15 Important Spectrum Analyzer Terms

Spectrum Analyzer

A spectrum analyzer is a testing instrument used to measure and audit the composition (including magnitude, bandwidth and distortion) of electrical impulses in acoustic and optical waves. Essentially, the device is used to create a visible description of the amplitude of an electrical signal in wave form. Spectrum analyzers are available in swept-tuned and FFT varieties, and are separated into three different forms. Form factors include handheld analyzers, bench top analyzers and portable spectrum analyzers.


An attenuator is an electronic testing instrument that decreases the magnitude or power of a signal. Due to its composition, this device can effectively diminish the amplitude of the signal without compromising signal purity or causing noticeable distortion. Whereas an amplifier increases the magnitude or frequency of optical or acoustic waves, an attenuator causes the amplitude to dissipate for closer examination of composition.

Displayed Average Noise Level (DANL)

Displayed average noise level refers to the mean, or average, measurement of perceptible noise in decibels. It is measured within the given frequency ranges using a spectrum analyzing device. It is connected directly to amplitude characteristics in a specified electromagnetic signal, as well as the signal-to-noise ratio of that signal.

Dynamic Range

Abbreviated as DR or DNR, dynamic range refers to the ratio (expressed in decibels) between the minimum and maximum perceptible values of a given quantity, specifically in acoustic and optical frequencies.

Frequency Span

Frequency span refers to the entire amount of spectra detected and captured by a spectrum analyzing device. The span's focus is concentrated around the middle of the frequency wave being analyzed. Along with center frequency, frequency span assigns the graphic range that is displayed in the front window of the spectrum analyzer.

Frequency Standard

A frequency standard is a device used to calibrate a given frequency and, through the use of harmonics, to provide a point of reference for said frequency for testing. The instrument operates by generating a primary frequency with a high level of precision and recording the point of reference captured.

Harmonic Distortion

Harmonic distortion refers to aberration of waves in alternating current caused by electromagnetic interference. This interference is most frequently the result of proximity of operational microprocessors (such as those found in desktop computers). Harmonic distortion can cause a variety of technical issues, including random tripping of breakers, voltage imbalance, poor power quality and overheating of electronic equipment. Overheating caused by harmonic distortion can potentially cause irreparable damage to testing equipment.


Markers are indicators on a spectrum analyzing device used to denote measured signal amplitude. They are used to demonstrate certain areas on the test sweep, including channel limits and bandwidth. Using an original point of reference (set to an absolute frequency), markers indicate changes in frequency and amplitude in a given signal.


An oscillator is a technical testing instrument in the form of an electronic circuit. It generates and transforms energy (in the form of a repeating signal) from a current source to an electric output. The two major types of oscillators, harmonic and relaxation oscillators, work in opposite ways. Harmonic (also referred to as linear) oscillators generate sinusoidal wave, while relaxation oscillators produce a non-sinusoidal signal. Oscillators are used as integral components of various electronic devices, including radio transmitters, watches, computers and video game systems.


A preamplifier, also referred to as a preamp, is an electronic device used to adapt a signal for augmentation. The instrument is most commonly situated next to a sensor during testing to lessen the effects of distortion caused by interference and superfluous noise. Used to boost the strength of the signal, the preamplifier's primary objective is to increase amplitude without compromising the integrity of the signal-to-noise ratio, or SNR.

Resolution Bandwidth

Resolution bandwidth (abbreviated as RB or RBW) is used to determine the frequency precision of a particular measurement, indicating the smallest frequency that can possibly be resolved in a given test. It is one of the two fundamental methods of measurement in the field of spectral analysis (the other is dynamic range).

Spectral Purity

Spectral purity refers to the degree and quality of a light sample's monochromatic character. Higher frequencies result in a higher level of spectral purity. Higher levels of spectral purity are easiest to generate with instruments that produce light in the visible and UV spectra.


A spectrogram is a photographic image or diagram of a spectrum. It continuously varies with time, indicating the density of the spectrum as it changes over a period of time. The electronic device that is used to create a spectrogram is called a spectrograph.

Spurious Response

Spurious response refers to the response of a given receiver (often a radio receiver) to a signal that is of a different type than that which the device is tuned to receive.

Zero span

Zero span is a useful (and commonly integrated) feature of a spectral analysis device. It provides the individual using the instrument with a visible representation of the incoming signal. The format of this information, however, is displayed as power versus time rather than the traditional power versus frequency.