Characteristics Of Radio Waves Research Articles

The extraction method used for English–Chinese machine translation corpus based on bilingual sentence pair coverage

Abstract To improve the effect of corpus extraction in bilingual English–Chinese machine translation (ECMT), this article combines a machine learning algorithm with the ECMT corpus extraction method based on bilingual sentence pair coverage. Aiming at the propagation characteristics of medium- and short-range speeches, and employing multi-band speech waveforms in the troposphere, the actual requirements of remote machine translation are combined with the free-space, 1546, and the dual-path models, respectively, to analyze three typical air-to-ground wave propagation models. A simulation is conducted for both predictions and comparisons. In addition, a radio wave propagation model within the line of sight in the troposphere is established. The results suggest that the improved dual-path model is consistent with the propagation characteristics of radio waves in the troposphere. Moreover, the experiments show that the proposed ECMT corpus extraction method based on bilingual sentence pair coverage can play an important role in more accurate English–Chinese translations.

A Comprehensive Review of Radio Signal Propagation Prediction for Terrestrial Wireless Communication Systems

The subject of study known as radio propagation prediction refers to predicting the behaviour and characteristics of radio waves as they propagate through the atmosphere. It is a basic element of all wireless communication systems, including satellite communications, broadcasting and cellular networks. While there is no study covers all the techniques used to predict the radio signal prediction, this study presents a review of the propagation prediction models between 2018-2023 used for terrestrial wireless communication systems; the classic empirical models were briefly explained, followed by the deterministic propagation models that have been developed using ray-tracing with deep and machine learning techniques. Recent studies on an improvement of the computational efficiency and accuracy of propagation prediction models were also reviewed, in addition to an overview of some of the traditional statistical models. Furthermore, some of the new techniques in propagation prediction were described. The results of these studies explain that techniques using ray tracing produce better results than other techniques.

Analysis and modeling of radio propagation fading characteristics in tunnel construction

With the development of underground rail transit, the concept of intelligent tunnel construction has been proposed and promoted. High-quality networking during tunnel construction is a prerequisite for this, making it highly urgent to establish networking during tunnel construction. When studying intra-tunnel networking, it is necessary to consider the propagation characteristics of radio waves in the tunnel. In this paper, according to the actual needs of engineering in tunnel construction and the characteristics of tunnel scenes, an improved ray tracing method is proposed, which considers the type and installation position of antennas, transceiver frequency band and power in channel modeling, and proposes a field strength calculation method under different coordinate systems according to the characteristics of straight and curved segments during tunnel construction. In addition, the propagation characteristics of radio waves in dynamic tunnel construction scenarios are quantitatively analyzed. In this paper, by establishing antenna diagram, two-dimensional and three-dimensional models of tunnels, the computer simulation method is applied to compare with the improved algorithm, and the results have good consistency, in addition, the improved algorithm does not require a lot of modeling work in the early stage, and has high applicability and portability. Not only that, this paper also makes actual measurements of the subway under construction in Zhengzhou, China in different scenarios, and verifies the effectiveness of the method.

Patch Antenna Dielectrics Reduction by Topology Optimization and Radio Wave Characteristics

This research is aimed at exploring the potential for reducing the overall mass of large space structures on which space systems are supported. A key component of these systems comprises microwave arrayed antennas, which are distributed across the surface of the structure. Given that dielectric materials constitute a significant portion of the antenna mass, this study is primarily concerned with minimizing the mass of these antenna dielectrics. It is crucial to note that while reducing mass is a priority, the stiffness of the antenna system must be preserved, as it needs to adhere securely to the structure’s surface. To achieve this objective, we embark on a process of optimizing the topological distribution of the dielectric material. We investigate how this optimized configuration impacts the microwave characteristics of a patch antenna. Our approach involves conducting topological optimization while concurrently ensuring structural stiffness. Subsequently, we assess the influence of this optimized distribution on the antenna’s patterns and gains using different materials.

A Software for RFI Analysis of Radio Environment around Radio Telescope

Radio astronomy uses radio telescopes to detect very faint emissions from celestial objects. However, human-made radio frequency interference (RFI) is currently a common problem faced by most terrestrial radio telescopes, and it is getting worse with the development of the economy and technology. Therefore, it is essential to monitor and evaluate interference during the planning, construction, and operation stages of the radio telescope and protect the quiet radio environment around the radio astronomical site. In this paper, we present a software for an RFI analysis of the radio environment around the telescope. In this software, information has been collected, including the location of the site; the technical specifications, such as aperture and the frequency range of the radio telescopes; and the terrain around the site. The software and its modules are composed of telescope, geographic, and meteorological databases, and analysis modules of terrestrial and space-based RFI. Combined with the propagation characteristics of radio waves, we can analyze and evaluate RFI on the ground and in space around the radio telescope. The feasibility of the software has been proved by the experimental implementation of the propagation properties and RFI source estimation. With this software, efficient technical support can be expected for protecting the radio environment around the telescope, as well as improving site selection for planned radio astronomical facilities.

Some Features of the Ionospheric Radio Wave Characteristics Over China Observed During the Solar Eclipse of 21 June 2020

AbstractThe Harbin Engineering University, the People's Republic of China, multifrequency multiple‐path coherent radio system operates continuously and provides data for post analysis. The data collected during the solar eclipse of 21 June 2020 have been chosen for this study with the objectives to interpret the variations in the Doppler spectra, Doppler shift, and in the reflected radio wave amplitudes that are associated with the solar eclipse, establish the magnitude and find physical significance of these variations, determine the reduction in the electron density caused by the solar eclipse, and to estimate an increase in wave activity in the ionosphere. The eclipse was accompanied by Doppler spectrum diffuseness resulting from an increase in the number of rays, the temporal variations in the Doppler shift were observed to be bi‐polar, asymmetrical, and anomalously small, with extreme Doppler shift magnitudes varying from −11 to −40 mHz and from 22 to 56 mHz. The duration of processes with negative Doppler shifts varied from 50 to 80 min, and the duration of processes with positive Doppler shifts changed from 30 to 80 min. The multi‐hop propagation (from two to five hops) took place along all propagation paths, with a 360 to 560‐km one‐hop length, due to the anomalous radio wave propagation via the sporadic‐E layer present about 80% of the time on 21 June 2020. The Doppler shift exhibited 4–18‐min period quasi‐sinusoidal variations with 20–10‐mHz amplitudes.

Polarization Characteristics of a Single Mode Radio Wave Traversing Through the Ionosphere: A Unique Observation From the RRI on ePOP/SWARM‐E

AbstractThe polarization characteristics of radio waves traversing the ionosphere can be determined using the cross‐dipole antennas of Radio Receiver Instrument (RRI) onboard the Enhanced Polar Outflow Probe payload on the CAScade, Smallsat, and Ionospheric Polar Explorer/Swarm‐E satellite. Numerous coordinated ground‐RRI transionospheric propagation experiments have been executed, with the present study using transmitted radio waves from a High Frequency (HF) ground transmitter located in Ottawa, Canada (45.41°N, 75.55°W). Most of these experiments have shown the HF radio waves to propagate with both magnetoionic propagation modes, the O‐ and X‐modes, combined. However, the coordinated ground‐RRI experiment on 12 May 2017 showed only one magnetoionic propagation mode. The observed polarization state had a stable orientation angle, but the ellipticity angle changed from −19° to linear (0°) and finally 30° within a latitude span of 15°. A detailed investigation using magnetoionic ray trace modeling and ground‐based ionogram observations revealed that the HF transmitted frequency and ionospheric conditions were such that only the O‐mode radio waves reached the satellite for the entire pass. This distinct observation is a unique opportunity to examine the radio wave polarization state during a transionospheric propagation of only O‐mode waves.

Disturbances in the Ionosphere and Distortion of Radio Wave Characteristics That Accompanied the Super Typhoon Lekima Event of 4–12 August 2019

AbstractWe acquired measurements of four observable parameters of refracted signals received from the ionosphere (Doppler shift, Doppler spectrum, number of rays, and signal amplitude) with the oblique HF Doppler technique in the city of Harbin during the super typhoon Lekima event of 4–12 August 2019. The ionospheric response was observed by the Harbin Engineering University multifrequency multiple path coherent radio system in the People's Republic of China. The maximum distortion of radio‐wave characteristics and ionospheric disturbances were observed to occur during the day when the super typhoon Lekima energy gained a maximum value and when the super typhoon approached close to the ionospheric part of the radio‐wave propagation paths. The magnitude of the ionospheric disturbances decreased with the distance between the super typhoon and propagation path midpoints. Both aperiodic (chaotic) and quasi‐sinusoidal disturbances were observed to accompany the action of the super typhoon in the ionosphere. The action of the typhoon was often accompanied by up to ±1.5 Hz broadening of the Doppler spectra, 10–30 dBV variations in the signal amplitude, and quasi‐sinusoidal variations in the Doppler shift with 0.10‐ to 0.40‐Hz amplitudes and periods of 20–30 to 70–80 min. The quasi‐sinusoidal variations in the signal amplitude with a ∼24‐min period, T, are due to focusing and defocusing of rays by wavelike disturbances in the electron density. The periods of the quasi‐sinusoidal disturbances were observed to be ∼12–24 min. Such periods pertain to atmospheric gravity waves. The atmospheric gravity waves generated by the super typhoon gave rise to quasi‐sinusoidal variations in the electron density with relative amplitudes of ∼3%–∼19%.

ОСОБЛИВОСТІ ВАРІАЦІЙ ХАРАКТЕРИСТИК ВЧ-РАДІОХВИЛЬ В ІОНОСФЕРІ ВПРОДОВЖ СОНЯЧНОГО ЗАТЕМНЕННЯ 21 ЧЕРВНЯ 2020 р. НАД КИТАЄМ

Subject and Purpose.The study of the effect that each new Solar eclipse (SE) has on radio wave characteristics is an actual scientific and technical issue. The purpose of the present work is to analyze the variations in Doppler spectra (DS), Doppler shift of frequency (DSF), and in the reflected wave amplitude (RWA) that were observed during the SE of June 21, 2020 over the People’s Republic of China. Methods and Methodology.The observations of HF radio wave characteristics were made using the Harbin Engineering University multi-frequency multipath coherent radio system. The temporal variations in DS, DSF of the main ray and RWA are analyzed further. The variations in the Doppler frequency shift (DSF) were subjected to a systematic spectral analysis that involved joint application of the windowed Fourier transform, adaptive Fourier decomposition, and the Morlet mother-function-based wavelet transformation. Results. The SE was accompanied by DS diffuseness resulting from an increase in the number of rays. The DSF temporal variations were observed to be bi-polar and asymmetrical, with extreme DSF magnitudes varying from –11 to –40 mHz and from 22 to 56 mHz. The duration of processes with negative DSF values varied from 50 to 80 min, and the duration of processes with positive DSF changed from 30 to 80 min. The multi-hop propagation (from two to five hops) took place along all propagation paths, with a 360 to 560-km one-hop range. The 4–5-min period quasi-periodic DSF variations showed 20–50 mHz amplitude, and the 8–18-min period variations exhibited 40–100 mHz amplitude. The relative amplitudes of the 4–5 min period quasi-periodic variations in the electron density were observed to be in the 0.3–6.2% range, and the amplitudes of the 8–18 min period variations were found to be in the 1.1–21.7% range. A decrease in the electron density along different propagation paths was observed to vary from –(12–16)% to –(20–26)%.

Polarization-Aware Prediction of Mobile Radio Wave Propagation Based on Complex-Valued and Quaternion Neural Networks

It is important to predict the characteristics of radio waves propagating in wireless environment for compensating information loss caused by fading effects. Though fading is often analyzed as the changes of intrinsic electric-field phasor describing a communication channel, it is also attributed greatly to its polarization state (PS). In this paper, we propose PS and phasor prediction methods based on quaternion neural networks (QNNs) and complex-valued neural networks (CVNNs). Quaternion is a hypercomplex number system for representing three dimensional (3-D) spatial rotation and orientation. It realizes adaptive prediction more stably and effectively than a real-valued rotation matrix. The time trajectories of PS are expressed as 3-D rotational motions on the Poincare sphere. We show that QNNs learn the spatiotemporal movements of the PS with high generalization ability and thus provide a superior prediction performance. In addition, CVNNs are efficient predictors for processing complex-valued signals such as the phasor of an incident wave. We evaluate the precision of the proposed QNN-CVNN prediction scheme in channel equalization in a time-division-duplex (TDD) orthogonal-frequency-division-multiplexing (OFDM) communication system. In physical wireless-environment experiments, we find that the proposed scheme provides 3.0 dB and 6.0 dB improvements of bit error rate (BER) at 10^-4, showing almost the same BER performance as a system perfectly knowing the actual radio-wave characteristics in future TDD frames. Accordingly, this work also reveals that PS needs to be considered as one of the significant characteristics in various radio-wave systems in the near-future technology.

ОСОБЛИВОСТІ ІОНОСФЕРНИХ ЕФЕКТІВ ЧАСТКОВОГО СОНЯЧНОГО ЗАТЕМНЕННЯ НАД ХАРКОВОМ 10 ЧЕРВНЯ 2021 Р.

Purpose: Solar eclipses pertain to high-energy sources of disturbance in the subsystems of the Sun–interplanetary-medium–magnetosphere–ionosphere–atmosphere–Earth and the Earth–atmosphere–ionosphere–magnetosphere systems. During the solar eclipse, the coupling between the subsystems in these systems activates, and the parameters of the dynamic processes become disturbed. Investigation of these processes contributes to understanding of the structure and dynamics of the subsystems. The ionospheric response to the solar eclipse depends on the season, local time, magnitude of the solar eclipse, phase of the solar cycle, the observation site, the state of space weather, etc. Therefore, the study of the effects, which each new solar eclipse has on the ionosphere remains an urgent geophysics and radio physics problem. The purpose of this paper is to describe the radio wave characteristics and ionospheric parameters, which accompanied the partial solar eclipse of 10 June 2021 over the City of Kharkiv. Design/methodology/approach: To make observations, the means of the HF Doppler measurements at vertical and oblique incidence available at the V. N. Karazin Kharkiv National University Radiophysical Observatory were employed. The data obtained at the “Lviv” Magnetic Observatory were used for making intercomparison. Findings: The radiophysical observations have been made of the dynamic processes acting in the ionosphere during the solar eclipse of 10 June 2021 and on the reference days. The temporal variations in the Doppler frequency shift observed at vertical and oblique radio paths have been found to be, as a whole, similar. Generally speaking, the Doppler spectra over these radio propagation paths were different. Over the oblique radio paths, the number of rays was greater. The solar eclipse was accompanied by wave activity enhancement in the atmosphere and ionosphere. At least three wave trains were observed. The values of the periods (about 5–12 min) and the relative amplitudes of perturbations in the electron density (δN≈0.3–0.6 %) give evidence that the wave disturbances were caused by atmospheric gravity waves. The amplitude of the 6–8-min period geomagnetic variations has been estimated to be 0.5–1 nT. Approximately the same value has been recorded in the X component of the geomagnetic field at the nearest Magnetic Observatory. The aperiodic effect of the solar eclipse has appeared to be too small (less than 0.01 Hz) to be observed confidently. The smallness of the effect was predetermined by an insignificant magnitude of the partial eclipse over the City of Kharkiv (no more than 0.11). Conclusions: The features of the solar eclipse of 10 June 2021 include an insignificant magnitude of the aperiodic effect and an enhancement in wave activity in the atmosphere and ionosphere. Key words: solar eclipse; ionosphere; Doppler spectrum; Doppler frequency shift; electron density; geomagnetic field; atmospheric gravity wave

Dynamic processes in the magnetic field and in the ionosphere during the 30 August–2 September 2019 geospace storm: influence on high frequency radio wave characteristics

Abstract. The concept that geospace storms are comprised of synergistically coupled magnetic storms, ionospheric storms, atmospheric storms, and storms in the electric field originating in the magnetosphere, the ionosphere, and the atmosphere (i.e., electrical storms) was validated a few decades ago. Geospace storm studies require the employment of multiple-method approaches to the Sun–interplanetary medium–magnetosphere–ionosphere–atmosphere–Earth system. This study provides general analysis of the 30 August–2 September 2019 geospace storm, the analysis of disturbances in the geomagnetic field and in the ionosphere, as well as the influence of the ionospheric storm on the characteristics of high frequency (HF) radio waves over the People's Republic of China. The main results of the study are as follows. The energy and power of the geospace storm have been estimated to be 1.5×1015 J and 1.5×1010 W, and thus, this storm is weak. The energy and power of the magnetic storm have been estimated to be 1.5×1015 J and 9×109 W, i.e., this storm is moderate, and a characteristic feature of this storm is the duration of the main phase of up to 2 d. The recovery phase also was lengthy and was no less than 2 d. On 31 August and 1 September 2019, the variations in the H and D components attained 60–70 nT, while the Z-component variations did not exceed 20 nT. On 31 August and 1 September 2019, the level of fluctuations in the geomagnetic field in the 100–1000 s period range increased from 0.2–0.3 to 2–4 nT, while the energy of the oscillations showed a maximum in the 300–400 to 700–900 s period range. During the geospace storm, a moderately to strongly negative ionospheric storm manifested itself by the reduction in the ionospheric F-region electron density by a factor of 1.4 to 2.4 times on 31 August and 1 September 2019, compared to the its values on the reference day. Appreciable disturbances were also observed to occur in the ionospheric E region and possibly in the Es layer. In the course of the ionospheric storm, the altitude of reflection of radio waves could sharply increase from ∼150 to ∼300–310 km. The atmospheric gravity waves generated within the geospace storm modulated the ionospheric electron density; for the ∼30 min period oscillation, the amplitude of the electron density disturbances could attain ∼40 %, while it did not exceed 6 % for the ∼15 min period. At the same time, the height of reflection of the radio waves varied quasi-periodically with a 20–30 km amplitude. The results obtained have made a contribution to the understanding of the geospace storm physics, to developing theoretical and empirical models of geospace storms, to the acquisition of detailed understanding of the adverse effects that geospace storms have on radio wave propagation, and to applying that knowledge to effective forecasting of these adverse influences.

Path loss prediction based on multi-layer perceptron artificial neural network

In order to better serve the network planning and optimization of the 5th generation and future communication systems, the path loss prediction based on multi-layer perceptron (MLP) neural network is carried out in this paper. A simple method to characterize the propagation environment is proposed by the limited clutter type information, avoiding the cumbersome three-dimensional (3D) scenario modeling. Combining with the measurement data and environmental features extracted by the environmental characterization method, the path loss model based on the MLP neural network is established. The comparative analysis of data experiments shows that the MLP neural network can achieve accurate prediction of path loss, and the introduction of environmental features can help improve the performance of the MLP-based path loss model. In order to solve the problem that interference clutters reduce the accuracy of the MLP-based path loss model and this model is sensitive to environmental changes, the environmental characterization method is improved based on the label that can judge whether it is line-of-sight (LoS) or non-line-of-sight (NLoS), which further enhances the stability and generalization ability of the MLP-based path loss model. This paper is designed to understand the propagation characteristics of radio wave, which can provide a theoretical basis for wireless network optimization and communication system design.

Simulation and Analysis of 45 GHz Millimeter-wave Propagation Characteristics in Living Room

In this paper, the characteristics of millimeter-wave propagation at 45 GHz in a living room are investigated based on simulation by the method of shooting and bounding ray tracing/image (SBR/IM). Path loss of co-polarization and crosspolarization is compared to verify the accuracy of simulation. The angle of arrival of different polarization is also revealed. Root mean square (RMS) delay spread of co-polarization and cross-polarization is studied. It is shown that the RMS delay of co-polarization is generally higher than that of cross-polarization in this environment. In addition, the influence of furniture on the propagation characteristics of radio waves in the line-of-sight (LOS) environment is discussed.

Mathematical modeling of the polarization characteristics of radio waves in the Earth’s equatorial ionosphere

Using the bicharacteristics method, mathematical modeling of the polarization parameters of P-band radio waves in the Earth’s ionosphere in the vicinity of the equatorial anomaly along the meridian path was carried out. The influence of the ionosphere on the phase deviation and the angle of the Faraday rotation during the passage of the spacecraft is studied taking into account changes in the magnitude and orientation of the Earth’s magnetic field.

Artificial Neural Network Based Path Loss Prediction for Wireless Communication Network

Accurate path loss (PL) prediction is essential for predicting transmitter coverage and optimizing wireless network performance. Traditional PL models are difficult to cope with the development trend of diversity, time-varying and mass wireless channels. In this work, the most widely used multilayer perceptron (MLP) neural network in artificial neural network (ANN) is employed to accurately predict PL. Three types of environmental features are defined and extracted, which describe the propagation environment only by considering limited environmental types instead of complex 3D environment modeling. Principal component analysis (PCA) is used to generate the low-dimensional environmental features, and eliminate redundant information among similar environmental types. Moreover, the information of base station (BS) and the receiver (Rx), including 3D locations, frequency, the transmitted power of BS, the antenna information, the feeder loss, and the received power of all the locations are obtained from the measurements. Different environmental features are combined with the information of BS and Rx to construct seven datasets for PL prediction models based on MLP neural networks. The impacts of the number of neurons in the hidden layer, the number of hidden layers, the number of training samples, and environmental features on PL prediction models are explored by considering the absolute value of mean error (AME), the mean absolute error (MAE), the standard deviation (STD) of error, the correlation coefficient, and the time ratio, respectively. This work aims to understand the propagation characteristics of radio waves, which can provide a theoretical basis for wireless network optimization and communication system design.

Effect of the plasma sheath on the propagation of low frequency radio waves

The plasma sheath formed around a hypersonic vehicle traveling through the atmosphere will affect the quality of wireless signals. To fully grasp this effect, it is necessary to comprise the vehicle antennas in the investigations, which is considered in our work. Firstly, the discrete plasma sheath data is generated by using COMSOL. Then, combining the shift-operator Finite-Difference Time-Domain method and numerical methods such as the high-dimensional Lagrange interpolation, an electromagnetic algorithm designed for the discrete plasma sheath data is developed. Based on this, the influence of the plasma sheath on the radio wave propagation is studied under different flight condition. Results show that, due to the influence both of the plasma sheath and of the vehicle antenna, the radio waves exhibit rich propagation behaviors, such as the frequency-band shift and the tail diffraction, etc. Compared with other studies, the results in this paper more approximately reflect the propagation characteristics of radio waves in the hypersonic environment, and can provide a reference for the related applications.

HF radio-wave characteristic variations over China during moderate earthquake in Japan on September 5, 2018

Urgency. The Earth's interior layers – atmosphere – ionosphere – magnetosphere (EAIM) form a one system, which is open, dynamic, and nonlinear. There are direct and reverse, positive and negative linkages among the subsystems within the EAIM system, which are currently insufficiently studied. The release of energy from a high-power source in one of the subsystems triggers the interaction among the subsystems. In this paper, a moderate earthquake of Richter magnitude M » 6.6 is considered as such a source. The aim of the paper is to describe time variations in the characteristics of the HF radio waves observed along the radio propagation paths over the People's Republic of China during the earthquake of September 5, 2018 in Japan. Techniques and Methodology. To observe the temporal variations in the characteristics of radio waves, we used the multi-frequency multiple-path coherent radio system at the Harbin Engineering University. Broadcasting stations located in the People's Republic of China, the South Korea, Japan, Russia, and Mongolia are used as transmitters. The time variations in the Doppler spectra, the Doppler shift of frequency of the main mode, and signal amplitudes were subjected to analysis. The measurements were performed in the frequency range of 5 – 10 MHz over 14 radio propagation paths extending from ~ 900 km to 1800 km and having various orientations. The Doppler spectra are calculated in 7.5-s step with the root-mean-square Doppler line error of 0.02 Hz. Results. The response of the ionosphere to a moderate earthquake was observed and studied. The delay time of the assumed response and the apparent speed of propagation of the disturbances were estimated. It was demonstrated that the seismic shock was followed by Doppler spectra spreading and the Doppler frequency shift of the main mode varying with time quasi-periodically with an ~3-min period of infrasound and an ~20 – 30-min period of atmospheric gravity wave. Conclusions: Moderate earthquakes are capable of launching disturbances in the ionosphere detectable at distances of ~1000 km from the epicenter of earthquake.

ESTIMATION OF SHAPE PARAMETERS OF SPACE OBJECTS WITH USE OF WIDEBAND RADAR SIGNALS

Theoretical questions of parametric descriptions of received broadband radar signals, in particular, signals with linear frequency modulation, and their processing for evaluation of form parameters of tracked space objects are considered. Analytical expressions for the received broadband radar signal at the output of the antenna system and its spectrum are obtained. Received expression take into account the spectral characteristics of polarization matrix of radio waves backscattering from space objects, as well as movement parameters of monitored objects. Address issues of physical diffraction theory methods for calculating spectral characteristics of radio waves backscattering from space objects. At considering of processing of received broadband signals from objects they are represented as the sum of component from individual «shining spots», then parameters of objects form are number of «shining spots», delays and complex amplitudes of their signals. It is shown that sufficient statistics at processing of received broadband signals to evaluate form parameters of space objects is the Fourier transform of product of complex conjugate of complex spectrum of envelope received signal and spectrum of complex envelope of sounding signal, modified in view of object movement. On the basis of computations of delay response functions for axisymmetric objects with circular kinked surfaces and sounding signals with linear frequency modulation the features of the task of evaluating the form parameters of space objects are shown and general requirements for parameters of sounding signals, for energy and a range of angles of observation are formulated.

Measurement of Body Water Content Using Attenuation Characteristics of Radio Waves

Measurement of Body Water Content Using Attenuation Characteristics of Radio Waves