scholarly journals Double-Frequency-Shift Acousto-Optic Modulator with Controllable Pulse Pair Frequency Difference

Photonics ◽  
2021 ◽  
Vol 8 (10) ◽  
pp. 436
Author(s):  
Yuhe Wang ◽  
Yudong Lian ◽  
Shiwei Han ◽  
Yang Yu ◽  
Xuan Qi ◽  
...  
Keyword(s):  
Frequency Shift ◽  
Crystal Size ◽  
Output Pulse ◽  
Frequency Difference ◽  
Acousto Optic Modulator ◽  
Double Frequency ◽  
Pulse Pair ◽  
Synchronization Signal ◽  
The Time Domain ◽  
Positive Frequency

A scheme for controlling the frequency difference of output pulse pair with double frequency shift loops is proposed. The frequency shift system includes two loop elements of 20 and 200 MHz. The first one carries out a single selective positive frequency shift of 1–20 MHz, and the second one can satisfy a single fixed positive frequency shift of 200 MHz. The reverse cascade technology of two acousto-optic crystals is introduced to solve the limitation of the small frequency shift of crystal size. A multichannel synchronization signal completes the time domain control of each acousto-optic modulator. Finally, the frequency shift difference of the output pulse pair ranges of 0–2 GHz, and the frequency shift accuracy is 5 MHz.

scholarly journals One-dimensional model describing eigenmode frequency shift during transverse excitation

2019 ◽  
Author(s):  
S. Webster ◽  
J. Hardi ◽  
M. Oschwald
Keyword(s):  
Frequency Shift ◽  
High Amplitude ◽  
Operating Conditions ◽  
Model Parameters ◽  
Amplitude Dependence ◽  
Acoustic Oscillations ◽  
One Dimensional ◽  
Hypothesis Model ◽  
The Time Domain ◽  
Combustion Tests

A shift in transverse eigenmode frequency was observed in an experimental combustion chamber when exposed to large amplitude acoustic oscillations during oxygen–hydrogen combustion tests. A shift in eigenmode frequency under acoustic conditions representative of combustion conditions is of critical importance when tuning acoustic absorbers or investigating injection coupled combustion instabilities. The experimentally observed frequency shift was observed both in the frequency domain and as an asymmetric amplitude response to a linear frequency ramp of an external excitation system in the time domain. The frequency shift was found to be dependent on amplitude and operating condition. A hypothesis is presented for the frequency shift based on change in speed-of-sound distributions due to flame contraction when exposed to high amplitude pressure oscillations. A one-dimensional (1D) model was created to test the hypothesis. Model parameters were based on relationships observed in experimental data. The model was found to accurately recreate the frequency shifting asymmetric response observed in test data as well as its amplitude dependence. Further development is required to investigate the influence of operating conditions and chamber design on the quantitative modeling of the frequency shift.

Biomolecular stiffness detection based on positive frequency shift of CMOS compatible gigahertz solidly mounted resonators

2017 ◽  
Vol 96 ◽  
pp. 206-212 ◽  
Author(s):  
Qingrui Yang ◽  
Shuting Pan ◽  
Yuan Zhao ◽  
Hao Zhang ◽  
Wei Pang ◽  
...  
Keyword(s):  
Frequency Shift ◽  
Cmos Compatible ◽  
Positive Frequency

The Synthesis of the Novel Vacuum Ultraviolet Double Frequency Crystal KBe2BO3F2 (KBBF)

2014 ◽  
Vol 1004-1005 ◽  
pp. 348-353
Author(s):  
Yao Wen Ban ◽  
Wen Li Wang ◽  
Wei Zhang ◽  
Jian Han
Keyword(s):  
Crystal Size ◽  
Vacuum Ultraviolet ◽  
Critical Factor ◽  
Raw Material ◽  
Phase Matching ◽  
The Novel ◽  
Reduced Pressure ◽  
Double Frequency ◽  
Growth Method ◽  
Growth Methods

KBe2BO3F2 (KBBF) crystal is a sole important and practical ultraviolet nonlinear optical material. It can realize the output of vacuum ultraviolet laser below 200nm with the method of phase-matching. However, it is difficult to grow a practical crystal size with the general growth methods such as fluxed melts, hydrothermal or prism-coupling technique because of the layering growth habit. A reduced-pressure melts growth method was presented to grow bulk KBBF crystal and how to achieve the high quality raw material for growth is a critical factor. In this paper, the influences of syntheses methods of raw material and experiment conditions were discussed, and the best syntheses method was selected.

scholarly journals Interpretation of Quartz Crystal Microbalance Behavior with Viscous Film Using a Mason Equivalent Circuit

Chemosensors ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 9
Author(s):  
Sawit Na Songkhla ◽  
Takamichi Nakamoto
Keyword(s):  
Frequency Shift ◽  
Equivalent Circuit ◽  
Quartz Crystal ◽  
Single Layer ◽  
Frequency Change ◽  
Sensing Applications ◽  
Sensitivity And Selectivity ◽  
Quartz Crystal Microbalances ◽  
Negative Frequency Shift ◽  
Positive Frequency

In odor sensing based on Quartz Crystal Microbalances (QCMs), the sensing film is crucial for both sensor sensitivity and selectivity. The typical response of the QCM due to sorption is a negative frequency shift. However, in some cases, the sorption causes a positive frequency shift, and then, Sauerbrey’s equation and Kanazawa’s equation cannot be applied to this situation. We model the QCM response with a Mason equivalent circuit. The model approximates a single layer of a uniform viscous coating on the QCM. The simulation of the equation circuit shows the possibility of the positive frequency change when the sorption occurs, which is the situation we find in some of the odor sensing applications. We measured the QCM frequency and resistance using the Vector Network Analyzer (VNWA). The QCMs were coated with glycerol, PEG2000, and PEG20M. To simulate odor exposure, a microdispenser was used to deposit the water. A positive frequency shift was observed in the case of PEG2000, and a negative frequency change was obtained for PEG20M. These results can be explained by the Mason equivalent circuit, with the assumption that when the film is exposed to water, its thickness increases and its viscosity decreases.

scholarly journals Bearing Estimation Using Double Frequency Reassignment for a Linear Passive Array

2017 ◽  
Vol 24 (3) ◽  
pp. 26-35 ◽  
Author(s):  
Krzysztof Czarnecki ◽  
Wojciech Leśniak
Keyword(s):  
Additive White Gaussian Noise ◽  
A Priori ◽  
Average Power ◽  
Spatial Spectrum ◽  
Spectrum Estimation ◽  
Energy Distributions ◽  
Double Frequency ◽  
Bearing Estimation ◽  
The Time Domain ◽  
Spatial Spectrum Estimation

AbstractThe paper demonstrates the use of frequency reassignment for bearing estimation. For this task, signals derived from a linear equispaced passive array are used. The presented method makes use of Fourier transformation based spatial spectrum estimation. It is further developed through the application of two-dimensional reassignment, which leads to obtaining highly concentrated energy distributions in the joint frequency-angle domain and sharp graphical imaging. The introduced method can be used for analysing,a priori, unknown signals of broadband, nonstationary, and/or multicomponent type. For such signals, the direction of arrival is obtained based upon the marginal energy distribution in the angle domain, through searching for arguments of its maxima. In the paper, bearing estimation of three popular types of sonar pulses, including linear and hyperbolic frequency modulated pulses, as well as no frequency modulation at all, is considered. The results of numerical experiments performed in the presence of additive white Gaussian noise are presented and compared to conventional digital sum-delay beamforming performed in the time domain. The root-mean-square error and the peak-to-average power ratio, also known as the crest factor, are introduced in order to estimate, respectively, the accuracy of the methods and the sharpness of the obtained energy distributions in the angle domain.

scholarly journals Asymmetric Binary Frequency Shift Keying and its Frequency Attribute

2013 ◽  
Vol 765-767 ◽  
pp. 1236-1239
Author(s):  
Shi Kai Zhang ◽  
Jian Li Jin
Keyword(s):  
Frequency Shift ◽  
High Speed ◽  
Continuous Phase ◽  
Spectrum Efficiency ◽  
Frequency Shift Keying ◽  
Modulation Format ◽  
Shift Keying ◽  
High Speed Data ◽  
The Time Domain ◽  
High Degree

An innovative asymmetric binary frequency shift keying (ABFSK) modulation format is presented and studied both in the time domain and frequency domain. First, the modulation function is demonstrated, it shows a quasi-continuous phase attribute and an ability of high speed data modulation. Second, the domain attribute is studied; it has a high degree of energy centralization. Thus, a narrow occupied bandwidth can be achieved after a proper filtering. Then, the finite spectrum can be conserved to improve spectrum efficiency.

Flexible high-resolution wavefront sensor using a double-frequency two-dimensional acousto-optic modulator

2013 ◽  
Vol 52 (3) ◽  
pp. 034401
Author(s):  
Tenghao Li ◽  
Lei Huang ◽  
Yuntao Qiu ◽  
Qiao Xue ◽  
Mali Gong
Keyword(s):  
High Resolution ◽  
Wavefront Sensor ◽  
Two Dimensional ◽  
Acousto Optic Modulator ◽  
Double Frequency

scholarly journals METHOD OF AUTOMATIC DETERMINATION OF THE CARRIER FREQUENCY OF SHORT-TIME FREQUENCY-SHIFT KEYING SIGNALS

2019 ◽  
pp. 146-154
Author(s):  
O. A. Nahorniuk
Keyword(s):  
Frequency Shift ◽  
Frequency Spectrum ◽  
Carrier Frequency ◽  
Frequency Difference ◽  
Signal Spectrum ◽  
Frequency Shift Keying ◽  
Time Frequency ◽  
Shift Keying ◽  
Short Time

Method for determination of the carrier frequency of short-time frequency-shift keying signals based on searching for dominant harmonics whose frequency difference is close to the subcarrier spacing frequency is proposed in the article. In telecommunication systems with burst transmissions, the symbol distribution law of the modulating sequence is not always uniform, which under a limited signal duration leads to an increase in the errors in determining the frequency-shift keying parameters. The increase in errors is due to distortion of the amplitude-frequency spectrum of the signal and a decrease in the probability of the correct identification of the subcarrier oscillations harmonics. To improve the accuracy of determining the carrier frequency proposed method uses a priori information about the value of the spacing frequency of the subcarrier oscillations and the multiplicity of frequency-shift keying. The developed approach consists in obtaining the amplitude-frequency spectrum of the signal, calculating the search threshold of dominant harmonics, determining their frequencies which correspond to subcarrier oscillations, and calculating the carrier frequency as their arithmetic mean value. To calculate the signal spectrum was used the modified Welch periodogram method with has a low dispersion of spectral estimates. The harmonic search threshold is determined automatically based on the statistical characteristics of the amplitude-frequency spectrum. Among harmonics with amplitudes greater than the threshold value, those are determined that the frequency difference between which is closest to the subcarrier spacing frequency. The simulations performed in the MATLAB software environment showed that the error in determining the carrier frequency was halved compared to the classical approach under signal-to-noise ratio from -15 dB, and the developed method was efficient if the symbol appearance probability were from 0,5 to 0,8.

Modulation transfer spectroscopy based on acousto-optic modulator with zero frequency shift

2018 ◽  
Vol 27 (11) ◽  
pp. 114203
Author(s):  
Chen-Fei Wu ◽  
Xue-Shu Yan ◽  
Li-Xun Wei ◽  
Pei Ma ◽  
Jian-Hui Tu ◽  
...  
Keyword(s):  
Frequency Shift ◽  
Modulation Transfer ◽  
Acousto Optic Modulator ◽  
Zero Frequency
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