RC Polyphase Filter as Complex Analog Hilbert Filter

2019 ◽  
Vol 888 ◽  
pp. 29-36 ◽  
Author(s):  
Yoshiro Tamura ◽  
Ryo Sekiyama ◽  
Shu Sasaki ◽  
Koji Asami ◽  
Haruo Kobayashi
Keyword(s):  
Numerical Simulations ◽  
Polyphase Filter ◽  
Order Case ◽  
Complex Analog ◽  
Polyphase Filters

This paper presents that the RC polyphase filer has characteristics as a complex analog Hilbert filter. Phase characteristics of the RC polyphase filter have the same as the Hilbert filter. Also its gain characteristics can be approximated as the Hilbert filter; as its order becomes higher, its gain characteristics become closer to the Hilbert filter. We have proved these for 1st to 4th RC polyphase filters, as well as in general n-th order case, and also confirmed with numerical simulations.

An Efficient Quadratic Conversion Architecture for Real-Time Wideband DDC

2014 ◽  
Vol 527 ◽  
pp. 180-184
Author(s):  
Liu Zhang
Keyword(s):  
Real Time ◽  
Polyphase Filter ◽  
Simulation Results ◽  
Process Cost ◽  
Sample Rate ◽  
Polyphase Filters ◽  
Frequency Mixing

This paper presents an efficient quadratic conversion architecture for real-time wideband DDC, it can move IF signal to baseband in two steps. Firstly, IF signal is moved to baseband nearby with the help of an structure based on polyphase filter, which places mixers after polyphase filters. Then, the signal is moved to baseband through conventional orthogonal frequency mixing. This presented architecture can reduce filter resources and effectively reduce the sample rate and process cost. Finally, simulation results are presented to illustrate the validity of the new structure.

Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

2020 ◽  
Vol 640 ◽  
pp. A53
Author(s):  
L. Löhnert ◽  
S. Krätschmer ◽  
A. G. Peeters
Keyword(s):  
Growth Rate ◽  
Numerical Simulations ◽  
Accretion Disks ◽  
Gravitational Instability ◽  
Turbulent Viscosity ◽  
Radial Distance ◽  
Maximum Growth ◽  
Wave Number ◽  
Radiative Cooling ◽  
Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

CHARACTERIZATION OF SPLASH-PLATE ATOMIZERS USING NUMERICAL SIMULATIONS

2007 ◽  
Vol 17 (4) ◽  
pp. 347-380 ◽  
Author(s):  
Mohammad P. Fard ◽  
Denise Levesque ◽  
Stuart Morrison ◽  
Nasser Ashgriz ◽  
J. Mostaghimi
Keyword(s):  
Numerical Simulations
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