Signal‐to‐noise ratio in lock‐in amplifier synchronous detection: A generalized communications systems approach with applications to frequency, time, and hybrid (rate window) photothermal measurements

1994 ◽  
Vol 65 (11) ◽  
pp. 3309-3323 ◽  
Author(s):  
Andreas Mandelis
Keyword(s):  
Systems Approach ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Synchronous Detection ◽  
Communications Systems ◽  
Noise Ratio ◽  
Lock In ◽  
Rate Window

scholarly journals Design of an Indigenised Electronic Lock-In Amplifier

2000 ◽  
Vol 23 (1) ◽  
pp. 53-60
Author(s):  
Umesh Kumar
Keyword(s):  
Narrow Band ◽  
Signal To Noise Ratio ◽  
Broad Band ◽  
Power Line ◽  
Frequency Drift ◽  
Noise Power ◽  
Signal To Noise ◽  
Band Noise ◽  
Noise Ratio ◽  
Lock In

An indigenised lock-in amplifier is designed that enables the accurate measurement of signals contaminated by broad-band noise, power-line pick-up, frequency drift, or other sources of interference. It does this by means of an extremely narrow band detector which has the centre of its passband locked to the frequency of the signal to be measured. Large improvements in signal-to-noise ratio are achieved.

Effect of Modulation Source Properties upon Signal-To-Noise Ratios of Inelastic Electron Tunneling Spectra

1986 ◽  
Vol 40 (8) ◽  
pp. 1180-1183 ◽  
Author(s):  
F. A. Dethomas ◽  
Cecil Dybowski ◽  
Harvey S. Gold
Keyword(s):  
Electron Tunneling ◽  
Second Harmonic ◽  
Signal To Noise Ratio ◽  
Harmonic Distortion ◽  
Inelastic Electron ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Inelastic Electron Tunneling ◽  
Electron Tunneling Spectroscopy ◽  
Lock In

Lock-in amplification using ac modulation and second-harmonic detection is routinely employed in such techniques as ac polarography, ac voltammetry, and inelastic electron tunneling spectroscopy (IETS). Properties of the modulation source are shown in the present IET studies to limit the obtainable signal-to-noise ratio of a spectrum. A single inelastic electron tunneling junction is used to demonstrate the effect of various commercial modulation sources on the IET spectrum of benzoic acid on alumina. With all other parameters being held constant, the signal-to-noise ratio of the IET spectrum is found to be inversely correlated with the total harmonic distortion of the modulation source.

Determination of the Best Emulsion for the Microscopy of Crystals

1981 ◽  
Vol 39 ◽  
pp. 32-33
Author(s):  
David A. Grano ◽  
Kenneth H. Downing
Keyword(s):  
Spatial Frequency ◽  
Information Transfer ◽  
Signal To Noise Ratio ◽  
Experimental Situation ◽  
Photographic Emulsion ◽  
Modulation Transfer ◽  
Signal To Noise ◽  
Frequency Space ◽  
Noise Ratio

The retrieval of high-resolution information from images of biological crystals depends, in part, on the use of the correct photographic emulsion. We have been investigating the information transfer properties of twelve emulsions with a view toward 1) characterizing the emulsions by a few, measurable quantities, and 2) identifying the “best” emulsion of those we have studied for use in any given experimental situation. Because our interests lie in the examination of crystalline specimens, we've chosen to evaluate an emulsion's signal-to-noise ratio (SNR) as a function of spatial frequency and use this as our critereon for determining the best emulsion.The signal-to-noise ratio in frequency space depends on several factors. First, the signal depends on the speed of the emulsion and its modulation transfer function (MTF). By procedures outlined in, MTF's have been found for all the emulsions tested and can be fit by an analytic expression 1/(1+(S/S0)2). Figure 1 shows the experimental data and fitted curve for an emulsion with a better than average MTF. A single parameter, the spatial frequency at which the transfer falls to 50% (S0), characterizes this curve.

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