What is a spectrum analyzer?  

Figure: Spectrum analyzer

A spectrum analyzer is an electronic instrument designed to measure and display an input signal’s amplitude (strength) versus frequency within the full frequency range of the instrument.  It displays signal magnitude in the Y-axis (in decibels) and frequency in the X-axis (in Hz). This instrument is primarily used to measure the power of the spectrum of known and unknown signals. A spectrum analyzer looks similar to an oscilloscope, which displays amplitude on the vertical axis (Y-axis) but time on the horizontal axis (X-axis).  

The spectrum analyzer usually displays raw, unprocessed signal information such as voltage, period, power, period, sidebands, wave-shape, sidebands, and frequency. It can also be used to analyze the spectra of electrical signals dominant frequency, power, harmonics, distortion, bandwidth, and other spectral components of a signal can be observed & analyzed that are not easily detectable in time domain waveforms (i.e., in oscilloscope). These signal parameters are useful in the characterization of electronic devices.  

Moreover, the spectrum analyzer is a useful tool for seeing the entire signal spectrum and other factors such as spurious signals, noise, modulated signal width, complex waveforms, electromagnetic signals, transient signals, etc. There are several types of spectrum analyzers. They are distinguished by the methods used to obtain the signal spectrum. The types include Swept-tuned or superheterodyne, Fast Fourier transform (FFT) based analyzers, and real-time spectrum analyzers.  

The spectrum analyzers are ideal for use in EMI pre-compliance testing, measuring cellular network performance, debugging wireless communications, testing radar systems, satellite communication link quality evaluation, testing aircraft avionics, R&D, education, production and maintenance, etc.  

Note: In EMC tests and measurements, the spectrum analyzer can be used for EMI pre-compliance testing, but it cannot be used for full EMC tests and measurements for certification purposes. Instead, an EMI receiver can be used. 

Key specification details of spectrum analyzers:  

Frequency: Represents the useable frequency range of the spectrum analyzer. The spectrum analyzers are available in a wide frequency range from KHz to GHz range. 

Amplitude accuracy: Accuracy in a measuring instrument means the difference between the measured value and the actual (true) value, i.e., the degree of closeness to the true value. Spectrum analyzer amplitude accuracy is measured in ± X dB. 

Resolution bandwidth (Hz): It refers to the minimum signal width that a spectrum analyzer can resolve. It is usually expressed in Hz. 

Power consumption: Represents the power consumption of the spectrum analyzer in W.