Radio Wave Signals Research Articles

Whistler echo trains triggered by energetic winter lightning

Lightning generated electromagnetic impulses propagating in the magnetospheric plasma disperse into whistlers – several seconds long radio wave signals with decreasing frequency. Sometimes, multiple reflections form long echo trains containing many whistlers with increasing dispersion. On January 3, 2017, two necessary prerequisites – a pronounced lightning activity and a magnetospheric plasma duct – allowed for observations of a large number of whistler echo trains by the high-latitude station in Kannuslehto, Finland. Our investigation reveals that the duct existed for nearly eight hours. We show that causative lightning sferics arrived to the duct entry from three different winter thunderstorms: a small storm at the Norwegian coast, which produced energetic lightning capable to trigger echo trains in 50% of cases, and two large storms at unexpectedly distant locations in the Mediterranean region. Our results show that intense thunderstorms can repetitively feed electromagnetic energy into a magnetospheric duct and form whistler echo trains after subionospheric propagation over distances as large as 4000 km.

Characterisation Free Space Path Loss: Sub-6ghz and Millimetre Wave Frequency

There is a free-space route loss in free-space propagation, which is the propagation path with no obstacles between the transmitter and the receiver. This is characterized as the radio wave signal’s loss during free space transit. In order to build communication systems that can function as efficiently as possible despite potential problems, it is imperative to determine the path loss. Path loss has also been utilized in wireless survey instruments and radio communications to determine the antennas’ signal strength. Given the growing significance of wireless devices, including software and survey instruments, it is now beneficial to comprehend the idea of radio path loss in its entirety. In order to gain a comprehensive understanding of the free space propagation path loss and the factors influencing it, the main objective of this paper is to simulate the phenomenon. MATLAB software is utilized in this process to generate graphs that provide a clear and easy-to-understand representation of the path loss. Four frequencies were chosen two from the sub-6 frequency range and another two from the milliwave frequency range, Results showed a trend of an increasing free space path loss with increase in distance and frequencies with a greater loss at milliwave, but loss can be mitigated with antenna gain and following other recommendations.

Analysis of influence of sensor placement for source localization based on TDOA algorithm

Locating the source of a radio wave signal is an essential research topic in various applications, such as tracking systems, navigation systems, and systems related to safety and security. This research has studied and analyzed the effect of sensor device positioning on the efficiency in determining the source’s location based on Time Difference of Arrival (TDOA) technology. We focused on the system’s efficiency in areas where sensors cannot be installed. The results and analysis demonstrate that the configuration pattern of the sensor device instantly influences the dimensions and coverage area at which the radiation source can be accurately detected. This research furnishes an essential basis for further developing and deploying transmitter detection approaches, particularly in inaccessible places.

Simultaneous detection of multi-channel signals in MHz bandwidth using nitrogen-vacancy centers in a diamond.

In this paper, we propose a method for simultaneously recovering multiple radio wave signals based on nitrogen-vacancy (NV) centers in diamond combining optically detected magnetic resonance (ODMR) spectrum. A controlled magnetic field gradient applied to the laser excitation area on the surface of diamond widens the detectable ODMR bandwidth to 200 MHz. Three different frequency-modulated (FM) signals with distinct carrier frequencies falling within the resonance frequency range are received and demodulated in real-time. Subsequently, the FM signal reception capability of this system is further investigated by measuring baseband signal frequencies ranging from 0.1 Hz to 200 Hz and adjusting the carrier power within a dynamic range from -10 dBm to 30 dBm. This proposal, which accomplishes multi-channel demodulation using a compact and single device, has potential applications in fields such as wireless communication, radar and navigation.

Development of a Path Loss Model for Radio Wave Signals for some Selected Routes in Enugu State, Nigeria

Abstract: This research focuses on developing a path loss model for radio wave signals propagating in a wavelength range of 0.37–6.12 m along some selected routes in Enugu state, Nigeria. A cable television signal strength meter was used to measure signal strength at 2 km intervals along the routes. The television signals examined were those from NTA Enugu. Path loss values were derived from the received signal strength for each route. The path loss obtained was plotted against the distance and the result shows that the path loss increases with the distance along each of the routes. A path loss model was developed by analyzing the path loss variation with distance. The path loss values obtained from the developed model were plotted against the distance and compared with the measured path losses for the NTA signals to assess how accurate the model is for the path loss prediction at the study locations. Some statistical tools (RMSE, ME, and SDE) were used to validate the developed model. The model predicted the path loss of NTA-Enugu signals with RMSE very close to zero (0). In addition, the values of the developed path loss model for the NTA signals were compared with the values of other empirical models. The results show that the other empirical path loss models overestimate the path loss of NTA-Enugu signals. Keywords: Nigeria Television Authority (NTA), Path loss, Radio waves, Signal strength, Terrestrial television, Ultra High Frequency (UHF). PACs: 84.40.Ua.

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.

Detection and Avoidance of Objects Robot with Internet Connectivity and Signal Strength-Based Location Tracking

This paper presents an object detection and avoidance robot with location tracking and internet connectivity capabilities. The robot is equipped with a hardware module that detects the highest frequency rate of radio wave signals and sends the detected signal, then from color sensors to the object avoidance robot to take a decision in search of the best signal strength. The robot moves forward in search of a better signal strength, then stays back if the signal is stronger or retreats if it is weak. When the signal strength is strong at a location, the robot informs the user of its current location and provides internet connectivity through a single-band dongle with a SIM card reader. Additionally, if the user wants the robot to return to the user's location, it backtracks the path with the help of an object detection and avoidance algorithm, whereas the user can track its activity. The proposed system has the potential to improve location tracking by object detection and avoidance in various applications, such as surveillance, search and rescue missions, military operations, and internet tracking connectivity for handicapped people in open spaces or remote areas. The proposed system here is used to track network signals and is predefined with an object detection and avoidance algorithm.

Anisotropic ionospheric scintillation in weak scattering regime

Transionospheric radio signals might undergo random modulations of their amplitude and phase caused by scattering on irregular structures in the ionosphere. These scintillation phenomena are highly anisotropic, depend on local geomagnetic field configuaration and on the relative position of the signal receiver and scattering irregularity. We derive analytical expressions of anisotropic amplitude and phase scintillation indices using the model of a thin random phase screen. These results extend the classical derivations of [C. Rino, Radio Sci. 14, 1135 (1979)] to a larger domain of applicability including very slant propagation links of the radio wave signals. The derived generalization is based on the assumption that the ionospheric scattering layer has a spherical symmetry as opposed to the original Rino’s assumption of a plan-parallel ionospheric layer. The derived scintillation indices have the simpler analytical form, determine the regions of enhanced scintillation by taking into account the finite curvature of the Earth and of the ionospheric shell, and are divergence-free for large zenith angles of propagation links. For the illustration we discuss the geometric enhancement of scintillation for communication links via a geostationary beacon satellite over the equator.

Spectral Characteristics of Phase Fluctuations at High Latitude

AbstractIt has long been established that ionospheric electron density irregularities cause random rapid amplitude and phase fluctuations in trans‐ionospheric radio signals. Various types of ground‐based measurements, including radar and Global Navigation Satellite System (GNSS) receivers, have been utilized to gain insights into the plasma mechanisms that could lead to the development of these ionospheric irregularities. The spectral characteristics of radio wave signals emitted by GNSSs and detected by the Canadian High Arctic Ionospheric Network Global Positioning System (GPS) receivers are analyzed to try and identify the spectral signatures of the ionospheric plasma irregularities. In the polar region, we have confirmed that phase fluctuations in the GPS signal are not always accompanied by amplitude fluctuations. For the first time, a systematic comparison is conducted on the spectral properties of phase‐fluctuation events in the absence and presence of amplitude scintillations, respectively. More specifically, a spectral characterization is performed on 41 events recorded by three receivers positioned within the auroral oval. When fluctuations above the background level are solely observed in the signal's phase, the spectrum of phase variations exhibits a consistent steepness. Conversely, the presence of amplitude scintillation is accompanied by an increase in power at higher frequencies, resulting in shallower spectra. This analysis provides yet another physical element suggesting that the rapid fluctuations observed in the signal's amplitude may be caused by Fresnel‐scale irregularities arising from a gradient‐drift‐like instability while the phase variations seem to be consistent with a refractive mechanism caused by large‐scale ionospheric structures.

Effects of temperature and relative humidity on UHF radio wave signals.

This research investigates the effects of temperature and relative humidity on UHF radio wave signals. A spectrum analyzer was used in measuring UHF signals while a digital thermometer and hygrometer was used in measuring temperature and relative humidity, respectively. From results obtained, relative humidity had no effect on UHF signal strengths while temperature had a positive correlation effect on path losses in UHF radio waves. This implies that an increase in temperature will lead to a decrease in received signal strength of UHF signals. Furthermore, a path loss propagation model for Calabar was obtained using multiple regression analysis and we believe that the result obtained in this study will be useful to radio engineers, for UHF signal propagation in the study terrain.

Penganalisaan Julat Hujan Bulanan Terburuk Di Malaysia Dari Tahun 2017 Hingga 2019

The degradation of radio wave signals in the frequency band more than 10 GHz is due to the factor of high rainfall intensity in tropical climates.Therefore, the prediction of rainfall attenuation on the propagation of using 1 minute intgration time of rainfall rate is important. This study uses 60 minute intergration time of rain rate ,observed at 10 station of the Deparment Irrigation and Drainange Malaysia through out Malaysia in a period of 3 years fro 2017. The Segal’s model was selected as the 1 minute integrated rainfall data conversion method due to the small probability error as well as the suitability for the tropics. The worst month rainfall distribution forecast was implemented by choosing the ITU-R model P.184-5. The result of this study has found that Sarawak showed the highest rain rate value compared to the Peninsular Malaysia. Apart from that, the worst month rain rate forecast also found the value of worst month coefficient, Q1 and β proposed by the International Union Telecommunication (ITU-R) model are not suitable for Malaysia where the new parameter value for Q1 and β were obtained so that better estimation for the worst month statistic could be published. The results of this study are not only in preparation for flooding but can also be used as a guideline in designing a more efficient satellite communications system.

A Calibration Method of Short‐Time Waveform Signals Passed Through Linear Time‐Invariant Systems: 1. Methodology and Simple Examples

AbstractWe propose an accurate calibration method for short‐time waveform signals passed through a linear time‐invariant (LTI) system that has a non‐negligible group delay. Typically, the calibration process of waveform data is expressed by the deconvolution in the time domain, and there is an equivalent operation in the frequency domain with the Fourier transform. For the short‐time data, if the short‐time Fourier transform is applied to the waveform data in the calibration process, multiplying the data by a window function is highly recommended to reduce side‐lobe effects. However, the multiplied window function is also modified in the calibration process. We analyzed the modification mathematically and derived a method to eliminate the modification of the multiplied window function. In the method, calibrated data in the frequency domain are inverse‐transformed into waveform data at each frequency, divided by a modified window function at each frequency, and accumulated over the frequencies. The principle of this method derived quantitatively indicates that the calibration accuracy depends on the transfer function of the system, frequency resolution of the Fourier transform, type of the window function, and typical frequency of the waveform data. Compared with conventional calibration methods, the proposed method provides more accurate results in various cases. This method should be useful for the calibration of general radio wave signals passed through LTI systems as well as for the calibration of plasma waves observed in space.

Reduction of secondary lobes in joint angle and delay estimation in angle of arrival localization to detect MAC address spoofing in wireless networks

in this paper, we solve the problem of secondary lobes that are due to noise that comes from constructive and destructive multipath interference that are resulted in received signal strength (RSS) variation over time. This is to develop a very efficient localization algorithm that uses a unique fingerprint angle of arrivals (AOAs), in a specified range, with associated time delays (TDs), in the surrounded sparsity design promoting multipath parameter (i.e:RSS). We solve this problem to detect physical identity spoofing of nodes in radio wireless networks, and localize adversaries and jammers of wireless networks. All radio waves are vulnerable to many types of attacks due to the ability to capture them and sniff or eavesdropping on them in the open space. Physical identity spoofing is used to launch many types of attacks against wireless networks like Denial of Service (DOS), Man-In-The-Middle and Session Hijacking and eavesdropping. Eavesdropping is a human-based social engineering attack. Active adversaries are able to jam and eavesdrop simultaneously, while passive adversaries can only eavesdrop on passed signals. In TCP/IP protocol for example, Media Access Card (MAC) Address is transferred in 802.11 frames. Detection process was carried out by analyzing electromagnetic radio waves that are used to transfer data, in the form of radio wave signals that are formed by the modulation process which mixes the electromagnetic wave, with another one of different frequency or amplitude to produce the signal with a specified pattern of frequency and amplitude. We depended on the angle of arrival of vectors and time delay across scattered areas in the surrounded space to solve the problem of co-location in detection and localization of jammers. We used Maximum Likelihood (ML) angle of arrival determination because ML approaches, known to their higher accuracy and enhanced resolution capabilities. And we assessed their computational complexity that was considered as the major drawback for designers to their implementation in practice. Our solution was tested on a jammer that changed the signal strength of received signal at the receiver at an angle of arrival 30 degree. And we used scatterers density to determine the angle of arrival of the sender. The simulation has observed that the power of the received signal has changed from the range of angles 20 to 40 degrees. We used scatterers because they describe the density of the signal power, and also enhance the signal to noise ratio, that resulted from the multipath fading of the signal strength. And also overcoming the problem of secondary lobes that are due to signal propagation, while determining the angle of arrival of a signal sender. So, we developed a new passive technique to detect MAC address spoofing based on angle of arrival localization. And assessed the computation complexity of the localization technique through depending on a range angle to estimate the angle of arrival of the adversary within it. And we reduced number of secondary lobes, and their peaks, in the importance function, while determining the angle of arrival, and so increasing the accuracy of angle of arrival measurement. We compared our work to other techniques and find that our technique is better than these techniques.

Study of Seasonal Surface Refractivity over North-Central Nigeria

Tropospheric radio wave signals experience loss due to multipath effect, scattering and other forms of attenuation through the atmospheric medium, primarily due to variations in weather conditions with time. The knowledge of surface refractivity profile is important for optimal planning of Very High Frequency/Ultra High Frequency (VHF/UHF) terrestrial radio links in a region. The study of surface refractivity (Ns) over the North-Central Nigeria was carried out using meteorological data from seven locations in North-Central zone of Nigeria. The seasonal variations of Ns were also derived using the monthly summaries of surface data obtained from Nigerian Meteorological Agency (NIMET) over seven stations of Abuja, Lafia, Lokoja, Makurdi, Jos, Minna and Ilorin between 2005 and 2010.The results indicated that the monthly averages of radio refractivity during the rainy season months (April to October) are greater than the Ns values during the dry season months (November to March) for all the locations throughout the years of the study. The computed of mean monthly Ns over all the seven stations in the first 1 km above the ground level is 348 N-units, which gives mean refractivity gradient (dN/dh) of -49 N/k, these shows that the region is characterised by low scale super-refraction. The mean k-factor over the entire region in the first 1 km above the ground level is 1.4; the mean Field Strength Variability (FSV) in first 1 km of height in the region was calculated to be 14 dB. The mean Radio Horizon distance within 1 km height for a transmitter height of 100 m over the stations is 42 km. The results provide useful information needed by radio engineers to set up new terrestrial radio propagation links or to improve on the existing ones especially at VHF, UHF in the North-Central region of Nigeria, as recommended by International Telecommunication Union Recommendations (ITU-R P.453, 2013), which observed the need for local reference data on refractivity and refractivity gradients all over the world.

Analysis of quasi-periodic space-time non-separable processes to support decision-making in medical monitoring systems

In many decisionsupport systemsthere are processedchaotic spatial-time processes which are non-separable and quasi-periodic. Some examples of such systemsareepidemic spreading, population development, fire spreading, radio wave signals, image processing, information encryption, radio vision, etc. Processes in these systems have periodic character, e.g. seasonal fluctuations(epidemic spreading, population development), harmonic fluctuations (pattern recognition, image processing),etc. In simulation block the existing systems use separable process models which are presented as multiplication of spatialand temporal parts and are linearized. This significantly reduces the quality of spatial-time non-separable processes. The quality model building of chaotic spa-tial-time non-separable processwhich is processed by decisionsupport systemis necessary for getting of learning set. Itis really complicated especially if the random process is formed. The implementation ensemble of chaotic spatial-time non-separable process requires high costs what causes reduction of the system efficiency. Moreover, in many cases the implementation ensemble of spatial-time processes is impossible to get. In this workthemathematical model of a quasi-periodic spatial-time non-separable process has been developed. Based on it the formation method of this process has been developed and investigated. The epidemic spreading pro-cessed was presented as an example.

Integrated High-Accuracy Correction Technology of Radio-Wave Refraction for Deep-Space (High-Orbit) Targets

The radio-wave refraction error caused by the troposphere and ionosphere badly affects accuracy in terms of the navigation, positioning, measurement, and control of a target; it is the main source of errors in high-accuracy measurement and control systems. The high-accuracy technology needed for radio-wave refraction error correction (mainly in the troposphere and ionosphere) has been the focus of research for a long time. At present, the correction methods used for radio-wave refraction errors have a low accuracy. For an S-band radio-wave signal, the accuracy of refraction error correction can generally only reach m-level (elevation angle of 15° and above), and thus has difficulty meeting the requirements of dm-level accuracy refraction error correction for deep-space and high-orbit targets. To improve the accuracy of radio-wave refraction error correction for deep-space and high-orbit targets, a novel correction method for tropospheric and ionospheric range error due to refraction is proposed in this study, on the basis of the measured data from a water vapor radiometer and dual-frequency Global Navigation Satellite System (GNSS). The comprehensive calibration test is conducted in combination with the Chinese Area Positioning System (CAPS) in Kunming. Results show that this method can effectively correct the range error due to refraction that is caused by the troposphere and ionosphere. For an S-band radio-wave signal, the accuracy of refraction error correction can reach dm-level accuracy (elevation angle of 15° and above), which is 50% higher than that achieved with traditional methods. This work provides an effective support system for major projects, such as lunar exploration and Mars exploration.

Spring‐Fall Asymmetry in VLF Amplitudes Recorded in the North Atlantic Region: The Fall‐Effect

AbstractA spring‐fall asymmetry is observed in daytime amplitude values of very low frequency (VLF) radio wave signals propagating over the North Atlantic during 2011–2019. We explore the processes behind this asymmetry by comparing against mesospheric mean temperatures and the semidiurnal solar tide (S2) in mesospheric winds. The solar radiation influence on VLF subionospheric propagation was removed from the daytime VLF amplitude values, isolating the fall‐effect. Similarly, the symmetric background level was removed from mesospheric mean temperatures undertaking comparable analysis. During fall, all three analyzed parameters experience significant deviation from their background levels. The VLF amplitude variation during spring is explained by the seasonal variation in solar illumination conditions, while the fall‐effect can be interpreted as a mean zonal wind reversal associated with both a S2 enhancement, and temperature reductions. Decreases in temperature can produce decreases in collision frequency, reducing VLF signal absorption, driving the observed VLF asymmetry.

Effect of Some Meteorological Variables and Conditions on Mobile Phone and 'TV' Satellite Signal

The study aimed to seek for the effect of meteorological parameters and conditions on wave transport for both radio wave band that used by mobile phone communication and microwave band that used in 'TV' satellites by showing which atmospheric variable and conditions have a positive or negative effect on signal strength. Data of study was recorded perfectly from one selected point by hand using the same devices for all recording to exclude the error caused by changing device types. The results showed that atmospheric conditions had a noticeable effect on microwave signal band that used by 'TV' satellite especially when there was a rainy case, and for atmospheric 'UV' index it had a direct positive effect on radio waveband used by mobile phone because there was an increase in signal strength corresponding with increasing of 'UV' index (from 1 to 5 of UV index range). For temperature, the result showed inverse proportion with radio waveband signal, but relative humidity didn't show up any relations with both study band's signals. Day time variation of signals was recorded for both wavebands, the result of radio waveband signal fluctuated in semi sine wave shape but with decreasing trend along day time, and for 'TV' satellite microwave band signal the result recorded increasing trend along day time, and this may because of solar radiation activity but in general, the satellite band signal was higher affected by weather condition as compared with mobile phone radio wave signal band.

Observing Spin Resonance in Two-Dimensional Conductivity Electrons in Contactless Geometry

Two fundamentally different non-contact techniques are used to observe electronic paramagnetic resonance (EPR) in a two-dimensional system based on the ZnO/MgZnO heterotransition. Spin resonance is detected in the first geometry for the transmission signal in a broadband coplanar waveguide applied to the surface of a sample. In the second, EPR manifests in a change of the power of a radio wave signal passing through a pair of T-shaped emitter/detector antennas having capacitive coupling with a two-dimensional channel. Results are compared to data measured using standard means of transport EPR detection.

English

Rain-based attenuation (RBA) is a major deteriorating factor affecting radio wave signals operating at microwave and millimetre wave bands for a typical Earth-Space Communication Link (ESCL). Although the international telecommunication union (ITU) recommended a standard model for predicting RBA along the terrestrial and ESCL, the technique underperforms in tropical environments. However, the model can be supported by appropriate modulation to enhance link performance. The present study assesses the performance of selected RBA models, namely the ITU, Moupfouma, and Garcá¼±a-Lὁpez models based on rain types for K-V frequency bands over some selected locations in Southwestern Nigeria. Link performance was further tested based on different modulation scaling to minimize signal degradation. The result shows that Garcίa-Lá½¹pez and ITU models performed well at low rain rate R ≤2 mm/h but underestimated at higher rain rates (except thunderstorms rain type) at the high-frequency band. However, the Moupfouma model performed well for all the rain types irrespective of the selected frequency band, while the ITU model underestimated attenuation for R < 5 mm/h (shower) and R > 30 mm/h (thunderstorm) rain type from the K-V band frequency, Garcia Lopez underestimates the RBA value for R < 5 mm/h and R > 5 mm/h up to the Ka frequency band. Considering the modulation scaling on link performance shows that the bit-error-rate (BER) will severely degrade with a high rain rate compared to the low rain rate across different frequencies. The BER for 8-PPM outperforms the other types of modulation schemes that were used in this study. Overall results revealed that modulation technique DPSK with selective combining diversity gave a marginal improvement with the increase in link distance and operating frequency. Key words: ESCL, rain attenuation models, modulation techniques, K-V frequency bands.