Comparison between spectrum analyzer and oscilloscope

 　　Traditionally, electrical signals are viewed in the time domain using an oscilloscope. The time domain is concerned with the characteristics of electrical signals: recovering the relationship between time and phase. However, not all circuit characteristics can be fully characterized using the time domain. Circuit components such as amplifiers, oscillators, mixers, modulators, detectors, and filters are best characterized by frequency response data. The best results are obtained by viewing them in the frequency domain. To measure the frequency domain, an instrument is needed that can identify the individual frequency components and read the level of each frequency component. One such instrument is a spectrum analyzer, which can display amplitude and other parameters relative to frequency in a graph on an oscilloscope screen.

　　Spectrum analyzers are more sensitive to low-level distortion than oscilloscopes. A sine wave can be seen on an oscilloscope (in the time domain), but in the frequency domain, its harmonic distortion can be seen. High sensitivity and wide dynamic range also allow spectrum analyzers to measure low-level modulation. AM, FM and pulse modulated RF signals can be measured. Spectrum analyzers can measure carrier frequency, modulation frequency, modulation level and modulation distortion. Characteristics of frequency conversion devices such as conversion loss, isolation and distortion can also be measured and read from the display.

　　The spectrum analyzer can be used to measure long-term and short-term frequency stability. For example, the noise sidebands of the oscillator, the residual FM and the frequency drift during the warm-up time can be measured using the calibrated bandwidth of the spectrum analyzer. Together with the spectrum analyzer swept frequency measurement, the swept frequency response of filters or amplifiers can be measured. This can be easily achieved using a tracking generator.

　　The spectrum analyzer can be used to check the wired and wireless systems such as remote controls, intercoms, measuring transmitters and receivers, cordless phones, CATV and communication equipment, as well as analyze and compare signal frequencies.

　　Electromagnetic compatibility test (EMC): It measures the harmful electromagnetic waves emitted by various electronic devices. In addition, the AM/FM detection signal can be output from the PHONE (headphone) jack, which can be used to identify the broadcast signal affected by noise. From the perspective of certification, measuring the radiated noise first is a very effective measurement function for prior assessment research.