This paper gives an overview of methods to convert electromagnetic interference for bandpass signals into bit error rates (BER). The different influence parameters are discussed and two possible interference detectors corresponding to bit error rate (weighting detector and an amplitude probability distribution measurement) are described The use of a pulsed sine-wave as an interference signal is discussed. Examples are given for the modulation scheme minimum shift keying (MSK).

Critical review of converting spectral data into prospective bit error rates

Determining the impact on digital communication systems from electromagnetic interference often requires complex analyses or computations. Therefore, there is a need for low-complexity approximate methods suitable in computer-based tools for intersystem interference analyses. A commonly used approximation is to treat the interference as additive white Gaussian noise (AWGN), when estimating the resulting bit error probability (BEP). However, the validity of this approximation varies for different types of interference. Previously, it has been shown that higher-order statistics (HOS) can be used to estimate the quality of the AWGN-approximation for periodic pulsed interference with fixed amplitude. In this paper, we show that it is possible to use HOS to estimate the quality of the AWGN-approximation for a more general pulsed interference with random amplitude and arrival time. The results open the possibility to use HOS as a quality measure of the resulting BEP when using low-complexity approximate methods in computer-based tools.

A new approach for estimating the impact of pulsed interference on digital communication systems

In this paper a method for calculating the impact of intersystem interference between frequency hopping systems is proposed. The results are given in form of the average bit error probability over all frequencies used by the system. The method includes both the transmitter spectrum with sidebands and the receiver selectivity with sidebands. Furthermore, the effects from partially overlapping frequency hopping bands are included in the model. A strength of the model is that it can be generalized to an arbitrary number of interfering frequency hopping systems. Moreover, in addition to frequency hopping systems, interference on a fix frequency from different kinds of systems can also be included. If measured interference spectra, for example from a computer or a background, are available they can be incorporated in the calculations as well. Results from using the model show that it is important to use correct models of both the transmitter spectrum and receiver sidebands. If the effects from transmitter sidebands and/or receiver selectivity is neglected the resulting bit error probability can be severely underestimated.

Intersystem interference model for frequency hopping systems

ADIATED emission from electronic equipment, co-located to a digital radio receiver, can severely affect receiving performance. It is therefore of great importance that this undesired emission be considered in the early design phase of a system containing radio equipment. For this purpose, methods to estimate the performance degradation on digital radio receivers in such environment must be available. Radiated emission is regulated by means of international standards in which special measurement methods, including a measurement detector, are specified. Furthermore, present emission standards are developed with respect to analog radio receivers, which is why an immediate connection to digital radio receivers does not exist. The work of developing measurement procedures considering a digital radio receiver has started both in CISPR and ITU. This work is, however, still in its beginning, and it will probably take a long time before new standards including a new measurement detector, can be presented and approved. This thesis presents a method of handeling present emission standards as well as a suggestion for which measurement detector could be used in future standards. A necessary basis for this work is proper models of the actual disturbance sources that affect communication performance. Therefore, a theoretical model of the dominant radiated disturbance signals from co-located personal computers has been developed. The model has been justified by measurements. In a military application, the communication system could also be subjected to hostile jamming. In this case, the ability to withstand jamming is degraded by the undesired disturbance, as the latter degrades the signal protection devices (e.g. error correcting codes) in the communication system. A tactical consequence of this is that the jammer can obtain the same result at a larger distance. A suggestion is given for how the performance degradation could be interpreted to parameters that are useful for tactical considerations. R _____________________________________________________________________________________ 2 _____________________________________________________________________________________ 3

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On digital radio receiver performance in electromagnetic interference environments

An automatic frequency control (AFC) device is provided. The AFC device includes an input module, a received signal strength indicator (RSSI) module and a carrier frequency offset (CFO) estimation module. The input module down converts and samples a received signal. The RSSI module is coupled to the input module and calculates a RSSI signal in response to the down converted and sampled received signal. The CFO estimation module is coupled to the input module and the RSSI module and calculates a moving average of binary elements of the down converted and sampled received signal. The CFO estimation module continues to calculate the moving average until the AFC converges.

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Digital auto frequency control for a general purpose if subsystem with multi-modulation schemes

Transmitters and electrical equipment co-located to a radio system can, due to its radiated electromagnetic interference, cause serious degradation on the system performance. In real system design, when predicting the loss of performance, with a set of interferences of various signal types, there is a need of simple approximations that simultaneously describe the interferences in a proper manner. The focus of this paper is to show how different interfering signals will affect the performance of a radio system. Furthermore, the consequences of approximating these interference signals as additive white Gaussian noise are investigated.

K. Wiklundh

Papers

A comparison between the impact of some signals on an MSK receiver