Research on inter-satellite ranging and velocity measurement method based on Doppler frequency measurement

2012 ◽  
Author(s):  
Lijing Wang ◽  
Xue Li ◽  
Yikang Yang ◽  
Lei Liu
Keyword(s):  
Velocity Measurement ◽  
Measurement Method ◽  
Doppler Frequency ◽  
Frequency Measurement

An Extracting Algorithm of Ultrasonic Doppler Shift for Multiphase Fluid Flow Measurement

2014 ◽  
Vol 494-495 ◽  
pp. 817-820
Author(s):  
Xin Liang Cao ◽  
Wei Cui ◽  
Meng De Wang
Keyword(s):  
Frequency Shift ◽  
Velocity Measurement ◽  
Doppler Frequency ◽  
Frequency Measurement ◽  
Average Frequency ◽  
Doppler Frequency Shift ◽  
Signal Frequency ◽  
Doppler Velocity ◽  
Transform Method ◽  
Multiphase Fluid

Because of the complexity for the frequency measurement about echo signal of ultrasonic Doppler flow, the acquisition methods directly affect the accuracy of Doppler frequency shift. The algorithm of power spectrum extraction has accurate to detection echo Doppler frequency of stationary signal for the flow-velocity measurement. The key is to obtain relative useful frequency information from complex echo velocity. This study is based on the principle of Doppler velocity measurement, by studying the average frequency algorithm of echoes, and the Fourier transform method is adopted to identify Doppler signal frequency and Doppler frequency shift which was polluted by aliasing noise. The MATLAB simulation results show: the useful frequency to obtain reliable, accurate, and also laid the foundation for the measurement of multiphase flow non-stationary signals.

Enhancement of Radar Imagery by Maximum Entropy Processing

1977 ◽  
Vol 21 (3) ◽  
pp. 241-243 ◽  
Author(s):  
Clanton E. Mancill
Keyword(s):  
Maximum Entropy ◽  
Signal To Noise Ratio ◽  
Super Resolution ◽  
Doppler Frequency ◽  
Frequency Measurement ◽  
Entropy Method ◽  
Frequency Resolution ◽  
Sampled Data ◽  
Maximum Entropy Spectrum ◽  
Using Data

The maximum entropy spectrum (MES), a sampled data power spectrum estimator, is applied to the enhancement of imagery obtained by synthetic array radar (SAR) imaging systems. MES offers better frequency resolution than conventional Fourier transform methods for certain signal classes. Since azimuth ground resolution in SAR systems is obtained by doppler frequency measurement of the radar return, the method is capable of enhancing the resolution of SAR maps. The principal signal requirement is adequate signal-to-noise ratio. The maximum entropy method has been tested using data obtained by the Hughes FLAMR radar system. The super-resolution capabilities of the method are demonstrated using FLAMR images of corner reflector arrays.

A novel velocity measurement method based on contact image sensor

2021 ◽  
Author(s):  
Xiaoxian Lian ◽  
Yichao Zhu ◽  
Lijing Zhang ◽  
Lianyou Lai ◽  
weijian xu
Keyword(s):  
Velocity Measurement ◽  
Measurement Method ◽  
Image Sensor

A New Airborne Passive DF Method only Based on Frequency Difference

2011 ◽  
Vol 219-220 ◽  
pp. 846-850
Author(s):  
Tao Yu
Keyword(s):  
Direction Cosine ◽  
Doppler Frequency ◽  
Frequency Measurement ◽  
Frequency Difference ◽  
Baseline Length ◽  
Direct Proportion ◽  
Unknown Parameters ◽  
Flight Direction ◽  
Phase Interference ◽  
Circular Functions

If three antenna units are divided into two set and two baselines are placed at right angles to each other in flight plain, in which the direction of one baseline is parallel to the actual flight direction of air vehicle, the sine and cosine function of target bearing respectively in two baseline directions can be simultaneously obtained according to the analysis principle of the direction cosine change rate. The angulations’ formula only based on Doppler frequency difference can be derived after eliminating the unknown parameters including angular velocity and wavelength by the specific value of two circular functions. The analog calculation shows that the relative error is in direct proportion to the baseline length provided that the incident wave is parallel in derivation. But the error analysis depicts that the measurement accuracy is in direct proportion to the baseline length. Moreover, the measurement error relies on mainly the accuracy of frequency measurement. Furthermore, the derived formula has irregularity in airborne axis direction. However, since the new method is not associated with wavelength, this new DF only based on Doppler frequency difference will be more adapted to passive sounding as compared with phase interference method.

Real-Time Measurement Method of Doppler Based on GPS Carrier Signals

2012 ◽  
Vol 226-228 ◽  
pp. 2050-2055 ◽  
Author(s):  
Shao Feng Dong ◽  
Bao Qiang Du ◽  
Wei Zhou
Keyword(s):  
Frequency Shift ◽  
Real Time ◽  
Measurement Method ◽  
Dynamic Range ◽  
Time Synchronization ◽  
Influencing Factor ◽  
Doppler Frequency ◽  
Time Measurement ◽  
Time Frequency ◽  
Real Time Measurement

According to Doppler effect of satellite on the time synchronization technology between satellite and the ground station, a real-time measurement method of Doppler is proposed based on GPS carrier signals. Using Doppler observations from GPS receiver, the method can real-timely measure Doppler frequency shift of GPS including dynamic Doppler and media Doppler whose error can be timely modified in the receiver end. Simulation results show that the frequency shift caused by dynamic Doppler, a main influencing factor in the course of transmission of time-frequency signal by GPS satellite, is between plus or minus several thousands Hz. Comparing to traditional measurement method of Doppler, the method makes it possible to fast track phase of signal in large dynamic range in synchronous technology.

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