A doppler frequency calibration method by ionosphere for skywave OTHR

2017 ◽  
Author(s):  
Yang Li ◽  
Chang Liu ◽  
Ning Zhang
Keyword(s):  
Doppler Frequency ◽  
Calibration Method ◽  
Frequency Calibration

scholarly journals A low complexity digital frequency calibration with high jitter immunity for ultra-low-power oscillators

2019 ◽  
Vol 17 ◽  
pp. 145-150
Author(s):  
Markus Scholl ◽  
Ralf Wunderlich ◽  
Stefan Heinen
Keyword(s):  
Low Power ◽  
Communication Systems ◽  
Calibration Method ◽  
Low Complexity ◽  
Frequency Stability ◽  
Wireless Communication Systems ◽  
Ultra Low Power ◽  
Wireless Transceiver ◽  
Digital Frequency ◽  
Frequency Calibration

Abstract. This paper presents a highly efficient digital frequency calibration method for ultra-low-power oscillators in wireless communication systems. This calibration method locks the ultra-low-power oscillator's output frequency to the reference clock of the wireless transceiver during its send- and receive-state to achieve frequency stability over process variation and temperature drifts. The introduced calibration scheme offers high jitter immunity and short locking periods overcoming frequency calibration errors for typical ultra-low-power oscillator's by utilizing non-linear segmented feedback levels. In measurements the proposed calibration method improves the frequency stability of an ultra-low-power 32 kHz oscillator from 53 to 10 ppm ∘C−1 over a wide temperature range for temperature drifts of less than 1 ∘C s−1 with an estimated power consumption of 185 nW while coping with relocking periods of 7 ms.

A Bandwidth and Frequency Calibration Method for OOK UWB-IR Transmitter with High Energy Efficiency

2019 ◽  
Vol 29 (09) ◽  
pp. 2050137
Author(s):  
Shengxi Diao ◽  
Fujiang Lin ◽  
Yuanjin Zheng
Keyword(s):  
Power Efficiency ◽  
Average Power ◽  
Calibration Method ◽  
High Energy ◽  
Impulse Radio ◽  
Ultra Wideband ◽  
Lc Oscillator ◽  
Data Rates ◽  
Pvt Variations ◽  
Frequency Calibration

In this paper, an offline bandwidth and frequency calibration method for an on–off LC oscillator-based ultra-wideband impulse radio (UWB-IR) transmitter is presented. Implemented in 0.18-[Formula: see text]m CMOS, the offline calibration circuits consume very little power. This allows the transmitter to consume an ultra-low average power of 319[Formula: see text][Formula: see text]W over 3–5[Formula: see text]GHz at 2[Formula: see text]Mbps. The calibration is critical to ensure the FCC spectral mask compliance despite the process–voltage–temperature (PVT) variations. The transmitter can deliver a large differential output swing of 1.8–3[Formula: see text]V to a 100-[Formula: see text] load with minimal power efficiency of 7% at different data rates (2–30[Formula: see text]Mbps). It is suitable for WPAN application with localization and positioning capabilities.

Calf blood flow and posture: Doppler ultrasound calibrated by plethysmography

1992 ◽  
Vol 72 (5) ◽  
pp. 1668-1674 ◽  
Author(s):  
B. E. Van Leeuwen ◽  
J. Lubbers ◽  
G. J. Barendsen ◽  
L. de Pater
Keyword(s):  
Blood Flow ◽  
Doppler Ultrasound ◽  
Doppler Frequency ◽  
Calibration Method ◽  
Rhythmic Contraction ◽  
Cross Sectional ◽  
Calf Blood Flow ◽  
Doppler Signals ◽  
Heart Cycle ◽  
The Relationship

A procedure was developed that enables measurement of rapid variations in calf blood flow during voluntary rhythmic contraction of the calf muscles in supine, sitting, and standing positions. During the exercise, maximum blood velocity is measured by Doppler ultrasound equipment in the popliteal artery. The Doppler signals are calibrated by plethysmography to enable calculation of blood flow during exercise in ml.100 ml-1.min-1. Knowledge of the cross-sectional area of the vessel and the angle of insonation is not required in this procedure. Evaluation of the calibration method with 10 healthy volunteers showed that for each subject a new calibration was necessary after a change in posture; the relationship between the blood flow and the maximum Doppler frequency averaged over one heart cycle was linear for each calibration.

Mid-Infrared Sources Using Dye Lasers in KTiOAsO4 and LiIO3

1996 ◽  
Vol 50 (6) ◽  
pp. 790-794 ◽  
Author(s):  
A. H. Kung ◽  
Suli Fei ◽  
H. L. Strauss
Keyword(s):  
Nd:Yag Laser ◽  
Second Harmonic ◽  
Damage Threshold ◽  
Calibration Method ◽  
Laser Damage Threshold ◽  
Infrared Source ◽  
Yag Lasers ◽  
Frequency Calibration ◽  
Infrared Sources ◽  
532 Nm

A coherent infrared source tunable from 3.4 to 5.3 μm has been constructed by difference-frequency mixing of the second harmonic of a Q-switched Nd:YAG laser and a pulsed dye laser using the new crystal KTiOAsO4 (KTA). A peak power of >50 kW and pulse energy of >250 μJ are measured at 4.4 μm. The results are compared with mixing in LiIO3. For a low-power Nd:YAG laser that produces 200 mJ of 532-nm radiation, the infrared power is similar for the two crystals. For high-power YAG lasers, calculation shows that commercial KTA crystals can produce over 10 mJ of IR power in the absence of absorption loss. The laser damage threshold of KTA at 532 nm is determined to be 300 ± 30 MW/cm2. Both the maximum IR power and the damage threshold are several times higher for KTA than for LiIO3. A simple frequency calibration method is described.

scholarly journals Star-Based Calibration of the Installation Between the Camera and Star Sensor of the Luojia 1-01 Satellite

2019 ◽  
Vol 11 (18) ◽  
pp. 2081 ◽  
Author(s):  
Zhichao Guan ◽  
Yonghua Jiang ◽  
Jingyin Wang ◽  
Guo Zhang
Keyword(s):  
High Frequency ◽  
Road Network ◽  
Reference Data ◽  
Calibration Method ◽  
Star Sensor ◽  
Control Points ◽  
Positioning Accuracy ◽  
Ground Control Points ◽  
Position Data ◽  
Frequency Calibration

Ground control points (GCPs) are generally used to calibrate the installation between the camera and star sensor of a satellite in orbit and improve the geometric positioning accuracy of the satellite. However, the use of GCPs for high-frequency calibration is difficult, and it is particularly difficult to acquire accurate GCPs for the image of a nightlight satellite. In this study, we developed a camera-star sensor installation calibration method that eliminates the need for GCPs. In the proposed method, the camera and star sensor lenses are simultaneously pointed at the star, and the camera-star sensor installation is accurately calibrated by processing the star map obtained by the camera and star sensors. Reference data such as road network and Moon position data were used to verify the proposed method and evaluate its positioning accuracy. The results of the application of the method to the positioning of the Luojia 1-01 satellite indicated an accuracy within 800 m, which is comparable with that of the traditional method.

Algorithm of Time and Frequency Remote Calibration System of SNSU-BSN

2020 ◽  
Vol 21 (2) ◽  
pp. 77-84
Author(s):  
A. Mohamad Boynawan ◽  
Ratnaningsih Ratnaningsih ◽  
Windi Kurnia P ◽  
Yulita Ika P ◽  
Asep Hapiddin ◽  
...  
Keyword(s):  
Atomic Clock ◽  
Calibration Method ◽  
Time Difference ◽  
National Metrology Institute ◽  
Calibration Laboratory ◽  
National Measurement ◽  
Frequency Calibration ◽  
Remote System ◽  
Client Side ◽  
Remote Calibration

National Measurement Standards-National Standardization Agency of Indonesia (SNSU-BSN) as the National Metrology Institute of Indonesia has provided time and frequency calibration services for customers. Time and frequency equipment should be calibrated to traceable to the SI units. The calibration process can be carried out in a calibration laboratory. However, some measuring devices cannot be sent to the calibration laboratory. One of the devices that cannot be sent to the calibration laboratory is Cesium atomic clock. It must be calibrated to get the time difference with the local coordinated universal time (UTC), namely UTC(IDN). Therefore, to calibrate the Cesium atomic clock, a remote calibration method is needed. The remote system is also intended to conduct the calibration more effectively and efficiently. This method requires two Global Positioning System (GPS) receiver devices placed on the client-side and a calibration laboratory. For this reason, an algorithm for remote calibration has been developed. The algorithm has been tested to calibrate Cesium-3 of SNSU-BSN against UTC(IDN). The time difference between Cesium-3 and UTC(IDN) was 5.8 microseconds by using the algorithm. Based on the algorithm that has been built, it was concluded that the algorithm can be used to perform remote calibration for the related customer.  

scholarly journals Mitigation of CSI Temporal Phase Rotation with B2B Calibration Method for Fine-Grained Motion Detection Analysis on Commodity Wi-Fi Devices

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3795 ◽  
Author(s):  
Nopphon Keerativoranan ◽  
Azril Haniz ◽  
Kentaro Saito ◽  
Jun-ichi Takada
Keyword(s):  
Motion Analysis ◽  
Visual Analysis ◽  
Doppler Frequency ◽  
Calibration Method ◽  
Motion Sensing ◽  
Fine Grained ◽  
Detection Analysis ◽  
Temporal Phase ◽  
Phase Rotation ◽  
Radio Frequency Signals

Limitations of optical devices for motion sensing such as small coverage, sensitivity to obstacles, and privacy exposure result in the need for improvement. As motion sensing based on radio frequency signals is not constrained by the limitation above, channel state information (CSI) from Wi-Fi devices could be used to improve sensing performance under the above circumstances. Unfortunately, CSI phase cannot be practically obtained due to the temporal phase rotation generated from Wi-Fi chips. Therefore, it would be rather complicated to realize motion analysis, especially the direction of motion. To mitigate the issue, this paper proposes a CSI calibration method that employs a back-to-back channel between Wi-Fi transceivers for phase rotation removal while preserving the original CSI phase. Through experiment, calibrated CSI showed a high similarity to the channel without phase rotation measured using a Vector Network Analyzer (VNA). Another experiment was conducted to observe Doppler frequency due to simple hand gestures using the Wavelet transform. A visual analysis revealed that the Doppler frequency of calibrated CSI could correctly capture the motion pattern. To the best of the authors’ knowledge, this is the first calibration method that maintains the original CSI and is applicable for in-depth motion analysis.

The Research of Time Delivering Technology in SDH Network

2014 ◽  
Vol 1023 ◽  
pp. 237-239
Author(s):  
Ying Yao
Keyword(s):  
Computational Model ◽  
Fiber Optic ◽  
Calibration Method ◽  
Network Configuration ◽  
Fiber Optic Network ◽  
Frequency Calibration ◽  
Optic Network

This paper proposed a precept on time deliver with consideration of the characteristic of SDH fiber-optic network. The computational model and Network configuration of the precepts was given in this paper. The method can be used to time deliver for SDH fiber optic network. And a calibration method is proposed in this paper that Single-ended one-way frequency calibration. The time precision of delivering can be improved by Single-ended one-way frequency calibration.

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