EMC assassement criteria and interference protection for basic radio services in accordance with ITU-R recommendations

The effect of unwanted energy due to one or a combination of several desired and unwanted emissions upon reception in a radio communication system results in performance degradation, misinterpretation or loss of information. Multiple sources of interference may affect the receiver input: services of the same type or other operating in the same frequency band, services operating in adjacent frequency bands, sources generating continuous or short term interferences, fixed or mobile sources, etc. To prevent such interfering situations, a key element is the standardization of appropriate criteria for electromagnetic compatibility (EMC) and interference protection (IPC). The purpose of the studies and analyzes in this article is to systematize the criteria for electromagnetic compatibility for basic radio services based on the Publications of ITU-R. Criteria for four important areas of radio communications covering fixed, fixed satellite, broadcasting and mobile radio services are compared. Contributions are the categorization of the criteria according to the type of interfering signal and the results of the analyses, which show that the regulatory requirements and practical methods for interference protection and EMC for different radio services differ. Detailed criteria for predicting the probability of interference being standardized only for some radio services.

Investigation of energy stealth of radar stations with band antennas from the radio monitoring complex

Using spectral representation of non-harmonic processes and partial characteristics of antennas, energy equations of transmissionreception of broadband signals in the radio channel with scattering on the object and the direct radio channel between the radar and the radio monitoring (RM) complex have been obtained. Energy of received signals is determined by value of product of spectral density of radiation power and partial moment of transmission-reception averaged in the range of cyclic frequencies. The signal-to-noise ratio at the receiver input reaches the highest value when the partial moment of transmission-reception of signals in the radio channel changes according to a linear law. At fixed average radar power, energy of information signals at incoherent accumulation can be increased due to selection of antennas with partial directive gain amplifying wave processes in areas of their spectra concentration. The range of the radar is proportional to the linear dimensions and significantly depends on the shape of the object. The rules of antenna characteristics selection are justified to ensure radar stealth from RM systems while maintaining the required range of target detection and recognition. When using an antenna with a partial directive gain constant in the range of working cyclic frequencies in the radar, and in the RM complex of an antenna system with a frequency-independent effective area, the partial moment of transmission-reception of signals in the forward radio channel is constant. Its value is determined by the product of partial directive gain at the central frequency of the range. Forms of pulses supplied to input of transmitting antenna and radiated into space coincide, and shape of signal at output of receiving antenna has the form of their derivative. Due to application of frequency-independent antennas in radar and RM complex, energy of probing signals increases compared to levels typical for antenna systems with partial directivity indices varying in proportion to current value of cyclic frequency in the first or second degree. This pattern is due to the significant effective area of the receiving antenna in the lower part of the frequency range, which parries the low efficiency of radiation of low-frequency components of the radar signal spectrum. In radio channels with partial moments of transmission-reception of signals varying with frequency increase according to linear law, energy supplied to receiver input increases in comparison with levels achievable at quadratic and cubic dependencies of partial moments on cyclic frequency due to the same type dependencies of partial directive gain antenna of radar and effective area of antenna of RM complex. Stealth of probing radiation increases as dimensions of radar antennas increase due to increase of partial directive gain and decreases as dimensions of antenna systems of RM complexes increase due to increase of their effective areas. The duty cycle of pulses forming regular sequences, established due to the condition of accumulation of energy of reflected signals due to irradiation of the object, which is required to complete the functional tasks of the radar, decreases in proportion to the increase of the partial directive gain antenna at the central cyclic frequency. Energy of information signals increases in proportion to coefficients depending on relative half-width of their spectra, and decreases with increase of central cyclic frequency to the second degree. As pulse repetition frequency increases at maximum permissible average density of radiation power limited by radar stealth requirements, energy density of probing signals decreases proportionally. The average power of the radar at a fixed level of spectral density varies in proportion to the bandwidth occupied by the probing signals due to a reduction in the following period.

Discrete representation of terrain reflections for land clutter simulation

The formation of a discrete terrain model is one of the tasks of simulation of land clutter simulation using digital modeling methods. The smaller the sampling step is, the fewer calculations are needed to recreate the echo signal. On the other hand, too large the step leads to significant errors in the parameters of a simulated signal. The article considers the task of determining the necessary sampling step provided that the signals are simulated with a given accuracy. The approach proposes the analysis of the dispersion and autocorrelation function of the signal at the output of the matched filter of the radar station receiver that is obtained by transmitting a simulated echo signal to receiver input. The expressions are obtained for calculating the sampling frequency depending on the distribution properties of terrain reflections and the probing signal parameters. They can be used to build terrain models for echo signal simulation.

INFLUENCE OF INTERACTION BETWEEN ELEMENTS OF THE RADAR ANTENNA–FEEDER NETWORK ON THE NOISE CHARACTERISTICS OF THE RECEPTION CHANNEL

The influence of the interaction effects of the transmitting and receiving antennas of a mil-limeter-range radar, as well as the direct transmission of the transmitter signal to the receiver input via the internal circuits of the microwave chip on the level of the decorrelated phase noise is under consideration. It is shown that for a certain amount of interaction between the anten-nas, the delay time of signal propagation along the paths of additional reception, the receiver noise factor and the level of phase noise of the carrier frequency of the transmitter at the detun-ing frequency equal to the frequency of the useful signal, the output noise power of the receiver converter by the additional receiving channel and the receiver’s own noise become comparable. Due to the additional noise reception channel, the signal-to-noise ratio decreases and the range of the radar action decreases as well. The calculation uses data for the noise factor of the re-ceiver and the spectral density of the phase noise of the synthesizer of the AWR1243 millimeter–wave transceiver chip from Texas Instruments in the frequency range from 77 till 81 GHz. The effect of a dielectric antenna shelter on the coupling between the transmitting and receiving antennas, and on the spectral noise power density at the receiver input, is considered. The de-pendences of the spectral density of the decorrelated phase noise due to additional communi-cation channels in comparison with the receiver’s own noise are show

Investigation of Wireless Channels of 802.11 Standard in the 5ghz Frequency Band

The paper presents the study of wireless channel over-the-air channels of the family of 802.11х standards within the 5GHz frequency band, taking into account the influence of architectural obstacles within premises. The following parameters have been selected as the main parameters in the course of the study: an efficient rate of information transmission, signal power at the receiver input, as well as channel carrying capacity. As a result of the experimental study, the author has found out relevant mathematical expression for estimation of the efficiency criterion of wireless channels of the family of 802.11х standards for the 5GHz frequency band, taking into account relevant architectural obstacles within premises.