Statistical characteristics of Doppler-frequency background oscillations of short radio waves with periods of from 1 to 200 sec

1993 ◽  
Vol 35 (6-7) ◽  
pp. 391-393
Author(s):  
�. B. Andabaev ◽  
V. M. Krasnov ◽  
G. M. Pelenitsyn ◽  
O. E. Ryaskov ◽  
N. M. Salikhov
Keyword(s):  
Doppler Frequency ◽  
Statistical Characteristics ◽  
Radio Waves

scholarly journals DIAGNOSTICS OF THE STOCHASTIC IONOSPHERIC CHANNEL IN THE DECAMETER BAND OF RADIO WAVES

2020 ◽  
Vol 6 (4) ◽  
pp. 66-73
Author(s):  
Nikolay Afanasiev ◽  
Stanislav Chudaev
Keyword(s):  
Radio Channel ◽  
Signal Transmission ◽  
Three Dimensional ◽  
Doppler Frequency ◽  
Time Correlation ◽  
Statistical Characteristics ◽  
Radio Waves ◽  
Probe Signal ◽  
Signal Characteristics ◽  
Ionospheric Channel

We propose a method for direct diagnostics of a stochastic ionospheric radio channel. This method can recalculate probe signal characteristics into transmitted signal characteristics. We derive analytical equations of second-order statistical moments for trajectory characteristics of the main and probe signals propagating in a three-dimensional randomly inhomogeneous ionosphere. We take into account boundary conditions at signal transmission and reception points. As a model of random irregularities of permittivity of the ionosphere, we utilize the concept of a changing space-time correlation ellipsoid, which is self-consistent with spatial changes in the average ionosphere. Time fluctuations of random irregularities are taken into account by the hypothesis of frozen transfer. We use analytical relationships to calculate the expected statistical characteristics of decameter signals along oblique probing paths of the ionosphere. An operational numerical algorithmization of the formulas derived is proposed. We report results of numerical experiments to determine the expected phase variances, group delay, and Doppler frequency shift of the main signal on a given single-hop path, based on measurements of these characteristics of a probe signal on a secondary path. We demonstrate the efficiency of the proposed method for diagnosing statistical trajectory characteristics of a decameter signal along single-hop paths under conditions when ground points of transmission and reception of the main and probe signals are outside the vicinity of focusing points of the wave field.

scholarly journals DIAGNOSTICS OF THE STOCHASTIC IONOSPHERIC CHANNEL IN THE DECAMETER BAND OF RADIO WAVES

2020 ◽  
Vol 6 (4) ◽  
pp. 77-85
Author(s):  
Nikolay Afanasiev ◽  
Stanislav Chudaev
Keyword(s):  
Radio Channel ◽  
Signal Transmission ◽  
Three Dimensional ◽  
Doppler Frequency ◽  
Time Correlation ◽  
Statistical Characteristics ◽  
Radio Waves ◽  
Probe Signal ◽  
Signal Characteristics ◽  
Ionospheric Channel

We propose a method for direct diagnostics of a stochastic ionospheric radio channel. This method can recalculate probe signal characteristics into transmitted signal characteristics. We derive analytical equations of second-order statistical moments for trajectory characteristics of the main and probe signals propagating in a three-dimensional randomly inhomogeneous ionosphere. We take into account boundary conditions at signal transmission and reception points. As a model of random irregularities of permittivity of the ionosphere, we utilize the concept of a changing space-time correlation ellipsoid, which is self-consistent with spatial changes in the average ionosphere. Time fluctuations of random irregularities are taken into account by the hypothesis of frozen transfer. We use analytical relationships to calculate the expected statistical characteristics of decameter signals along oblique probing paths of the ionosphere. An operational numerical algorithmization of the formulas derived is proposed. We report results of numerical experiments to determine the expected phase variances, group delay, and Doppler frequency shift of the main signal on a given single-hop path, based on measurements of these characteristics of a probe signal on a secondary path. We demonstrate the efficiency of the proposed method for diagnosing statistical trajectory characteristics of a decameter signal along single-hop paths under conditions when ground points of transmission and reception of the main and probe signals are outside the vicinity of focusing points of the wave field.

scholarly journals Reception of OAM Radio Waves Using Pseudo-Doppler Interpolation Techniques: A Frequency-Domain Approach

2019 ◽  
Vol 9 (6) ◽  
pp. 1082 ◽  
Author(s):  
Marek Klemes
Keyword(s):  
Frequency Domain ◽  
Doppler Frequency ◽  
Practical Method ◽  
Far Field ◽  
Radio Waves ◽  
Antenna Structure ◽  
Transmitting Antenna ◽  
Doppler Frequency Shifts ◽  
Weighting Coefficients ◽  
Frequency Domain Approach

This paper presents a practical method of receiving waves having orbital angular momentum (OAM) in the far field of an antenna transmitting multiple OAM modes, each carrying a separate data stream at the same radio frequency (RF). The OAM modes are made to overlap by design of the transmitting antenna structure. They are simultaneously received at a known far-field distance using a minimum of two antennas separated by a short distance tangential to the OAM conical beams’ maxima and endowed with different pseudo-Doppler frequency shifts by a modulating arrangement that dynamically interpolates their phases between the two receiving antennas. Subsequently down-converted harmonics of the pseudo-Doppler shifted spectra are linearly combined by sets of weighting coefficients which effectively separate each OAM mode in the frequency domain, resulting in a higher signal-to-noise ratios (SNR) than possible using spatial-domain OAM reception techniques. Moreover, no more than two receiving antennas are necessary to separate any number of OAM modes in principle, unlike conventional MIMO (Multi-Input, Multi-Output) which requires at least K antennas to resolve K spatial modes.

scholarly journals Simplified Regional Prediction Model of Long-Term Trend for Critical Frequency of Ionospheric F2 Region over East Asia

2019 ◽  
Vol 9 (16) ◽  
pp. 3219 ◽  
Author(s):  
Jian Wang ◽  
Hongmei Bai ◽  
Xiangdong Huang ◽  
Yuebin Cao ◽  
Qiang Chen ◽  
...  
Keyword(s):  
East Asia ◽  
Critical Frequency ◽  
Statistical Characteristics ◽  
Radio Waves ◽  
Distinctive Features ◽  
Ionosphere Model ◽  
Proposed Model ◽  
Regional Prediction ◽  
Critical Frequency Fof2

To improve the accuracy of predictions and simplify the difficulty with the algorithm, a simplified empirical model is proposed in developing a long-term predictive approach in determining the ionosphere’s F2-layer critical frequency (foF2). The main distinctive features introduced in this model are: (1) Its vertical incidence sounding data, which were obtained from 18 ionosonde stations in east Asia between 1949 and 2017, used in reconstructing the model and verification; (2) the use of second-order polynomial and triangle harmonic functions, instead of linear ones, to obtain the relationship between the seasonal vs. solar-cycle variations of foF2 and solar activity parameters; (3) the flux of solar radio waves at 10.7 cm and sunspot number are together introduced in reconstructing the temporal characteristics of foF2; and (4) the use of the geomagnetic dip coordinates rather than geographic coordinates in reconstructing the spatial characteristics of foF2. The statistical results reveal that foF2 values calculated from the proposed model agree well with the trend in the monthly median statistical characteristics obtained from measurements. The results are better than those obtained from the International Reference Ionosphere model using both the CCIR and URSI coefficients. Furthermore, the proposed model has enabled some useful guidelines to be established for a more complete and accurate Asia regional or global model in the future.

scholarly journals A Space-Time Adaptive Processing Method Based on Sparse Reconstruction of Reverberation Interference

2020 ◽  
Vol 38 (6) ◽  
pp. 1179-1187
Author(s):  
Siwei Kou ◽  
Xi'an Feng ◽  
Hui Huang ◽  
Yang Bi
Keyword(s):  
Covariance Matrix ◽  
Cone Angle ◽  
Doppler Frequency ◽  
Space Time ◽  
Processing Method ◽  
Statistical Characteristics ◽  
Distribution Model ◽  
Sparse Reconstruction ◽  
Adaptive Processing ◽  
Space Time Adaptive Processing

Aiming at the problem of how to obtain reverberation samples and estimate their covariance matrix in the space-time adaptive processing(STAP) of sonar system, a new space-time adaptive processing method is proposed based on sparse reconstruction of reverberation in this paper. Firstly, according to the space-time distribution characteristics of reverberation received by moving platform sonar, a space-time steering dictionary for sparse reconstruction of reverberation is designed along the relation curve between Doppler frequency shift and incident cone angle cosine of the reverberation unit. Then, a reverberation sample in the rangecell under test (RUT) is reconstructed with high precision by sparse decomposition of signals obtained from the sonar array in the space-time steering dictionary. Finally, based on the prior information of reverberation probability distribution model, a sufficient number of reverberation samples are generated to meet the requirement of performance loss index on reverberation sample size in the space-time adaptive processing, so as to correctly obtain estimation of the covariance matrix of reverberation. This method can reconstruct the reverberation samples and estimate the reverberation covariance matrix directly from the data in RUT without relying on the auxiliary data from units adjacent to the RUT. Therefore, it is not only suitable for the environment with constant reverberation statistical characteristics, but also suitable for the environment with varying statistical characteristics. Simulation results of sonar forward-looking array and side-looking array indicate that the improvement factor of the proposed method is about 10dB lower than the traditional space-time adaptive processing method. So this new STAP method has good anti-reverberation performance.

scholarly journals Development of an optimization method for measuring the Doppler frequency of a packet taking into account the fluctuations of the initial phases of its radio pulses

2021 ◽  
Vol 2 (9 (110)) ◽  
pp. 6-15
Author(s):  
Serhii Yevseiev ◽  
Oleksandr Kuznietsov ◽  
Sergey Herasimov ◽  
Stanislav Horielyshev ◽  
Anton Karlov ◽  
...  
Keyword(s):  
Radio Pulse ◽  
Internal Noise ◽  
Doppler Frequency ◽  
Frequency Measurement ◽  
Optimization Method ◽  
Statistical Characteristics ◽  
Radar Signal ◽  
Time Range ◽  
Phase Fluctuations ◽  
Time Frequency

The necessity of estimating the decrease in the accuracy of measuring the informative parameters of a radar signal in real conditions of its propagation and reflection has been substantiated. The results of the estimation determine the requirements for optimizing this measurement to achieve the required efficiency. A numerical analysis of the decrease in the accuracy of measuring the Doppler frequency of a coherent packet is presented, depending on the statistical characteristics of fluctuations of the initial phases of its radio pulses. Expressions are given for calculating the fluctuation component of the measurement error of radio pulse packet frequency for various coefficients of interpulse correlation of phase fluctuations. An assessment is made of the possibility of increasing the accuracy of Doppler frequency measurement, which can be ensured by statistical optimization of the algorithm for time-frequency processing of a given radar signal by taking into account its phase fluctuations. The conditions for the multiplicative influence of phase fluctuations of radio pulses of the received packet are substantiated, which determine the efficiency of optimization of Doppler frequency measurement. Based on the results of the study, an optimization method for measuring the Doppler frequency of the packet taking into account fluctuations in the initial phases of its radio pulses is proposed. The accuracy of Doppler frequency measurement under the influence of both the internal noise of the radar receiver and the correlated phase fluctuations of its radio pulses is estimated. The efficiency of optimization of measuring the Doppler frequency of the packet is estimated taking into account fluctuations of the initial phases of its radio pulses by means of computer simulation. It is proved that, under the influence of phase fluctuations, the accuracy of Doppler frequency measurement can be increased due to the performed optimization from 1.86 to 6.29 times. This opens the way to improving the existing algorithms for measuring the higher time range derivatives to improve the quality of tracking complex maneuvering aerodynamic objects. This explains the importance and usefulness of the work for the radar theory.

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