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Narda’s hand held direction finder detects signals under signals

The IDA 2 Interference and Direction Analyzer from Narda Safety Test Solutions now generates persistence spectrums, which means that interference hidden beneath strong signals can now be detected and traced on the spot.

Sources of electromagnetic radiation that interfere with radio or wireless communications can be difficult to localize if they are swamped by the regular signals. The interference is hidden beneath the useful signal when subjected to conventional spectrum analysis. For this reason, the IDA 2 has now been equipped with a Persistence Spectrum display mode that shows the changing useful signals and the underlying interference signals at the same time.

For example, interference beneath GSM downlink signals with their changing channel allocations or hidden under a DAB channel can be seen because it leaves traces in the persistence spectrum in the modulation gaps that correspond to the ‘null’ symbols.

IDA 2 captures persistence spectrums with a usable bandwidth of up to 22 MHz. Various triggers can be set in order to capture brief events. Even unknown interferers can be ‘nailed’, thanks to the resolution bandwidth (RBW) down to 0.1 Hz, and time resolution as fine as 1 μs as well as the display of level characteristics versus time at up to 32 ns resolution.

The persistence spectrum display mode is based on the I/Q Analyzer operating mode. To produce a persistence spectrum, the IDA 2 writes a certain number of spectrums computed from a stored I/Q data set one on top of the other. The colors indicate how often a particular level value occurred. Persistence spectrums resemble the afterglow effect spectrums produced by older spectrum analyzers, but are much more precise and informative. This feature is therefore often found in modern high price laboratory instruments.

However, the IDA 2 is a hand held device, which has been designed to identify and localize the sources of electromagnetic signals. Its uses cover the fields of communications and security. For communications, it is important to locate and eliminate intrinsic or extrinsic interference. For security, the device can be used to trace unknown sources and identify potential dangers.

Here, the IDA 2 can automatically determine the direction of the source based on a horizontal scan, and display the bearing angle on a polar diagram. The IDA 2 then automatically computes the position of the interferer from several bearing results and displays it. This result can be superimposed on readily available electronic maps, allowing the source to be localized down to street level with pinpoint accuracy – just like a navigation system.

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