The Fundamentals of a Wireless Spectrum Analyzer

By: Courtney Hamby on May 7th, 2015

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The Fundamentals of a Wireless Spectrum Analyzer

wireless  |  frequency  |  Analog  |  Digital  |  bandwidth  |  spectrum analyzer  |  wireless spectrum analyzer  |  fundamentals  |  RF attenuator

spectrum_analysis-1A Wireless Spectrum Analyzer can be described as a frequency-selective, peak-responding voltmeter adjusted to display the rms value of a sine wave. It can be used to display power directly but cannot be used as a power meter. This can only be done as long as we know some value of the sine wave and the resistance across which we measure this value, only then one can calibrate the Wireless Spectrum Analyzer to indicate power. Here is a study of the fundamentals of Wireless Spectrum Analyzer:


Low Pass Filter Or Preselector

A low pass filter blocks high frequency signals from reaching the mixer which prevents out of band signals from mixing with the local oscillator, creating unwanted responses on the display. Wireless Spectrum Analyzer replaces low-pass filter with a preselector that rejects all the unwanted frequencies.


RF Attenuator 

RF Attenuator ensures that the signal enters the mixer at the appropriate level in order to prevent gain compression, distortion and overload. It forms a protective circuit for the Wireless Spectrum Analyzer.


Tuning Of The Analyzer

Tuning is a function of the centre frequency of the IF Filter and the range of frequency allowed to reach the mixer. The two frequencies emerging with the greatest amplitude are therefore the most desirable.


Resolving Signals

  • Analog Filters: A Wireless Spectrum Analyzer is capable of frequency resolution, which means, it can separate two input sinusoids into distinct responses. Two signals, no matter how distinct in frequency, should appear as two lines on the display.
  • Digital Filters: In order to realize the resolution bandwidth filters, some Wireless Spectrum Analyzers use digital techniques. These techniques can drastically improve bandwidth selectivity.


Residual FM

In order to determine the minimum usable resolution bandwidth, the residual FM is brought to use in a Wireless Spectrum Analyzer. It was impossible to have resolution bandwidths narrower than 1 kHz in order to determine the cause of the instability in the display. However, modern Wireless Spectrum Analyzers have drastically improved the residual FM which allows bandwidth as low as 1 Hz in many Wireless Spectrum Analyzers.


People involved in wireless communications are extremely interested in out-of-band and unauthentic emissions. Therefore, government regulatory agencies allocate different frequencies for various radio services, such as broadcast television and radio, mobile phone systems, police and emergency communications and several other applications. With the advent of new technologies and scientific inventions, Wireless Spectrum Analyzer has been enabled with advanced capabilities that have been made possible with the use of digital technology and digital signal processing.

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