The Doppler frequency of reflected radio waves from a travelling ionospheric disturbance in the mode of a sinusoidal surface

2002 ◽  
Author(s):  
O.L. Ivantyshyn ◽  
V.V. Koshevoj ◽  
O.E. Levitski
Keyword(s):  
Ionospheric Disturbance ◽  
Doppler Frequency ◽  
Radio Waves ◽  
Sinusoidal Surface

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 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 Wind Turbine Clutter Mitigation in Coastal UHF Radar

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Jing Yang ◽  
Chao Pan ◽  
Caijun Wang ◽  
Dapeng Jiang ◽  
Biyang Wen
Keyword(s):  
Wind Turbine ◽  
Electromagnetic Waves ◽  
Doppler Frequency ◽  
Radio Waves ◽  
Time Frequency ◽  
Wave Radar ◽  
Close Range ◽  
Uhf Radar ◽  
Surface Dynamic ◽  
Unique Capability

Coastal UHF radar provides a unique capability to measure the sea surface dynamic parameters and detect small moving targets, by exploiting the low energy loss of electromagnetic waves propagating along the salty and good conducting ocean surface. It could compensate the blind zone of HF surface wave radar at close range and reach further distance than microwave radars. However, its performance is susceptible to wind turbines which are usually installed on the shore. The size of a wind turbine is much larger than the wavelength of radio waves at UHF band, which results in large radar cross section. Furthermore, the rotation of blades adds time-varying Doppler frequency to the clutter and makes the suppression difficult. This paper proposes a mitigation method which is based on the specific periodicity of wind turbine clutter and performed mainly in the time-frequency domain. Field experimental data of a newly developed UHF radar are used to verify this method, and the results prove its effectiveness.

scholarly journals Correlation between the Orientation of Cross-Field Axes of Small-Scale Anisotropic Irregularities in Midlatitude Ionosphere and Drift Direction in the F Region

2019 ◽  
Vol 22 (4) ◽  
pp. 53-65
Author(s):  
Valery A. Panchenko ◽  
Viktor A. Telegin ◽  
Natalia Yu. Romanova
Keyword(s):  
Magnetic Field ◽  
Doppler Frequency ◽  
Small Scale ◽  
Model Parameters ◽  
Radio Waves ◽  
Medium Scale ◽  
Middle Latitudes ◽  
Midlatitude Ionosphere ◽  
Wave Radar ◽  
Drift Direction

Introduction. It was previously reported that small-scale irregularities (SSI) in the polar ionosphere are elongated along the magnetic field and anisotropic in its cross-field direction. At the same time, the largest of the SSI cross-field axes tends to orient along the SSI drift direction. This is also indirectly confirmed for the midlatitude ionosphere, however, direct correlations of the SSI anisotropy and ionospheric drift directions in the middle latitudes are absent.Objective. The main objective of this work is a direct comparison of the experimental data of SSI shape with motion parameters of irregularities, which are measured at the same place (Moscow) at the same time. Previously, experimentally obtained values of the SSI cross-field anisotropy orientation in the midlatitude ionosphere were compared only with the neutral winds model.Materials and methods. A tomographic approach is used to determine the SSI anisotropy parameters by processing radio scintillation signals while overfly of several navigation satellites emitting on frequencies of 150 MHz and 400 MHz. Estimations of ratio between the ellipsoids axes and cross-field anisotropy orientations in the framework of SSI model in a form of magnetic field oriented ellipsoids with three different dimensions along and across the Earth's magnetic field are obtained. Irregularities parameters are obtained by selecting the model parameters when the calculated logarithm dispersion of the satellite signals relative amplitude while they orbiting is the closest to the experimentally obtained curve. Estimations of the velocity and drift direction of medium-scale irregularities (MSI) by using DPS-4 ionosonde data acquired while decameter-wave radar studies of ionosphere from the Earth's surface are obtained. The socalled "sky maps" presenting the energy distribution of scattered radio waves on incident angles are used. Simultaneous measurements of Doppler frequency shifts and incident angles of scattered waves allow obtaining estimations of three components of the medium-scale irregularities drift velocity.Results. A good correlation between the drift direction of medium-scale irregularities and cross-field anisotropy orientation of small-scale irregularities is found.Conclusion. The correlation between the cross-field anisotropy orientation of the elongated irregularities and their drift direction can be useful under conditions of the lack of information on ionospheric irregularities.

scholarly journals HF RADAR MAPPING OF EXTENSIVE OCEAN WINDFIELDS

1980 ◽  
Vol 1 (17) ◽  
pp. 20 ◽  
Author(s):  
P.E. Dexter ◽  
R.C. Casey
Keyword(s):  
Meteorological Data ◽  
Wave Spectrum ◽  
Surface Wind ◽  
Doppler Frequency ◽  
Hf Radar ◽  
Sea Surface ◽  
Propagation Mode ◽  
Wave Spectra ◽  
Radio Waves ◽  
Sea Wave

The possibility of deriving parameters of sea wave spectra remotely from characteristics of radio waves at high frequency (HF) scattered from the sea surface was first raised when Crombie (1955) correctly deduced that Doppler frequency shifts in the signal returned from short range in his HF radar resulted uniquely from components of the sea wave spectrum having wavelengths exactly one-half the radio wavelength, and travelling radially with respect to the radar. Since then the technique has been expanded in two directions: (a) The use of ionospherically propagated-JiF radio waves ('Skywave' HF radar) to^ examine extensive ocean areas out to some 4000 km from the observing site, to obtain oceanographic and meteorological data suitable for input to synoptic observation systems. This approach has been developed through the experimental work of Tveten (1967) and Ward (1969), and the empirical technique proposed by Long and Trizna (1973) to allow the simple extraction of sea surface wind vectors from Doppler spectra of the backscattered radio signals. (b) The determination of directional sea wave spectra and sea surface currents at short ranges with HF radars operating in the groundwave propagation mode, based on theoretical analyses of the scattering process such as those of Barrick (1972). The HF Skywave radar constructed and operated at Townsville by the Physics Department of James Cook University has been employed for some years now on research into the possibilities for mapping sea states and sea surface winds over ocean areas surrounding Australia (Ward, 1969; Ward and Dexter, 1976; Dexter and Casey, 1978).

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