Seamless real-time analysis of frequency hopping

February 17, 2015 // By Wolfgang Wendler, Rohde & Schwarz
Wireless communication systems that use frequency hopping have the advantage that their data transmission is less susceptible to interference and that diverse applications can share one frequency band. In order to analyze such frequency agile systems, it is essential that the signals are displayed accurately and without gaps. This is also a prerequisite for being able to analyze brief interference effects such as those caused by frequency hops or digital circuits and to examine frequency hopping algorithms. Real-time spectrum analysis is ideal for performing this task.

Wireless communication systems such as cordless headsets and microphones, for example, operate very reliably in an extremely small space and in the same frequency band, thanks to frequency hopping. The same technology is also useful for tactical radios or radar applications in which, among other things, the influence of wanted interference must be minimized as well. For analyzing frequency agile systems a signal and spectrum analyzer has to support real-time analysis over all relevant frequency bands. Even infrequent and ultrashort events should be made visible in a spectrogram display. For the task of real-time analysis of frequency hopping, Rohde & Schwarz provides the FSW signal and spectrum analyzer equipped with the 160 MHz real-time spectrum analyzer option (FSW-K160R, see Figure 1) that measures the spectrum in a frequency band up to 160 MHz wide, and calculates up to 600 000 spectra per second.

Figure 1: The FSW signal and spectrum analyzer, equipped with the FSW-K160R option, analyzes almost 600 000 spectra per second in real-time. That makes it twice as fast as competitor products.

The solution even detects signals with a duration of only 1.87 μs with accurate level and at a probability of intercept (POI) of 100 %. In order to achieve different resolution bandwidths, the FFT length is adjustable between 32 and 16 384. It offers a real-time spectrogram in addition to the instantaneous spectrum and, in persistence mode, all real-time spectra shown in different colors according to their frequency of occurrence (persistence spectrum). The seamless spectra overlap by 67 % in the time domain so that the observer does not miss even the smallest of signals.

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