Radio Interference Sources Research Articles

Research on a Method of Locating Civil Aviation Radio Interference Sources Based on Time Difference of Arrival and Frequency Difference of Arrival for Four Unmanned Aerial Vehicles.

Monitoring and analyzing radio interference sources play a crucial role in ensuring the safe operation of civil aviation navigation, communication, airport management, and air traffic control. Traditional ground monitoring methods are slow and inadequate for tracking aerial and mobile interference sources effectively. Although flight methods such as helicopters and airships can effectively monitor aerial interference, the flight approval process is time-consuming and expensive. This paper investigates a novel approach to locating civil aviation radio interference sources using four unmanned aerial vehicles (UAVs) to address this issue. It establishes a model for aerial positioning of radio interference sources with the four UAVs and proposes a method for time synchronization and data communication among them. The paper conducts simulations of the four-UAV time-frequency difference positioning method, analyzing the geometric accuracy dilution with different deployment configurations of the UAVs, positioning biases, and root mean square errors (RMSEs) under varying interference source movement speeds. The simulation results provide crucial data to support subsequent experiments.

Method for detecting the source of radio interference affecting train radio communication in the band of 2.13 and 2.15 MHz

There are many factors that infl uence the process of organising train movements, quality radio communication being one of the most important. The intelligibility of the dispatcher’s commands to the driver is important in deciding what action to take, and in informing the dispatcher of the train situation on a particular section of the track. Sources of radio interference that have an interfering effect on the quality of the train radio signal are natural and artifi cial interference. The sources are mainly low-frequency interference. One of the constant sources of high-frequency emissions that affect stable operation of train radio communications refers to discharges generated in the high-voltage insulation of power lines, including discharges generated in the insulation of overhead wires. Spark discharges, the source of radio interference, occur both on the surface of the insulator (usually called surface partial discharges (SPD)) and inside the insulation (such discharges are called partial discharges (PD)). In the operation of high voltage insulation, those insulators that contain PD and PPD are called defective insulators. PD and PD diagnostics are carried out twice a year by means of a laboratory car. Discharge registration is performed in the visible and ultraviolet range. There are acoustic methods for registering PD and SPD. It is proposed to register discharges in the electromagnetic frequency range. For prompt detection radio interference, it is recommended to place antennas on the laboratory car, and combine measurements with current diagnostics of high-voltage insulation, that will allow increasing reliability of the results received in the course of diagnostics. To increase the accuracy of radio interference source detection, two antennas are considered to be placed on the laboratory car.

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A method for determining the limits of the maximum size of the stable radio reception area in the UHF / VHF range for mobile radio communication under the conditions of the radio interference system is proposed. The radio is intended to use a directional antenna or screen. Increasing the size of the stable radio reception area is provided by the optimal orientation at each point of the antenna device in azimuth and angle using the model of the radio channel, which allows to calculate the signal / interference ratio taking into account the spatial location of radio interference sources and digital 3D antenna pattern. receiver. The problem of determining the boundaries of the zone of stable radio exchange of mobile radio means using directional antennas in the conditions of real interference is formulated in the form of the problem of finding a single isoline in a scalar field. To determine the coordinates of the points of the map belonging to the isoline, a modification of the wave algorithm is proposed, which is low complexity and unambiguous results. Examples of practical use of the proposed numerical method allow us to conclude that the results are inconsistent with the data obtained in the known works by the analytical method for a particular case. At the same time, the numerical approach used significantly expands the possibilities of calculations by taking into account the location of multiple sources of radio interference at different altitudes, as well as the optimal orientation of the digital 3D - pattern of the antenna device of the signal receiver. The effectiveness of the proposed method is confirmed by increasing the area of the noise-tolerant radio exchange zone by 2.8 times in relation to the option of using a mobile radio with a dipole antenna. For the case of optimal orientation of the directional antenna of the receiver by the azimuth angle, additional optimization by the angle of the place gives a gain of 1.5 times.

APPLICATION OF DISTRIBUTED ANTENNA SYSTEMS FOR DETERMINATION OF RADIATION SOURCE COORDINATES WITH USE OF PHASE METHOD IN FRESNEL ZONE

Background. Talking about evolution of passive radar systems and multifunction antenna systems, it is necessary to acknowledge that distributed antenna systems (DAS) are supposed to be widely spread in the very near future in many areas of human activity, such as organization of high-quality mobile communication in large offices, shopping centers, fitness buildings and so on. Structurally, DAS consist of different groups of antennas and base stations with active and passive repeaters of radio signals. Generally, mutual location of such antennas and base stations can be chosen experimentally according to the criterion of service area maximization. For the further quality of service improvement, it is necessary to use smart antennas in DAS as basic structure elements. The use of smart antennas will allow tracking the subscriber`s (or SOR – source of radiation) location by means of direction-finding (DF) and to increase radiation power of radio signal towards SOR thus decreasing interference to other subscribers. It is important to note that amplitude methods of DF are unacceptable in this case because base stations have antenna beam patterns which are rather wide. Use of phase methods for direction finding is actual but constrained because of electromagnetic waves (EMW) multipath propagation and large DF errors caused by the following reason – it happens that SOR is located in Fresnel zone of direction-finder antenna system. So, consideration of the phenomenon of EMW front curvature in DAS is very important in order to construct direction-finders. Objective. Consideration of EMW phase front sphericity (curvature) and its influence on the accuracy of SOR coordinates determination measured by DAS phase methods. Scheme technical decisions of phase direction-finders (PDF) based on this process are also represented. Methods. To study the effect of the EMW phase front curvature on the accuracy of determining the coordinates of the SOR analytical dependencies are synthesized. Calculations of the direction characteristics, errors in determining the phase shifts between the antenna elements of the phase direction-finder, as well as the error in determining the distance to SOR in the Fresnel zone as a function of the range to SOR and its bearing were made based on MathCad 14 program. Results. During the process of SOR angular coordinates determination in Fresnel zone with use of EMW phase front curvature оn the basis of planar antenna array, it is necessary to execute consistently two operations: 1) to define the fact of presence of EMW phase front curvature; 2) to switch PDF from the mode of bearing and tilt angles estimation (when it is in plane phase front) to the mode of bearing and tilt angles estimation (and also distance to SOR if needed) with phase front curvature of EMW. Taking into account the analysis relating to errors of bearing angle measurements in Fresnel zone (depending on the location of rough, but exact bases, for three-element sparse LAA) it is possible to conclude that their position doesn’t impact on exactness of bearing angle measuring in PDF. But to support more exact determination of SOR distance they must be placed in the center of exact, but ambiguous bases of PDF. Conclusions. Failure to take into account EMW phase front curvature from SOR harmonic signal leads to errors of SOR coordinate calculation under conditions of its location in Fresnel zone and absence of other SORs. Knowledge of distance to SOR can be used in passive radar systems, in radio monitoring systems of radio interference sources which have bearing angles equal with useful SOR ones, but located on different distances from useful SOR. This knowledge can also be used in mobile communication networks to strengthen signal level on certain distance with EMW energy focusing, in vehicle control systems on the basis of the satellite navigation systems etc.

Influence of AC voltage on the positive DC corona current pulses in a wire-cylinder gap View Document

In the development of hybrid HVDC and HVAC transmission lines, the study of radio interference is an important issue. Positive corona current pulses from high voltage transmission lines are the main source of radio interference. In this paper, the design of a wire-cylinder gap electrode system is presented to study the influence of AC voltage on the characteristics of positive corona current pulses. The study shows that the mode of the current pulses is different from that of either DC or AC corona discharge. Waveform parameters of the pulses, such as rise time, half wave time, duration time, repetition rates, average amplitude, and time intervals of secondary pulses are all statistically analyzed in this study. The empirical formulas for the repetition rates with different AC voltages are presented. A theoretical explanation based on an ion cloud model is given to reveal the mechanism behind the influence of AC voltage on positive corona discharge. The experimental results could provide some references for the prediction of radio interference from hybrid AC/DC transmission lines.

Engine-driven electrization of aircraft as a radio interference source

Field measurements of the quasi-static electrical fields emerging due to the in-flight electrization of low-speed low-altitude aircraft (helicopters) were performed for the first time. It was found that the electrization of helicopters with gas turbine power plants is of a engine-driven nature: the accumulation of static positive charge at the fuselage is induced by a unipolar negatively charged exhaust stream. A static positive fuselage potential that reaches +30 or even +35 kV for certain helicopter models was determined. If dielectric and composite materials are used in the construction of helicopters and specific parts of the aircraft are isolated electrically from the fuselage, differential electrization occurs. In view of the high absolute value of the fuselage potential, this electrization results in the generation of high-voltage discharges that serve as a source of intense radio interference within a frequency band of from several megahertz to several hundred megahertz.

Accurate measurement of original current pulses because of positive corona in the coaxial cylindrical arrangement

Current pulse because of positive corona discharge is a main source of radio interference (RI). An accurate measurement of the original corona pulse is necessary to study corona-generated RI. However, the corona pulse is likely to be distorted by either LC oscillation or reflection. In this study, an experiment system with single corona source is built which can provide a nearly free-reflection path for the current pulses, and measurements are carried out in the system. The magnitude of the measured waveform is close to one half of the original pulse, which proves the accuracy of the measurement method. In order to obtain the original current pulse, a comprehensive model for the current pulses’ path, taking the stray capacitance and stray inductance into consideration, is established. Based on the model, an inversion method to derive the original pulse is proposed. In combination with the obtained original pulse, the model gives the calculated results for other experimental conditions. The calculated results agree well with the measured results, which provide solid validation for the accuracy of the measurement. Another advantage of the proposed measurement method is that the long cables enable the accurate measurements to be achieved under any terminal conditions.

Outline of MOS‐1 verification program (MVP)

Abstract Marine Observation Satellite 1 (MOS‐1) was successfully launched from Tanegashima Space Center, NASDA by N‐II launch vehicle at 10:23 JST (1:23 UT) on February 19, 1987. The MOS‐1 has 4 mission instruments: (1) Multi‐Spectral Electronic Self Scanning Radiometer (MESSR), (2) Visible and Thermal Infrared Radiometer (VTIR), (3) Microwave Scanning Radiometer (MSR) and (4) Data Collection System Transponder (DCST). All mission instruments were found to be satisfactory during mission check period (three months after the launch) though there was interference problem in DCS due to the outer radio interference source which was resolved by changing the frequency of Data Collection Platform (DCP). NASDA planned and initiated MOS‐1 Verification Program (MVP) to evaluate MOS‐1 observation system since March, 1987. NASDA is conducting MVP in collaboration with joint research organizations, domestic and foreign organizations. As a part of the MVP, NASDA conducted airborne experiments in summer and winter in sev...