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spectrum analyzer[′spek·trəm ′an·ə‚līz·ər]
a laboratory measuring instrument used for studying the frequency spectra observed on the screen of an electron-ray tube as well as the pulse- and amplitude-modulated oscillations in 3– and 10–cm wave bands. In order to obtain oscillographic patterns of the spectra of the oscillations under investigation in “power-frequency” coordinates, a superheterodyne radio receiver is used in the spectrum analyzer. In this receiver the incoming oscillations are weakened (if necessary) by attenuators, transformed according to frequency, and strengthened; then they enter on the vertically deflected plate of the electron-ray tube. The frequency of the receiver’s oscillator varies linearly by ±8 mHz (in a 10–cm band) or ±30 mHz (in a 3–cm band) in step with the saw-toothed tension sweep, which is simultaneously fed into the loops that change the heterodyne’s frequency and on the horizontal plates of the electron-ray tube. Frequency calibration is provided for in the analyzer by an oscillator with calibrated markers, having smooth control of amplitude and frequency ranging from 1 to 10 mHz. The spectrum analyzer can measure the oscillator’s frequency drift, minor differences in the frequency of two oscillators, and so forth.
REFERENCEShkurin, G. P. Spravochnik po elektroizmeritel’nym i radioizmeritel’nym priboram, 3rd ed., vol. 2. Moscow, 1960.
spectrum analyzerA hardware device or software used to examine the frequency and power components of a signal. It provides more information than an oscilloscope, because it can display the signals over a range of frequencies. For example, whereas an oscilloscope would show total noise level, a spectrum analyzer would show the noise as related to frequency. Available in both analog and digital models, digital analyzers sample the incoming waveforms and convert them to fast fourier transforms (FFTs).
The range of frequencies being analyzed is the "bandwidth," while the width of the individual samples is the "bandwidth resolution." In the following example, the bandwidth is 86 Hz to 20 kHz, and the bandwidth resolution is 40 Hz. Each sample represents a 40 Hz section of the displayed 19,914 Hz band. See oscilloscope.
|An Audio Analysis|
|This example shows the power levels and frequencies of an audio signal as displayed in a software-based spectrum analyzer.|