Characteristics & Frequency Range of Spectrum Analyzer

Chapter Characteristics

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

  • 8 | Guide to Spectrum and Signal AnalysisThis is the basic tuning equation that determines the frequency range of a spectrum/signal analyzer. Using the super heterodyne technique enables high sensitivity through the use of intermediate frequency (IF) amplifiers and extended frequency range by using the harmonics of the local oscillator (LO). This technique is not, however, real time and sweep rates must be consistent with the IF filter bandwidth charge time.CharacteristicsSpectrum and signal analyzers have the following characteristics:a) Wide frequency range.b) Amplitude and frequency calibration via internal calibration source and error correction routines.c) Flat frequency response where amplitude is independent of frequency.d) Good frequency stability using synthesized local oscillators and reference source.e) Low internal distortion.f) Good frequency resolution.g) High amplitude sensitivity.h) Linear and logarithmic display modes for amplitude (voltage and dB scaling).i) Absolute and relative measurement capabilities.Frequency RangeThe lower frequency limit of a spectrum analyzer is determined by the sideband noise of the local oscillator. The local oscillator feedthrough occurs even when there is no input signal present.The sensitivity at the lower frequency is also limited by the LO. sideband noise. Figure 7 shows typical data of average noise level vs. frequency for two IF bandwidths.Figure 710 kHz RBW1 kHz RBW