The prediction of severe electromagnetic environments for operational electronic surveillance systems and other radiofrequency receiving systems has led to the development of a simulation technique that can simulate electromagnetic environments in the laboratory A measure of the seventy of the electromagnetic environment is made by postulating a certain density of radar emitters in which the receiving system is expected to operate Scenarios are predicted where the mean pulse density in the environment exceeds one million pulses per second.

At any moment, the electromagnetic environment will be caused by the concurrent emissions from many different radars Each radar will have a signature a pulsed radar will be characterized by a carrier frequency, a pulse repetition interval, and a pulse width Any or all of these parameters could be modulated from pulse to pulse A radar with an electrical or mechanical scanning antenna system will modulate the amplitude of each transmitted pulse

Electronic surveillance systems will attempt to identify the active radar emitters by analysing samples of the received emissions. The surveillance system will also attempt to locate the positions of the radar emitters. Various direction-finding antenna systems will be used to provide bearings of the emitters, and the received powers can be used to estimate ranges Electronic surveillance systems are used on land, at sea, and in the au In any environment the situation will not be static Radar emitters and the surveillance system aboard platforms will have relative motions, and radars controlling weapons systems will react in response to the scenario Such dynamic effects will cause the peaks and troughs in the pulse density at the surveillance receiver.

For certain types of electronic surveillance systems an assessment of their performance must be carried out in realistic scenarios. The operation of the surveillance equipment can depend on the type of mission and intelligence information about the deployment of emitters. The operational performance of electronic surveillance systems is crucial For this reason it has been necessary to develop a simulator that can generate a high pulse density environment with high fidelity and is able to introduce the realistic effects of operational scenarios. The generation of a high pulse density electromagnetic environment in the laboratory requires radiofrequency generating hardware which is modulated at high speed The modulations, when suitably controlled, completely describe each radiofrequency pulse With the use of fast tuning microwave sources a small number of RF channels are used to create efficiently the high pulse density electromagnetic environment RF emissions can be either radiated directly or input directly to the receiving system by transmission line after suitable simulation of the direction finding antennas Control data for the RF generator originate in a distal processor which runs the distal simulation of the scenario. The distal processor is programmable so that the simulation can be changed for different scenarios Figure 1 shows the simulator configuration.

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