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Spectrum analyzer

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	Spectrum analyzer
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	Topics Spectrum analyzer Topic Home A spectrum analyzer or spectral analyzer is a device used to examine the spectral composition of some electricalElectricity Electricity is a general term for the variety of phenomena resulting from the presence and flow of electric charge.... , acousticAcoustics Acoustics is a branch of physics that studies sound, namely mechanical waves in gases, liquids, and solids.... , or opticalOptics Optics is a branch of physics that describes the behavior and properties of light and the interaction of light with matter.... waveformWaveform Waveform means the shape and form of a signal, such as a wave moving across the surface of water, or the vibration of a pluc... . It may also measure the power spectrumSpectral density In applied mathematics and physics, the spectral density, power spectral density, or energy spectral density is ... . There are analogAnalog computer Overview An analog computer is a form of computer that uses electrical or mechanical phenomena to model the problem being solved by u... and digitalDigital A digital system is one that uses discrete numbers, especially binary numbers, or non-numeric symbols such as letters or ico... spectrum analyzers: An analog spectrum analyzer uses either a variable band-pass filterBand-pass filter A band-pass filter is a device that passes frequencies within a certain range and rejects frequencies outside that range.... whose mid-frequency is automatically tunedTuner Tuner may refer to:* Antenna tuner, a device to adjust the resonant frequency of an antenna or transmission line... (shifted, swept) through the range of frequencies of which the spectrum is to be measured or a superheterodyne receiverSuperheterodyne receiver The superheterodyne receiver was invented by Edwin Armstrong in 1918.... where the local oscillatorFacts About Local oscillator A local oscillator is a device used to generate a signal which is beat against the signal of interest to mix it to a differe... is swept through a range of frequencies. A digital spectrum analyzer computes the discrete Fourier transformFacts About Discrete Fourier transform In mathematics, the discrete Fourier transform , sometimes called the finite Fourier transform, is a Fourier transform... (DFT), a mathematical process that transforms a waveform into the components of its frequency spectrumFrequency spectrum Familiar concepts associated with a frequency are colors, musical notes, radio/TV channels, and even the regular rotation of the e... . Some spectrum analyzers (such as Tektronix's family of "real-time spectrum analyzers") use a hybrid technique where the incoming signal is first down-convertedSuperheterodyne receiver The superheterodyne receiver was invented by Edwin Armstrong in 1918.... to a lower frequency using superheterodyne techniques and then analyzed using fast fourier transformation (FFT) techniques. Operation Usually, a spectrum analyzer displays a power spectrum over a given frequency range in real time, changing the display as the properties of the signal change. There is a trade-off between how quickly the display can be updated and the frequency resolution, which is for example relevant for distinguishing frequency components that are close together. With a digital spectrum analyzer, the frequency resolution is , the inverse of the time T over which the waveform is measured and Fourier transformed. With an analog spectrum analyzer, it is dependent on the bandwidth setting of the bandpass filter. However, an analog spectrum analyzer will not produce meaningful results if the filter bandwidth (in Hz) is smaller than the square root of the sweep speed (in Hz/s), which means that an analog spectrum analyzer can never beat a digital one in terms of frequency resolution for a given acquisition time. Choosing a wider bandpass filter will improve the signal-to-noise ratioSignal-to-noise ratio Signal-to-noise ratio is an electrical engineering concept defined as the ratio of a given transmitted signal to the backgr... at the expense of a decreased frequency resolution. With Fourier transform analysis in a digital spectrum analyzer, it is necessary to sample the input signal with a sampling frequency that is at least twice the highest frequency that is present in the signal, due to the Nyquist limitNyquist frequency The Nyquist frequency, named after Harry Nyquist or the NyquistShannon sampling theorem, is half the sampling frequency of a... . A Fourier transform will then produce a spectrum containing all frequencies from zero to . This can place considerable demands on the required analog-to-digital converterAnalog-to-digital converter An analog-to-digital converter is an electronic circuit that converts continuous signals to discrete digital numbers.... and processing power for the Fourier transform. Often, one is only interested in a narrow frequency range, for example between 88 and 108 MHz, which would require at least a sampling frequency of 216 MHz, not counting the low-pass anti-aliasing filter. In such cases, it can be more economic to first use a superheterodyne receiver to transform the signal to a lower range, such as 8 to 28 MHz, and then sample the signal at 56 MHz. This is how an analog-digital-hybrid spectrum analyzer works. For use with very weak signals, a pre-amplifier can be used, although harmonicTotal harmonic distortion The total harmonic distortion, or THD, of a signal is a measurement of the harmonic distortion present and is defined ... and intermodulationIntermodulation Summary Intermodulation or intermod is the result of two signals of different frequencies being mixed together, forming additi... distortion may lead to the creation of new frequency components that were not present in the original signal. Acoustic uses In acousticsAcoustics Acoustics is a branch of physics that studies sound, namely mechanical waves in gases, liquids, and solids.... , a spectrograph converts a sound waveSound Sound is a disturbance of mechanical energy that propagates through matter as a wave.... into a sound spectrogramSpectrogram The spectrogram is the result of calculating the frequency spectrum of windowed frames of a compound signal.... . The first acoustic spectrograph was developed during World War II at Bell Telephone LaboratoriesBell Labs Summary Bell Laboratories was the main research and development arm of the United States Bell System.... , and was widely used in speech scienceSpeech and language pathology Speech-language pathology is the study of disorders that affect a person's speech, language, cognition, voice, swallowing a... , acoustic phoneticsAcoustic phonetics Acoustic phonetics is a subfield of phonetics which deals with acoustic aspects of speech sounds.... and audiologyAudiology Audiology is the branch of science that studies hearing, balance, and their disorders.... research, before eventually being superseded by digital signal processingDigital signal processing Digital signal processing is the study of signals in a digital representation and the processing methods of these signals.... techniques. Now spectrum analyzers cover the acoustic range. RF uses In telecommunications, for example, spectrum analyzers are used to determine occupied bandwidth and track interference sources. Cellplanners use this equipment to determine interference sources in the GSM/TETRA and UMTS technology. See also Spectral MusicSpectral music Spectral music is music that is concerned with timbral structures, especially when decisions about timbre are informed by a ... Frequency SpectrumFrequency spectrum Familiar concepts associated with a frequency are colors, musical notes, radio/TV channels, and even the regular rotation of the e... SpectrometerSpectrometer A spectrometer is an optical instrument used to measure properties of light over a specific portion of the electromagnetic s... Electromagnetic SpectrumElectromagnetic spectrum The electromagnetic spectrum is the range of all possible electromagnetic radiation.... Measuring ReceiverMeasuring Receiver Measuring ReceiverA measuring receiver, also known as measurement receiver, is a device used to perform traceab... External links Sri Welaratna, "", Sound and Vibration (January 1997, 30th anniversary issue). A historical review of hardware spectrum-analyzer devices. Manufacturer (alphabetic) Agilent TechnologiesAgilent Technologies Agilent Technologies is a measurement and instrument company headquartered in Palo Alto, California.... AnritsuAnritsu is a Japanese corporation that is a major presence in the test and measurement market.... Rohde & SchwarzRohde & Schwarz Rohde & Schwarz is an independent group of companies specializing in electronics.... Tektronix