Signal Analyzers & Basic Operation of Spectrum Analyzer

Chapter Signal Analyzers

Guide to Spectrum and Signal Analysis
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Guide to Spectrum and Signal Analysis

  • | 7Signal AnalyzersSignal analyzers sample a range of frequencies simultaneously, thus preserving the time dependency and phase between signals. This technique allows both transient and periodic / random signals to be displayed (Figure 5). Signal Analyzers and Spectrum analyzers have very similar RF block diagrams, differing in frequency range (bandwidth) of the IF processing. The high bandwidth processing offers many advantages, but at increased cost.Basic OperationBoth spectrum analyzers and signal analyzers are based on a super heterodyne receiver principle (Figure 6). The input signal, fIN, is converted to an intermediate frequency, fIF, via a mixer and a tunable local oscillator fLO. When the frequency difference between the input signal and the local oscillator is equal to the intermediate frequency then there is a response on the display.InputSignalRF InputAttenuatorMixerIF GainADCDDCDisplayCPU / FFTI / QPre-selector, orLow-pass FilterStepSynthesizerReferenceOscillatorInputSignal1st Mixer2nd Mixer3rd MixerB.P.FDisplayCPUVertHorizStepSynthesizerReferenceOscillatorfIN = fLO ± fIFFigure 6Figure 5