How Does a Spectrum Analyzer Work

A spectrum analyzer is a powerful tool used in

• Telecommunications to measure the performance of cellular networks and debug wireless communications.
• The defense industry to test radar systems and detect hostile emitters.
• Satellite communications to evaluate link quality and monitor interference.
• Broadcasting to ensure compliance with regulations and optimize transmitter performance.
• The aerospace industry to test aircraft avionics and ground-based radar systems.
• Medical research to study brain waves and investigate the effects of electromagnetic radiation.

For engineers learning about spectrum analyzers, another piece of test equipment often used in conjunction with them is an oscilloscope. Using a spectrum analyzer and an oscilloscope together provides a complete picture of a signal.

Spectrum analyzers measure the amplitude of a signal as a function of frequency. They characterize signals spread out over a wide range of frequencies, such as those generated by RF transmitters. On the other hand, oscilloscopes measure a signal's voltage as a time (time domain). They are often used to troubleshoot electrical circuits by observing the waveforms of the various signals passing through them over short and long intervals.

For example, if you are trying to optimize an RF transmitter, you may use an analyzer to measure the output power as a function of frequency. Then you can use an oscilloscope to measure the shape of the transmitter's output waveform. By looking at both the power spectral density and the waveform, you can better understand how the transmitter is performing and identify any areas that need improvement.

These analyzers are also excellent at detecting and measuring noise and spurious signals. Signal noise is any unwanted signal that is present in a system. Spurious signals are not supposed to be present in a system. Together, these two types of interference can diminish and distort a signal.

By analyzing the frequency spectrum of a signal, a spectrum analyzer produces a graph that shows the signal's amplitude versus frequency. The amplitude measurement is in decibels, and the frequency is in hertz. By comparing these two measurements, you can identify any out-of-band signals or noise that may be present. This allows you to isolate and remove noise and spurious signals, ensuring accurate measurements.