Determination of chip rate and center frequency for a spread spectrum acoustic ranging system

2003 ◽  
Author(s):  
H. Farrokhi ◽  
R. Palmer
Keyword(s):  
Spread Spectrum ◽  
Center Frequency ◽  
Acoustic Ranging

Determination of the Ultrasonic Velocity on a Recent and Aged Pine Wood

2021 ◽  
Author(s):  
Héctor Carreon ◽  
Mayra Carrillo
Keyword(s):  
Ultrasonic Velocity ◽  
Research Work ◽  
Physical And Mechanical Properties ◽  
Degradation Process ◽  
Ultrasonic Transducers ◽  
Center Frequency ◽  
Ultrasonic Emission ◽  
Significant Mass

Abstract Aging in wood is the inevitable modification of physical and mechanical properties due to deterioration caused by different factors such as organisms that destroy wood, photodegradation, weathering or long-term loading. During the wood degradation process, significant mass, stiffness and strength are lost. Therefore, it is relevant to monitor the wood decomposition process to guarantee the structural requirements in buildings. This research work aims to report the influence of degradation in wood due to deterioration through the use of ultrasonic measurements. Longitudinal and transverse ultrasonic velocities were calculated using the ultrasonic emission-transmission technique for aged and unaged Mexican pine (Pinus Strobus) wood. The experimental measurements were carried out using longitudinal and shear wave ultrasonic transducers with a center frequency of 1.0 MHz and 0.5MHz respectively. Scanning electron microscopy (SEM) was performed to establish a direct correlation with the behavior of the ultrasonic wave developed in naturally aged and unaged wood. Measurements revealed higher ultrasonic velocity values for unaged wood samples in longitudinal, tangential and radial directions compared to aged wood samples, but no significant differences were found in all other wood directions.

scholarly journals Easily-Deployable Acoustic Local Positioning System Based on Auto-Calibrated Wireless Beacons

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1385 ◽  
Author(s):  
José Moreno ◽  
Fernando Álvarez ◽  
Teodoro Aguilera ◽  
José Paredes
Keyword(s):  
Spread Spectrum ◽  
Low Cost ◽  
Experimental Tests ◽  
Real Time System ◽  
Positioning Systems ◽  
Local Positioning System ◽  
Update Rate ◽  
Positioning Algorithm ◽  
Node Position

Self-calibrated Acoustic Local Positioning Systems (ALPS) generally require a high consumption of hardware and software resources to obtain the user’s position at an acceptable update rate. To address this limitation, this work proposes a self-calibrated ALPS based on a software/hardware co-design approach. This working architecture allows for efficient communications, signal processing tasks, and the running of the positioning algorithm on low-cost devices. This fact also enables the real-time system operation. The proposed system is composed of a minimum of four RF-synchronized active acoustic beacons, which emit spread-spectrum modulated signals to position an unlimited number of receiver nodes. Each receiver node estimates the beacons’ position by means of an auto-calibration process and then computes its own position by means of a 3D multilateration algorithm. A set of experimental tests has been carried out where the feasibility of the proposed system is demonstrated. In these experiments, accuracies below 0.1 m are obtained in the determination of the receptor node position with respect to the set of previously-calibrated beacons.

scholarly journals Design of double ring lock ring in extensible frequency clock generator chip

2021 ◽  
Vol 2137 (1) ◽  
pp. 012041
Author(s):  
Chao Xu ◽  
Yumeng Xie ◽  
Yuan Zhou
Keyword(s):  
Spread Spectrum ◽  
Electromagnetic Interference ◽  
Phase Locked Loop ◽  
Center Frequency ◽  
Good Effect ◽  
Clock Generator ◽  
Clock Frequency ◽  
Noise Interference ◽  
Main Loop ◽  
Secondary Loop

Abstract With the continuous development of computer technology and the continuous improvement of interface data rate, the clock frequency has reached the demand of several gigahertz, which makes the electromagnetic interference problem very serious. Spread spectrum clock is an effective method to reduce electromagnetic interference of digital chips. Therefore, this paper designs a double-loop phase-locked loop that can spread spectrum and has strong anti-electromagnetic noise interference ability. The designed dual-loop phase-locked loop can be used in the clock generator chip. The overall structure of the circuit consists of a main loop and a secondary loop. The main loop is an adjustable phase-locked loop circuit that can provide an output with a center frequency of 500MHz. The secondary loop can realize the spread spectrum function by charging and discharging the filter capacitor of the main loop loop, and at the same time, the spreading depth can be set by the feedback based on the frequency division. The dual-loop phase-locked loop designed in this paper has a good effect in spread spectrum and anti-electromagnetic interference noise.

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