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A technique of high computational efficiency for EMC diagnostics of complex co-located set of radio systems is presented. The technique is based on the following: the use of worst-case models of electromagnetic spurious couplings between antennas (in order to eliminate the second-type errors in detection of dangerous couplings), iterative refinement of these models for the potentially dangerous couplings in the process of solving an EMC problem, and the extra efficient discrete technique for nonlinear behavior simulation of radio receiver operation in complex electromagnetic environment.

An improved computationally efficient technique for EMC diagnostics of radio equipment of complex on-board radio-electronic systems is presented. The first improvement is based on the use of worst-case and conditionally worst-case mathematical models to describe unwanted electromagnetic (EM) interactions between transmitters and receivers of the system, which allows to detect all potentially dangerous interactions rapidly and avoid second-type errors when assessing the danger of these interactions. The second improvement concerns the iterative refinement of worst-case and conditionally worst-case models of potentially dangerous interactions (including models of transmitter radiation spectra, receivers susceptibility characteristics, amplitude-frequency characteristics of decoupling antenna filters and EM spurious couplings between antennas of on-board system) by the use of both numerical simulation methods and measurements to improve the accuracy of EMC diagnostics. The third improvement is associated with the use of an extremely effective technique of discrete nonlinear behavior simulation of radio receivers’ operation in a severe EM environment formed by a set of powerful EM radiations from radio transmitters of the analyzed on-board system and a variety of external EM fields generated by various radio systems of different services.

A behavioral model for analysis of intermodulation interference that may arise in a radio receiver operating in complicated electromagnetic environment is developed. The model makes it possible to predict the levels of unequal-power multi-signal intermodulation interference (generated by involving the receiver input signals and the local oscillator signal, including its main tone and harmonics) on the basis of information about the levels of receiver susceptibility to mixer-generated spurious responses and to two-signal intermodulation of different kinds and orders. The model combines the worst case nature of intermodulation level prediction (which is a distinctive feature of conventional methods for analysis of intermodulation) with the high speed of computations (which is implemented by the use of the discrete nonlinear analysis technology). The experimental analysis of intermodulation interference in the AOR AR5000 receiver is performed in order to validate the developed model; the measurements were implemented with the use of the double-frequency test technique, which makes it possible to detect all kinds of two-signal intermodulation interference arising in a receiver.

The technique for EMC computer diagnostics of ship radio equipment is presented. This technique is based on preliminary detection and identification of all potentially dangerous on-board electromagnetic spurious couplings between antennas with the use of the broadband analytical worst-case model developed within the framework of IEMCAP program, and further corrected EMC diagnostics with the use of the adjusted worst-case models for the elements of potentially dangerous interference propagation paths identified before (adjusted numerical models of frequency characteristics of spurious couplings, numerical or analytical models of emission spectra and susceptibility characteristics of the equipment), and discrete nonlinear EMC analysis with the use of high-order front-end nonlinearity models and frequency selectivity models of radio receivers (these models are obtained on the basis of the results of double-frequency testing of the receivers). High computational efficiency are the main advantages of the technique; that is demonstrated by the example of EMC diagnostics of ship on-board system containing a set of HF, VHF, UHF and SHF radio equipment operating in severe external electromagnetic environment.

The technology for step-by-step computer diagnostics of EMC of radio equipment contained in a complex on-board system is developed. At the first stage, all potentially dangerous paths of interference propagation are identified with the use of the broadband analytical worst-case model developed within IEMCAP program; the model allows to calculate spurious couplings between antennas of radio equipment. At the second stage, refined worst-case models for the elements of potentially-dangerous interference propagation paths identified before (i.e., numerical models of frequency characteristics of spurious couplings, numerical or analytical models of emission spectra and susceptibility characteristics of the equipment) are developed; then EMC diagnostics is performed on the basis of the refined models. The final stage of the diagnostics is discrete nonlinear analysis of EMC, which is made with the help of the high order nonlinearity models and radio receivers' selectivity models; these models are obtained on the basis of the results of double-frequency testing of the receivers. The use of the developed technology makes it possible to achieve high computational efficiency of EMC diagnostics; this is demonstrated by way of the example of EMC diagnostics for on-board system containing a set of HF, VHF, and UHF radio stations installed on the small-sized mobile object.

Co-site interference is becoming an increasingly significant issue in electronic vehicular systems. Communication system designers are facing challenges due to the ever increasing demand for higher performance systems on one hand, and the need for multi-channels communication in congested electromagnetic environments on the other. Solutions to mitigate the electromagnetic interference in sophisticated system are therefore crucial to enable reliable satellite communications and VHF communications. In this paper, a procedure of interference diagnosing is introduced, and an approach for the mitigation of the interference from Satellite Communication (SatCom) on-the-move system to co-site VHF system is proposed, where a simulation is performed to verify the interference mode and to optimize the suppressing process. In the final test, the result shows that the suppression method of controlling the interference propagation paths is effective.

Techniques for experimental evaluation of the amplitude-frequency characteristic of a radio receiver input filter on basis of the measured frequency characteristic of the receiver susceptibility to two-signal (or three-signal) third-order intermodulation are developed: the known technique based on the fitting of parameters of the filter's theoretical model is generalized to deal with a switchable input filter having a high shape factor of the amplitude-frequency characteristic; two new techniques which do not require solving the optimization problem are proposed. The developed techniques are validated experimentally by examination of two radio-receiving paths with different types of the preselection filter: with narrow-band tunable filter and with wide-band switchable filter. The techniques are useful for synthesis of a receiver's behavioral model (describing the intermodulation and other nonlinear effects) on basis of experimental data.

A technique of two-phase EMC diagnostics of complex ground-based radio systems with the use of worst-case models of electromagnetic spurious couplings between antennas is introduced. At the first phase, the ultra wideband analytical model of antenna coupling developed in the framework of IEMCAP program is used, and the ensemble of potentially dangerous spurious couplings is found. For these couplings, the improved numerical worst-case models for the reduced frequency bands, as well as for given types, orientations, and relative positions of the antennas are developed at the second phase of EMC diagnostics. Each of these improved models is obtained by finding the envelope of results of multiple (based on variations of model parameter values) FDTD modeling of the corresponding coupling. The example of application of the introduced technique for diagnostics of intrasystem EMC of an operating radio-TV complex is provided: the computer model of its radio mast is developed, and the two-phase EMC diagnostics of this complex (which contains radio equipment of more than 20 systems of radio-TV broadcasting, fixed and mobile radio communication, radio navigation, and other services) is performed. The obtained results have confirmed the efficiency of the presented technique for the analysis of intrasystem EMC due to significant improvement in estimation of potentially dangerous spurious couplings between antennas at the second phase of EMC diagnostics (by 5…20 dB in comparison with analytical model of IEMCAP) with acceptable computational burden.

A computationally effective wideband worst-case model of spurious coupling between monopoles placed at line of sight of each other is proposed. The model is constructed by combining analytic solutions of the problem for low-frequency and high-frequency bands by means of weight function determined empirically. The low-frequency solution is used at frequencies below the main resonance frequency of the longer monopole, and it is based on induced emf method. This solution takes into account the mismatch of antennas with a source and a load, and it is validated in three-decade frequency range. The high-frequency solution is based on the equation for free-space transmission of radio waves. The model can be used in the framework of express analysis of EMC to calculate mutual influence of monopoles installed on the fuselage of an aircraft. Validation of the proposed model and determination of its applicability region are performed by comparing results computed by the model with results of numerical modeling by the method of moments (MoM) for the following values of parameters: ratio of the fuselage diameter to the antenna length is varied from 1.75 to 12.5, ratio of a distance between the antennas to the antenna length is varied from 1.00 to 12.5. For additional validation, the comparison of results computed by the proposed model with results of numerical modeling by the finite element method (FEM) for two blade antennas AT-1076 installed at KC-135B airplane is performed.

In this paper, we developed an analytical model that makes it possible to estimate the response (i.e., the voltage or current at the output) of a dipole antenna to arbitrary-shaped electromagnetic pulse if the minimum information about the antenna is available (it is enough to know the following parameters of the antenna: working frequency range, gain, and wave impedance of the radiofrequency port). The developed model is validated by comparing the computed responses of VHF- and UHF-band dipole antennas to wideband electromagnetic pulses with the measurement results published in the literature. The validation demonstrates that the model estimates the values of the most important antenna-response parameters (total energy, amplitude, and voltage rate), which define the requirements to the radio-equipment terminal protection devices, with reasonable accuracy. The possibilities of increasing the response estimation accuracy by numerical modeling of the antenna are investigated (MoM and FDTD methods are involved).

A technique for detection of reverse intermodulation components (which are generated if an external interfering signal received by the transmitting antenna influences on the output stages of the transmitter) by measuring the interference frequency response of the transmitter output spectrum and visualizing that response as a double-frequency diagram is developed. A technique for automated recognition (identification) of the reverse intermodulation types and orders on the basis of the double-frequency diagram is proposed. Both techniques are validated by the experiments. Amplitude responses for reverse intermodulation components of various types and orders are measured.

A technique for calculation of currents in transmission lines in a wide frequency range is proposed. The technique is based on a generalization of the lumped-circuit calculation methods to the case of long transmission lines by the introduction of refinement functions. A worst-case model for the amplitude-frequency characteristics of currents in the transmission line is developed on the basis of the proposed technique. The model is intended for diagnostics (express analysis) of electromagnetic compatibility in complexes of radio and electronic equipment. Worst-case nature of the model is provided by construction of the envelope of the current's maxima (observed at resonances) for the high-frequency band. The validity of the model is checked by comparison with the results of numerical simulation of single wire above ground plane, twowire, coaxial, and triaxial transmission lines in a wide range of parameter values: the frequency is varied from 10 kHz to 8 GHz, the length of the line is from 20 cm to 5 m, height of the line above the ground surface is from 2 mm to 100 mm, the ratio of the load capacitance (inductance) to the line capacitance (inductance) is from 10−40 to 104. Straight and piecewise-straight lines (both parallel and non-parallel to the ground plane) are considered during the validation.

A worst-case approach to development of nonlinear models for RF front-ends and components is proposed. This approach makes it possible to avoid the omission of nonlinear interference in process of the computer simulation, which is very important for EMC analysis. Based on the proposed approach, we developed a technique for synthesis of the models intended for the use in framework of the discrete nonlinear analysis technology. For validation of the developed technique, nonlinear behavioral model of a microwave amplifier was synthesized.

Features and limitations of the radio receiver's front-end nonlinearity characterization technique based on measurements of spurious-free dynamic ranges for intermodulation of different orders are investigated. The technique is familiarly illustrated by the case study (a high-quality radiomonitoring receiver is used as an example): the dynamic ranges for intermodulation of all detected orders (up to 81st) are measured by the instrumentality of the automated double-frequency test system, models of the receiver's front-end nonlinearity are then extracted from the measurement results and validated by experiment.

Capabilities of the nonlinearity-filter (Hammerstein) cascade for amplitude demodulator simulation at the system level are described. This behavioral model is then validated for the diode envelope demodulator notwithstanding that the model structure is not compliant with the physical description of the demodulator.

It is suggested to use the method of signal-to-interference ratio (SIR) estimation by the minimum of interference power in combination with the technique of discrete nonlinear analysis of radio receivers. The method of the interference power minimum is compared to the SIR estimation methods being used in the framework of the discrete nonlinear analysis (method of two iterations and frequency selection method) in terms of applicability and computational efficiency.