Optimum Optical Local Oscillator Power Levels Impact on Signal-to-Noise Ratio in Heterodyne

2010 ◽  
Author(s):  
Yan-Chao Li ◽  
Long Gao ◽  
Hai-Fang Cong ◽  
Yang Qu ◽  
Jie Gao ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Local Oscillator ◽  
Signal To Noise ◽  
Noise Ratio

Télémètre à détection coherente avec un laser CO2 à ondes entretenues : étude et conception

1983 ◽  
Vol 61 (2) ◽  
pp. 318-331 ◽  
Author(s):  
Denis Vincent ◽  
Gabriel Otis
Keyword(s):  
Detection System ◽  
Signal To Noise Ratio ◽  
Optical Power ◽  
Experimental System ◽  
Intermediate Frequency ◽  
Local Oscillator ◽  
Heterodyne Detection ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Rotating Target

We performed a theoretical and experimental study of a 10.6 μm heterodyne detection system with nonlinear postdetection. A single laser serves as both transmitter and local oscillator; the intermediate frequency is given by the Doppler effect due to a rotating target. An electrooptic crystal modulates the amplitude of the laser beam at a frequency of 15 kHz; a synchronous voltmeter measures the return signal after the nonlinear element. Values of the signal-to-noise ratio with respect to incident optical power agree with the results of the theoretical model. In particular, experimentally measured target-induced frequency spreading effects on the signal-to-noise ratio correspond to the predictions of the model. We also describe an experimental system.

scholarly journals Bitstream Photon Counting Chirped AM Lidar with Digital I/Q Demodulation

2020 ◽  
Author(s):  
Brian Redman
Keyword(s):  
Integrated Circuits ◽  
Single Channel ◽  
Signal To Noise Ratio ◽  
Photon Counting ◽  
Complementary Metal Oxide Semiconductor ◽  
Local Oscillator ◽  
Oxide Semiconductor ◽  
Signal To Noise ◽  
Receiver Architecture ◽  
Noise Ratio

This paper is a follow-up to two previous papers, one introducing the new bitstream Photon Counting Chirped Amplitude Modulation (AM) Lidar (PC-CAML) with the unipolar Digital Logic Local Oscillator (DLLO) concept, and the other paper introducing the improvement thereof using the bipolar DLLO. In that previous work, there was only a single channel of digital mixing of the DLLO with the received photon counting signal. This paper introduces a new bitstream PC-CAML receiver architecture with an in-phase (I) digital mixing channel and a quadrature phase (Q) digital mixing channel for digital I/Q demodulation with the bipolar DLLO to improve the signal-to-noise ratio (SNR) by 3 dB compared to that for the single digital mixing channel with the bipolar DLLO and by 5.5 dB compared to that for the single digital mixing channel with the unipolar DLLO. (patent pending) The bipolar DLLO with digital I/Q demodulation architecture discussed in this paper retains the key advantages of the previous bitstream PC-CAML with a DLLO systems since it also replaces bulky, power-hungry, and expensive wideband RF analog electronics with digital components that can be implemented in inexpensive silicon complementary metal-oxide-semiconductor (CMOS) read-out integrated circuits (ROICs) to make the bitstream PC-CAML with a DLLO more suitable for compact lidar-on-a-chip systems and lidar array receivers than previous PC-CAML systems. This paper introduces the bipolar DLLO with digital I/Q demodulation receiver architecture for bitstream PC-CAML and presents the initial signal-to-noise ratio (SNR) theory with comparisons to Monte Carlo simulation results.

Analysis of Signal to Noise Ratio for Laser Heterodyne with Weak Local Oscillator Based on Multi-pixel Photon Counter

2013 ◽  
Vol 40 (3) ◽  
pp. 0308008
Author(s):  
张合勇 Zhang Heyong ◽  
刘立生 Liu Lisheng ◽  
赵帅 Zhao Shuai ◽  
王挺峰 Wang Tingfeng ◽  
郭劲 Guo Jin
Keyword(s):  
Signal To Noise Ratio ◽  
Local Oscillator ◽  
Signal To Noise ◽  
Photon Counter ◽  
Laser Heterodyne ◽  
Noise Ratio

scholarly journals Bipolar Digital Logic Local Oscillator for Bitstream Photon Counting Chirped AM Lidar

2019 ◽  
Author(s):  
Brian Redman
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Signal To Noise Ratio ◽  
Photon Counting ◽  
Local Oscillator ◽  
Digital Logic ◽  
Quantization Noise ◽  
Signal To Noise ◽  
Simulation Results ◽  
Noise Ratio

This paper is a follow-up to a previous paper introducing the new bitstream Photon Counting Chirped Amplitude Modulation (AM) Lidar (PC-CAML) with a Digital Logic Local Oscillator (DLLO) concept. In that previous work, the DLLO was unipolar. In this paper, a new bipolar DLLO for the bitstream PC-CAML is introduced (patent pending). The bipolar DLLO retains the key advantages of the unipolar DLLO for the bitstream PC-CAML since it also replaces bulky, power-hungry, and expensive wideband RF analog electronics with digital components that can be implemented in inexpensive silicon complementary metal-oxide-semiconductor (CMOS) read-out integrated circuits (ROICs) to make the bitstream PC-CAML with a DLLO more suitable for compact lidar-on-a-chip systems and lidar array receivers than previous PC-CAML systems. In addition, the bipolar DLLO improves the electrical power signal-to-noise ratio (SNR) of the bitstream PC-CAML by about 2.5 dB compared to that of the unipolar DLLO as shown by the theoretical and Monte Carlo simulation results presented in this paper. Theoretically, there should be a 3 dB improvement for the bipolar DLLO from the elimination of the signal power loss to the DC component of the intermediate frequency (IF) spectrum that occurs with the unipolar DLLO. However, this improvement is partially offset by a higher quantization noise for the bipolar DLLO compared to that of the unipolar DLLO as explained in this paper.This paper introduces the bipolar DLLO for bitstream PC-CAML concept and presents the initial signal-to-noise ratio (SNR) theory with comparisons to Monte Carlo simulation results.

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.

Experiments in Bright-Field Imaging with Hollow-Cone Illumination

1981 ◽  
Vol 39 ◽  
pp. 226-227
Author(s):  
W. Kunath ◽  
K. Weiss ◽  
E. Zeitler
Keyword(s):  
Signal To Noise Ratio ◽  
Carbon Support ◽  
Electronic System ◽  
Optic Axis ◽  
Hollow Cone ◽  
Signal To Noise ◽  
Bright Field ◽  
Noise Ratio ◽  
Single Field ◽  
Field Imaging

Bright-field images taken with axial illumination show spurious high contrast patterns which obscure details smaller than 15 ° Hollow-cone illumination (HCI), however, reduces this disturbing granulation by statistical superposition and thus improves the signal-to-noise ratio. In this presentation we report on experiments aimed at selecting the proper amount of tilt and defocus for improvement of the signal-to-noise ratio by means of direct observation of the electron images on a TV monitor.Hollow-cone illumination is implemented in our microscope (single field condenser objective, Cs = .5 mm) by an electronic system which rotates the tilted beam about the optic axis. At low rates of revolution (one turn per second or so) a circular motion of the usual granulation in the image of a carbon support film can be observed on the TV monitor. The size of the granular structures and the radius of their orbits depend on both the conical tilt and defocus.

Information capacity and bandwidth limitations in the SEM

1989 ◽  
Vol 47 ◽  
pp. 84-85
Author(s):  
D. C. Joy ◽  
R. D. Bunn
Keyword(s):  
Signal To Noise Ratio ◽  
Critical Dimension ◽  
Information Capacity ◽  
Acquisition Time ◽  
Signal To Noise ◽  
Sem Image ◽  
Probe Size ◽  
Minimum Number ◽  
Noise Ratio ◽  
Signal Channel

The information available from an SEM image is limited both by the inherent signal to noise ratio that characterizes the image and as a result of the transformations that it may undergo as it is passed through the amplifying circuits of the instrument. In applications such as Critical Dimension Metrology it is necessary to be able to quantify these limitations in order to be able to assess the likely precision of any measurement made with the microscope.The information capacity of an SEM signal, defined as the minimum number of bits needed to encode the output signal, depends on the signal to noise ratio of the image - which in turn depends on the probe size and source brightness and acquisition time per pixel - and on the efficiency of the specimen in producing the signal that is being observed. A detailed analysis of the secondary electron case shows that the information capacity C (bits/pixel) of the SEM signal channel could be written as :

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