Measurements Of Radio Signals Research Articles

Determination of the vector velocity of artificial ionospheric irregularities based on Doppler measurements by the bi-static scatter method of HF radio signals propagating over long radio paths

During experiments on the modification of the high-latitude ionosphere by high-power HF radio waves of ordinary or extraordinary polarization of the EISCAT/Heating facility (Tromsø, Norway) in 2013, 2016, and 2019, Doppler measurements of diagnostic HF radio signals over long radio paths were carried out by the bistatic scatter method. We studied characteristics of Doppler frequency variations in bistatic scattered radio signals, using the experimental results obtained along radio paths of different lengths (up to ~8500 km) and orientation. We examined numerical dependences of the Doppler frequency variations in a radio signal on the azimuth of the wave vector of a radio wave incident onto an artificially disturbed region, on the bistatic scattering angle, and on the azimuthal direction of irregularity motion in an artificially disturbed region of the ionosphere. From simultaneous measurements of the Doppler frequency fD of the radio signal along two diagnostic radio paths, we numerically estimated the velocity vector of irregularities in the artificially disturbed region of the ionosphere. The total vector velocity of artificial ionospheric irregularities can be calculated from measurements of the Doppler frequency shift along several long diagnostic radio paths after preliminary analysis of experimental observations with the results of trajectory modeling of diagnostic HF radio signals.

Определение вектора скорости искусственных ионосферных неоднородностей по данным доплеровских измерений методом ракурсного рассеяния КВ радиосигналов, распространяющихся на протяженных радиотрассах

During experiments on the modification of the high-latitude ionosphere by high-power HF radio waves of ordinary or extraordinary polarization of the EISCAT/Heating facility (Tromsø, Norway) in 2013, 2016, and 2019, Doppler measurements of diagnostic HF radio signals over long radio paths were carried out by the bistatic scatter method. We studied characteristics of Doppler frequency variations in bistatic scattered radio signals, using the experimental results obtained along radio paths of different lengths (up to ~8500 km) and orientation. We examined numerical dependences of the Doppler frequency variations in a radio signal on the azimuth of the wave vector of a radio wave incident onto an artificially disturbed region, on the bistatic scattering angle, and on the azimuthal direction of irregularity motion in an artificially disturbed region of the ionosphere. From simultaneous measurements of the Doppler frequency fD of the radio signal along two diagnostic radio paths, we numerically estimated the velocity vector of irregularities in the artificially disturbed region of the ionosphere. The total vector velocity of artificial ionospheric irregularities can be calculated from measurements of the Doppler frequency shift along several long diagnostic radio paths after preliminary analysis of experimental observations with the results of trajectory modeling of diagnostic HF radio signals.

Two‐Component Phase Scintillation Spectra in the Auroral Region: Observations and Model

AbstractThe random amplitude and phase fluctuations observed in trans‐ionospheric radio signals are caused by the presence of electron density irregularities in the ionosphere. Ground‐based measurements of radio wave signals provide information about the medium through which these signals propagate. The Canadian High Arctic Ionospheric Network (CHAIN) Global Position System (GPS) receivers record radio signals emitted by the GPS satellites, enabling the study of their spectral characteristics. This study presents examples of phase spectra with two power‐law components. These components exhibit steeper spectral slopes at higher frequencies and shallower ones at lower frequencies. To be more specific, we conducted a spectral characterization of sixty one (61) events recorded by the CHAIN Churchill GPS receiver, which is located in the auroral oval. When fluctuations above the background level are only observed in the phase, the spectra tend to be systematically steeper. Conversely, the power increase in higher frequency fluctuations accompanying amplitude scintillation tends to result in shallower spectra. A basic yet powerful model of radio wave propagation through a turbulent ionosphere, characterized by a power law electron density spectrum, can help to explain the two power laws observed in the scintillation events presented in this study by identifying the role played by small‐scale ionospheric irregularities in diffraction.

Metrological traceability of the results of testing for electromagnetic compatibility in accordance with the NATO standards

Ensuring the electromagnetic compatibility of special-purpose equipment used in a complex saturated radio frequency environment requires testing in accordance with procedures that guarantee a valid verification of its immunity to external electromagnetic fields. The paper presents the national measurement standards and equipment used at the National Scientific Centre “Institute of Metrology” for the NRE02, NRE03 and NRS02 testing in accordance with the AESTR-500 standard. It is shown how metrological traceability to the SI units of the measurement results is ensured during tests. The paper presents the results of evaluating the uncertainty of the results of measurements of the electromagnetic field strength using the NARDA-550 meter for the frequency ranges of 10 kHz – 1 GHz when using the GTEM chamber, and for the frequency ranges of 1-43 GHz when using the anechoic chamber. The studies have proven that the measurement uncertainties, when calibrating the antenna in the anechoic chamber, and the uneven distribution of the electromagnetic field in the GTEM chamber are the most critical. The obtained results of the uncertainty evaluation of the NARDA-550 calibration coefficient are used for high-precision measurements of radio frequency signals both at emission and being exposed to electromagnetic fields when the disturbances have limit values as regards the provisions of these standards. These results with a discrepancy of no more than 0.05 dB confirm the characteristics of the device provided by the manufacturer. It is shown that the set of national measurement standards and test equipment of the NSC “Institute of Metrology” allows testing special equipment for electromagnetic compatibility according to the NATO standards with the required accuracy.

Broadband radio frequency signal measurement based on quantum compression sensing

With the rapid development of radio frequency technology such as radar, electronic warfare and 5G communication, the measurement and real-time spectrum characterization of broadband radio frequency signals become increasingly important. The traditional radio frequency signal real-time measurement technology is limited by the sampling rate of analog-to-digital converter and the ability to process digital signals, and encounters the problems of narrow measurement band, large data volume, and susceptibility to electromagnetic interference. This work is to study a radio frequency signal measurement technology based on quantum compression sensing, which uses integrated electro-optical crystal as radio frequency sensor, and constructs a compression sensing machine by modulating the photon wave function of the measured radio frequency signal to realize the compression measurement of broadband radio frequency signal, significantly improving the spectrum sensing bandwidth. The experiment demonstrates the long-term spectrum monitoring of power frequency and intermediate frequency high voltage signals, and the real-time spectrum measurement of high frequency radio frequency signals. Under the Fourier limit spectrum resolution, the real-time spectrum analysis bandwidth of GHz magnitude is realized, and the data compression rate reaches 1.7×10<sup>–5</sup>, which can meet the needs of 5G wireless communication, cognitive radio and other applications for broadband radio frequency signal spectrum measurement, and provide a new technical path for developing the next-generation broadband spectrum sensing technology.

Identification of Anomalous Measurements of Radio Signals by a Satellite Radio Navigation System by the Method of Statistical Processing of Measurement Discharges

Identification of Anomalous Measurements of Radio Signals by a Satellite Radio Navigation System by the Method of Statistical Processing of Measurement Discharges

Bluetooth low energy indoor localization for large industrial areas and limited infrastructure

Systems using Bluetooth Low Energy (BLE) communication are widely used in various industrial applications, which benefit from the efficient low-power operation and pervasive availability of BLE transceivers in a large number of devices and sensors. It is no different in Smart Factory and Smart Farming settings, where BLE systems are already used for asset monitoring, management, tracking, and localization. The existing BLE-based localization systems aim at high accuracy and precision using radio propagation models and multilateration, or radio fingerprinting. Both methods use the received signal strength indicator (RSSI) measurements and the dependency of RSSI on the distance between the transmitter and the receiver. Because RSSI measurements are highly inaccurate and susceptible to radio propagation phenomena, high localization accuracy is only possible if the anchor devices are densely deployed, and the propagation conditions are stable. Unfortunately, these requirements do not hold in industrial systems where radio propagation is complex, the number of anchors is limited, and propagation conditions change because the environment is dynamic. Therefore, localization methods for industrial applications have to balance system complexity (e.g., anchor density, energy cost) and localization accuracy so that practical benefits can be attained. This paper presents a set of localization algorithms that require limited infrastructure, have low complexity, and can provide valuable location information at low costs. The proposed algorithms were verified in a real-life Smart Farming application where BLE is used to monitor well-being of farm animals. The animal localization was integrated with the already existing system and proved to operate reliably despite system-level constraints and varying propagation conditions — interference, signal attenuation, and unavailability of raw radio signal measurements. The proposed approaches allow localizing animals in the cowshed of 1600m2, using only 10 anchors with an average positioning error below 8m. The algorithms are based on signal strength measurement, so they can be applied to other radio technologies.

Novel Modelling Approach for Obtaining the Parameters of Low Ionosphere under Extreme Radiation in X-Spectral Range

Strong radiation from solar X-ray flares can produce increased ionization in the terrestrial D-region and change its structure. Moreover, extreme solar radiation in X-spectral range can create sudden ionospheric disturbances and can consequently affect devices on the terrain as well as signals from satellites and presumably cause numerous uncontrollable catastrophic events. One of the techniques for detection and analysis of solar flares is studying the variations in time of specific spectral lines. The aim of this work is to present our study of solar X-ray flare effects on D-region using very low-frequency radio signal measurements over a long path in parallel with the analysis of X-spectral radiation, and to obtain the atmospheric parameters (sharpness, reflection height, time delay). We introduce a novel modelling approach and give D-region coefficients needed for modelling this medium, as well as a simple expression for electron density of lower ionosphere plasmas. We provide the analysis and software on GitHub.

Analysis of acoustic-gravity waves in the mesosphere using VLF radio signal measurements

A simple method has been proposed to determine acoustic-gravity wave (AGW) characteristics at lower ionosphere (mesosphere) heights by measuring VLF radio signal amplitudes. For relatively short radio paths (less than ∼ 1500 km long) we obtained the simple relations for estimation of AGW neutral density fluctuation and for vertical displacement of an elementary volume of atmospheric gas. The proposed method has been verified by using VLF radio wave amplitude measurements on several radio paths. AGW properties based on these measurements are approximately calculated at heights of radio signal reflection. The relative fluctuation of 3%–6% of neutral particle concentration and elementary volume displacement of 0.6–1.2 km have been obtained. These results are in good agreement with AGW theory in the Earth atmosphere.

Analysis of Acoustic-Gravity Waves in the Mesosphere Using VLF Radio Signal Measurements

A simple method has been proposed to determine acoustic-gravity wave (AGW) characteristics at lower ionosphere (mesosphere) heights by measuring VLF radio signal amplitudes. For relatively short radio paths (less than ~ 2000 km long) it has been obtained the simple relations for estimation of AGW neutral density fluctuation and for vertical displacement of an elementary volume of atmospheric gas. The proposed method has been verified by using VLF radio wave amplitude measurements on several radio paths. AGW properties based on these measurements are approximately calculated at heights of radio signal reflection. The relative fluctuation of 3—6 % of neutral particle concentration and elementary volume displacement of 0.6--1.2 km have been obtained. These results are in good agreement with AGW theory in the Earth atmosphere.

A Precise Tracking Algorithm Using PDR and Wi-Fi/iBeacon Corrections for Smartphones

Considering smartphone-based indoor localization and tracking, combination of Wi-Fi fingerprinting and pedestrian dead reckoning (PDR) becomes prevalent due to wide deployment of indoor Wi-Fi access points and easily access of inertial measurement units (IMUs) on smartphones. Since Wi-Fi fingerprinting depends on the similarities between online and offline received signal strengths, it suffers from the fluctuation of radio signal measurements. Meanwhile, the PDR relies on the IMUs, which undergo accumulated errors in long walking distance. In this paper, we aim to improve the indoor tracking accuracy, while filling up the gap between two popular Android and iOS platforms. In particular, we propose a hybrid tracking algorithm that integrates the PDR with Wi-Fi/iBeacon signal features. There are three key points in our paper. First, we process Wi-Fi/iBeacon signals to build conversion functions to convert signals to related proximity distances. Besides, in order to support mobile tracking, we introduce a placement methodology for iBeacon installation for a specific region of interest. Second, a mobile smartphone uses an improved PDR to localize itself, while incorporating Wi-Fi/iBeacon data for estimating a starting point and correcting its location along the walking path. Finally, we build an iOS app to implement the proposed scheme and display visual tracking results. Experiment results show that our proposed scheme is more robust and accurate compared to the conventional schemes.

Availability of Maritime Radio Beacon Signals for R-Mode in the Southern Baltic Sea

This paper presents an overview of the development of a terrestrial positioning system called Ranging Mode (R-Mode) in the Southern Baltic Sea region which utilizes already existing maritime radio infrastructure. Here, an R-Mode testbed is planned to be set up until 2020 that meets maritime user needs for resilient PNT. First measurements of radio beacon signals on-board a vessel sailing in the Southern Baltic Sea show the good availability of beacon signals in this region. A comparison of received signals with a coverage prediction based on the nominal range of radio beacons shows the shortcoming of this approach and emphasizes the need for more elaborated coverage predictions which consider all effects of medium frequency wave propagation at day and night. In the measurements results the skywave has a major impact on the beacon signal stability in the night. The time stability of the signal amplitude seems to be a good indicator for disturbed reception conditions.

Gated Recurrent Unit Neural Networks for Automatic Modulation Classification With Resource-Constrained End-Devices

The continuous increase in the number of mobile and Internet of Things (IoT) devices, as well as in the wireless data traffic they generate, represents an essential challenge in terms of spectral coexistence. As a result, these devices are now expected to make efficient and dynamic use of the spectrum by employing Cognitive Radio (CR) techniques. In this work, we focus on the Automatic Modulation Classification (AMC). AMC is essential to carry out multiple CR techniques, such as dynamic spectrum access, link adaptation and interference detection, aimed at improving communications throughput and reliability and, in turn, spectral efficiency. In recent years, multiple Deep Learning (DL) techniques have been proposed to address the AMC problem. These DL techniques have demonstrated better generalization, scalability and robustness capabilities compared to previous solutions. However, most of these techniques require high processing and storage capabilities that limit their applicability to energy- and computation-constrained end-devices. In this work, we propose a new gated recurrent unit neural network solution for AMC that has been specifically designed for resource-constrained IoT devices. We trained and tested our solution with over-the-air measurements of real radio signals. Our results show that the proposed solution has a memory footprint of 73.5 kBytes, 51.74% less than the reference model, and achieves a classification accuracy of 92.4%.

Tropospheric dry delay for microwaves using a model based on surface measurements on a global scale

A new model for the estimation of the dry path delay affecting electromagnetic waves traversing the neutral atmosphere (troposphere and stratosphere) is presented. For instance, an accurate evaluation of this parameter is necessary to directly get the amount of water vapour in the atmosphere from measurements of radio signals total delay available from global navigation satellite systems observations. The new model is based on a modification of the conventional Saastamoinen model and it is still based on surface data. It has been experimentally developed by linear regression exploiting a large set of radiosonde observations (107,168 for the training phase, 17,654 for the test phase) covering all latitudes and seasons with the purpose to obtain a high accuracy in the zenith dry delay (ZDD) estimation process employing dependence on surface temperature and pressure. The testing procedure has shown good performances with respect to the ZDD computed from radiosondes profiles (zero-error bias, error standard deviation 0.48 cm) and a simple and general applicability of the formulated model design over a global range of spatial and temporal scales.

Fusing Similarity-Based Sequence and Dead Reckoning for Indoor Positioning Without Training

The traditional fingerprinting-based positioning approach usually requires a laborious training phase to collect the measurements in an environment, which is a challenge for applications involving large buildings. In this paper, we propose a novel approach to fuse similarity-based sequence and dead reckoning to track the positions of users in wireless indoor environments. The reference fingerprinting map is constructed without the need for training and is based upon the geometrical relationships of the transmitters, whose positions are known and can be obtained offline. The fingerprint used for online positioning is represented by a ranked sequence of transmitters based on the measured received signal strength (RSS), which is referred to as RSS sequence in this paper. The similarities between this sequence and the reference fingerprints are computed and embedded into a particle filter to locate a user. The displacement estimation from inertial measurement unit is then integrated into the particle filter to track a mobile user. Moreover, the proposed approach can be easily extended to include other sources of sensors. In this paper, frequency modulation radio signal measurements are used as the example to fuse with Wi-Fi measurements to achieve a better tracking accuracy. Extensive experiments are also conducted to evaluate the proposed approach.

Influence of Partial Solar Eclipse on the Radio Signal during 9 March 2016

The occasion of the partial solar eclipse in Malaysia occurred on 9th March 2016 covered almost 60% to 90% of the whole Sun. During the maximum time of partial solar eclipse, some of the solar radiations and sunlight was blocked to reach the Earth’s surface. In order to see this effect to a radio signal, the analysis of radio signal pattern before and during solar eclipse at Balai Cerap KUSZA, Merang, Terengganu was done. The radio signal measurement was taken in the wideband frequency region from 0Hz to 9GHz. The radio signal data had been analysis to compare between before and during the eclipse by calculating their average.Initial analysis shows that there a different number of peak signal between two observations. Then, the solar radiation data during the partial solar eclipse also was analysed. Furthermore, solar events data from National Oceanic and Atmospheric Administration (NOAA) also added into this work. It shows that there not enough prove that the partial solar eclipse affect the radio signal pattern.

МИНИМИЗАЦИЯ ДОМИНИРУЮЩЕЙ ПОГРЕШНОСТИ В ЗАДАЧАХ ИЗМЕРЕНИЯ ИНФОРМАЦИОННЫХ ПАРАМЕТРОВ «ЗАШУМЛЕННОЙ» ВЫБОРКИ СИГНАЛА

Background. The task of informative parameters of radio engineering signal measurement in the case of domination in target result error the component that generated by additive noises of an external environment of measurement is characteristic for many applications of radio engineering, monitoring of the environment, monitoring and technical diagnostics. The optimal solution of “weight’s” minimization of the dominating error in mean squared sense as a result of measurement for the purpose of its approximation to the reference is considered. Objective. The aim of the paper is the application of preprocessing with the adaptive filtering of additive noises in the task of minimization of the dominating measurement error of informative parameters of “noisy” sampling of a radio engineering signal. Methods. Scientific novelty of work consists in modification of the form of the operator measurement’s equation of information parameters considering specifics of procedure of bleaching. The problem of preprocessing of observed selection for automatic matching of measurement’s procedure with input signal parameters and receiving the maximum number of information on an input of measuring instrument is solved. Efficiency of such preprocessing is estimated by information criterion which generalized measure is the modified entropy metrics according to Shannon. Results. Problem situations in informative parameters measurement tasks of a radio engineering signal against additive noises of arbitrary intensity are considered. Operator and algorithmic forms of the modified measurement equation of signal’s information parameters, and also option of their implementation in the form of the device of the preprocessing with the adaptive filtering performed according to the diagram of the linear weight summing are provided. Efficiency of the adaptive filtering “noisy” sampling of a measuring signal is estimated and validity of operation of preprocessing which allows minimizing information losses on measurement instrument input is confirmed. Conclusions. Features of the measuring task solution are investigated and propositions on application of the preprocessing technology with the adaptive filtering additive noises of an external environment for minimization of “weight” of the dominating error in the result of measurement are formulated.

Inversion Method for Obtaining Electrical Parameters for Soil in the Rural Region in Brazil

This paper presents an inversion methodology through weighted least squares to obtain the electrical parameters for the soil of a typical mid-western region in Brazil using the model based in the formalism of the parabolic equations to calculate the electric field intensity received. To validate this methodology, the results of the radio signal measurement campaign conducted in six radial routes leaving the city of Brasilia, Federal District, where the transmitter was located, were used. The measurements were compared to computer simulations and, thus, the optimal values for the electric conductivity and relative permittivity for the soil of the region could be estimated. Finally, a quantitative analysis of these parameters was performed with the values found in the literature, which demonstrated the effectiveness of the proposed methodology.

Measurement-Based Spectrum Database for Flexible Spectrum Management

In this paper, we propose the novel concept of a spectrum database for improving the efficiency of spectrum utilization. In the current design of TV white space spectrum databases, a propagation model is utilized to determine the spectrum availability. However, this propagation model has poor accuracy for radio environment estimation because it requires a large interference margin for the PU coverage area to ensure protection of primary users (PUs); thus, it decreases the spectrum sharing efficiency. The proposed spectrum database consists of radio environment measurement results from sensors on mobile terminals such as vehicles and smart phones. In the proposed database, actual measurements of radio signals are used to estimate radio information regarding PUs. Because the sensors on mobile terminals can gather a large amount of data, accurate propagation information can be obtained, including information regarding propagation loss and shadowing. In this paper, we first introduce the architecture of the proposed spectrum database. Then, we present experimental results for the database construction using actual TV broadcast signals. Additionally, from the evaluation results, we discuss the extent to which the proposed database can mitigate the excess interference margin.

Low‐latitude ionospheric D region dependence on solar zenith angle

AbstractPhase and amplitude measurements of VLF radio signals on a short, nearly all‐sea path between two Hawaiian Islands are used to find the height and sharpness of the lower edge of the daytime tropical D region as a function of solar zenith angle (SZA). The path used was from U.S. Navy transmitter NPM (21.4 kHz) on Oahu to Keauhou, 306 km away, on the west coast of the Big Island of Hawaii, where ionospheric sensitivity was high due to the destructive interference between the ionospherically reflected wave and the ground wave, particularly around the middle of the day. The height and sharpness are thus found to vary from H′ = 69.3 ± 0.3 km and β = 0.49 ± 0.02 km−1 for SZA ~10°, at midday, to H′ > 80 km and β ~ 0.30 km−1 as the SZA approached ~70°–90°, near dawn and dusk for this tropical path. Additional values for the variations of H′ and β with solar zenith angle are also found from VLF phase and amplitude observations on other similar paths: the short path, NWC to Karratha (in NW Australia), and the long paths, NWC to Kyoto in Japan and NAU, Puerto Rico, to St. John's Canada. Significant differences in the SZA variations of H′ and β were found between low and middle latitudes resulting from the latitudinally varying interplay between Lyman α and galactic cosmic rays in forming the lower D region. Both latitude ranges showed β < 0.30 km−1 during sunrise/sunset conditions.