Provides high-resolution spectrograms that make it easy to analyze wireless signals
Narda Safety Test Solutions has expanded its Interference and Direction Analyzer, incorporating high-resolution spectrograms, up to 1 µs, which allow signals to be observed with a precision that until now was only possible with expensive laboratory equipment. Thus, it is capable of detecting interference and locating hidden transmitters, even those that use highly changing frequencies.
Since the frequency spectrum is limited, modern communication methods increasingly rely on FHSS (Frequency Hopping Spread Spectrum) techniques. By continually changing the frequency, devices can more easily find unoccupied frequencies or channels. Typical applications in the ISM band are, for example, WLAN and Bluetooth, along with remote control of drones. Some GSM modes of operation also employ frequency hopping. Illegal transmitters also resort to this method, to make it difficult to locate them. This type of interference can even occur accidentally in legal transmitters. For example, if several mobile phone transmitters are co-located, the rectifying effect of a few rusty rivets on the mast can cause interference that is very difficult to distinguish from valid signals.
In the new display mode "High Resolution Spectrogram" of the IDA-2, the type of signal can be identified according to its variation in time, the instrument records the spectrum line by line, indicating the different levels by means of different colors, which allows you to see at a glance the spectral and temporal relationships. And with the 1 µs resolution, you can see, for example, LTE frames, immediately distinguishing them from other underlying signals, due to their different frequency and time characteristics.
Technical fundamentals
The High Resolution Spectrogram and Magnitude modes are based on the I/Q Analyzer mode. The IDA 2 operates with “Zero span” (zero dispersion), that is, it is tuned to a fixed frequency or to a specific channel, selectively capturing and recording the digitized data. A special feature of this equipment is its ability to select channel bandwidths (CBW) up to 32 MHz.
In High Resolution Spectrogram mode, the IDA 2 analyzes the data with an FFT algorithm using user-defined parameters. For example, the FFT produces a usable bandwidth of 22 MHz for a channel bandwidth (CBW) of 32 MHz. With an FFT of 256 points, the IDA 2 calculates the spectrum with a resolution bandwidth (RBW ) of approximately 240 kHz. If a window with an overlap of 87.5% is selected, the spectra obtained will have 1 µs of temporal resolution, that is, one million spectra per second. For this reason, conventional analyzers compress data to resolutions of 20 ms or better. The IDA 2 is the first portable device that stores the data uncompressed and can display it at its native resolution, like a Zoom: each row of pixels corresponds exactly to one spectrum and the color corresponds to the particular level. The marks can be used to show each independent spectrum in the conventional way, level vs. frequency.
