Frequency‐domain description of a lock‐in amplifier

1994 ◽  
Vol 62 (2) ◽  
pp. 129-133 ◽  
Author(s):  
John H. Scofield
Keyword(s):  
Frequency Domain ◽  
Domain Description ◽  
Lock In

Estimation of Eccentric Distance for Four-Tooth End Mills Based on Amplitude Spectrum

2013 ◽  
Vol 278-280 ◽  
pp. 207-211
Author(s):  
Can Liu ◽  
Jing Quan Wu ◽  
Guang Hui Li ◽  
Guang Yu Tan
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Mathematical Reasoning ◽  
Spectral Characteristics ◽  
Amplitude Spectrum ◽  
Frequency Component ◽  
Milling Force ◽  
End Mills ◽  
Domain Description ◽  
Eccentric Distance

Time-domain expressions of nominal component and eccentric component that composing horizontal peripheral milling force are derived from geometry of down milling, they are periodic functions with fundamental frequencies same as tooth-frequency and spindle-frequency respectively. By expanding these two time-domain expressions with Taylor series, the frequency-domain description of periheral milling force is obtained. Further mathematical reasoning is exerted on this frequency-domain description, and it proved that as for four-tooth end mills, even-order harmonics of eccentric milling force do not exist, and the amplitude of spindle-frequency component be linear with eccentric distance, but irrelevant with eccentric angle. Above research results imply that the tooth-frequency component of four-tooth end mills is irrelevant with eccentricity, and that eccentric distance can be estimated with amplitudes of tooth-frequency and spindle-frequency components. Results of milling experiment imply that this eccentric-distance estimating method be effective. Spectral characteristics of eccentric milling force for four-tooth end mills are revealed with theory deduction, and the estimation algorithm for eccentric distance with simple calculation is present. Study conclusions can be used in eccentric-geometry estimating and in milling-force modeling.

Single-Pixel Spatial Frequency Domain Imaging System Based on Lock-in Photon-Counting Detection

2019 ◽  
Vol 39 (4) ◽  
pp. 0412002
Author(s):  
赵宽心 Zhao Kuanxin ◽  
李同心 Li Tongxin ◽  
侯茜 Hou Xi ◽  
但迈 Dan Mai ◽  
高峰 Gao Feng
Keyword(s):  
Spatial Frequency ◽  
Frequency Domain ◽  
Imaging System ◽  
Photon Counting ◽  
Spatial Frequency Domain Imaging ◽  
Lock In ◽  
Single Pixel ◽  
Spatial Frequency Domain

Low-frequency electromagnetic fields in applied geophysics: Waves or diffusion?

Geophysics ◽  
2006 ◽  
Vol 71 (4) ◽  
pp. W29-W40 ◽  
Author(s):  
Lars O. Løseth ◽  
Hans M. Pedersen ◽  
Bjørn Ursin ◽  
Lasse Amundsen ◽  
Svein Ellingsrud
Keyword(s):  
Frequency Domain ◽  
Low Frequency ◽  
Wave Theory ◽  
Signal Propagation ◽  
Dipole Source ◽  
Conductive Materials ◽  
Em Field ◽  
Domain Description ◽  
Ray Series ◽  
Low Frequency Waves

Low-frequency electromagnetic (EM) signal propagation in geophysical applications is sometimes referred to as diffusion and sometimes as waves. In the following we discuss the mathematical and physical approaches behind the use of the different terms. The basic theory of EM wave propagation is reviewed. From a frequency-domain description we show that all of the well-known mathematical tools of wave theory, including an asymptotic ray-series description, can be applied for both nondispersive waves in nonconductive materials and low-frequency waves in conductive materials. We consider the EM field from an electric dipole source and show that a common frequency-domain description yields both the undistorted pulses in nonconductive materials and the strongly distorted pulses in conductive materials. We also show that the diffusion-equation approximation of low-frequency EM fields in conductive materials gives the correct mathematical description, and this equation has wave solutions. Having considered both a wave-picture approach and a diffusion approach to the problem, we discuss the possible confusion that the use of these terms might lead to.

scholarly journals Frequency Domain Repercussions of Instantaneous Granger Causality

2021 ◽  
Author(s):  
Luiz Antonio Baccalá ◽  
Koichi Sameshima
Keyword(s):  
Time Series ◽  
Transfer Function ◽  
Frequency Domain ◽  
Granger Causality ◽  
Partial Directed Coherence ◽  
Directed Transfer Function ◽  
Vector Autoregressive Models ◽  
Vector Autoregressive ◽  
Standard Vector ◽  
Domain Description

Using Directed Transfer Function (DTF) and Partial Directed Coherence (PDC) in their information version, this paper extends their theoretical framework to incorporate instantaneous Granger Causality (iGC)’s frequency domain description into a single unified perspective. We show that standard vector autoregressive models allow portraying iGC’s repercussions associated with Granger Connectivity where interactions mediated without delay between time series can be easily detected.

Sign in / Sign up

Export Citation Format

Share Document