressure wave. To attenuate the low frequency noise, an active cancellation system rather than a passive one is developed. This research uses a model tunnel to examine the characteristic of the pressure wave and investigates the possibility to reduce the low frequency noise by reducing the pressure wave gradient with active cancellation.

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